draft-ietf-mmusic-rfc2326bis-04.txt   draft-ietf-mmusic-rfc2326bis-05.txt 
skipping to change at page 1, line 14 skipping to change at page 1, line 14
Internet Draft H. Schulzrinne Internet Draft H. Schulzrinne
Columbia U. Columbia U.
A. Rao A. Rao
Cisco Cisco
R. Lanphier R. Lanphier
RealNetworks RealNetworks
M. Westerlund M. Westerlund
Ericsson Ericsson
A. Narasimhan A. Narasimhan
Sun Sun
draft-ietf-mmusic-rfc2326bis-05.txt
draft-ietf-mmusic-rfc2326bis-04.txt October 27, 2003
June 30, 2003 Expires: April, 2004
Expires: December, 2003
Real Time Streaming Protocol (RTSP) Real Time Streaming Protocol (RTSP)
STATUS OF THIS MEMO STATUS OF THIS MEMO
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference mate- time. It is inappropriate to use Internet-Drafts as reference
rial or to cite them other than as "work in progress". material or to cite them other than as "work in progress".
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
To view the list Internet-Draft Shadow Directories, see To view the list Internet-Draft Shadow Directories, see
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
This memorandum is a revision of RFC 2326, which is currently a Pro- This memorandum is a revision of RFC 2326, which is currently a
posed Standard. Proposed Standard.
The Real Time Streaming Protocol, or RTSP, is an application-level The Real Time Streaming Protocol, or RTSP, is an application-level
protocol for control over the delivery of data with real-time protocol for control over the delivery of data with real-time
properties. RTSP provides an extensible framework to enable con- properties. RTSP provides an extensible framework to enable
trolled, on-demand delivery of real-time data, such as audio and controlled, on-demand delivery of real-time data, such as audio and
video. Sources of data can include both live data feeds and stored video. Sources of data can include both live data feeds and stored
clips. This protocol is intended to control multiple data delivery clips. This protocol is intended to control multiple data delivery
sessions, provide a means for choosing delivery channels such as UDP, sessions, provide a means for choosing delivery channels such as UDP,
multicast UDP and TCP, and provide a means for choosing delivery multicast UDP and TCP, and provide a means for choosing delivery
mechanisms based upon RTP (RFC 1889). mechanisms based upon RTP (RFC 3550).
1 Introduction 1 Introduction
1.1 The Update of the RTSP Specification 1.1 The Update of the RTSP Specification
This is the draft to an update of RTSP which is currently a proposed This is the draft to an update of RTSP which is currently a proposed
standard defined in RFC 2326 [21]. Many flaws have been found in standard defined in RFC 2326 [21]. Many flaws have been found in
RTSP since it was published. While this draft tries to address the RTSP since it was published. While this draft tries to address the
flaws, not all known issues have been resolved. flaws, not all known issues have been resolved.
The goal of the current work on RTSP is to progress it to draft stan- The goal of the current work on RTSP is to progress it to draft
dard status. Whether this is possible without first publishing RTSP standard status. Whether this is possible without first publishing
as a proposed standard depends on the changes necessary to make the RTSP as a proposed standard depends on the changes necessary to make
protocol work. The list of changes in chapter F indicates the issues the protocol work. The list of changes in chapter F indicates the
that have already been addressed. The currently open issues are issues that have already been addressed. The currently open issues
listed in chapter E. are listed in chapter E.
There is also a list of reported bugs available at "http://rtsp- There is also a list of reported bugs available at
spec.sourceforge.net". These bugs should be taken into account when "http://rtspspec.sourceforge.net". These bugs should be taken into
reading this specification. While a lot of these bugs are addressed, account when reading this specification. While a lot of these bugs
not all are yet accounted for in this specification. Input on the are addressed, not all are yet accounted for in this specification.
unresolved bugs and other issues can be sent via e-mail to the MMUSIC Input on the unresolved bugs and other issues can be sent via e-mail
WG's mailing list mmusic@ietf.org and the authors. to the MMUSIC WG's mailing list mmusic@ietf.org and the authors.
Take special notice of the following: Take special notice of the following:
+ The example section 15 has not yet been revised since the o The example section 15 has not yet been revised since the
changes to protocol have not been completed. changes to protocol have not been completed.
+ The BNF chapter 16 has not been compiled completely. o The BNF chapter 16 has not been compiled completely.
+ Not all of the contents of RFC 2326 are part of this draft. In o Not all of the contents of RFC 2326 are part of this draft.
an attempt to prevent the draft from exploding in size, the spec- In an attempt to prevent the draft from exploding in size, the
ification has been reduced and split. The content of this draft specification has been reduced and split. The content of this
is the core specification of the protocol. It contains the gen- draft is the core specification of the protocol. It contains
eral idea behind RTSP and the basic functionality necessary to the general idea behind RTSP and the basic functionality
establish an on-demand play-back session. It also contains the necessary to establish an on-demand play-back session. It also
mechanisms for extending the protocol. Any other functionality contains the mechanisms for extending the protocol. Any other
will be published as extension documents. Two proposals exist at functionality will be published as extension documents. Two
this time: proposals exist at this time:
+ NAT and FW traversal mechanisms for RTSP are described in a docu- o NAT and FW traversal mechanisms for RTSP are described in a
ment called "How to make Real-Time Streaming Protocol (RTSP) tra- document called "How to make Real-Time Streaming Protocol
verse Network Address Translators (NAT) and interact with Fire- (RTSP) traverse Network Address Translators (NAT) and interact
walls." [33]. with Firewalls." [33].
+ The MUTE extension [34] contains a proposal on adding functional- o The MUTE extension [34] contains a proposal on adding
ity to mute and unmute media streams in an aggregated media ses- functionality to mute and unmute media streams in an
sion without affecting the time-line of the playback. aggregated media session without affecting the time-line of
the playback.
There have also been discussions about the following extensions to There have also been discussions about the following extensions to
RTSP: RTSP:
+ Transport security for RTSP messages (rtsps). o Transport security for RTSP messages (rtsps).
+ Unreliable transport of RTSP messages (rtspu). o Unreliable transport of RTSP messages (rtspu).
+ The Record functionality. o The Record functionality.
+ A text body type with suitable syntax for basic parameters to be o A text body type with suitable syntax for basic parameters to
used in SET_PARAMETER, and GET_PARAMETER. Including IANA registry be used in SET_PARAMETER, and GET_PARAMETER. Including IANA
within the defined name space. registry within the defined name space.
+ A RTSP MIB. o A RTSP MIB.
However, so far, they have not become concrete proposals. However, so far, they have not become concrete proposals.
1.2 Purpose 1.2 Purpose
The Real-Time Streaming Protocol (RTSP) establishes and controls sin- The Real-Time Streaming Protocol (RTSP) establishes and controls
gle or several time-synchronized streams of continuous media such as single or several time-synchronized streams of continuous media such
audio and video. Put simply, RTSP acts as a "network remote control" as audio and video. Put simply, RTSP acts as a "network remote
for multimedia servers. control" for multimedia servers.
There is no notion of a RTSP connection in the protocol. Instead, a There is no notion of a RTSP connection in the protocol. Instead, a |
RTSP server maintains a session labelled by an identifier to associ- RTSP server maintains a session labelled by an identifier to |
ate groups of media streams and their states. A RTSP session is nor- associate groups of media streams and their states. A RTSP session is |
mally not tied to a transport-level connection such as a TCP connec- not tied to a transport-level connection such as a TCP connection. |
tion. During a session, a client may open and close many reliable During a session, a client may open and close many reliable transport |
transport connections to the server to issue RTSP requests for that connections to the server to issue RTSP requests for that session.
session.
This memorandum describes the use of RTSP over a reliable connection This memorandum describes the use of RTSP over a reliable connection
based transport level protocol such as TCP. RTSP may be implemented based transport level protocol such as TCP. RTSP may be implemented
over an unreliable connectionless transport protocol such as UDP. over an unreliable connectionless transport protocol such as UDP.
While nothing in RTSP precludes this, additional definition of this While nothing in RTSP precludes this, additional definition of this
problem area must be handled as an extension to the core specifica- problem area must be handled as an extension to the core
tion. specification.
The mechanisms of RTSP's operation over UDP were left out of The mechanisms of RTSP's operation over UDP were left out
this spec. because they were poorly defined in RFC 2336 [21] of this spec. because they were poorly defined in RFC 2336
and the tradeoff in size and complexity of this spec. for a [21] and the tradeoff in size and complexity of this spec.
small gain in a targeted problem space was not deemed justifi- for a small gain in a targeted problem space was not deemed
able. justifiable.
The set of streams to be controlled is defined by a presentation The set of streams to be controlled is defined by a presentation
description. This memorandum does not define a format for the description. This memorandum does not define a format for the
presentation description. The streams controlled by RTSP may use RTP presentation description. The streams controlled by RTSP may use RTP
[1] for their data transport, but the operation of RTSP does not [1] for their data transport, but the operation of RTSP does not
depend on the transport mechanism used to carry continuous media. The depend on the transport mechanism used to carry continuous media. The
protocol is intentionally similar in syntax and operation to HTTP/1.1 protocol is intentionally similar in syntax and operation to HTTP/1.1
[26] so that extension mechanisms to HTTP can in most cases also be [26] so that extension mechanisms to HTTP can in most cases also be
added to RTSP. However, RTSP differs in a number of important added to RTSP. However, RTSP differs in a number of important
aspects from HTTP: aspects from HTTP:
+ RTSP introduces a number of new methods and has a different pro- o RTSP introduces a number of new methods and has a different
tocol identifier. protocol identifier.
+ RTSP has the notion of a session built into the protocol. o RTSP has the notion of a session built into the protocol.
+ A RTSP server needs to maintain state by default in almost all o A RTSP server needs to maintain state by default in almost all
cases, as opposed to the stateless nature of HTTP. cases, as opposed to the stateless nature of HTTP.
+ Both a RTSP server and client can issue requests. o Both a RTSP server and client can issue requests.
+ Data is usually carried out-of-band by a different protocol. o Data is usually carried out-of-band by a different protocol.
Session descriptions returned in a DESCRIBE response (see Section Session descriptions returned in a DESCRIBE response (see
11.2) and interleaving of RTP with RTSP over TCP are exceptions Section 11.2) and interleaving of RTP with RTSP over TCP are
to this rule (see Section 11.11). exceptions to this rule (see Section 11.11).
+ RTSP is defined to use ISO 10646 (UTF-8) rather than ISO 8859-1, o RTSP is defined to use ISO 10646 (UTF-8) rather than ISO
consistent with current HTML internationalization efforts [3]. 8859-1, consistent with current HTML internationalization
efforts [3].
+ The Request-URI always contains the absolute URI. Because of o The Request-URI always contains the absolute URI. Because of
backward compatibility with a historical blunder, HTTP/1.1 [26] backward compatibility with a historical blunder, HTTP/1.1
carries only the absolute path in the request and puts the host [26] carries only the absolute path in the request and puts
name in a separate header field. the host name in a separate header field.
This makes "virtual hosting" easier, where a single host This makes "virtual hosting" easier, where a single
with one IP address hosts several document trees. host with one IP address hosts several document trees.
The protocol supports the following operations: The protocol supports the following operations:
Retrieval of media from media server: The client can request a pre- Retrieval of media from media server: The client can request a
sentation description via HTTP or some other method. If the presentation description via HTTP or some other method. If
presentation is being multicast, the presentation description the presentation is being multicast, the presentation
contains the multicast addresses and ports to be used for the description contains the multicast addresses and ports to
continuous media. If the presentation is to be sent only to be used for the continuous media. If the presentation is
the client via unicast, the client provides the destination to be sent only to the client via unicast, the client
for security reasons. provides the destination for security reasons.
Invitation of a media server to a conference: A media server can be | Invitation of a media server to a conference: A media server can
"invited" to join an existing conference to play back media | be "invited" to join an existing conference to play back
into the presentation. This mode is useful for distributed | media into the presentation. This mode is useful for
teaching applications. Several parties in the conference may | distributed teaching applications. Several parties in the
take turns "pushing the remote control buttons". conference may take turns "pushing the remote control
buttons".
Addition of media to an existing presentation: Particularly for Addition of media to an existing presentation: Particularly for
live presentations, it is useful if the server can tell the live presentations, it is useful if the server can tell the
client about additional media becoming available. client about additional media becoming available.
RTSP requests may be handled by proxies, tunnels and caches as in RTSP requests may be handled by proxies, tunnels and caches as in
HTTP/1.1 [26]. HTTP/1.1 [26].
1.3 Requirements 1.3 Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [4]. document are to be interpreted as described in RFC 2119 [4].
1.4 Terminology 1.4 Terminology
Some of the terminology has been adopted from HTTP/1.1 [26]. Terms Some of the terminology has been adopted from HTTP/1.1 [26]. Terms
not listed here are defined as in HTTP/1.1. not listed here are defined as in HTTP/1.1.
Aggregate control: The concept of controlling multiple streams Aggregate control: The concept of controlling multiple streams
using a single timeline, generally maintained by the server. A using a single timeline, generally maintained by the
client, for example, uses aggregate control when it issues a server. A client, for example, uses aggregate control when
single play or pause message to simultaneously control both it issues a single play or pause message to simultaneously
the audio and video in a movie. control both the audio and video in a movie.
Aggregate control URI: The URI used in a RTSP request to refer to Aggregate control URI: The URI used in a RTSP request to refer
and control an aggregated session. It normally, but not to and control an aggregated session. It normally, but not
always, corresponds to the presentation URI specified in the always, corresponds to the presentation URI specified in
session description. See Section 11.3 for more information. the session description. See Section 11.3 for more
information.
Conference: a multiparty, multimedia presentation, where "multi" Conference: a multiparty, multimedia presentation, where "multi"
implies greater than or equal to one. implies greater than or equal to one.
Client: The client requests media service from the media server. Client: The client requests media service from the media server.
Connection: A transport layer virtual circuit established between Connection: A transport layer virtual circuit established
two programs for the purpose of communication. between two programs for the purpose of communication.
Container file: A file which may contain multiple media streams Container file: A file which may contain multiple media streams
which often comprise a presentation when played together. RTSP which often comprise a presentation when played together.
servers may offer aggregate control on these files, though the RTSP servers may offer aggregate control on these files,
concept of a container file is not embedded in the protocol. though the concept of a container file is not embedded in
the protocol.
Continuous media: Data where there is a timing relationship between Continuous media: Data where there is a timing relationship
source and sink; that is, the sink must reproduce the timing between source and sink; that is, the sink must reproduce
relationship that existed at the source. The most common exam- the timing relationship that existed at the source. The
ples of continuous media are audio and motion video. Continu- most common examples of continuous media are audio and
ous media can be real-time (interactive), where there is a motion video. Continuous media can be real-time
"tight" timing relationship between source and sink, or (interactive), where there is a "tight" timing relationship
streaming (playback), where the relationship is less strict. between source and sink, or streaming (playback), where the
relationship is less strict.
Entity: The information transferred as the payload of a request or Entity: The information transferred as the payload of a request
response. An entity consists of meta-information in the form or response. An entity consists of meta-information in the
of entity-header fields and content in the form of an entity- form of entity-header fields and content in the form of an
body, as described in Section 8. entity-body, as described in Section 8.
Feature-tag: A tag representing a certain set of functionality, Feature-tag: A tag representing a certain set of functionality,
i.e. a feature. i.e. a feature.
Media initialization: Datatype/codec specific initialization. This Media initialization: Datatype/codec specific initialization.
includes such things as clockrates, color tables, etc. Any This includes such things as clockrates, color tables, etc.
transport-independent information which is required by a Any transport-independent information which is required by
client for playback of a media stream occurs in the media ini- a client for playback of a media stream occurs in the media
tialization phase of stream setup. initialization phase of stream setup.
Media parameter: Parameter specific to a media type that may be Media parameter: Parameter specific to a media type that may be
changed before or during stream playback. changed before or during stream playback.
Media server: The server providing playback services for one or | Media server: The server providing playback services for one or
more media streams. Different media streams within a presenta- | more media streams. Different media streams within a
tion may originate from different media servers. A media | presentation may originate from different media servers. A
server may reside on the same or a different host as the web | media server may reside on the same or a different host as
server the presentation is invoked from. the web server the presentation is invoked from.
Media server indirection: Redirection of a media client to a dif- Media server indirection: Redirection of a media client to a
ferent media server. different media server.
(Media) stream: A single media instance, e.g., an audio stream or a (Media) stream: A single media instance, e.g., an audio stream
video stream as well as a single whiteboard or shared applica- or a video stream as well as a single whiteboard or shared
tion group. When using RTP, a stream consists of all RTP and application group. When using RTP, a stream consists of all
RTCP packets created by a source within an RTP session. This RTP and RTCP packets created by a source within an RTP
is equivalent to the definition of a DSM-CC stream([5]). session. This is equivalent to the definition of a DSM-CC
stream([5]).
Message: The basic unit of RTSP communication, consisting of a Message: The basic unit of RTSP communication, consisting of a
structured sequence of octets matching the syntax defined in structured sequence of octets matching the syntax defined
Section 16 and transmitted via a connection or a connection- in Section 16 and transmitted via a connection or a
less protocol. connectionless protocol.
Non-Aggregated Control: Control of a single media stream. Only Non-Aggregated Control: Control of a single media stream. Only
possible in RTSP sessions with a single media. possible in RTSP sessions with a single media.
Participant: Member of a conference. A participant may be a | Participant: Member of a conference. A participant may be a
machine, e.g., a playback server. machine, e.g., a playback server.
Presentation: A set of one or more streams presented to the client Presentation: A set of one or more streams presented to the
as a complete media feed, using a presentation description as client as a complete media feed, using a presentation
defined below. In most cases in the RTSP context, this implies description as defined below. In most cases in the RTSP
aggregate control of those streams, but does not have to. context, this implies aggregate control of those streams,
but does not have to.
Presentation description: A presentation description contains Presentation description: A presentation description contains
information about one or more media streams within a presenta- information about one or more media streams within a
tion, such as the set of encodings, network addresses and presentation, such as the set of encodings, network
information about the content. Other IETF protocols such as addresses and information about the content. Other IETF
SDP (RFC 2327 [24]) use the term "session" for a live presen- protocols such as SDP (RFC 2327 [24]) use the term
tation. The presentation description may take several differ- "session" for a live presentation. The presentation
ent formats, including but not limited to the session descrip- description may take several different formats, including
tion format SDP. but not limited to the session description format SDP.
Response: A RTSP response. If an HTTP response is meant, that is Response: A RTSP response. If an HTTP response is meant, that is
indicated explicitly. indicated explicitly.
Request: A RTSP request. If an HTTP request is meant, that is indi- Request: A RTSP request. If an HTTP request is meant, that is
cated explicitly. indicated explicitly.
RTSP session: A stateful abstraction upon which the main control RTSP session: A stateful abstraction upon which the main control
methods of RTSP operate. A RTSP session is a server entity; it methods of RTSP operate. A RTSP session is a server entity;
is created, maintained and destroyed by the server. It is it is created, maintained and destroyed by the server. It
established by a RTSP server upon the completion of a success- is established by a RTSP server upon the completion of a
ful SETUP request (when 200 OK response is sent) and is successful SETUP request (when 200 OK response is sent) and
labelled by a session identifier at that time. The session is labelled by a session identifier at that time. The
exists until timed out by the server or explicitly removed by session exists until timed out by the server or explicitly
a TEARDOWN request. A RTSP session is also a stateful entity; removed by a TEARDOWN request. A RTSP session is also a
a RTSP server maintains an explicit session state machine (see stateful entity; a RTSP server maintains an explicit
Appendix A) where most state transitions are triggered by session state machine (see Appendix A) where most state
client requests. The existence of a session implies the exis- transitions are triggered by client requests. The existence
tence of state about the session's media streams and their of a session implies the existence of state about the
respective transport mechanisms. A given session can have zero session's media streams and their respective transport
or more media streams associated with it. A RTSP server uses mechanisms. A given session can have zero or more media
the session to aggregate control over multiple media streams. streams associated with it. A RTSP server uses the session
to aggregate control over multiple media streams.
Transport initialization: The negotiation of transport information Transport initialization: The negotiation of transport
(e.g., port numbers, transport protocols) between the client information (e.g., port numbers, transport protocols)
and the server. between the client and the server.
1.5 Protocol Properties 1.5 Protocol Properties
RTSP has the following properties: RTSP has the following properties:
Extendable: New methods and parameters can be easily added to RTSP. Extendable: New methods and parameters can be easily added to
RTSP.
Easy to parse: RTSP can be parsed by standard HTTP or MIME parsers. Easy to parse: RTSP can be parsed by standard HTTP or MIME
parsers.
Secure: RTSP re-uses web security mechanisms, either at the trans- Secure: RTSP re-uses web security mechanisms, either at the
port level (TLS, RFC 2246 [27]) or within the protocol itself. transport level (TLS, RFC 2246 [27]) or within the protocol
All HTTP authentication mechanisms such as basic (RFC 2616 itself. All HTTP authentication mechanisms such as basic
[26]) and digest authentication (RFC 2069 [6]) are directly (RFC 2616 [26]) and digest authentication (RFC 2069 [6])
applicable. are directly applicable.
Transport-independent: RTSP does not preclude the use of an unreli- Transport-independent: RTSP does not preclude the use of an
able datagram protocol (UDP) (RFC 768 [7]), a reliable data- unreliable datagram protocol (UDP) (RFC 768 [7]), a
gram protocol (RDP, RFC 1151, not widely used [8]) or a reli- reliable datagram protocol (RDP, RFC 1151, not widely used
able stream protocol such as TCP (RFC 793 [9]) as it imple- [8]) or a reliable stream protocol such as TCP (RFC 793
ments application-level reliability. The use of a connection- [9]) as it implements application-level reliability. The
less datagram protocol such as UDP or RDP requires additional use of a connectionless datagram protocol such as UDP or
definition that may be provided as extensions to the core RTSP RDP requires additional definition that may be provided as
specification. extensions to the core RTSP specification.
Multi-server capable: Each media stream within a presentation can Multi-server capable: Each media stream within a presentation
reside on a different server. The client automatically estab- can reside on a different server. The client automatically
lishes several concurrent control sessions with the different establishes several concurrent control sessions with the
media servers. Media synchronization is performed at the different media servers. Media synchronization is
transport level. performed at the transport level.
Separation of stream control and conference initiation: Stream con- Separation of stream control and conference initiation: Stream
trol is divorced from inviting a media server to a conference. control is divorced from inviting a media server to a
In particular, SIP [10] or H.323 [28] may be used to invite a conference. In particular, SIP [10] or H.323 [28] may be
server to a conference. used to invite a server to a conference.
Suitable for professional applications: RTSP supports frame-level Suitable for professional applications: RTSP supports frame-
accuracy through SMPTE time stamps to allow remote digital level accuracy through SMPTE time stamps to allow remote
editing. digital editing.
Presentation description neutral: The protocol does not impose a Presentation description neutral: The protocol does not impose a
particular presentation description or metafile format and can particular presentation description or metafile format and
convey the type of format to be used. However, the presenta- can convey the type of format to be used. However, the
tion description must contain at least one RTSP URI. presentation description must contain at least one RTSP
URI.
Proxy and firewall friendly: The protocol should be readily handled Proxy and firewall friendly: The protocol should be readily
by both application and transport-layer (SOCKS [11]) fire- handled by both application and transport-layer (SOCKS
walls. A firewall may need to understand the SETUP method to [11]) firewalls. A firewall may need to understand the
open a "hole" for the UDP media stream. SETUP method to open a "hole" for the UDP media stream.
HTTP-friendly: Where sensible, RTSP reuses HTTP concepts, so that HTTP-friendly: Where sensible, RTSP reuses HTTP concepts, so
the existing infrastructure can be reused. This infrastructure that the existing infrastructure can be reused. This
includes PICS (Platform for Internet Content Selection infrastructure includes PICS (Platform for Internet Content
[12,13]) for associating labels with content. However, RTSP Selection [12,13]) for associating labels with content.
does not just add methods to HTTP since the controlling con- However, RTSP does not just add methods to HTTP since the
tinuous media requires server state in most cases. controlling continuous media requires server state in most
cases.
Appropriate server control: If a client can start a stream, it must Appropriate server control: If a client can start a stream, it
be able to stop a stream. Servers should not start streaming must be able to stop a stream. Servers should not start
to clients in such a way that clients cannot stop the stream. streaming to clients in such a way that clients cannot stop
the stream.
Transport negotiation: The client can negotiate the transport Transport negotiation: The client can negotiate the transport
method prior to actually needing to process a continuous media method prior to actually needing to process a continuous
stream. media stream.
Capability negotiation: If basic features are disabled, there must Capability negotiation: If basic features are disabled, there
be some clean mechanism for the client to determine which must be some clean mechanism for the client to determine
methods are not going to be implemented. This allows clients which methods are not going to be implemented. This allows
to present the appropriate user interface. For example, if clients to present the appropriate user interface. For
seeking is not allowed, the user interface must be able to example, if seeking is not allowed, the user interface must
disallow moving a sliding position indicator. be able to disallow moving a sliding position indicator.
An earlier requirement in RTSP was multi-client capability. An earlier requirement in RTSP was multi-client capability.
However, it was determined that a better approach was to make However, it was determined that a better approach was to
sure that the protocol is easily extensible to the multi- make sure that the protocol is easily extensible to the
client scenario. Stream identifiers can be used by several multi-client scenario. Stream identifiers can be used by
control streams, so that "passing the remote" would be possi- several control streams, so that "passing the remote" would
ble. The protocol would not address how several clients nego- be possible. The protocol would not address how several
tiate access; this is left to either a "social protocol" or clients negotiate access; this is left to either a "social
some other floor control mechanism. protocol" or some other floor control mechanism.
1.6 Extending RTSP 1.6 Extending RTSP
Since not all media servers have the same functionality, media Since not all media servers have the same functionality, media
servers by necessity will support different sets of requests. For servers by necessity will support different sets of requests. For
example: example:
+ A server may not be capable of seeking (absolute positioning) if o A server may not be capable of seeking (absolute positioning)
it is to support live events only. if it is to support live events only.
+ Some servers may not support setting stream parameters and thus o Some servers may not support setting stream parameters and
not support GET_PARAMETER and SET_PARAMETER. thus not support GET_PARAMETER and SET_PARAMETER.
A server SHOULD implement all header fields described in Section 13. A server SHOULD implement all header fields described in Section 13.
It is up to the creators of presentation descriptions not to ask the It is up to the creators of presentation descriptions not to ask the
impossible of a server. This situation is similar in HTTP/1.1 [26], impossible of a server. This situation is similar in HTTP/1.1 [26],
where the methods described in [H19.5] are not likely to be supported where the methods described in [H19.5] are not likely to be supported
across all servers. across all servers.
RTSP can be extended in three ways, listed here in order of the mag- RTSP can be extended in three ways, listed here in order of the
nitude of changes supported: magnitude of changes supported:
+ Existing methods can be extended with new parameters, as long as o Existing methods can be extended with new parameters, as long
these parameters can be safely ignored by the recipient. (This is as these parameters can be safely ignored by the recipient.
equivalent to adding new parameters to an HTML tag.) If the (This is equivalent to adding new parameters to an HTML tag.)
client needs negative acknowledgement when a method extension is If the client needs negative acknowledgement when a method
not supported, a tag corresponding to the extension may be added extension is not supported, a tag corresponding to the
in the Require: field (see Section 13.32). extension may be added in the Require: field (see Section
13.32).
+ New methods can be added. If the recipient of the message does o New methods can be added. If the recipient of the message does
not understand the request, it responds with error code 501 (Not not understand the request, it responds with error code 501
Implemented) and the sender should not attempt to use this method (Not Implemented) and the sender should not attempt to use
again. A client may also use the OPTIONS method to inquire about this method again. A client may also use the OPTIONS method
methods supported by the server. The server SHOULD list the meth- to inquire about methods supported by the server. The server
ods it supports using the Public response header. SHOULD list the methods it supports using the Public response
header.
+ A new version of the protocol can be defined, allowing almost all o A new version of the protocol can be defined, allowing almost
aspects (except the position of the protocol version number) to all aspects (except the position of the protocol version
change. number) to change.
The basic capability discovery mechanism can be used to both discover The basic capability discovery mechanism can be used to both discover
support for a certain feature and to ensure that a feature is avail- support for a certain feature and to ensure that a feature is
able when performing a request. For detailed explanation of this see available when performing a request. For detailed explanation of this
chapter 10. see chapter 10.
1.7 Overall Operation 1.7 Overall Operation
Each presentation and media stream may be identified by a RTSP URL. Each presentation and media stream may be identified by a RTSP URL.
The overall presentation and the properties of the media the presen- The overall presentation and the properties of the media the
tation is made up of are defined by a presentation description file, presentation is made up of are defined by a presentation description
the format of which is outside the scope of this specification. The file, the format of which is outside the scope of this specification.
presentation description file may be obtained by the client using The presentation description file may be obtained by the client using
HTTP or other means such as email and may not necessarily be stored HTTP or other means such as email and may not necessarily be stored
on the media server. on the media server.
For the purposes of this specification, a presentation description is For the purposes of this specification, a presentation description is
assumed to describe one or more presentations, each of which main- assumed to describe one or more presentations, each of which
tains a common time axis. For simplicity of exposition and without maintains a common time axis. For simplicity of exposition and
loss of generality, it is assumed that the presentation description without loss of generality, it is assumed that the presentation
contains exactly one such presentation. A presentation may contain description contains exactly one such presentation. A presentation
several media streams. may contain several media streams.
The presentation description file contains a description of the media The presentation description file contains a description of the media
streams making up the presentation, including their encodings, lan- streams making up the presentation, including their encodings,
guage, and other parameters that enable the client to choose the most language, and other parameters that enable the client to choose the
appropriate combination of media. In this presentation description, most appropriate combination of media. In this presentation
each media stream that is individually controllable by RTSP is description, each media stream that is individually controllable by
identified by a RTSP URL, which points to the media server handling RTSP is identified by a RTSP URL, which points to the media server
that particular media stream and names the stream stored on that handling that particular media stream and names the stream stored on
server. Several media streams can be located on different servers; that server. Several media streams can be located on different
for example, audio and video streams can be split across servers for servers; for example, audio and video streams can be split across
load sharing. The description also enumerates which transport methods servers for load sharing. The description also enumerates which
the server is capable of. transport methods the server is capable of.
Besides the media parameters, the network destination address and Besides the media parameters, the network destination address and
port need to be determined. Several modes of operation can be distin- port need to be determined. Several modes of operation can be
guished: distinguished:
Unicast: The media is transmitted to the source of the RTSP Unicast: The media is transmitted to the source of the RTSP
request, with the port number chosen by the client. Alterna- request, with the port number chosen by the client.
tively, the media is transmitted on the same reliable stream Alternatively, the media is transmitted on the same
as RTSP. reliable stream as RTSP.
Multicast, server chooses address: The media server picks the mul- Multicast, server chooses address: The media server picks the
ticast address and port. This is the typical case for a live multicast address and port. This is the typical case for a
or near-media-on-demand transmission. live or near-media-on-demand transmission.
Multicast, client chooses address: If the server is to participate Multicast, client chooses address: If the server is to
in an existing multicast conference, the multicast address, participate in an existing multicast conference, the
port and encryption key are given by the conference descrip- multicast address, port and encryption key are given by the
tion, established by means outside the scope of this specifi- conference description, established by means outside the
cation. scope of this specification.
1.8 RTSP States 1.8 RTSP States
RTSP controls a stream which may be sent via a separate protocol, RTSP controls a stream which may be sent via a separate protocol,
independent of the control channel. For example, RTSP control may independent of the control channel. For example, RTSP control may
occur on a TCP connection while the data flows via UDP. Thus, data occur on a TCP connection while the data flows via UDP. Thus, data
delivery continues even if no RTSP requests are received by the media delivery continues even if no RTSP requests are received by the media
server. Also, during its lifetime, a single media stream may be con- server. Also, during its lifetime, a single media stream may be
trolled by RTSP requests issued sequentially on different TCP connec- controlled by RTSP requests issued sequentially on different TCP
tions. Therefore, the server needs to maintain "session state" to be connections. Therefore, the server needs to maintain "session state"
able to correlate RTSP requests with a stream. The state transitions to be able to correlate RTSP requests with a stream. The state
are described in Appendix A. transitions are described in Appendix A.
Many methods in RTSP do not contribute to state. However, the follow- | Many methods in RTSP do not contribute to state. However, the
ing play a central role in defining the allocation and usage of | following play a central role in defining the allocation and usage of
stream resources on the server: SETUP, PLAY, PAUSE, REDIRECT, PING | stream resources on the server: SETUP, PLAY, PAUSE, REDIRECT, PING
and TEARDOWN. and TEARDOWN.
SETUP: Causes the server to allocate resources for a stream and SETUP: Causes the server to allocate resources for a stream and
create a RTSP session. create a RTSP session.
PLAY: Starts data transmission on a stream allocated via SETUP. | PLAY: Starts data transmission on a stream allocated via SETUP.
PAUSE: Temporarily halts a stream without freeing server resources. PAUSE: Temporarily halts a stream without freeing server
resources.
REDIRECT: Indicates that the session should be moved to new server REDIRECT: Indicates that the session should be moved to new
/ location server / location
PING: Prevents the identified session from being timed out. PING: Prevents the identified session from being timed out.
TEARDOWN: Frees resources associated with the stream. The RTSP TEARDOWN: Frees resources associated with the stream. The RTSP
session ceases to exist on the server. session ceases to exist on the server.
RTSP methods that contribute to state use the Session header field RTSP methods that contribute to state use the Session header field
(Section 13.37) to identify the RTSP session whose state is being (Section 13.37) to identify the RTSP session whose state is being
manipulated. The server generates session identifiers in response to manipulated. The server generates session identifiers in response to
SETUP requests (Section 11.3). SETUP requests (Section 11.3).
1.9 Relationship with Other Protocols 1.9 Relationship with Other Protocols
RTSP has some overlap in functionality with HTTP. It also may inter- RTSP has some overlap in functionality with HTTP. It also may
act with HTTP in that the initial contact with streaming content is interact with HTTP in that the initial contact with streaming content
often to be made through a web page. The current protocol specifica- is often to be made through a web page. The current protocol
tion aims to allow different hand-off points between a web server and specification aims to allow different hand-off points between a web
the media server implementing RTSP. For example, the presentation server and the media server implementing RTSP. For example, the
description can be retrieved using HTTP or RTSP, which reduces presentation description can be retrieved using HTTP or RTSP, which
roundtrips in web-browser-based scenarios, yet also allows for stan- reduces roundtrips in web-browser-based scenarios, yet also allows
dalone RTSP servers and clients which do not rely on HTTP at all. for standalone RTSP servers and clients which do not rely on HTTP at
However, RTSP differs fundamentally from HTTP in that most data all. However, RTSP differs fundamentally from HTTP in that most data
delivery takes place out-of-band in a different protocol. HTTP is an delivery takes place out-of-band in a different protocol. HTTP is an
asymmetric protocol where the client issues requests and the server asymmetric protocol where the client issues requests and the server
responds. In RTSP, both the media client and media server can issue responds. In RTSP, both the media client and media server can issue
requests. RTSP requests are also stateful; they may set parameters requests. RTSP requests are also stateful; they may set parameters
and continue to control a media stream long after the request has and continue to control a media stream long after the request has
been acknowledged. been acknowledged.
Re-using HTTP functionality has advantages in at least two Re-using HTTP functionality has advantages in at least two
areas, namely security and proxies. The requirements are very areas, namely security and proxies. The requirements are
similar, so having the ability to adopt HTTP work on caches, very similar, so having the ability to adopt HTTP work on
proxies and authentication is valuable. caches, proxies and authentication is valuable.
RTSP assumes the existence of a presentation description format that RTSP assumes the existence of a presentation description format that
can express both static and temporal properties of a presentation can express both static and temporal properties of a presentation
containing several media streams. Session Description Protocol (SDP) containing several media streams. Session Description Protocol (SDP)
[24] is generally the format of choice; however, RTSP is not bound to [24] is generally the format of choice; however, RTSP is not bound to
it. For data delivery, most real-time media will use RTP as a trans- it. For data delivery, most real-time media will use RTP as a
port protocol. While RTSP works well with RTP, it is not tied to RTP. transport protocol. While RTSP works well with RTP, it is not tied to
RTP.
2 Notational Conventions 2 Notational Conventions
Since many of the definitions and syntax are identical to HTTP/1.1, Since many of the definitions and syntax are identical to HTTP/1.1,
this specification only points to the section where they are defined this specification only points to the section where they are defined
rather than copying it. For brevity, [HX.Y] is to be taken to refer rather than copying it. For brevity, [HX.Y] is to be taken to refer
to Section X.Y of the current HTTP/1.1 specification (RFC 2616 [26]). to Section X.Y of the current HTTP/1.1 specification (RFC 2616 [26]).
All the mechanisms specified in this document are described in both All the mechanisms specified in this document are described in both
prose and an augmented Backus-Naur form (BNF) similar to that used in prose and an augmented Backus-Naur form (BNF) similar to that used in
[H2.1]. It is described in detail in RFC 2234 [14], with the differ- [H2.1]. It is described in detail in RFC 2234 [14], with the
ence that this RTSP specification maintains the "#" notation for difference that this RTSP specification maintains the "#" notation
comma-separated lists from [H2.1]. for comma-separated lists from [H2.1].
In this draft, we use indented and smaller-type paragraphs to provide In this draft, we use indented and smaller-type paragraphs to provide
background and motivation. This is intended to give readers who were background and motivation. This is intended to give readers who were
not involved with the formulation of the specification an understand- not involved with the formulation of the specification an
ing of why things are the way that they are in RTSP. understanding of why things are the way that they are in RTSP.
b
3 Protocol Parameters 3 Protocol Parameters
3.1 RTSP Version 3.1 RTSP Version
HTTP Specification Section [H3.1] applies, with HTTP replaced by HTTP Specification Section [H3.1] applies, with HTTP replaced by
RTSP. This specification defines version 1.0 of RTSP. RTSP. This specification defines version 1.0 of RTSP.
3.2 RTSP URL 3.2 RTSP URL
The "rtsp", "rtsps" and "rtspu" schemes are used to refer to network The "rtsp", "rtsps" and "rtspu" schemes are used to refer to network
resources via the RTSP protocol. This section defines the scheme-spe- resources via the RTSP protocol. This section defines the scheme-
cific syntax and semantics for RTSP URLs. The RTSP URL is case sensi- specific syntax and semantics for RTSP URLs. The RTSP URL is case
tive. | sensitive.
rtsp_URL = ( "rtsp:" / "rtspu:" / "rtsps:" ) ||
"//" host [ ":" port ] [ abs_path [ "?" query ]] ||
host = As defined by RFC 2732 [30] ||
abs_path = As defined by RFC 2396 [22] ||
port = *DIGIT ||
query = As defined by RFC 2396 [22] ||
Note that fragment and query identifiers do not have a well- rtsp_URL = ( "rtsp:" / "rtspu:" / "rtsps:" )
defined meaning at this time, with the interpretation left to "//" host [ ":" port ] [ abs_path [ "?" query ]]
the RTSP server. host = As defined by RFC 2732 [30]
abs_path = As defined by RFC 2396 [22]
port = *DIGIT
query = As defined by RFC 2396 [22]
Note that fragment and query identifiers do not have a
well-defined meaning at this time, with the interpretation
left to the RTSP server.
The scheme rtsp requires that commands are issued via a reliable pro- | The scheme rtsp requires that commands are issued via a reliable
tocol (within the Internet, TCP), while the scheme rtspu identifies | protocol (within the Internet, TCP), while the scheme rtspu
an unreliable protocol (within the Internet, UDP). The scheme rtsps | identifies an unreliable protocol (within the Internet, UDP). The
identifies a reliable transport using secure transport, perhaps TLS | scheme rtsps identifies a reliable transport using secure transport,
[27]. The rtspu and rtsps is not defined in this specification and if | perhaps TLS [27]. The rtspu and rtsps is not defined in this
for future extensions of the protocol. specification, and are for future extensions of the protocol to
define.
If the port is empty or not given, port 554 SHALL be assumed. The If the port is empty or not given, port 554 SHALL be assumed. The
semantics are that the identified resource can be controlled by RTSP semantics are that the identified resource can be controlled by RTSP
at the server listening for TCP (scheme "rtsp") connections or UDP at the server listening for TCP (scheme "rtsp") connections or UDP
(scheme "rtspu") packets on that port of host, and the Request-URI (scheme "rtspu") packets on that port of host, and the Request-URI
for the resource is rtsp_URL. for the resource is rtsp_URL.
The use of IP addresses in URLs SHOULD be avoided whenever possible The use of IP addresses in URLs SHOULD be avoided whenever possible
(see RFC 1924 [16]). Note: Using qualified domain names in any URL is (see RFC 1924 [16]). Note: Using qualified domain names in any URL is
one requirement for making it possible for RFC 2326 implementations one requirement for making it possible for RFC 2326 implementations
of RTSP to use IPv6. This specification is updated to allow for lit- of RTSP to use IPv6. This specification is updated to allow for
eral IPv6 addresses in RTSP URLs using the host specification in RFC literal IPv6 addresses in RTSP URLs using the host specification in
2732 [30]. RFC 2732 [30].
A presentation or a stream is identified by a textual media identi- A presentation or a stream is identified by a textual media
fier, using the character set and escape conventions [H3.2] of URLs identifier, using the character set and escape conventions [H3.2] of
(RFC 2396 [22]). URLs may refer to a stream or an aggregate of URLs (RFC 2396 [22]). URLs may refer to a stream or an aggregate of
streams, i.e., a presentation. Accordingly, requests described in streams, i.e., a presentation. Accordingly, requests described in
Section 11 can apply to either the whole presentation or an individ- Section 11 can apply to either the whole presentation or an
ual stream within the presentation. Note that some request methods individual stream within the presentation. Note that some request
can only be applied to streams, not presentations and vice versa. methods can only be applied to streams, not presentations and vice
versa.
For example, the RTSP URL: For example, the RTSP URL:
rtsp://media.example.com:554/twister/audiotrack rtsp://media.example.com:554/twister/audiotrack
identifies the audio stream within the presentation "twister", which can identifies the audio stream within the presentation "twister", which
be controlled via RTSP requests issued over a TCP connection to port 554 can be controlled via RTSP requests issued over a TCP connection to
of host media.example.com port 554 of host media.example.com
Also, the RTSP URL: Also, the RTSP URL:
rtsp://media.example.com:554/twister rtsp://media.example.com:554/twister
identifies the presentation "twister", which may be composed of audio identifies the presentation "twister", which may be composed of audio
and video streams. and video streams.
This does not imply a standard way to reference streams in This does not imply a standard way to reference streams in
URLs. The presentation description defines the hierarchical URLs. The presentation description defines the hierarchical
relationships in the presentation and the URLs for the indi- relationships in the presentation and the URLs for the
vidual streams. A presentation description may name a stream individual streams. A presentation description may name a
"a.mov" and the whole presentation "b.mov". stream "a.mov" and the whole presentation "b.mov".
The path components of the RTSP URL are opaque to the client and do The path components of the RTSP URL are opaque to the client and do
not imply any particular file system structure for the server. not imply any particular file system structure for the server.
This decoupling also allows presentation descriptions to be This decoupling also allows presentation descriptions to be
used with non-RTSP media control protocols simply by replacing used with non-RTSP media control protocols simply by
the scheme in the URL. replacing the scheme in the URL.
3.3 Session Identifiers 3.3 Session Identifiers
Session identifiers are strings of any arbitrary length. A session | Session identifiers are strings of any arbitrary length. A session
identifier MUST be chosen randomly and MUST be at least eight charac- | identifier MUST be chosen randomly and MUST be at least eight
ters long to make guessing it more difficult. (See Section 17.) characters long to make guessing it more difficult. (See Section 17.)
session-id = 8*( ALPHA / DIGIT / safe ) session-id = 8*( ALPHA / DIGIT / safe )
3.4 SMPTE Relative Timestamps 3.4 SMPTE Relative Timestamps
A SMPTE relative timestamp expresses time relative to the start of A SMPTE relative timestamp expresses time relative to the start of
the clip. Relative timestamps are expressed as SMPTE time codes for the clip. Relative timestamps are expressed as SMPTE time codes for
frame-level access accuracy. The time code has the format frame-level access accuracy. The time code has the format
hours:minutes:seconds:frames.subframes, hours:minutes:seconds:frames.subframes,
with the origin at the start of the clip. The default smpte format with the origin at the start of the clip. The default smpte format
skipping to change at page 1, line 707 skipping to change at page 16, line 8
minute. If the frame value is zero, it may be omitted. Subframes are minute. If the frame value is zero, it may be omitted. Subframes are
measured in one-hundredth of a frame. measured in one-hundredth of a frame.
smpte-range = smpte-type "=" smpte-range-spec smpte-range = smpte-type "=" smpte-range-spec
smpte-range-spec = ( smpte-time "-" [ smpte-time ] ) smpte-range-spec = ( smpte-time "-" [ smpte-time ] )
/ ( "-" smpte-time ) / ( "-" smpte-time )
smpte-type = "smpte" / "smpte-30-drop" / "smpte-25" smpte-type = "smpte" / "smpte-30-drop" / "smpte-25"
; other timecodes may be added ; other timecodes may be added
smpte-time = 1*2DIGIT ":" 1*2DIGIT ":" 1*2DIGIT smpte-time = 1*2DIGIT ":" 1*2DIGIT ":" 1*2DIGIT
[ ":" 1*2DIGIT [ "." 1*2DIGIT ] ] [ ":" 1*2DIGIT [ "." 1*2DIGIT ] ]
Examples: Examples:
smpte=10:12:33:20- smpte=10:12:33:20-
smpte=10:07:33- smpte=10:07:33-
smpte=10:07:00-10:07:33:05.01 smpte=10:07:00-10:07:33:05.01
smpte-25=10:07:00-10:07:33:05.01 smpte-25=10:07:00-10:07:33:05.01
3.5 Normal Play Time 3.5 Normal Play Time
Normal play time (NPT) indicates the stream absolute position rela- Normal play time (NPT) indicates the stream absolute position
tive to the beginning of the presentation, not to be confused with relative to the beginning of the presentation, not to be confused
the Network Time Protocol (NTP). The timestamp consists of a decimal with the Network Time Protocol (NTP). The timestamp consists of a
fraction. The part left of the decimal may be expressed in either decimal fraction. The part left of the decimal may be expressed in
seconds or hours, minutes, and seconds. The part right of the decimal either seconds or hours, minutes, and seconds. The part right of the
point measures fractions of a second. decimal point measures fractions of a second.
The beginning of a presentation corresponds to 0.0 seconds. Negative The beginning of a presentation corresponds to 0.0 seconds. Negative
values are not defined. The special constant now is defined as the values are not defined. The special constant now is defined as the
current instant of a live event. It MAY only be used for live events, current instant of a live event. It MAY only be used for live events,
and SHALL NOT be used for on-demand content. and SHALL NOT be used for on-demand content.
NPT is defined as in DSM-CC: "Intuitively, NPT is the clock the NPT is defined as in DSM-CC: "Intuitively, NPT is the clock the
viewer associates with a program. It is often digitally displayed on viewer associates with a program. It is often digitally displayed on
a VCR. NPT advances normally when in normal play mode (scale = 1), a VCR. NPT advances normally when in normal play mode (scale = 1),
advances at a faster rate when in fast scan forward (high positive advances at a faster rate when in fast scan forward (high positive
skipping to change at page 1, line 754 skipping to change at page 17, line 12
npt-hh = 1*DIGIT ; any positive number npt-hh = 1*DIGIT ; any positive number
npt-mm = 1*2DIGIT ; 0-59 npt-mm = 1*2DIGIT ; 0-59
npt-ss = 1*2DIGIT ; 0-59 npt-ss = 1*2DIGIT ; 0-59
Examples: Examples:
npt=123.45-125 npt=123.45-125
npt=12:05:35.3- npt=12:05:35.3-
npt=now- npt=now-
The syntax conforms to ISO 8601. The npt-sec notation is opti- The syntax conforms to ISO 8601. The npt-sec notation is
mized for automatic generation, the ntp-hhmmss notation for optimized for automatic generation, the ntp-hhmmss notation
consumption by human readers. The "now" constant allows for consumption by human readers. The "now" constant allows
clients to request to receive the live feed rather than the clients to request to receive the live feed rather than the
stored or time-delayed version. This is needed since neither stored or time-delayed version. This is needed since
absolute time nor zero time are appropriate for this case. neither absolute time nor zero time are appropriate for
this case.
3.6 Absolute Time 3.6 Absolute Time
Absolute time is expressed as ISO 8601 timestamps, using UTC (GMT). Absolute time is expressed as ISO 8601 timestamps, using UTC (GMT).
Fractions of a second may be indicated. Fractions of a second may be indicated.
utc-range = "clock" "=" utc-range-spec utc-range = "clock" "=" utc-range-spec
utc-range-spec = ( utc-time "-" [ utc-time ] ) / ( "-" utc-time ) utc-range-spec = ( utc-time "-" [ utc-time ] ) / ( "-" utc-time )
utc-time = utc-date "T" utc-time "Z" utc-time = utc-date "T" utc-time "Z"
utc-date = 8DIGIT ; < YYYYMMDD > utc-date = 8DIGIT ; < YYYYMMDD >
utc-time = 6DIGIT [ "." fraction ] ; < HHMMSS.fraction > utc-time = 6DIGIT [ "." fraction ] ; < HHMMSS.fraction >
fraction = 1*DIGIT fraction = 1*DIGIT
Example for November 8, 1996 at 14h37 and 20 and a quarter seconds Example for November 8, 1996 at 14h37 and 20 and a quarter seconds
UTC: UTC:
19961108T143720.25Z 19961108T143720.25Z
3.7 Feature-tags 3.7 Feature-tags
Feature-tags are unique identifiers used to designate new features in Feature-tags are unique identifiers used to designate features in
RTSP. These tags are used in in Require (Section 13.32), Proxy- RTSP. These tags are used in Require (Section 13.32), Proxy-Require
Require (Section 13.27), Unsupported (Section 13.41), and Supported (Section 13.27), Unsupported (Section 13.41), and Supported (Section
(Section 13.38) header fields. 13.38) header fields.
Syntax: Syntax:
feature-tag = token feature-tag = token
The creator of a new RTSP feature-tag should either prefix the fea- Feature tag needs to indicate if they apply to servers only, proxies |
ture-tag with a reverse domain name (e.g., "com.foo.mynewfeature" is only, or both server and proxies.
an apt name for a feature whose inventor can be reached at
The creator of a new RTSP feature-tag should either prefix the
feature-tag with a reverse domain name (e.g., "com.foo.mynewfeature"
is an apt name for a feature whose inventor can be reached at
"foo.com"), or register the new feature-tag with the Internet "foo.com"), or register the new feature-tag with the Internet
Assigned Numbers Authority (IANA), see IANA Section 18. Assigned Numbers Authority (IANA), see IANA Section 18.
4 RTSP Message 4 RTSP Message
RTSP is a text-based protocol and uses the ISO 10646 character set in RTSP is a text-based protocol and uses the ISO 10646 character set in
UTF-8 encoding (RFC 2279 [18]). Lines are terminated by CRLF, but UTF-8 encoding (RFC 2279 [18]). Lines are terminated by CRLF, but
receivers should be prepared to also interpret CR and LF by them- receivers should be prepared to also interpret CR and LF by
selves as line terminators. themselves as line terminators.
Text-based protocols make it easier to add optional parameters Text-based protocols make it easier to add optional
in a self-describing manner. Since the number of parameters parameters in a self-describing manner. Since the number of
and the frequency of commands is low, processing efficiency is parameters and the frequency of commands is low, processing
not a concern. Text-based protocols, if done carefully, also efficiency is not a concern. Text-based protocols, if done
allow easy implementation of research prototypes in scripting carefully, also allow easy implementation of research
languages such as Tcl, Visual Basic and Perl. prototypes in scripting languages such as Tcl, Visual Basic
and Perl.
The 10646 character set avoids tricky character set switching, but is The 10646 character set avoids tricky character set switching, but is
invisible to the application as long as US-ASCII is being used. This invisible to the application as long as US-ASCII is being used. This
is also the encoding used for RTCP. ISO 8859-1 translates directly is also the encoding used for RTCP. ISO 8859-1 translates directly
into Unicode with a high-order octet of zero. ISO 8859-1 characters into Unicode with a high-order octet of zero. ISO 8859-1 characters
with the most-significant bit set are represented as 1100001x with the most-significant bit set are represented as 1100001x
10xxxxxx. (See RFC 2279 [18]) 10xxxxxx. (See RFC 2279 [18])
RTSP messages can be carried over any lower-layer transport protocol RTSP messages can be carried over any lower-layer transport protocol
that is 8-bit clean. RTSP messages are vulnerable to bit errors and that is 8-bit clean. RTSP messages are vulnerable to bit errors and
skipping to change at page 1, line 838 skipping to change at page 19, line 18
4.2 Message Headers 4.2 Message Headers
See [H4.2]. See [H4.2].
4.3 Message Body 4.3 Message Body
See [H4.3] See [H4.3]
4.4 Message Length 4.4 Message Length
When a message body is included with a message, the length of that When a message body is included with a message, the length of that
body is determined by one of the following (in order of precedence): body is determined by one of the following (in order of precedence):
1. Any response message which MUST NOT include a message body 1. Any response message which MUST NOT include a message body
(such as the 1xx, 204, and 304 responses) is always terminated (such as the 1xx, 204, and 304 responses) is always
by the first empty line after the header fields, regardless of terminated by the first empty line after the header fields,
the entity-header fields present in the message. (Note: An regardless of the entity-header fields present in the
empty line consists of only CRLF.) message. (Note: An empty line consists of only CRLF.)
2. If a Content-Length header field (section 13.14) is present, 2. If a Content-Length header field (section 13.14) is
its value in bytes represents the length of the message-body. present, its value in bytes represents the length of the
If this header field is not present, a value of zero is message-body. If this header field is not present, a value
assumed. of zero is assumed.
Note that RTSP does not (at present) support the HTTP/1.1 "chunked" Note that RTSP does not (at present) support the HTTP/1.1 "chunked"
transfer coding(see [H3.6.1]) and requires the presence of the Con- transfer coding(see [H3.6.1]) and requires the presence of the
tent-Length header field. Content-Length header field.
Given the moderate length of presentation descriptions Given the moderate length of presentation descriptions
returned, the server should always be able to determine its returned, the server should always be able to determine its
length, even if it is generated dynamically, making the chun- length, even if it is generated dynamically, making the
ked transfer encoding unnecessary. chunked transfer encoding unnecessary.
5 General Header Fields 5 General Header Fields
See [H4.5], except that Pragma, Trailer, Transfer-Encoding, Upgrade, See [H4.5], except that Pragma, Trailer, Transfer-Encoding, Upgrade,
and Warning headers are not defined. RTSP further defines the CSeq, and Warning headers are not defined. RTSP further defines the CSeq,
and Timestamp: and Timestamp:
general-header = Cache-Control ; Section 13.9 general-header = Cache-Control ; Section 13.9
/ Connection ; Section 13.10 / Connection ; Section 13.10
/ CSeq ; Section 13.17 / CSeq ; Section 13.17
/ Date ; Section 13.18 / Date ; Section 13.18
/ Timestamp ; Section 13.39 / Timestamp ; Section 13.39
/ Via ; Section 13.44 / Via ; Section 13.44
6 Request 6 Request
A request message from a client to a server or vice versa includes, A request message from a client to a server or vice versa includes,
within the first line of that message, the method to be applied to within the first line of that message, the method to be applied to
the resource, the identifier of the resource, and the protocol ver- the resource, the identifier of the resource, and the protocol
sion in use. version in use.
Request = Request-Line ; Section 6.1 Request = Request-Line ; Section 6.1
*( general-header ; Section 5 *( general-header ; Section 5
/ request-header ; Section 6.2 / request-header ; Section 6.2
/ entity-header ) ; Section 8.1 / entity-header ) ; Section 8.1
CRLF CRLF
[ message-body ] ; Section 4.3 [ message-body ] ; Section 4.3
6.1 Request Line 6.1 Request Line
skipping to change at page 1, line 933 skipping to change at page 21, line 27
/ Session ; Section 13.37 / Session ; Section 13.37
/ Speed ; Section 13.35 / Speed ; Section 13.35
/ Supported ; Section 13.38 / Supported ; Section 13.38
/ Transport ; Section 13.40 / Transport ; Section 13.40
/ User-Agent ; Section 13.42 / User-Agent ; Section 13.42
Note that in contrast to HTTP/1.1 [26], RTSP requests always contain Note that in contrast to HTTP/1.1 [26], RTSP requests always contain
the absolute URL (that is, including the scheme, host and port) the absolute URL (that is, including the scheme, host and port)
rather than just the absolute path. rather than just the absolute path.
HTTP/1.1 requires servers to understand the absolute URL, but HTTP/1.1 requires servers to understand the absolute URL,
clients are supposed to use the Host request header. This is but clients are supposed to use the Host request header.
purely needed for backward-compatibility with HTTP/1.0 This is purely needed for backward-compatibility with
servers, a consideration that does not apply to RTSP. HTTP/1.0 servers, a consideration that does not apply to
RTSP.
The asterisk "*" in the Request-URI means that the request does not The asterisk "*" in the Request-URI means that the request does not
apply to a particular resource, but to the server or proxy itself, apply to a particular resource, but to the server or proxy itself,
and is only allowed when the method used does not necessarily apply and is only allowed when the method used does not necessarily apply
to a resource. to a resource.
One example would be as follows: One example would be as follows:
OPTIONS * RTSP/1.0 OPTIONS * RTSP/1.0
skipping to change at page 1, line 995 skipping to change at page 23, line 5
defined in Section 12. The Reason-Phrase is intended to give a short defined in Section 12. The Reason-Phrase is intended to give a short
textual description of the Status-Code. The Status-Code is intended textual description of the Status-Code. The Status-Code is intended
for use by automata and the Reason-Phrase is intended for the human for use by automata and the Reason-Phrase is intended for the human
user. The client is not required to examine or display the Reason- user. The client is not required to examine or display the Reason-
Phrase. Phrase.
The first digit of the Status-Code defines the class of response. The The first digit of the Status-Code defines the class of response. The
last two digits do not have any categorization role. There are 5 last two digits do not have any categorization role. There are 5
values for the first digit: values for the first digit:
+ 1xx: Informational - Request received, continuing process o 1xx: Informational - Request received, continuing process
+ 2xx: Success - The action was successfully received, understood, o 2xx: Success - The action was successfully received,
and accepted understood, and accepted
+ 3rr: Redirection - Further action must be taken in order to com- o 3rr: Redirection - Further action must be taken in order to
plete the request complete the request
+ 4xx: Client Error - The request contains bad syntax or cannot be o 4xx: Client Error - The request contains bad syntax or cannot
fulfilled be fulfilled
+ 5xx: Server Error - The server failed to fulfill an apparently
o 5xx: Server Error - The server failed to fulfill an apparently
valid request valid request
The individual values of the numeric status codes defined for The individual values of the numeric status codes defined for
RTSP/1.0, and an example set of corresponding Reason-Phrase's, are RTSP/1.0, and an example set of corresponding Reason-Phrase's, are
presented below. The reason phrases listed here are only recommended presented below. The reason phrases listed here are only recommended
-- they may be replaced by local equivalents without affecting the -- they may be replaced by local equivalents without affecting the
protocol. Note that RTSP adopts most HTTP/1.1 [26] status codes and protocol. Note that RTSP adopts most HTTP/1.1 [26] status codes and
adds RTSP-specific status codes starting at x50 to avoid conflicts adds RTSP-specific status codes starting at x50 to avoid conflicts
with newly defined HTTP status codes. with newly defined HTTP status codes.
skipping to change at page 1, line 1071 skipping to change at page 24, line 36
/ "551" ; Option not supported / "551" ; Option not supported
/ extension-code / extension-code
extension-code = 3DIGIT extension-code = 3DIGIT
Reason-Phrase = *<TEXT, excluding CR, LF> Reason-Phrase = *<TEXT, excluding CR, LF>
RTSP status codes are extensible. RTSP applications are not required RTSP status codes are extensible. RTSP applications are not required
to understand the meaning of all registered status codes, though such to understand the meaning of all registered status codes, though such
understanding is obviously desirable. However, applications MUST understanding is obviously desirable. However, applications MUST
understand the class of any status code, as indicated by the first understand the class of any status code, as indicated by the first
digit, and treat any unrecognized response as being equivalent to the digit, and treat any unrecognized response as being equivalent to the
x00 status code of that class, with the exception that an unrecog- x00 status code of that class, with the exception that an
nized response MUST NOT be cached. For example, if an unrecognized unrecognized response MUST NOT be cached. For example, if an
status code of 431 is received by the client, it can safely assume unrecognized status code of 431 is received by the client, it can
that there was something wrong with its request and treat the safely assume that there was something wrong with its request and
response as if it had received a 400 status code. In such cases, user treat the response as if it had received a 400 status code. In such
agents SHOULD present to the user the entity returned with the cases, user agents SHOULD present to the user the entity returned
response, since that entity is likely to include human-readable with the response, since that entity is likely to include human-
information which will explain the unusual status. readable information which will explain the unusual status.
7.1.2 Response Header Fields
The response-header fields allow the request recipient to pass
additional information about the response which cannot be placed in
the Status-Line. These header fields give information about the
server and about further access to the resource identified by the
Request-URI.
response-header = Accept-Ranges ; Section
13.4
/ Location ; Section 13.25
/ Proxy-Authenticate ; Section 13.26
/ Public ; Section 13.28
/ Range ; Section 13.29
/ Retry-After ; Section 13.31
/ RTP-Info ; Section 13.33
/ Scale ; Section 13.34
/ Session ; Section 13.37
/ Server ; Section 13.36
/ Speed ; Section 13.35
/ Transport ; Section 13.40
/ Unsupported ; Section 13.41
/ Vary ; Section 13.43
/ WWW-Authenticate ; Section 13.45
Response-header field names can be extended reliably only in
combination with a change in the protocol version. However, new or
experimental header fields MAY be given the semantics of response-
header fields if all parties in the communication recognize them to
be response-header fields. Unrecognized header fields are treated as
entity-header fields.
8 Entity
Request and Response messages MAY transfer an entity if not otherwise
restricted by the request method or response status code. An entity
consists of entity-header fields and an entity-body, although some
responses will only include the entity-headers.
In this section, both sender and recipient refer to either the client
or the server, depending on who sends and who receives the entity.
8.1 Entity Header Fields
Entity-header fields define optional meta-information about the
entity-body or, if no body is present, about the resource identified
by the request.
entity-header = Allow ; Section 13.5
Code Reason Method Code Reason Method
-------------------------------------------------------- _______________________________________________________
100 Continue all 100 Continue all
--------------------------------------------------------
_______________________________________________________
200 OK all 200 OK all
201 Created RECORD 201 Created RECORD
250 Low on Storage Space RECORD 250 Low on Storage Space RECORD
-------------------------------------------------------- _______________________________________________________
300 Multiple Choices all 300 Multiple Choices all
301 Moved Permanently all 301 Moved Permanently all
302 Found all 302 Found all
303 See Other all 303 See Other all
305 Use Proxy all 305 Use Proxy all
350 Going Away all 350 Going Away all
351 Load Balancing all 351 Load Balancing all
--------------------------------------------------------
Code Reason Method _______________________________________________________
--------------------------------------------------------
400 Bad Request all 400 Bad Request all
401 Unauthorized all 401 Unauthorized all
402 Payment Required all 402 Payment Required all
403 Forbidden all 403 Forbidden all
404 Not Found all 404 Not Found all
405 Method Not Allowed all 405 Method Not Allowed all
406 Not Acceptable all 406 Not Acceptable all
407 Proxy Authentication Required all 407 Proxy Authentication Required all
408 Request Timeout all 408 Request Timeout all
410 Gone all 410 Gone all
skipping to change at page 1, line 1125 skipping to change at page 26, line 49
453 Not Enough Bandwidth SETUP 453 Not Enough Bandwidth SETUP
454 Session Not Found all 454 Session Not Found all
455 Method Not Valid In This State all 455 Method Not Valid In This State all
456 Header Field Not Valid all 456 Header Field Not Valid all
457 Invalid Range PLAY, PAUSE 457 Invalid Range PLAY, PAUSE
458 Parameter Is Read-Only SET_PARAMETER 458 Parameter Is Read-Only SET_PARAMETER
459 Aggregate Operation Not Allowed all 459 Aggregate Operation Not Allowed all
460 Only Aggregate Operation Allowed all 460 Only Aggregate Operation Allowed all
461 Unsupported Transport all 461 Unsupported Transport all
462 Destination Unreachable all 462 Destination Unreachable all
-------------------------------------------------------- _______________________________________________________
500 Internal Server Error all 500 Internal Server Error all
501 Not Implemented all 501 Not Implemented all
502 Bad Gateway all 502 Bad Gateway all
503 Service Unavailable all 503 Service Unavailable all
504 Gateway Timeout all 504 Gateway Timeout all
505 RTSP Version Not Supported all 505 RTSP Version Not Supported all
551 Option not support all
Table 1: Status codes and their usage with RTSP methods Table 1: Status codes and their usage with RTSP methods
7.1.2 Response Header Fields
The response-header fields allow the request recipient to pass addi-
tional information about the response which cannot be placed in the
Status-Line. These header fields give information about the server
and about further access to the resource identified by the Request-
URI.
response-header = Accept-Ranges ; Section 13.4
/ Location ; Section 13.25
/ Proxy-Authenticate ; Section 13.26
/ Public ; Section 13.28
/ Range ; Section 13.29
/ Retry-After ; Section 13.31
/ RTP-Info ; Section 13.33
/ Scale ; Section 13.34
/ Session ; Section 13.37
/ Server ; Section 13.36
/ Speed ; Section 13.35
/ Transport ; Section 13.40
/ Unsupported ; Section 13.41
/ Vary ; Section 13.43
/ WWW-Authenticate ; Section 13.45
Response-header field names can be extended reliably only in combina-
tion with a change in the protocol version. However, new or experi-
mental header fields MAY be given the semantics of response-header
fields if all parties in the communication recognize them to be
response-header fields. Unrecognized header fields are treated as
entity-header fields.
8 Entity
Request and Response messages MAY transfer an entity if not otherwise
restricted by the request method or response status code. An entity
consists of entity-header fields and an entity-body, although some
responses will only include the entity-headers.
In this section, both sender and recipient refer to either the client
or the server, depending on who sends and who receives the entity.
8.1 Entity Header Fields
Entity-header fields define optional meta-information about the
entity-body or, if no body is present, about the resource identified
by the request.
entity-header = Allow ; Section 13.5
/ Content-Base ; Section 13.11 / Content-Base ; Section 13.11
/ Content-Encoding ; Section 13.12 / Content-Encoding ; Section 13.12
/ Content-Language ; Section 13.13 / Content-Language ; Section 13.13
/ Content-Length ; Section 13.14 / Content-Length ; Section 13.14
/ Content-Location ; Section 13.15 / Content-Location ; Section 13.15
/ Content-Type ; Section 13.16 / Content-Type ; Section 13.16
/ Expires ; Section 13.19 / Expires ; Section 13.19
/ Last-Modified ; Section 13.24 / Last-Modified ; Section 13.24
/ extension-header / extension-header
extension-header = message-header extension-header = message-header
skipping to change at page 1, line 1209 skipping to change at page 27, line 31
8.2 Entity Body 8.2 Entity Body
See [H7.2] with the addition that a RTSP message with an entity body See [H7.2] with the addition that a RTSP message with an entity body
MUST include a Content-Type header. MUST include a Content-Type header.
9 Connections 9 Connections
RTSP requests can be transmitted in several different ways: RTSP requests can be transmitted in several different ways:
+ persistent transport connections used for several request- o persistent transport connections used for several request-
response transactions; response transactions;
+ one connection per request/response transaction; o one connection per request/response transaction;
+ connectionless mode. o connectionless mode.
The type of transport connection is defined by the RTSP URI (Section The type of transport connection is defined by the RTSP URI (Section
3.2). For the scheme "rtsp", a connection is assumed, while the 3.2). For the scheme "rtsp", a connection is assumed, while the
scheme "rtspu" calls for RTSP requests to be sent without setting up scheme "rtspu" calls for RTSP requests to be sent without setting up
a connection. a connection.
Unlike HTTP, RTSP allows the media server to send requests to the Unlike HTTP, RTSP allows the media server to send requests to the
media client. However, this is only supported for persistent connec- media client. However, this is only supported for persistent
tions, as the media server otherwise has no reliable way of reaching connections, as the media server otherwise has no reliable way of
the client. Also, this is the only way that requests from media reaching the client. Also, this is the only way that requests from
server to client are likely to traverse firewalls. media server to client are likely to traverse firewalls.
9.1 Pipelining 9.1 Pipelining
A client that supports persistent connections or connectionless mode A client that supports persistent connections or connectionless mode
MAY "pipeline" its requests (i.e., send multiple requests without MAY "pipeline" its requests (i.e., send multiple requests without
waiting for each response). A server MUST send its responses to those waiting for each response). A server MUST send its responses to those
requests in the same order that the requests were received. requests in the same order that the requests were received.
9.2 Reliability and Acknowledgements 9.2 Reliability and Acknowledgements |
Requests are acknowledged by the receiver unless they are sent to a The transmission of RTSP over UDP was optionally to implement and |
multicast group. If there is no acknowledgement, the sender may specified in RFC 2326. However that definition was not satisfactory |
resend the same message after a timeout of one round-trip time (RTT). for interoperable implementations. Due to lack of interest, this |
The round-trip time is estimated as in TCP (RFC 1123) [15], with an specification does not specify how RTSP over UDP shall be |
initial round-trip value of 500 ms. An implementation MAY cache the implemented. However to maintain backwards compatibility in the |
last RTT measurement as the initial value for future connections. message format certain RTSP headers must be maintained. These |
mechanism are described below. The next section Unreliable Transport |
(section 9.3) provides documentation of certain features that are |
necessary for transport protocols like UDP. |
If a reliable transport protocol is used to carry RTSP, requests MUST Any RTSP request according to this specification SHALL NOT be sent to |
NOT be retransmitted; the RTSP application MUST instead rely on the a multicast address. Any RTSP request SHALL be acknowledged. If a |
underlying transport to provide reliability. reliable transport protocol is used to carry RTSP, requests MUST NOT |
be retransmitted; the RTSP application MUST instead rely on the |
underlying transport to provide reliability. |
If both the underlying reliable transport such as TCP and the If both the underlying reliable transport such as TCP and |
RTSP application retransmit requests, it is possible that each the RTSP application retransmit requests, it is possible |
packet loss results in two retransmissions. The receiver can- that each packet loss results in two retransmissions. The |
not typically take advantage of the application-layer retrans- receiver cannot typically take advantage of the |
mission since the transport stack will not deliver the appli- application-layer retransmission since the transport stack |
cation-layer retransmission before the first attempt has will not deliver the application-layer retransmission |
reached the receiver. If the packet loss is caused by conges- before the first attempt has reached the receiver. If the |
tion, multiple retransmissions at different layers will exac- packet loss is caused by congestion, multiple |
erbate the congestion. retransmissions at different layers will exacerbate the |
congestion. |
If RTSP is used over a small-RTT LAN, standard procedures for opti- Each request carries a sequence number in the CSeq header (Section |
mizing initial TCP round trip estimates, such as those used in T/TCP 13.17), which MUST be incremented by one for each distinct request |
(RFC 1644) [19], can be beneficial. transmitted to the destination end-point. The initial sequence |
number MAY be chosen arbitrary, but is RECOMMENDED to begin with 0. |
If a request is repeated because of lack of acknowledgement, the |
request MUST carry the original sequence number (i.e., the sequence |
number is not incremented). |
The Timestamp header (Section 13.39) is used to avoid the retransmis- 9.3 Unreliable Transport |
sion ambiguity problem [20] and obviates the need for Karn's algo-
rithm.
Each request carries a sequence number in the CSeq header (Section This section provides some information to future specification of |
13.17), which MUST be incremented by one for each distinct request RTSP over unreliable transport. |
transmitted. If a request is repeated because of lack of acknowledge- Requests are acknowledged by the receiver unless they are sent to a |
ment, the request MUST carry the original sequence number (i.e., the multicast group. If there is no acknowledgement, the sender may |
sequence number is not incremented). resend the same message after a timeout of one round-trip time (RTT). |
The round-trip time is estimated as in TCP (RFC 1123) [15], with an |
initial round-trip value of 500 ms. An implementation MAY cache the |
last RTT measurement as the initial value for future connections. |
Systems implementing RTSP MUST support carrying RTSP over TCP and MAY If RTSP is used over a small-RTT LAN, standard procedures for |
support UDP. The default port for the RTSP server is 554 for both UDP optimizing initial TCP round trip estimates, such as those used in |
and TCP. T/TCP (RFC 1644) [19], can be beneficial. |
A number of RTSP packets destined for the same control end point may The Timestamp header (Section 13.39) is used to avoid the |
be packed into a single lower-layer PDU or encapsulated into a TCP retransmission ambiguity problem [20] and obviates the need for |
stream. RTSP data MAY be interleaved with RTP and RTCP packets. Karn's algorithm. |
Unlike HTTP, an RTSP message MUST contain a Content-Length header If a request is repeated because of lack of acknowledgement, the |
field whenever that message contains a payload. Otherwise, an RTSP request must carry the original sequence number (i.e., the sequence |
packet is terminated with an empty line immediately following the number is not incremented). |
last message header.
9.3 The usage of connections A number of RTSP packets destined for the same control end point may |
be packed into a single lower-layer PDU or encapsulated into a TCP |
stream. RTSP data MAY be interleaved with RTP and RTCP packets. |
The default port for the RTSP server is 554 for UDP.
9.4 The usage of connections
Systems implementing RTSP MUST support carrying RTSP over TCP. The |
default port for the RTSP server is 554 for TCP. A number of RTSP |
packets destined for the same control end point may be encapsulated |
into a TCP stream. RTSP data MAY be interleaved with RTP and RTCP |
packets. Unlike HTTP, an RTSP message MUST contain a Content-Length |
header field whenever that message contains a payload (entity). |
Otherwise, an RTSP packet is terminated with an empty line |
immediately following the last message header.
TCP can be used for both persistent connections and for one message TCP can be used for both persistent connections and for one message
exchange per connection, as presented above. This section gives fur- exchange per connection, as presented above. This section gives
ther rules and recommendations on how to handle these connections so further rules and recommendations on how to handle these connections
maximum interoperability and flexibility can be achieved. so maximum interoperability and flexibility can be achieved.
A server SHALL handle both persistent connections and one A server SHALL handle both persistent connections and one
request/response transaction per connection. A persistent connection request/response transaction per connection. A persistent connection
MAY be used for all transactions between the server and client, MAY be used for all transactions between the server and client,
including messages to multiple RTSP sessions. However the persistent including messages to multiple RTSP sessions. However the persistent
connection MAY also be closed after a few message exchanges, e.g. the connection MAY also be closed after a few message exchanges, e.g. the
initial setup and play command in a session. Later when the client initial setup and play command in a session. Later when the client
wishes to send a new request, e.g. pause, to the session a new con- wishes to send a new request, e.g. pause, to the session a new
nection is opened. This connection may either be for a single message connection is opened. This connection may either be for a single
exchange or can be kept open for several messages, i.e. persistent. message exchange or can be kept open for several messages, i.e.
persistent.
A major motivation for allowing non-persistent connections are that A major motivation for allowing non-persistent connections are that
they ensure fault tolerance. A server and client supporting non-per- they ensure fault tolerance. A second one is to allow for application
sistent connection can survive a loss of a TCP connection, e.g. due layer mobility. A server and client supporting non-persistent
to a NAT timeout. When the it is discovered that the TCP connection connection can survive a loss of a TCP connection, e.g. due to a NAT
has been lost one sets up a new one. timeout. When the client has discovered that the TCP connection has
been lost, it can set up a new one when there is need to communicate.
The client MAY close the connection at any time when no outstanding | The client MAY close the connection at any time when no outstanding
request/response transactions exist. The server SHOULD NOT close the | request/response transactions exist. The server SHOULD NOT close the
connection unless at least one RTSP session timeout period has passed | connection unless at least one RTSP session timeout period has passed
without data traffic. A server MUST NOT initiate a close of a connec- | without data traffic. A server MUST NOT initiate a close of a
tion directly after responding to a TEARDOWN request for the whole | connection directly after responding to a TEARDOWN request for the
session. A server MUST NOT close the connection as a result of | whole session. A server MUST NOT close the connection as a result of
responding to a request with an error code. Doing this would prevent | responding to a request with an error code. Doing this would prevent
or result in extra overhead for the client when testing advanced or | or result in extra overhead for the client when testing advanced or
special types of requests. special types of requests.
The client SHOULD NOT have more than one connection to the server at The client SHOULD NOT have more than one connection to the server at
any given point. If a client or proxy handles multiple RTSP sessions any given point. If a client or proxy handles multiple RTSP sessions
on the same server, it is RECOMMENDED to use only a single connec- on the same server, it is RECOMMENDED to use only a single
tion. connection.
Older services which was implemented according to RFC 2326 sometimes Older services which was implemented according to RFC 2326 sometimes
requires the client to use persistent connection. The client closing requires the client to use persistent connection. The client closing
the connection may result in that the server removes the session. To the connection may result in that the server removes the session. To
achieve interoperability with old servers any client is strongly REC- achieve interoperability with old servers any client is strongly
OMMENDED to use persistent connections. RECOMMENDED to use persistent connections.
A Client is also strongly RECOMMENDED to use persistent connections A Client is also strongly RECOMMENDED to use persistent connections
as it allows the server to send request to the client. In cases as it allows the server to send request to the client. In cases
where no connection exist between the server and the client, this may where no connection exist between the server and the client, this may
cause the server to be forced to drop the RTSP session without noti- cause the server to be forced to drop the RTSP session without
fying the client why,due to the lack of signalling channel. An exam- notifying the client why,due to the lack of signalling channel. An
ple of such a case is when the server desires to send a REDIRECT example of such a case is when the server desires to send a REDIRECT
request for a RTSP session to the client. request for a RTSP session to the client.
If a service requires the use of persistent connection an feature-tag
is specified for usage in the Require and Proxy-Require headers.
con.persistent
A server implemented according to this specification MUST respond A server implemented according to this specification MUST respond
that it supports the "play.basic" feature-tag above. A client MAY that it supports the "play.basic" feature-tag above. A client MAY
send a request including the Supported header in a request to deter- send a request including the Supported header in a request to
mine support of non-persistent connections. A server supporting non- determine support of non-persistent connections. A server supporting
persistent connections will return the "play.basic" feature-tag in non-persistent connections will return the "play.basic" feature-tag
its response. If the client receives the feature-tag in the response, in its response. If the client receives the feature-tag in the
it can be certain that the server handles non-persistent connections. response, it can be certain that the server handles non-persistent
connections.
9.4 Use of IPv6 9.5 Use of IPv6
This specification has been updated so that it supports IPv6. How- This specification has been updated so that it supports IPv6.
ever this support was not present in RFC 2326 therefore some interop- However this support was not present in RFC 2326 therefore some
erability issues exist. A RFC 2326 implementation can support IPv6 as interoperability issues exist. A RFC 2326 implementation can support
long as no explicit IPv6 addresses are used within RTSP messages. IPv6 as long as no explicit IPv6 addresses are used within RTSP
This require that any RTSP URL pointing at a IPv6 host must use fully messages. This require that any RTSP URL pointing at a IPv6 host must
qualified domain name and not a IPv6 address. Further the Transport use fully qualified domain name and not a IPv6 address. Further the
header must not use the parameters source and destination. Transport header must not use the parameters source and destination.
Implementations according to this specification MUST understand IPv6 Implementations according to this specification MUST understand IPv6
addresses in URLs, and headers. By this requirement the feature-tag addresses in URLs, and headers. By this requirement the feature-tag
"play.basic" can be used to determine that a server or client is "play.basic" can be used to determine that a server or client is
capable of handling IPv6 within RTSP. capable of handling IPv6 within RTSP.
10 Capability Handling 10 Capability Handling
This chapter describes the capability handling mechanism available in This chapter describes the capability handling mechanism available in
RTSP which allows RTSP to be extended. Extensions too this version of RTSP which allows RTSP to be extended. Extensions to this version of
the protocol are basically done in two ways. First, new headers can the protocol are basically done in two ways. First, new headers can
be added. Secondly, new methods can be added. The capability handling be added. Secondly, new methods can be added. The capability handling
mechanism is designed to handle these two cases. mechanism is designed to handle these two cases.
When a method is added the involved parties can use the OPTIONS When a method is added the involved parties can use the OPTIONS
method to discover if it is supported. This is done by issuing a method to discover if it is supported. This is done by issuing a
OPTIONS request to the other party. Depending on the URL it will OPTIONS request to the other party. Depending on the URL it will
either apply in regards to a certain media resource, the whole server either apply in regards to a certain media resource, the whole server
in general, or simply the next hop. The OPTIONS response will contain in general, or simply the next hop. The OPTIONS response will contain
a Public which declares all methods supported for the indicated a Public header which declares all methods supported for the
resource. indicated resource.
It is not necessary to use OPTIONS to discover support of a method, It is not necessary to use OPTIONS to discover support of a method, |
it is possible to simple try it. If the receiver of the request does the client could simply try the method. If the receiver of the |
not support the method it will respond with an error code indicating request does not support the method it will respond with an error |
the the method are either not implemented (501) or does not apply for code indicating the the method is either not implemented (501) or |
the resource (405). The choice between the two discovery methods does not apply for the resource (405). The choice between the two |
depends on the requirements of the service. discovery methods depends on the requirements of the service.
To handle functionality additions that are not new methods feature- To handle functionality additions that are not new methods feature-
tags are defined. Each feature-tag represents a certain block of tags are defined. Each feature-tag represents a certain block of
functionality. The amount of functionality that a feature-tag repre- functionality. The amount of functionality that a feature-tag
sents can vary significant. A simple feature-tag can simple represent represents can vary significantly. A simple feature-tag can simple
the functionality a single header gives. Another feature-tag is represent the functionality a single header gives. Another feature-
"play.basic" which represents the minimal playback implementation tag is "play.basic" which represents the minimal playback
according to the updated specification. implementation according to the updated specification.
The feature-tags are then used to determine if the client, server or The feature-tags are then used to determine if the client, server or
proxy supports the functionality that is necessary to achieve the proxy supports the functionality that is necessary to achieve the
desired service. To determine support of a feature-tag several dif- desired service. To determine support of a feature-tag several
ferent headers can be used, each explained below: different headers can be used, each explained below:
Supported: The supported header are used to determine the complete Supported: The supported header is used to determine the
set of functionality that both client and server has. The complete set of functionality that both client and server
intended usage is to determine before one needs to use a func- has. The intended usage is to determine before one needs to
tionality that it is supported. If can be used in any method use a functionality that it is supported. If can be used in
however OPTIONS is the most suitable as one at the same time any method however OPTIONS is the most suitable as one at
determines all methods that are implemented. When sending a the same time determines all methods that are implemented.
request the requestor declares all its capabilities by includ- When sending a request the requestor declares all its
ing all supported feature-tags. The results in that the capabilities by including all supported feature-tags. The
receiver learns the requestors feature support. The receiver results in that the receiver learns the requestors feature
then includes its set of features in the response. support. The receiver then includes its set of features in
the response.
Require: The Require header can be included in any request where Require: The Require header can be included in any request where
the end point, i.e. the client or server, is required to the end point, i.e. the client or server, is required to
understand the feature to correctly perform the request. This understand the feature to correctly perform the request.
can for example be a SETUP request where the server must This can for example be a SETUP request where the server
understand a certain parameter to be able to set up the media must understand a certain parameter to be able to set up
delivery correctly. Ignoring this parameter would not have the the media delivery correctly. Ignoring this parameter would
desired effect and is not acceptable. Therefore the end-point not have the desired effect and is not acceptable.
receiving a request containing a Require must negatively Therefore the end-point receiving a request containing a
acknowledge any feature that it does not understand and not Require must negatively acknowledge any feature that it
perform the request. The response in cases where features are does not understand and not perform the request. The
not understood are 551 (Option Not Supported). Also the response in cases where features are not understood are 551
features that are not understood are given in the Unsupported (Option Not Supported). Also the features that are not
header in the response. understood are given in the Unsupported header in the
response.
Proxy-Require: This method has the same purpose and workings as Proxy-Require: This method has the same purpose and workings as
Require except that it only applies to proxies and not the end Require except that it only applies to proxies and not the
point. Features that needs to be supported by both proxies and end point. Features that needs to be supported by both
end-point needs to be included in both the Require and Proxy- proxies and end-point needs to be included in both the
Require header. Require and Proxy-Require header.
Unsupported: This header is used in 551 error response to tell Unsupported: This header is used in 551 error response to tell
which feature(s) that was not supported. Such a response is which feature(s) that was not supported. Such a response is
only the result of the usage of the Require and/or Proxy- only the result of the usage of the Require and/or Proxy-
Require header where one or more feature where not supported. Require header where one or more feature where not
This information allows the requestor to make the best of sit- supported. This information allows the requestor to make
uations as it knows which features that was not supported. the best of situations as it knows which features that was
not supported.
11 Method Definitions 11 Method Definitions
The method token indicates the method to be performed on the resource The method token indicates the method to be performed on the resource
identified by the Request-URI case-sensitive. New methods may be identified by the Request-URI case-sensitive. New methods may be
defined in the future. Method names may not start with a $ character defined in the future. Method names may not start with a $ character
(decimal 24) and must be a token as defined by the ABNF. Methods are (decimal 24) and must be a token as defined by the ABNF. Methods are
summarized in Table 2. summarized in Table 2.
method direction object Server req. Client req. method direction object Server req. Client req.
---------------------------------------------------------------- ___________________________________________________________________
DESCRIBE C->S P,S recommended recommended DESCRIBE C->S P,S recommended recommended
GET_PARAMETER C->S, S->C P,S optional optional GET_PARAMETER C->S, S->C P,S optional optional
OPTIONS C->S, S->C P,S R=Req, Sd=Opt Sd=Req, R=Opt OPTIONS C->S, S->C P,S R=Req, Sd=Opt Sd=Req, R=Opt
PAUSE C->S P,S recommended recommended PAUSE C->S P,S recommended recommended
PING C->S, S->C P,S recommended optional PING C->S, S->C P,S recommended optional
PLAY C->S P,S required required PLAY C->S P,S required required
REDIRECT S->C P,S optional optional REDIRECT S->C P,S optional optional
SETUP C->S S required required SETUP C->S S required required
SET_PARAMETER C->S, S->C P,S optional optional SET_PARAMETER C->S, S->C P,S optional optional
TEARDOWN C->S P,S required required TEARDOWN C->S P,S required required
Table 2: Overview of RTSP methods, their direction, and what objects Table 2: Overview of RTSP methods, their direction, and what objects
(P: presentation, S: stream) they operate on. Legend: R=Responde to, (P: presentation, S: stream) they operate on. Legend: R=Responde to,
Sd=Send, Opt: Optional, Req: Required, Rec: Recommended Sd=Send, Opt: Optional, Req: Required, Rec: Recommended
Notes on Table 2: PAUSE is recommended, but not required in that a Notes on Table 2: PAUSE is recommended, but not required in that a
fully functional server can be built that does not support this fully functional server can be built that does not support this
method, for example, for live feeds. If a server does not support a method, for example, for live feeds. If a server does not support a
particular method, it MUST return 501 (Not Implemented) and a client particular method, it MUST return 501 (Not Implemented) and a client
SHOULD not try this method again for this server. SHOULD NOT try this method again for this server.
11.1 OPTIONS 11.1 OPTIONS
The behavior is equivalent to that described in [H9.2]. An OPTIONS The behavior is equivalent to that described in [H9.2]. An OPTIONS
request may be issued at any time, e.g., if the client is about to request may be issued at any time, e.g., if the client is about to
try a nonstandard request. It does not influence the session state. try a nonstandard request. It does not influence the session state.
The Public header MUST be included in responses to indicate which The Public header MUST be included in responses to indicate which
methods that are supported by the server. To specify which methods methods that are supported by the server. To specify which methods
that are possible to use for the specified resource, the Allow MAY be that are possible to use for the specified resource, the Allow MAY be
used. By including in the OPTIONS request a Supported header, the used. By including in the OPTIONS request a Supported header, the
requester can determine which features the other part supports. requester can determine which features the other part supports.
The request URI determines which scope the OPTIONS request has. By The request URI determines which scope the OPTIONS request has. By
giving the URI of a certain media the capabilities regarding this giving the URI of a certain media the capabilities regarding this
media will be responded. By using the "*" URI the request regards the media will be responded. By using the "*" URI the request regards the
next hop only, while having a URL with only the host address regards next hop only, while having a URL with only the host address regards
the server without any media relevance. the server without any media relevance.
The OPTIONS method can be used for RTSP session keep alive
signalling, however this method is not the most recommended one, see
section 13.37 for a preference list. A keep alive OPTIONS request
SHOULD use the media or aggregated control URI.
Example: Example:
C->S: OPTIONS * RTSP/1.0 C->S: OPTIONS * RTSP/1.0
CSeq: 1 CSeq: 1
User-Agent: PhonyClient/1.2 User-Agent: PhonyClient/1.2
Require: Require:
Proxy-Require: gzipped-messages Proxy-Require: gzipped-messages
Supported: play-basic Supported: play-basic
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 1 CSeq: 1
Public: DESCRIBE, SETUP, TEARDOWN, PLAY, PAUSE Public: DESCRIBE, SETUP, TEARDOWN, PLAY, PAUSE
Supported: play-basic, implicit-play, gzipped-messages Supported: play-basic, implicit-play, gzipped-messages
Server: PhonyServer/1.0 Server: PhonyServer/1.0
Note that some of the feature-tags in Require and Proxy-Require are Note that some of the feature-tags in Require and Proxy-Require are
necessarily fictional features (one would hope that we would not pur- necessarily fictional features (one would hope that we would not
posefully overlook a truly useful feature just so that we could have purposefully overlook a truly useful feature just so that we could
a strong example in this section). have a strong example in this section).
11.2 DESCRIBE 11.2 DESCRIBE
The DESCRIBE method retrieves the description of a presentation or The DESCRIBE method retrieves the description of a presentation or
media object identified by the request URL from a server. It may use media object identified by the request URL from a server. It may use
the Accept header to specify the description formats that the client the Accept header to specify the description formats that the client
understands. The server responds with a description of the requested understands. The server responds with a description of the requested
resource. The DESCRIBE reply-response pair constitutes the media ini- resource. The DESCRIBE reply-response pair constitutes the media
tialization phase of RTSP. initialization phase of RTSP.
Example: Example:
C->S: DESCRIBE rtsp://server.example.com/fizzle/foo RTSP/1.0 C->S: DESCRIBE rtsp://server.example.com/fizzle/foo RTSP/1.0
CSeq: 312 CSeq: 312
User-Agent: PhonyClient 1.2 User-Agent: PhonyClient 1.2
Accept: application/sdp, application/rtsl, application/mheg Accept: application/sdp, application/rtsl, application/mheg
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 312 CSeq: 312
skipping to change at page 1, line 1543 skipping to change at page 35, line 22
u=http://www.cs.ucl.ac.uk/staff/M.Handley/sdp.03.ps u=http://www.cs.ucl.ac.uk/staff/M.Handley/sdp.03.ps
e=mjh@isi.edu (Mark Handley) e=mjh@isi.edu (Mark Handley)
c=IN IP4 224.2.17.12/127 c=IN IP4 224.2.17.12/127
t=2873397496 2873404696 t=2873397496 2873404696
a=recvonly a=recvonly
m=audio 3456 RTP/AVP 0 m=audio 3456 RTP/AVP 0
m=video 2232 RTP/AVP 31 m=video 2232 RTP/AVP 31
m=application 32416 UDP WB m=application 32416 UDP WB
a=orient:portrait a=orient:portrait
The DESCRIBE response MUST contain all media initialization informa- The DESCRIBE response MUST contain all media initialization
tion for the resource(s) that it describes. If a media client obtains information for the resource(s) that it describes. If a media client
a presentation description from a source other than DESCRIBE and that obtains a presentation description from a source other than DESCRIBE
description contains a complete set of media initialization parame- and that description contains a complete set of media initialization
ters, the client SHOULD use those parameters and not then request a parameters, the client SHOULD use those parameters and not then
description for the same media via RTSP. request a description for the same media via RTSP.
Additionally, servers SHOULD NOT use the DESCRIBE response as a means Additionally, servers SHOULD NOT use the DESCRIBE response as a means
of media indirection. of media indirection.
By forcing a DESCRIBE response to contain all media initial- By forcing a DESCRIBE response to contain all media
ization for the set of streams that it describes, and discour- initialization for the set of streams that it describes,
aging use of DESCRIBE for media indirection, we avoid looping and discouraging use of DESCRIBE for media indirection, we
problems that might result from other approaches. avoid looping problems that might result from other
approaches.
Media initialization is a requirement for any RTSP-based system, but Media initialization is a requirement for any RTSP-based system, but
the RTSP specification does not dictate that this must be done via the RTSP specification does not dictate that this must be done via
the DESCRIBE method. There are three ways that an RTSP client may the DESCRIBE method. There are three ways that an RTSP client may
receive initialization information: receive initialization information:
+ via RTSP's DESCRIBE method; o via RTSP's DESCRIBE method;
+ via some other protocol (HTTP, email attachment, etc.); o via some other protocol (HTTP, email attachment, etc.);
+ via the command line or standard input (thus working as a browser o via the command line or standard input (thus working as a
helper application launched with an SDP file or other media ini- browser helper application launched with an SDP file or other
tialization format). media initialization format).
It is RECOMMENDED that minimal servers support the DESCRIBE method, It is RECOMMENDED that minimal servers support the DESCRIBE method,
and highly recommended that minimal clients support the ability to and highly recommended that minimal clients support the ability to
act as a "helper application" that accepts a media initialization act as a "helper application" that accepts a media initialization
file from standard input, command line, and/or other means that are file from standard input, command line, and/or other means that are
appropriate to the operating environment of the client. appropriate to the operating environment of the client.
11.3 SETUP 11.3 SETUP
The SETUP request for a URI specifies the transport mechanism to be The SETUP request for a URI specifies the transport mechanism to be |
used for the streamed media. A client can issue a SETUP request for a used for the streamed media. The SETUP method may be used in two |
stream that is already set up or playing in the session to change different cases; Create a RTSP session or add a media to a session, |
transport parameters, which a server MAY allow. If it does not allow and change the transport parameters of already set up media stream. |
this, it MUST respond with error 455 (Method Not Valid In This Using SETUP to create or add media to a session when in PLAY state |
State). are not allowed. Otherwise SETUP can be used in all three states; |
INIT, and READY, for both purposes and in PLAY to change the |
transport parameters. |
A server MAY allow a client to do SETUP while in playing state to add The Transport header, see section 13.40, specifies the transport |
additional media streams. If not supported, the server SHALL respond parameters acceptable to the client for data transmission; the |
with error 455 (Method Not Allowed In This State). If supported, the response will contain the transport parameters selected by the |
added media SHALL then start to play in sync with the already playing server. This allows the client to enumerate in priority order the |
media. To be able to sync the media with the already playing streams transport mechanisms and parameters acceptable to it, while the |
the SETUP response MUST include a RTP-Info header with the timestamp server can select the most appropriate. All transport parameters |
value, and a Range header with the corresponding normal play time. To SHOULD be included in the Transport header, the use of other headers |
indicate support for this optional feature the feature-tag: for this purpose is discouraged due to middle boxes. |
"setup.playing" is defined.
The Transport header specifies the transport parameters acceptable to For the benefit of any intervening firewalls, a client SHOULD |
the client for data transmission; the response will contain the indicate the transport parameters even if it has no influence over |
transport parameters selected by the server. these parameters, for example, where the server advertises a fixed |
multicast address. |
C->S: SETUP rtsp://example.com/foo/bar/baz.rm RTSP/1.0 Since SETUP includes all transport initialization |
CSeq: 302 information, firewalls and other intermediate network |
Transport: RTP/AVP;unicast;client_port=4588-4589 devices (which need this information) are spared the more |
S->C: RTSP/1.0 200 OK arduous task of parsing the DESCRIBE response, which has |
CSeq: 302 been reserved for media initialization. |
Date: 23 Jan 1997 15:35:06 GMT
Server: PhonyServer 1.0
Session: 47112344
Transport: RTP/AVP;unicast;
client_port=4588-4589;server_port=6256-6257
For the benefit of any intervening firewalls, a client must indicate In a SETUP response the server SHOULD include the Accept-Ranges |
the transport parameters even if it has no influence over these header (see section 13.4 to indicate which time formats that are |
parameters, for example, where the server advertises a fixed multi- acceptable to use for this media resource. |
cast address.
Since SETUP includes all transport initialization information, C->S: SETUP rtsp://example.com/foo/bar/baz.rm RTSP/1.0 |
firewalls and other intermediate network devices (which need CSeq: 302 |
this information) are spared the more arduous task of parsing Transport: RTP/AVP;unicast;client_port=4588-4589, |
the DESCRIBE response, which has been reserved for media ini- RTP/AVP/TCP;unicast;interleave=0-1 |
tialization.
The server generates a session identifier in response to a SETUP S->C: RTSP/1.0 200 OK |
request. If a SETUP request to a server includes a session identi- CSeq: 302 |
fier, the server MUST bundle this setup request into the existing Date: 23 Jan 1997 15:35:06 GMT |
session (aggregated session) or return error 459 (Aggregate Operation Server: PhonyServer 1.0 |
Not Allowed) (see Section 12.4.11). An Aggregate control URI MUST be Session: 47112344 |
used to control an aggregated session. This URI MUST be different Transport: RTP/AVP;unicast;client_port=4588-4589; |
from the stream control URIs of the individual media streams included server_port=6256-6257;ssrc=2A3F93ED |
in the aggregate. The Aggregate control URI SHOULD be specified by Accept-Ranges: NPT |
the session description since there is no general rule for deriving
it from the various stream control URIs in the session. If an Aggre-
gate control URI is not specified in the session description, a
client MUST create an URI for aggregate control of the session. This
URI MUST contain the servers host address and MUST contain the port,
if applicable. Once an URI is used to refer to an aggregation for a
given session, that URI MUST be used to refer to that aggregation for
the duration of the session. If the contents of the aggregation
change, then a different aggregate control URI SHOULD be used.
While the session ID has enough information for aggregate con- In the above example the client want to create a RTSP session |
trol of a session, the Aggregate control URI is still impor- containing the media resource "rtsp://example.com/foo/bar/baz.rm". |
tant for some methods such as SET_PARAMETER where the control The transport parameters acceptable to the client is either |
URI enables the resource in question to be easily identified. RTP/AVP/UDP (UDP per default) to be received on client port 4588 and |
The Aggregate control URI is also useful for proxies, enabling 4589 or RTP/AVP interleaved on the RTSP control channel. The server |
them to route the request to the appropriate server, and for selects the RTP/AVP/UDP transport and adds the ports it will send and |
logging, where it is useful to note the actual resource that a received RTP and RTCP from, and the RTP SSRC that will be used by the |
request was operating on. Finally, presence of the Aggregate server. |
control URI allows for backwards compatibility with RFC 2326
[21]. The server MUST generate a session identifier in response to a |
successful SETUP request, unless a SETUP request to a server includes |
a session identifier, in which case the server MUST bundle this setup |
request into the existing session (aggregated session) or return |
error 459 (Aggregate Operation Not Allowed) (see Section 12.4.11). |
An Aggregate control URI MUST be used to control an aggregated |
session. This URI MUST be different from the stream control URIs of |
the individual media streams included in the aggregate. The Aggregate |
control URI is to be specified by the session description if the |
server supports aggregated control and aggregated control is desired |
for the session. However even if aggregated control is offered the |
client MAY chose to not set up the session in aggregated control. |
If an Aggregate control URI is not specified in the session |
description, it is probably a indication that non-aggregated control |
should be used. However a client MAY try to SETUP the session in |
aggregated control. If the server refuse to aggregate the specified |
media, the server SHALL use the 459 error code. If the server allows |
the aggregation, then the client MUST create an URI for aggregate |
control of the session. This URI MUST contain the servers host |
address and MUST contain the port, if applicable (e.g. not default |
port). Once an URI is used to refer to an aggregation for a given |
session, that URI MUST be used to refer to that aggregation for the |
duration of the session. |
While the session ID sometimes has enough information for |
aggregate control of a session, the Aggregate control URI |
is still important for some methods such as SET_PARAMETER |
where the control URI enables the resource in question to |
be easily identified. The Aggregate control URI is also |
useful for proxies, enabling them to route the request to |
the appropriate server, and for logging, where it is useful |
to note the actual resource that a request was operating |
on. Finally, presence of the Aggregate control URI allows |
for backwards compatibility with RFC 2326 [21].
A session will exist until it is either removed by a TEARDOWN request A session will exist until it is either removed by a TEARDOWN request
or is timed-out by the server. The server MAY remove a session that or is timed-out by the server. The server MAY remove a session that
has not demonstrated liveness signs from the client within a certain has not demonstrated liveness signs from the client within a certain
timeout period. The default timeout value is 60 seconds; the server timeout period. The default timeout value is 60 seconds; the server
MAY set this to a different value and indicate so in the timeout MAY set this to a different value and indicate so in the timeout
field of the Session header in the SETUP response. For further dis- field of the Session header in the SETUP response. For further
cussion see chapter 13.37. Signs of liveness for a RTSP session are: discussion see chapter 13.37. Signs of liveness for a RTSP session
are:
+ Any RTSP request from a client which includes a Session header o Any RTSP request from a client which includes a Session header
with that session's ID. with that session's ID.
+ If RTP is used as a transport for the underlying media streams, o If RTP is used as a transport for the underlying media
an RTCP sender or receiver report from the client for any of the streams, an RTCP sender or receiver report from the client for
media streams in that RTSP session. any of the media streams in that RTSP session.
If a SETUP request on a session fails for any reason, the session | If a SETUP request on a session fails for any reason, the session |
state, as well as transport and other parameters for associated | state, as well as transport and other parameters for associated |
streams SHALL remain unchanged from their values as if the SETUP | streams SHALL remain unchanged from their values as if the SETUP |
request had never been received by the server. request had never been received by the server. |
A client MAY issue a SETUP request for a stream that is already set |
up or playing in the session to change transport parameters, which a |
server MAY allow. If it does not allow this, it MUST respond with |
error 455 (Method Not Valid In This State). Reasons to support |
changing transport parameters, is to allow for application layer |
mobility and flexibility to utilize the best available transport as |
it becomes available. |
In a SETUP response for a request to change the transport parameters |
while in Play state, the server SHOULD include the Range to indicate |
from what point the new transport parameters are used. Further if RTP |
is used for delivery the server SHOULD also include the RTP-Info |
header to indicate from what timestamp and RTP sequence number the |
change has taken place. If both RTP-Info and Range is included in the |
response the "rtp_time" parameter and range MUST be for the |
corresponding time, i.e. be used in the same way as for PLAY to |
ensure the correct synchronization information is present. |
If the transport parameter change while in PLAY state results in a |
change of synchronization related information, for example changing |
RTP SSRC, the server MUST provide in the SETUP response the necessary |
synchronization information. However the server is RECOMMENDED to |
avoid changing the synchronization information if possible. |
11.4 PLAY 11.4 PLAY
The PLAY method tells the server to start sending data via the mecha- The PLAY method tells the server to start sending data via the |
nism specified in SETUP. A client MUST NOT issue a PLAY request until mechanism specified in SETUP. A client MUST NOT issue a PLAY request |
any outstanding SETUP requests have been acknowledged as successful. until any outstanding SETUP requests have been acknowledged as |
successful. PLAY requests are valid when the session is in READY |
state; the use of PLAY requests when the session is in PLAY state is |
deprecated. A PLAY request MUST include a Session header to indicate |
which session the request applies to.
In an aggregated session the PLAY request MUST contain an aggregated In an aggregated session the PLAY request MUST contain an aggregated
control URL. A server SHALL responde with error 460 (Only Aggregate control URL. A server SHALL responde with error 460 (Only Aggregate
Operation Allowed) if the client PLAY request URI is for one of the Operation Allowed) if the client PLAY request URI is for one of the
media. The media in an aggregate SHALL be played in sync. If a client media. The media in an aggregate SHALL be played in sync. If a client
want individual control of the media it must use separate RTSP ses- want individual control of the media it must use separate RTSP
sions for each media. sessions for each media.
The PLAY request positions the normal play time to the beginning of The PLAY request SHALL position the normal play time to the beginning |
the range specified by the Range header and delivers stream data of the range specified by the Range header and delivers stream data |
until the end of the range is reached. To allow for precise composi- until the end of the range if given, else to the end of the media is |
tion multiple ranges MAY be specified. The range values are valid if reached. To allow for precise composition multiple ranges MAY be |
all given ranges are part of any media. If a given range value points specified in one PLAY Request. The range values are valid if all |
outside of the media, the response SHALL be the 457 (Invalid Range) given ranges are part of any media within the aggregate. If a given |
error code. range value points outside of the media, the response SHALL be the |
457 (Invalid Range) error code.
The below example will first play seconds 10 through 15, then, imme- The below example will first play seconds 10 through 15, then,
diately following, seconds 20 to 25, and finally seconds 30 through immediately following, seconds 20 to 25, and finally seconds 30
the end. through the end.
C->S: PLAY rtsp://audio.example.com/audio RTSP/1.0 C->S: PLAY rtsp://audio.example.com/audio RTSP/1.0
CSeq: 835 CSeq: 835
Session: 12345678 Session: 12345678
Range: npt=10-15, npt=20-25, npt=30- Range: npt=10-15, npt=20-25, npt=30-
See the description of the PAUSE request for further examples. See the description of the PAUSE request for further examples.
A PLAY request without a Range header is legal. It starts playing a A PLAY request without a Range header is legal. It SHALL start |
stream from the beginning unless the stream has been paused. If a playing a stream from the beginning (npt=0-) unless the stream has |
stream has been paused via PAUSE, stream delivery resumes at the been paused. If a stream has been paused via PAUSE, stream delivery |
pause point. resumes at the pause point. The stream SHALL play until the end of |
the media.
The Range header MUST NOT contain a time parameter. The usage of time | The Range header MUST NOT contain a time parameter. The usage of time
has been deprecated. in PLAY method has been deprecated.
Server MUST include a "Range" header in any PLAY response. The | Server MUST include a "Range" header in any PLAY response. The |
response MUST use the same format as the request's range header con- | response MUST use the same format as the request's range header |
tained. If no Range header was in the request, the NPT time format | contained. If no Range header was in the request, the NPT time format |
SHOULD be used unless the client showed support for other formats. | SHOULD be used unless the client showed support for an other format. |
For a session with live media streams the Range header MUST also be | Also for a session with live media streams the Range header MUST |
given, containing a valid time indication. It is RECOMMENDED that | indicate a valid time. It is RECOMMENDED that normal play time is |
either "npt=now-" or a absolute time value (clock) for the corre- | used, either the "now" indicator, for example "npt=now-", or the time |
sponding time is given, i.e. "clock=20030213T143205Z-". The UTC | since session start as an open interval, e.g. "npt=96.23-". An |
clock format SHOULD only be used if client has shown support for it. absolute time value (clock) for the corresponding time MAY be given, |
i.e. "clock=20030213T143205Z-". The UTC clock format SHOULD only be |
used if client has shown support for it. |
For a on-demand stream, the server MUST reply with the actual range A media server only supporting playback MUST support the npt format |
that will be played back. This may differ from the requested range if and MAY support the clock and smpte formats. |
alignment of the requested range to valid frame boundaries is
required for the media source. If no range is specified in the
request, the start position SHALL still be returned in the reply. The
unit of the range in the reply is the same as that in the request. If
the medias part of an aggregate has different lengths the PLAY
request and any Range SHALL be performed as long it is valid for the
longest media. Media will be sent whenever it is available for the
given play-out point.
After playing the desired range, the presentation is NOT automati- For a on-demand stream, the server MUST reply with the actual range |
cally paused, media deliver simply stops. A PAUSE request MUST be that will be played back. This may differ from the requested range if |
issued before another PLAY request can issued. Note: This is one alignment of the requested range to valid frame boundaries is |
change resulting in a non-operability with RFC 2326 implementations. required for the media source. If no range is specified in the |
A client not issuing a PAUSE request before a new PLAY will be stuck request, the start position SHALL still be returned in the reply. If |
in PLAYING state. A client desiring to play the media from the begin- the medias that are part of an aggregate has different lengths, the |
ning MUST send a PLAY request with a Range header pointing at the PLAY request SHALL be performed as long as the given range is valid |
beginning, e.g. npt=0-. for any media, for example the longest media. Media will be sent |
whenever it is available for the given play-out point. |
After playing the desired range, the presentation is NOT |
automatically paused, media delivery simply stops. A PAUSE request |
MUST be issued before another PLAY request can be issued. Note: This |
is one change resulting in a non-operability with RFC 2326 |
implementations. A client not issuing a PAUSE request before a new |
PLAY will be stuck in PLAY state. |
A client desiring to play the media from the beginning MUST send a |
PLAY request with a Range header pointing at the beginning, e.g. |
npt=0-. If a PLAY request is received without a Range header when |
media delivery has stopped at the end, the server SHOULD respond with |
a 457 "Invalid Range" error response. In that response the current |
pause point in a Range header SHALL be included.
The following example plays the whole presentation starting at SMPTE The following example plays the whole presentation starting at SMPTE
time code 0:10:20 until the end of the clip. The playback is to start time code 0:10:20 until the end of the clip. Note: The RTP-Info
at 15:36 on 23 Jan 1997. Note: The RTP-Info headers has been broken headers has been broken into several lines to fit the page.
into several lines to fit the page.
C->S: PLAY rtsp://audio.example.com/twister.en RTSP/1.0 C->S: PLAY rtsp://audio.example.com/twister.en RTSP/1.0
CSeq: 833 CSeq: 833
Session: 12345678 Session: 12345678
Range: smpte=0:10:20-;time=19970123T153600Z Range: smpte=0:10:20-
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 833 CSeq: 833
Date: 23 Jan 1997 15:35:06 GMT Date: 23 Jan 1997 15:35:06 GMT
Server: PhonyServer 1.0 Server: PhonyServer 1.0
Range: smpte=0:10:22-;time=19970123T153600Z Range: smpte=0:10:22-
RTP-Info:url=rtsp://example.com/twister.en; RTP-Info:url=rtsp://example.com/twister.en;
seq=14783;rtptime=2345962545 seq=14783;rtptime=2345962545
For playing back a recording of a live presentation, it may be desir- For playing back a recording of a live presentation, it may be
able to use clock units: desirable to use clock units:
C->S: PLAY rtsp://audio.example.com/meeting.en RTSP/1.0 C->S: PLAY rtsp://audio.example.com/meeting.en RTSP/1.0
CSeq: 835 CSeq: 835
Session: 12345678 Session: 12345678
Range: clock=19961108T142300Z-19961108T143520Z Range: clock=19961108T142300Z-19961108T143520Z
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 835 CSeq: 835
Date: 23 Jan 1997 15:35:06 GMT Date: 23 Jan 1997 15:35:06 GMT
Server:PhonyServer 1.0 Server:PhonyServer 1.0
Range: clock=19961108T142300Z-19961108T143520Z Range: clock=19961108T142300Z-19961108T143520Z
RTP-Info:url=rtsp://example.com/meeting.en; RTP-Info:url=rtsp://example.com/meeting.en;
seq=53745;rtptime=484589019 seq=53745;rtptime=484589019
A media server only supporting playback MUST support the npt format
and MAY support the clock and smpte formats.
All range specifiers in this specification allow for ranges with All range specifiers in this specification allow for ranges with
unspecified begin times (e.g. "npt=-30"). When used in a PLAY unspecified begin times (e.g. "npt=-30"). When used in a PLAY
request, the server treats this as a request to start/resume playback request, the server treats this as a request to start/resume playback
from the current pause point, ending at the end time specified in the from the current pause point, ending at the end time specified in the
Range header. If the pause point is located later than the given end Range header. If the pause point is located later than the given end
value, a 457 (Invalid Range) response SHALL be given. value, a 457 (Invalid Range) response SHALL be given.
The queued play functionality described in RFC 2326 [21] is removed The queued play functionality described in RFC 2326 [21] is removed
and multiple ranges can be used to achieve a similar performance. If and multiple ranges can be used to achieve a similar performance. If
a server receives a PLAY request while in the PLAY state, the server a server receives a PLAY request while in the PLAY state, the server
SHALL responde using the error code 455 (Method Not Valid In This SHALL responde using the error code 455 (Method Not Valid In This
State). This will signal the client that queued play are not sup- State). This will signal the client that queued play are not
ported. supported.
The use of PLAY for keep-alive signaling, i.e. PLAY request without a
range header, has also been depreciated. Instead a client can use,
PING, SET_PARAMETER or OPTIONS for keep alive. A server receiving a
PLAY keep alive SHALL respond with the 455 error code.
When playing live media, indicated by the Accept-Ranges header the | The use of PLAY for keep-alive signaling, i.e. PLAY request without a |
session are in a live state. This live state will put some restric- | range header in PLAY state, has also been depreciated. Instead a |
tions on the action available for a client. A PLAY request without a | client can use, PING, SET_PARAMETER or OPTIONS for keep alive. A |
Range header will start media deliver at the current point in the | server receiving a PLAY keep alive SHALL respond with the 455 error |
live presentation, i.e. now. Any seeking in the media will be impos- | code.
sible. The only allowed usage of the Range header is npt=now-, and |
certain clock units. The usage of npt=now- is unnecessary as it has |
the exact same meaning as a request without Range header. The clock |
format can be used to specify start and stop times for media delivery |
in a live session.
11.5 PAUSE 11.5 PAUSE
The PAUSE request causes the stream delivery to be interrupted | The PAUSE request causes the stream delivery to be interrupted
(halted) temporarily. A PAUSE request MUST be done with the aggre- | (halted) temporarily. A PAUSE request MUST be done with the
gated control URI for aggregated sessions, resulting in all media | aggregated control URI for aggregated sessions, resulting in all
being halted, or the media URI for non-aggregated sessions. Any | media being halted, or the media URI for non-aggregated sessions.
attempt to do muting of a single media with an PAUSE request in an | Any attempt to do muting of a single media with an PAUSE request in
aggregated session SHALL be responded with error 460 (Only Aggregate | an aggregated session SHALL be responded with error 460 (Only
Operation Allowed). After resuming playback, synchronization of the | Aggregate Operation Allowed). After resuming playback,
tracks MUST be maintained. Any server resources are kept, though | synchronization of the tracks MUST be maintained. Any server
servers MAY close the session and free resources after being paused | resources are kept, though servers MAY close the session and free
for the duration specified with the timeout parameter of the Session | resources after being paused for the duration specified with the
header in the SETUP message. timeout parameter of the Session header in the SETUP message.
Example: Example: |
C->S: PAUSE rtsp://example.com/fizzle/foo RTSP/1.0 C->S: PAUSE rtsp://example.com/fizzle/foo RTSP/1.0 |
CSeq: 834 CSeq: 834 |
Session: 12345678 Session: 12345678 |
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK |
CSeq: 834 CSeq: 834 |
Date: 23 Jan 1997 15:35:06 GMT Date: 23 Jan 1997 15:35:06 GMT |
Range: npt=45.76 Range: npt=45.76- |
The PAUSE request may contain a Range header specifying when the The PAUSE request MAY contain a Range header specifying when the
stream or presentation is to be halted. We refer to this point as the stream or presentation is to be halted. We refer to this point as the
"pause point". The time parameter in the Range MUST NOT be used. | "pause point". The time parameter in the Range MUST NOT be used. The
The header MUST contain a single value, expressed as the beginning Range header MUST contain a single value, expressed as the beginning
value an open range. For example, the following clip will be played value an open range. For example, the following clip will be played
from 10 seconds through 21 seconds of the clip's normal play time, from 10 seconds through 21 seconds of the clip's normal play time,
under the assumption that the PAUSE request reaches the server within under the assumption that the PAUSE request reaches the server within
11 seconds of the PLAY request. Note that some lines has been broken 11 seconds of the PLAY request. Note that some lines has been broken
in an non-correct way to fit the page: in an non-correct way to fit the page:
C->S: PLAY rtsp://example.com/fizzle/foo RTSP/1.0 C->S: PLAY rtsp://example.com/fizzle/foo RTSP/1.0
CSeq: 834 CSeq: 834
Session: 12345678 Session: 12345678
Range: npt=10-30 Range: npt=10-30
skipping to change at page 1, line 1870 skipping to change at page 43, line 39
CSeq: 835 CSeq: 835
Session: 12345678 Session: 12345678
Range: npt=21- Range: npt=21-
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 835 CSeq: 835
Date: 23 Jan 1997 15:35:09 GMT Date: 23 Jan 1997 15:35:09 GMT
Server: PhonyServer 1.0 Server: PhonyServer 1.0
Range: npt=21- Range: npt=21-
Session: 12345678 Session: 12345678
The pause request becomes effective the first time the server is |
encountering the time point specified in any of the multiple ranges. |
If the Range header specifies a time outside any range from the PLAY |
request, the error 457 (Invalid Range) SHALL be returned. If a media |
unit (such as an audio or video frame) starts presentation at exactly |
the pause point, it is not played. If the Range header is missing, |
stream delivery is interrupted immediately on receipt of the message |
and the pause point is set to the current normal play time. However, |
the pause point in the media stream MUST be maintained. A subsequent |
PLAY request without Range header resumes from the pause point and |
play until media end.
The actual pause point after any PAUSE request SHALL be returned to The pause request becomes effective the first time the server is
the client by adding a Range header with what remains unplayed of the encountering the time point specified in any of the multiple ranges.
PLAY request's ranges, i.e. including all the remaining ranges part If the Range header specifies a time outside any range from the PLAY
of multiple range specification. If one desires to resume playing a request, the error 457 (Invalid Range) SHALL be returned. If a media
ranged request, one simple included the Range header from the PAUSE unit (such as an audio or video frame) starts presentation at exactly
response. the pause point, it is not played. If the Range header is missing,
stream delivery is interrupted immediately on receipt of the message
and the pause point is set to the current normal play time. However,
the pause point in the media stream MUST be maintained. A subsequent
PLAY request without Range header SHALL resume from the pause point
and play until media end.
For example, if the server have a play request for ranges 10 to 15 If the server has already sent data beyond the time specified in the |
and 20 to 29 pending and then receives a pause request for NPT 21, it PAUSE request's Range header, a PLAY without range SHALL resume at |
would start playing the second range and stop at NPT 21. If the pause the point in time specified by the PAUSE request's Range header, as |
request is for NPT 12 and the server is playing at NPT 13 serving the it is assumed that the client has discarded data after that point. |
first play request, the server stops immediately. If the pause This ensures continuous pause/play cycling without gaps. |
request is for NPT 16, the server returns a 457 error message. To
prevent that the second range is played and the server stops after
completing the first range, a PAUSE request for 20 must be issued.
As another example, if a server has received requests to play ranges The pause point after any PAUSE request SHALL be returned to the |
10 to 15 and then 13 to 20 (that is, overlapping ranges), the PAUSE client by adding a Range header with what remains unplayed of the |
request for NPT=14 would take effect while the server plays the first PLAY request's ranges, i.e. including all the remaining ranges part |
range, with the second range effectively being ignored, assuming the of multiple range specification. If one desires to resume playing a |
PAUSE request arrives before the server has started playing the sec- ranged request, one simple included the Range header from the PAUSE |
ond, overlapping range. Regardless of when the PAUSE request arrives, response. Note that this server behavior was not mandated previously |
it sets the pause point to 14. and servers implementing according to RFC 2326 will probably not |
return the range header. |
If the server has already sent data beyond the time specified in the For example, if the server have a play request for ranges 10 to 15 |
the PAUSE request Range header, a PLAY without range would still and 20 to 29 pending and then receives a pause request for NPT 21, it |
resume at that point in time, specified by the PAUSE request's Range would start playing the second range and stop at NPT 21. If the pause |
header, as it is assumed that the client has discarded data after request is for NPT 12 and the server is playing at NPT 13 serving the |
that point. This ensures continuous pause/play cycling without gaps. first play request, the server stops immediately. If the pause |
request is for NPT 16, the server returns a 457 error message. To |
prevent that the second range is played and the server stops after |
completing the first range, a PAUSE request for 20 must be issued. |
If a client issues a PAUSE request and the server acknowledges and As another example, if a server has received requests to play ranges |
enters the ready state, the proper server response, if the player 10 to 15 and then 13 to 20 (that is, overlapping ranges), the PAUSE |
issues another PAUSE, is 200 OK. The 200 OK response MUST include the request for NPT=14 would take effect while the server plays the first |
Range header with the current pause point, even if the PAUSE request range, with the second range effectively being ignored, assuming the |
is asking for some other pause point. See examples below: PAUSE request arrives before the server has started playing the |
second, overlapping range. Regardless of when the PAUSE request |
arrives, it sets the pause point to 14. The below example messages is |
for the above case when the PAUSE request arrives before the first |
occurrence of NPT=14. |
C->S: PLAY rtsp://example.com/fizzle/foo RTSP/1.0 |
CSeq: 834 |
Session: 12345678 |
Range: npt=10-15, npt=13-20 |
S->C: RTSP/1.0 200 OK |
CSeq: 834 |
Date: 23 Jan 1997 15:35:06 GMT |
Server: PhonyServer 1.0 |
Range: npt=10-15, npt=13-20 |
RTP-Info:url=rtsp://example.com/fizzle/audiotrack; |
seq=5712;rtptime=934207921, |
url=rtsp://example.com/fizzle/videotrack; |
seq=57654;rtptime=2792482193 |
Session: 12345678 |
C->S: PAUSE rtsp://example.com/fizzle/foo RTSP/1.0 |
CSeq: 835 |
Session: 12345678 |
Range: npt=14- |
S->C: RTSP/1.0 200 OK |
CSeq: 835 |
Date: 23 Jan 1997 15:35:09 GMT |
Server: PhonyServer 1.0 |
Range: npt=14-15, npt=13-20 |
Session: 12345678 |
If a client issues a PAUSE request and the server acknowledges and |
enters the READY state, the proper server response, if the player |
issues another PAUSE, is still 200 OK. The 200 OK response MUST |
include the Range header with the current pause point, even if the |
PAUSE request is asking for some other pause point. See examples |
below:
Examples: Examples:
C->S: PAUSE rtsp://example.com/fizzle/foo RTSP/1.0 C->S: PAUSE rtsp://example.com/fizzle/foo RTSP/1.0
CSeq: 834 CSeq: 834
Session: 12345678 Session: 12345678
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 834 CSeq: 834
Session: 12345678 Session: 12345678
skipping to change at page 1, line 1934 skipping to change at page 46, line 4
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 834 CSeq: 834
Session: 12345678 Session: 12345678
Date: 23 Jan 1997 15:35:06 GMT Date: 23 Jan 1997 15:35:06 GMT
Range: npt=45.76- Range: npt=45.76-
C->S: PAUSE rtsp://example.com/fizzle/foo RTSP/1.0 C->S: PAUSE rtsp://example.com/fizzle/foo RTSP/1.0
CSeq: 835 CSeq: 835
Session: 12345678 Session: 12345678
Range: 86- Range: 86-
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 835 CSeq: 835
Session: 12345678 Session: 12345678
Date: 23 Jan 1997 15:35:07 GMT Date: 23 Jan 1997 15:35:07 GMT
Range: npt=45.76- Range: npt=45.76-
11.6 TEARDOWN 11.6 TEARDOWN
The TEARDOWN request stops the stream delivery for the given URI, The TEARDOWN client to server request stops the stream delivery for |
freeing the resources associated with it. If the URI is the aggre- the given URI, freeing the resources associated with it. TEARDOWN |
gated control URI for this presentation, any RTSP session identifier MAY be done using either an aggregated or a media control URI. |
associated with the session is no longer valid. The use of "*" as URI However some restrictions apply depending on the current state. The |
in TEARDOWN will also result in that the session is removed indepen- TEARDOWN request SHALL contain a Session header indicating what |
dent of the number of medias that was part of it. If the URI in the session the request applies to. |
request was for a media within an aggregated session that media is
removed from the aggregate. However the session and any other media
stream yet not torn down remains, and any valid request, e.g. PLAY or
SETUP, can be issued. As an optional feature a server MAY keep the
session in case the last remaining media is torn down with a TEARDOWN
request with an URI equal to the media URI. To Indicate what has been
performed, a server that after any TEARDOWN request, still has a
valid session MUST in the response return a session header.
A server MAY choose to allow TEARDOWN of individual media while in A TEARDOWN using the aggregated control URI or the media URI in a |
PLAY state. When this is not allowed the response SHALL be 455 session under non-aggregated control MAY be done in any state (Ready, |
(Method Not Valid In This State). If a server implements TEARDOWN and and Play). A successful request SHALL result in that media delivery |
SETUP in PLAY state it MUST signal this using the "setup.playing" is immediately halted and the session state is destroyed. This SHALL |
feature-tag. be indicated through the lack of a Session header in the response. |
A TEARDOWN using a media URI in an aggregated session MAY only be |
done in Ready state. Such a request only removes the indicated media |
stream and associated resources from the session. This may result in |
that a session returns to non-aggregated control. In the response to |
TEARDOWN request resulting in that the session still exist SHALL |
contain a Session header to indicate this. |
Note, the indication with the session header if sessions state remain |
may not be done correctly by a RFC 2326 client, but will be for any |
server signalling the "play.basic" tag.
Example: Example:
C->S: TEARDOWN rtsp://example.com/fizzle/foo RTSP/1.0 C->S: TEARDOWN rtsp://example.com/fizzle/foo RTSP/1.0
CSeq: 892 CSeq: 892
Session: 12345678 Session: 12345678
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 892 CSeq: 892
Server: PhonyServer 1.0 Server: PhonyServer 1.0
skipping to change at page 1, line 2003 skipping to change at page 47, line 34
C->S: RTSP/1.0 200 OK C->S: RTSP/1.0 200 OK
CSeq: 431 CSeq: 431
Content-Length: 46 Content-Length: 46
Content-Type: text/parameters Content-Type: text/parameters
packets_received: 10 packets_received: 10
jitter: 0.3838 jitter: 0.3838
The "text/parameters" section is only an example type for The "text/parameters" section is only an example type for
parameter. This method is intentionally loosely defined with parameter. This method is intentionally loosely defined
the intention that the reply content and response content will with the intention that the reply content and response
be defined after further experimentation. content will be defined after further experimentation.
11.8 SET_PARAMETER 11.8 SET_PARAMETER
This method requests to set the value of a parameter for a presenta- This method requests to set the value of a parameter for a
tion or stream specified by the URI. presentation or stream specified by the URI.
A request is RECOMMENDED to only contain a single parameter to allow A request is RECOMMENDED to only contain a single parameter to allow
the client to determine why a particular request failed. If the the client to determine why a particular request failed. If the
request contains several parameters, the server MUST only act on the request contains several parameters, the server MUST only act on the
request if all of the parameters can be set successfully. A server request if all of the parameters can be set successfully. A server
MUST allow a parameter to be set repeatedly to the same value, but it MUST allow a parameter to be set repeatedly to the same value, but it
MAY disallow changing parameter values. If the receiver of the MAY disallow changing parameter values. If the receiver of the
request does not understand or can locate a parameter error 451 request does not understand or can locate a parameter error 451
(Parameter Not Understood) SHALL be used. In the case a parameter is (Parameter Not Understood) SHALL be used. In the case a parameter is
not allowed to change the error code 458 (Parameter Is Read-Only). not allowed to change the error code 458 (Parameter Is Read-Only).
The response body SHOULD contain only the parameters that has errors. The response body SHOULD contain only the parameters that has errors.
Otherwise no body SHALL be returned. Otherwise no body SHALL be returned.
Note: transport parameters for the media stream MUST only be set with Note: transport parameters for the media stream MUST only be set with
the SETUP command. the SETUP command.
Restricting setting transport parameters to SETUP is for the Restricting setting transport parameters to SETUP is for
benefit of firewalls. the benefit of firewalls.
The parameters are split in a fine-grained fashion so that The parameters are split in a fine-grained fashion so that
there can be more meaningful error indications. However, it there can be more meaningful error indications. However, it
may make sense to allow the setting of several parameters if may make sense to allow the setting of several parameters
an atomic setting is desirable. Imagine device control where if an atomic setting is desirable. Imagine device control
the client does not want the camera to pan unless it can also where the client does not want the camera to pan unless it
tilt to the right angle at the same time. can also tilt to the right angle at the same time.
Example: Example:
C->S: SET_PARAMETER rtsp://example.com/fizzle/foo RTSP/1.0 C->S: SET_PARAMETER rtsp://example.com/fizzle/foo RTSP/1.0
CSeq: 421 CSeq: 421
Content-length: 20 Content-length: 20
Content-type: text/parameters Content-type: text/parameters
barparam: barstuff barparam: barstuff
skipping to change at page 1, line 2050 skipping to change at page 48, line 37
CSeq: 421 CSeq: 421
Content-length: 20 Content-length: 20
Content-type: text/parameters Content-type: text/parameters
barparam: barstuff barparam: barstuff
S->C: RTSP/1.0 451 Parameter Not Understood S->C: RTSP/1.0 451 Parameter Not Understood
CSeq: 421 CSeq: 421
Content-length: 10 Content-length: 10
Content-type: text/parameters Content-type: text/parameters
barparam barparam
The "text/parameters" section is only an example type for The "text/parameters" section is only an example type for
parameter. This method is intentionally loosely defined with parameter. This method is intentionally loosely defined
the intention that the reply content and response content will with the intention that the reply content and response
be defined after further experimentation. content will be defined after further experimentation.
11.9 REDIRECT 11.9 REDIRECT
A redirect request informs the client that it MUST connect to another | A redirect request informs the client that it MUST connect to another |
server location. The REDIRECT request MAY contain the header Loca- | server location. The REDIRECT request MAY contain the header |
tion, which indicates that the client should issue requests for that | Location, which indicates that the client should issue requests for |
URL. If the Location URL only contains a host address the client | that URL. The lack of a Location header in the response SHALL be |
shall connect to the given host, while using the path from the URL on | interpreted as that the server can't any longer fulfill the current |
the current server. | request, but has no alternative at the present where the client |
continue. |
If a REDIRECT request contains a Session header, it is end-to-end and | If a REDIRECT request contains a Session header, it is end-to-end and |
applies only to the given session. If there are proxies in the | applies only to the given session. If there are proxies in the |
request chain, they SHOULD NOT disconnect the control channel unless | request chain, they SHOULD NOT disconnect the control channel unless |
there are no remaining sessions. | there are no remaining sessions. If the Location header is included |
it SHALL contain a full absolute URI pointing out the resource to |
reconnect too, i.e. the Location SHALL NOT contain only host and |
port. |
If a REDIRECT request does not contain a Session header, it is next- | If a REDIRECT request does not contain a Session header, it is next- |
hop and applies to the control connection. The Location header SHOULD | hop and applies also to the control connection. If the Location |
only contain a host address. If there are proxies in the request | header is included it SHOULD only contain an absolute URI containing |
chain, they SHOULD do all of the following: (1) respond to the REDI- | the host address and OPTIONAL the port number. If there are proxies |
RECT request, (2) disconnect the control channel from the requestor, | in the request chain, they SHOULD do all of the following: (1) |
(3) reconnect to the given host address, and (4) pass the request to | respond to the REDIRECT request, (2) disconnect the control channel |
each applicable client (typically those clients with an active ses- | from the requestor, (3) reconnect to the given host address, and (4) |
sion or unanswered request from the requestor). Note that the proxy | pass the request to each applicable client (typically those clients |
is responsible for accepting the REDIRECT response from its clients | with an active session or unanswered request from the requestor). |
and these responses MUST NOT be passed on to either the requesting or | Note that the proxy is responsible for accepting the REDIRECT |
the destination server. response from its clients and these responses MUST NOT be passed on |
to either the requesting or the destination server.
The redirect request MAY contain the header Range, which indicates The redirect request MAY contain the header Range, which indicates
when the redirection takes effect. If the Range contains a "time=" when the redirection takes effect. If the Range contains a "time="
value that is the wall clock time that the redirection MUST at the value that is the wall clock time that the redirection MUST at the
latest take place. When the "time=" parameter is present the range latest take place. When the "time=" parameter is present the range
value MUST be ignored. However the range entered MUST be syntactical value MUST be ignored. However the range entered MUST be syntactical
correct and SHALL point at the beginning of any on-demand content. If correct and SHALL point at the beginning of any on-demand content. If
no time parameter is part of the Range header then redirection SHALL no time parameter is part of the Range header then redirection SHALL
take place when the media playout from the server reaches the given take place when the media playout from the server reaches the given
time. The range value MUST be a single value in the open ended form, time. The range value MUST be a single value in the open ended form,
e.g. npt=59-. e.g. npt=59-.
If the client wants to continue to send or receive media for this A server upon receiving a successful (2xx) response for a REDIRECT |
resource, the client MUST issue a TEARDOWN request for the current request without any Range header SHALL consider the session as |
session. A new session must be established with the designated host. removed and can free any session state. For this type of requests the |
A client SHOULD issue a new DESCRIBE request with the URL given in rest of this paragraph applies. The server MAY close the signalling |
the Location header, unless the URL only contains a host address. In connection upon receiving the response for REDIRECT requests without |
the cases the Location only contains a host address the client MAY a Session header. The client SHOULD close the signaling connection |
assume that the media on the server it is redirected to is identical. after having given the 2xx response to a REDIRECT response, unless it |
Identical media means that all media configuration information from has several sessions on the server. If the client has multiple |
the old session still is valid except for the host address. In the session on the server it SHOULD close the connection when it has |
case of absolute URLs in the location header the media redirected to received and responded to REDIRECT requests for all sessions. |
can be either identical, slightly different or totally different.
This is the reason why a new DESCRIBE request SHOULD be issued. A client receiving a REDIRECT request with a Range header SHALL issue |
a TEARDOWN request when the in indicated redirect point is reached. |
The client SHOULD for REDIRECT requests with Range header close the |
signalling connection after a 2xx response on its TEARDOWN request. |
The normal connection considerations apply for the server. This |
differentiation from REDIRECT requests without range headers is to |
allow clear an explicit state handling. As the state in the server |
needs to be kept until the point of redirection, the handling becomes |
more clear if the client is required to tear down the session at that |
point. |
If the client wants to continue to send or receive media for this |
resource, the client will have to establish a new session with the |
designated host. A client SHOULD issue a new DESCRIBE request with |
the URL given in the Location header, unless the URL only contains a |
host address. In the cases the Location only contains a host address |
the client MAY assume that the media on the server it is redirected |
to is identical. Identical media means that all media configuration |
information from the old session still is valid except for the host |
address. In the case of absolute URLs in the location header the |
media redirected to can be either identical, slightly different or |
totally different. This is the reason why a new DESCRIBE request |
SHOULD be issued.
This example request redirects traffic for this session to the new This example request redirects traffic for this session to the new
server at the given absolute time: server at the given absolute time:
S->C: REDIRECT rtsp://example.com/fizzle/foo RTSP/1.0 S->C: REDIRECT rtsp://example.com/fizzle/foo RTSP/1.0
CSeq: 732 CSeq: 732
Location: rtsp://bigserver.com:8001 Location: rtsp://bigserver.com:8001
Range: npt=0- ;time=19960213T143205Z Range: npt=0- ;time=19960213T143205Z
Session: uZ3ci0K+Ld-M Session: uZ3ci0K+Ld-M
11.10 PING 11.10 PING
This method is a bi-directional mechanism for server or client live- This method is a bi-directional mechanism for server or client
ness checking. It has no side effects. The issuer of the request MUST liveness checking. It has no side effects. The issuer of the request
include a session header with the session ID of the session that is MUST include a session header with the session ID of the session that
being checked for liveness. is being checked for liveness.
Prior to using this method, an OPTIONS method is RECOMMENDED to be Prior to using this method, an OPTIONS method is RECOMMENDED to be
issued in the direction which the PING method would be used. This issued in the direction which the PING method would be used. This
method MUST NOT be used if support is not indicated by the Public method MUST NOT be used if support is not indicated by the Public
header. Note: That an 501 (Not Implemented) response means that the header. Note: That an 501 (Not Implemented) response means that the
keep-alive timer has not been updated. keep-alive timer has not been updated.
When a proxy is in use, PING with a * indicates a single-hop liveness When a proxy is in use, PING with a * indicates a single-hop liveness
check, whereas PING with a URL including an host address indicates an check, whereas PING with a URL including an host address indicates an
end-to-end liveness check. end-to-end liveness check.
skipping to change at page 1, line 2152 skipping to change at page 51, line 33
11.11 Embedded (Interleaved) Binary Data 11.11 Embedded (Interleaved) Binary Data
Certain firewall designs and other circumstances may force a server Certain firewall designs and other circumstances may force a server
to interleave RTSP messages and media stream data. This interleaving to interleave RTSP messages and media stream data. This interleaving
should generally be avoided unless necessary since it complicates should generally be avoided unless necessary since it complicates
client and server operation and imposes additional overhead. Also client and server operation and imposes additional overhead. Also
head of line blocking may cause problems. Interleaved binary data head of line blocking may cause problems. Interleaved binary data
SHOULD only be used if RTSP is carried over TCP. SHOULD only be used if RTSP is carried over TCP.
Stream data such as RTP packets is encapsulated by an ASCII dollar Stream data such as RTP packets is encapsulated by an ASCII dollar
sign (24 decimal), followed by a one-byte channel identifier, fol- sign (24 decimal), followed by a one-byte channel identifier,
lowed by the length of the encapsulated binary data as a binary, two- followed by the length of the encapsulated binary data as a binary,
byte integer in network byte order. The stream data follows immedi- two-byte integer in network byte order. The stream data follows
ately afterwards, without a CRLF, but including the upper-layer pro- immediately afterwards, without a CRLF, but including the upper-layer
tocol headers. Each $ block contains exactly one upper-layer protocol protocol headers. Each $ block contains exactly one upper-layer
data unit, e.g., one RTP packet. protocol data unit, e.g., one RTP packet.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| "$" = 24 | Channel ID | Length in bytes | | "$" = 24 | Channel ID | Length in bytes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Length number of bytes of binary data : : Length number of bytes of binary data :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The channel identifier is defined in the Transport header with the The channel identifier is defined in the Transport header with the
interleaved parameter(Section 13.40). interleaved parameter(Section 13.40).
When the transport choice is RTP, RTCP messages are also interleaved When the transport choice is RTP, RTCP messages are also interleaved
by the server over the TCP connection. The usage of RTCP messages is by the server over the TCP connection. The usage of RTCP messages is
indicated by including a range containing a second channel in the indicated by including a range containing a second channel in the
interleaved parameter of the Transport header, see section 13.40. If interleaved parameter of the Transport header, see section 13.40. If
RTCP is used, packets SHALL be sent on the first available channel RTCP is used, packets SHALL be sent on the first available channel
skipping to change at page 1, line 2176 skipping to change at page 52, line 16
The channel identifier is defined in the Transport header with the The channel identifier is defined in the Transport header with the
interleaved parameter(Section 13.40). interleaved parameter(Section 13.40).
When the transport choice is RTP, RTCP messages are also interleaved When the transport choice is RTP, RTCP messages are also interleaved
by the server over the TCP connection. The usage of RTCP messages is by the server over the TCP connection. The usage of RTCP messages is
indicated by including a range containing a second channel in the indicated by including a range containing a second channel in the
interleaved parameter of the Transport header, see section 13.40. If interleaved parameter of the Transport header, see section 13.40. If
RTCP is used, packets SHALL be sent on the first available channel RTCP is used, packets SHALL be sent on the first available channel
higher than the RTP channel. The channels are bi-directional and higher than the RTP channel. The channels are bi-directional and
therefore RTCP traffic are sent on the second channel in both direc- therefore RTCP traffic are sent on the second channel in both
tions. directions.
RTCP is needed for synchronization when two or more streams RTCP is needed for synchronization when two or more streams
are interleaved in such a fashion. Also, this provides a con- are interleaved in such a fashion. Also, this provides a
venient way to tunnel RTP/RTCP packets through the TCP control convenient way to tunnel RTP/RTCP packets through the TCP
connection when required by the network configuration and control connection when required by the network
transfer them onto UDP when possible. configuration and transfer them onto UDP when possible.
C->S: SETUP rtsp://foo.com/bar.file RTSP/1.0 C->S: SETUP rtsp://foo.com/bar.file RTSP/1.0
CSeq: 2 CSeq: 2
Transport: RTP/AVP/TCP;unicast;interleaved=0-1 Transport: RTP/AVP/TCP;unicast;interleaved=0-1
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 2 CSeq: 2
Date: 05 Jun 1997 18:57:18 GMT Date: 05 Jun 1997 18:57:18 GMT
Transport: RTP/AVP/TCP;unicast;interleaved=5-6 Transport: RTP/AVP/TCP;unicast;interleaved=5-6
Session: 12345678 Session: 12345678
skipping to change at page 1, line 2230 skipping to change at page 53, line 28
12.1.1 100 Continue 12.1.1 100 Continue
See, [H10.1.1]. See, [H10.1.1].
12.2 Success 2xx 12.2 Success 2xx
12.2.1 250 Low on Storage Space 12.2.1 250 Low on Storage Space
The server returns this warning after receiving a RECORD request that The server returns this warning after receiving a RECORD request that
it may not be able to fulfill completely due to insufficient storage it may not be able to fulfill completely due to insufficient storage
space. If possible, the server should use the Range header to indi- space. If possible, the server should use the Range header to
cate what time period it may still be able to record. Since other indicate what time period it may still be able to record. Since other
processes on the server may be consuming storage space simultane- processes on the server may be consuming storage space
ously, a client should take this only as an estimate. simultaneously, a client should take this only as an estimate.
12.3 Redirection 3xx 12.3 Redirection 3xx
The notation "3rr" indicates response codes from 300 to 399 inclusive The notation "3rr" indicates response codes from 300 to 399 inclusive
which are meant for redirection. The response code 304 is excluded which are meant for redirection. The response code 304 is excluded
from this set, as it is not used for redirection. from this set, as it is not used for redirection.
See [H10.3] for definition of status code 300 to 305. However com- See [H10.3] for definition of status code 300 to 305. However
ments are given for some to how they apply to RTSP. comments are given for some to how they apply to RTSP.
Within RTSP, redirection may be used for load balancing or redirect- Within RTSP, redirection may be used for load balancing or
ing stream requests to a server topologically closer to the client. redirecting stream requests to a server topologically closer to the
Mechanisms to determine topological proximity are beyond the scope of client. Mechanisms to determine topological proximity are beyond the
this specification. scope of this specification.
If the the Location header is used in a response it SHALL contain an |
absolute URI pointing out the media resource the client is redirected |
to, the URI SHALL NOT only contain the host name.
12.3.1 300 Multiple Choices 12.3.1 300 Multiple Choices
12.3.2 301 Moved Permanently 12.3.2 301 Moved Permanently
The request resource are moved permanently and resides now at the URI The request resource are moved permanently and resides now at the URI
given by the location header. The user client SHOULD redirect auto- given by the location header. The user client SHOULD redirect
matically to the given URI. This response MUST NOT contain a message- automatically to the given URI. This response MUST NOT contain a
body. message-body.
12.3.3 302 Found 12.3.3 302 Found
The requested resource reside temporarily at the URI given by the The requested resource reside temporarily at the URI given by the
Location header. The Location header MUST be included in the Location header. The Location header MUST be included in the
response. Is intended to be used for many types of temporary redi- response. Is intended to be used for many types of temporary
rects, e.g. load balancing. It is RECOMMENDED that one set the reason redirects, e.g. load balancing. It is RECOMMENDED that one set the
phrase to something more meaningful than "Found" in these cases. The reason phrase to something more meaningful than "Found" in these
user client SHOULD redirect automatically to the given URI. This cases. The user client SHOULD redirect automatically to the given
response MUST NOT contain a message-body. URI. This response MUST NOT contain a message-body.
12.3.4 303 See Other 12.3.4 303 See Other
This status code SHALL NOT be used in RTSP. However as it was allowed This status code SHALL NOT be used in RTSP. However as it was allowed
to use in RFC 2326 it is possible that such response may be received. to use in RFC 2326 it is possible that such response may be received.
12.3.5 304 Not Modified 12.3.5 304 Not Modified
If the client has performed a conditional DESCRIBE or SETUP (see If the client has performed a conditional DESCRIBE or SETUP (see
12.23) and the requested resource has not been modified, the server 12.23) and the requested resource has not been modified, the server
SHOULD send a 304 response. This response MUST NOT contain a message- SHOULD send a 304 response. This response MUST NOT contain a
body. message-body.
The response MUST include the following header fields: The response MUST include the following header fields:
+ Date o Date
+ ETag and/or Content-Location, if the header would have been sent o ETag and/or Content-Location, if the header would have been
in a 200 response to the same request. sent in a 200 response to the same request.
+ Expires, Cache-Control, and/or Vary, if the field-value might o Expires, Cache-Control, and/or Vary, if the field-value might
differ from that sent in any previous response for the same vari- differ from that sent in any previous response for the same
ant. variant.
This response is independent for the DESCRIBE and SETUP requests. This response is independent for the DESCRIBE and SETUP requests.
That is, a 304 response to DESCRIBE does NOT imply that the resource That is, a 304 response to DESCRIBE does NOT imply that the resource
content is unchanged and a 304 response to SETUP does NOT imply that content is unchanged and a 304 response to SETUP does NOT imply that
the resource description is unchanged. The ETag and If-Match headers the resource description is unchanged. The ETag and If-Match headers
may be used to link the DESCRIBE and SETUP in this manner. may be used to link the DESCRIBE and SETUP in this manner.
12.3.6 305 Use Proxy 12.3.6 305 Use Proxy
See [H10.3.6]. See [H10.3.6].
12.4 Client Error 4xx 12.4 Client Error 4xx
12.4.1 400 Bad Request 12.4.1 400 Bad Request
The request could not be understood by the server due to malformed The request could not be understood by the server due to malformed
syntax. The client SHOULD NOT repeat the request without modifica- syntax. The client SHOULD NOT repeat the request without
tions [H10.4.1]. If the request does not have a CSeq header, the modifications [H10.4.1]. If the request does not have a CSeq header,
server MUST NOT include a CSeq in the response. the server MUST NOT include a CSeq in the response.
12.4.2 405 Method Not Allowed 12.4.2 405 Method Not Allowed
The method specified in the request is not allowed for the resource The method specified in the request is not allowed for the resource
identified by the request URI. The response MUST include an Allow identified by the request URI. The response MUST include an Allow
header containing a list of valid methods for the requested resource. header containing a list of valid methods for the requested resource.
This status code is also to be used if a request attempts to use a This status code is also to be used if a request attempts to use a
method not indicated during SETUP, e.g., if a RECORD request is method not indicated during SETUP, e.g., if a RECORD request is
issued even though the mode parameter in the Transport header only issued even though the mode parameter in the Transport header only
specified PLAY. specified PLAY.
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contained in the request.When returning this error message the sender contained in the request.When returning this error message the sender
SHOULD return a entity body containing the offending parameter(s). SHOULD return a entity body containing the offending parameter(s).
12.4.4 452 reserved 12.4.4 452 reserved
This error code was removed from RFC 2326 [21] and is obsolete. This error code was removed from RFC 2326 [21] and is obsolete.
12.4.5 453 Not Enough Bandwidth 12.4.5 453 Not Enough Bandwidth
The request was refused because there was insufficient bandwidth. The request was refused because there was insufficient bandwidth.
This may, for example, be the result of a resource reservation fail- This may, for example, be the result of a resource reservation
ure. failure.
12.4.6 454 Session Not Found 12.4.6 454 Session Not Found
The RTSP session identifier in the Session header is missing, The RTSP session identifier in the Session header is missing,
invalid, or has timed out. invalid, or has timed out.
12.4.7 455 Method Not Valid in This State 12.4.7 455 Method Not Valid in This State
The client or server cannot process this request in its current The client or server cannot process this request in its current
state. The response SHOULD contain an Allow header to make error state. The response SHOULD contain an Allow header to make error
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Accept-Ranges header SHOULD be returned to inform the client of which Accept-Ranges header SHOULD be returned to inform the client of which
format(s) that are allowed. format(s) that are allowed.
12.4.9 457 Invalid Range 12.4.9 457 Invalid Range
The Range value given is out of bounds, e.g., beyond the end of the The Range value given is out of bounds, e.g., beyond the end of the
presentation. presentation.
12.4.10 458 Parameter Is Read-Only 12.4.10 458 Parameter Is Read-Only
The parameter to be set by SET_PARAMETER can be read but not modi- The parameter to be set by SET_PARAMETER can be read but not
fied. When returning this error message the sender SHOULD return a modified. When returning this error message the sender SHOULD return
entity body containing the offending parameter(s). a entity body containing the offending parameter(s).
12.4.11 459 Aggregate Operation Not Allowed 12.4.11 459 Aggregate Operation Not Allowed
The requested method may not be applied on the URL in question since The requested method may not be applied on the URL in question since
it is an aggregate (presentation) URL. The method may be applied on a it is an aggregate (presentation) URL. The method may be applied on a
media URL. media URL.
12.4.12 460 Only Aggregate Operation Allowed 12.4.12 460 Only Aggregate Operation Allowed
The requested method may not be applied on the URL in question since The requested method may not be applied on the URL in question since
it is not an aggregate control (presentation) URL. The method may be it is not an aggregate control (presentation) URL. The method may be
applied on the aggregate control URL. applied on the aggregate control URL.
12.4.13 461 Unsupported Transport 12.4.13 461 Unsupported Transport
The Transport field did not contain a supported transport specifica- The Transport field did not contain a supported transport
tion. specification.
12.4.14 462 Destination Unreachable 12.4.14 462 Destination Unreachable
The data transmission channel could not be established because the The data transmission channel could not be established because the
client address could not be reached. This error will most likely be client address could not be reached. This error will most likely be
the result of a client attempt to place an invalid Destination param- the result of a client attempt to place an invalid Destination
eter in the Transport field. parameter in the Transport field.
12.5 Server Error 5xx 12.5 Server Error 5xx
12.5.1 551 Option not supported 12.5.1 551 Option not supported
An feature-tag given in the Require or the Proxy-Require fields was An feature-tag given in the Require or the Proxy-Require fields was
not supported. The Unsupported header SHOULD be returned stating the not supported. The Unsupported header SHOULD be returned stating the
feature for which there is no support. feature for which there is no support.
13 Header Field Definitions 13 Header Field Definitions
The general syntax for header fields is covered in Section 4.2 This
section lists the full set of header fields along with notes on syn-
tax, meaning, and usage. Throughout this section, we use [HX.Y] to
refer to Section X.Y of the current HTTP/1.1 specification RFC 2616
[26]. Examples of each header field are given.
Information about header fields in relation to methods and proxy pro-
cessing is summarized in Table 4 and Table 5.
The "where" column describes the request and response types in which
the header field can be used. Values in this column are:
method direction object acronym Body method direction object acronym Body
----------------------------------------------- _________________________________________________
DESCRIBE C->S P,S DES r DESCRIBE C->S P,S DES r
GET_PARAMETER C->S, S->C P,S GPR R,r GET_PARAMETER C->S, S->C P,S GPR R,r
OPTIONS C->S P,S OPT OPTIONS C->S P,S OPT
S->C S->C
PAUSE C->S P,S PSE PAUSE C->S P,S PSE
PING C->S, S->C P,S PNG PING C->S, S->C P,S PNG
PLAY C->S P,S PLY PLAY C->S P,S PLY
REDIRECT S->C P,S RDR REDIRECT S->C P,S RDR
SETUP C->S S STP SETUP C->S S STP
SET_PARAMETER C->S, S->C P,S SPR R,r SET_PARAMETER C->S, S->C P,S SPR R,r
TEARDOWN C->S P,S TRD TEARDOWN C->S P,S TRD
Table 3: Overview of RTSP methods, their direction, and what objects Table 3: Overview of RTSP methods, their direction, and what objects
(P: presentation, S: stream) they operate on. Body notes if a method (P: presentation, S: stream) they operate on. Body notes if a method
is allowed to carry body and in which direction, R = Request, is allowed to carry body and in which direction, R = Request,
r=response. Note: It is allowed for all error messages 4xx and 5xx to r=response. Note: It is allowed for all error messages 4xx and 5xx to
have a body have a body
The general syntax for header fields is covered in Section 4.2 This
section lists the full set of header fields along with notes on
syntax, meaning, and usage. Throughout this section, we use [HX.Y]
to refer to Section X.Y of the current HTTP/1.1 specification RFC
2616 [26]. Examples of each header field are given.
Information about header fields in relation to methods and proxy
processing is summarized in Table 4 and Table 5.
The "where" column describes the request and response types in which
the header field can be used. Values in this column are:
R: header field may only appear in requests; R: header field may only appear in requests;
r: header field may only appear in responses; r: header field may only appear in responses;
2xx, 4xx, etc.: A numerical value or range indicates response codes 2xx, 4xx, etc.: A numerical value or range indicates response
with which the header field can be used; codes with which the header field can be used;
c: header field is copied from the request to the response. c: header field is copied from the request to the response.
An empty entry in the "where" column indicates that the header field An empty entry in the "where" column indicates that the header field
may be present in all requests and responses. may be present in all requests and responses.
The "proxy" column describes the operations a proxy may perform on a The "proxy" column describes the operations a proxy may perform on a
header field: header field:
a: A proxy can add or concatenate the header field if not present. a: A proxy can add or concatenate the header field if not
present.
m: A proxy can modify an existing header field value. m: A proxy can modify an existing header field value.
d: A proxy can delete a header field value. d: A proxy can delete a header field value.
r: A proxy must be able to read the header field, and thus this r: A proxy must be able to read the header field, and thus this
header field cannot be encrypted. header field cannot be encrypted.
The rest of the columns relate to the presence of a header field in a The rest of the columns relate to the presence of a header field in a
method. The method names when abbreviated, are according to table 3: method. The method names when abbreviated, are according to table 3:
c: Conditional; requirements on the header field depend on the con- c: Conditional; requirements on the header field depend on the
text of the message. context of the message.
m: The header field is mandatory. m: The header field is mandatory.
m*: The header field SHOULD be sent, but clients/servers need to be m*: The header field SHOULD be sent, but clients/servers need to
prepared to receive messages without that header field. be prepared to receive messages without that header field.
o: The header field is optional. o: The header field is optional.
*: The header field is required if the message body is not empty. *: The header field is required if the message body is not
See sections 13.14, 13.16 and 4.3 for details. empty. See sections 13.14, 13.16 and 4.3 for details.
-: The header field is not applicable. -: The header field is not applicable.
"Optional" means that a Client/Server MAY include the header field in "Optional" means that a Client/Server MAY include the header field in
a request or response, and a Client/Server MAY ignore the header a request or response, and a Client/Server MAY ignore the header
field if present in the request or response (The exception to this field if present in the request or response (The exception to this
rule is the Require header field discussed in 13.32). A "mandatory" rule is the Require header field discussed in 13.32). A "mandatory"
header field MUST be present in a request, and MUST be understood by header field MUST be present in a request, and MUST be understood by
the Client/Server receiving the request. A mandatory response header the Client/Server receiving the request. A mandatory response header
field MUST be present in the response, and the header field MUST be field MUST be present in the response, and the header field MUST be
understood by the Client/Server processing the response. "Not appli- understood by the Client/Server processing the response. "Not
cable" means that the header field MUST NOT be present in a request. applicable" means that the header field MUST NOT be present in a
If one is placed in a request by mistake, it MUST be ignored by the request. If one is placed in a request by mistake, it MUST be ignored
Client/Server receiving the request. Similarly, a header field by the Client/Server receiving the request. Similarly, a header field
labeled "not applicable" for a response means that the Client/Server labeled "not applicable" for a response means that the Client/Server
MUST NOT place the header field in the response, and the MUST NOT place the header field in the response, and the
Client/Server MUST ignore the header field in the response. Client/Server MUST ignore the header field in the response.
A Client/Server SHOULD ignore extension header parameters that are A Client/Server SHOULD ignore extension header parameters that are
not understood. not understood.
The From, Location, and RTP-Info header fields contain a URI. If the The From, Location, and RTP-Info header fields contain a URI. If the
URI contains a comma, or semicolon, the URI MUST be enclosed in dou- URI contains a comma, or semicolon, the URI MUST be enclosed in
ble quotas ("). Any URI parameters are contained within these quotas. double quotas ("). Any URI parameters are contained within these
If the URI is not enclosed in double quotas, any semicolon- delimited quotas. If the URI is not enclosed in double quotas, any semicolon-
parameters are header-parameters, not URI parameters. delimited parameters are header-parameters, not URI parameters.
13.1 Accept 13.1 Accept
The Accept request-header field can be used to specify certain pre- The Accept request-header field can be used to specify certain
sentation description content types which are acceptable for the presentation description content types which are acceptable for the
response. response.
The "level" parameter for presentation descriptions is
properly defined as part of the MIME type registration, not
here.
See [H14.1] for syntax.
Example of use:
Accept: application/rtsl q=1.0, application/sdp;level=2
13.2 Accept-Encoding
See [H14.3]
13.3 Accept-Language
See [H14.4]. Note that the language specified applies to the
presentation description and any reason phrases, not the media
content.
13.4 Accept-Ranges
The Accept-Ranges response-header field allows the server to indicate
its acceptance of range requests and possible formats for a resource: |
Accept-Ranges = "Accept-Ranges" ":" acceptable-ranges |
acceptable-ranges = 1#range-unit / "none" |
range-unit = NPT / SMPTE / UTC / extension-format |
extension-format = token |
This header has the same syntax as [H14.5]. However new range-units |
are defined. Inclusion of any of the time formats indicates |
acceptance by the server for PLAY and PAUSE requests with this |
format. The headers value is valid for the resource specified by the |
URI in the request, this response corresponds to. A server is SHOULD |
to use this header in SETUP responses to indicate to the client which |
range time formats the media supports. The header SHOULD also be |
included in "456" responses which is a result of use of unsupported |
range formats. |
13.5 Allow
The Allow entity-header field lists the methods supported by the
resource identified by the request-URI. The purpose of this field is
to strictly inform the recipient of valid methods associated with the
resource. An Allow header field MUST be present in a 405 (Method Not
Allowed) response. See [H14.7] for syntax definition.
Example of use:
Allow: SETUP, PLAY, SET_PARAMETER
13.6 Authorization
See [H14.8]
13.7 Bandwidth
The Bandwidth request-header field describes the estimated bandwidth
available to the client, expressed as a positive integer and measured
in bits per second. The bandwidth available to the client may change
during an RTSP session, e.g., due to modem retraining.
Bandwidth = "Bandwidth" ":" 1*DIGIT
Example:
Header Where Proxy DES OPT SETUP PLAY PAUSE TRD Header Where Proxy DES OPT SETUP PLAY PAUSE TRD
-------------------------------------------------------------- _____________________________________________________________
Accept R o - - - - - Accept R o - - - - -
Accept-Encoding R r o - - - - - Accept-Encoding R r o - - - - -
Accept-Language R r o - - - - - Accept-Language R r o - - - - -
Accept-Ranges r r - - o - - - Accept-Ranges r r - - o - - -
Accept-Ranges 456 r - - - o o - Accept-Ranges 456 r - - - o o -
Allow r - o - - - - Allow r - o - - - -
Allow 405 - - - m m - Allow 405 - - - m m -
Authorization R o o o o o o Authorization R o o o o o o
Bandwidth R o o o o - - Bandwidth R o o o o - -
Blocksize R o - o o - - Blocksize R o - o o - -
skipping to change at page 1, line 2537 skipping to change at page 61, line 37
Content-Length r r * - - - - - Content-Length r r * - - - - -
Content-Length 4xx r * * * * * * Content-Length 4xx r * * * * * *
Content-Location r o - - - - - Content-Location r o - - - - -
Content-Location 4xx o o o o o o Content-Location 4xx o o o o o o
Content-Type r * - - - - - Content-Type r * - - - - -
Content-Type 4xx * * * * * * Content-Type 4xx * * * * * *
CSeq Rc m m m m m m CSeq Rc m m m m m m
Date am o o o o o o Date am o o o o o o
Expires r r o - - - - - Expires r r o - - - - -
From R r o o o o o o From R r o o o o o o
Host o o o o o o Host - - - - - -
If-Match R r - - o - - - If-Match R r - - o - - -
If-Modified-Since R r o - o - - - If-Modified-Since R r o - o - - -
Last-Modified r r o - - - - - Last-Modified r r o - - - - -
Location 3rr o o o o o o Location 3rr o o o o o o
Proxy-Authenticate 407 amr m m m m m m Proxy-Authenticate 407 amr m m m m m m
Proxy-Require R ar o o o o o o Proxy-Require R ar o o o o o o
Public r admr - m* - - - - Public r admr - m* - - - -
Public 501 admr m* m* m* m* m* m* Public 501 admr m* m* m* m* m* m*
Range R - - - o o - Range R - - - o o -
Range r - - c m* m* - Range r - - c m* m* -
Referer R o o o o o o Referer R o o o o o o
Require R o o o o o o Require R o o o o o o
Retry-After 3rr,503 o o o - - - Retry-After 3rr,503 o o o - - -
RTP-Info r - - o m - -
Header Where Proxy DES OPT SETUP PLAY PAUSE TRD Header Where Proxy DES OPT SETUP PLAY PAUSE TRD
---------------------------------------------------------- _________________________________________________________
Scale - - - o - - Scale - - - o - -
Session R - o o m m m Session R - o o m m m
Session r - c m m m o Session r - c m m m o
Server R - o - - - - Server R - o - - - -
Server r o o o o o o Server r o o o o o o
Speed - - - o - - Speed - - - o - -
Supported R o o o o o o Supported R o o o o o o
Supported r c c c c c c Supported r c c c c c c
Timestamp R o o o o o o Timestamp R o o o o o o
Timestamp c m m m m m m Timestamp c m m m m m m
Transport - - m - - - Transport - - m - - -
Unsupported r c c c c c c Unsupported r c c c c c c
User-Agent R m* m* m* m* m* m* User-Agent R m* m* m* m* m* m*
Vary r c c c c c c Vary r c c c c c c
Via R amr o o o o o o Via R amr o o o o o o
Via c dr m m m m m m Via c dr m m m m m m
WWW-Authenticate 401 m m m m m m WWW-Authenticate 401 m m m m m m
----------------------------------------------------------
_________________________________________________________
Header Where Proxy DES OPT SETUP PLAY PAUSE TRD Header Where Proxy DES OPT SETUP PLAY PAUSE TRD
Table 4: Overview of RTSP header fields related to methods DESCRIBE, Table 4: Overview of RTSP header fields related to methods DESCRIBE,
OPTIONS, SETUP, PLAY, PAUSE, and TEARDOWN. OPTIONS, SETUP, PLAY, PAUSE, and TEARDOWN.
The "level" parameter for presentation descriptions is prop- Bandwidth: 4000
erly defined as part of the MIME type registration, not here.
See [H14.1] for syntax. 13.8 Blocksize
Example of use: The Blocksize request-header field is sent from the client to the
media server asking the server for a particular media packet size.
This packet size does not include lower-layer headers such as IP,
UDP, or RTP. The server is free to use a blocksize which is lower
than the one requested. The server MAY truncate this packet size to
the closest multiple of the minimum, media-specific block size, or
override it with the media-specific size if necessary. The block size
MUST be a positive decimal number, measured in octets. The server
only returns an error
Accept: application/rtsl q=1.0, application/sdp;level=2 (400) if the value is syntactically invalid.
Blocksize = "Blocksize" ":" 1*DIGIT
Header Where Proxy GPR SPR RDR PNG Header Where Proxy GPR SPR RDR PNG
----------------------------------------------------- __________________________________________________
Allow 405 - - - - Allow 405 - - - -
Authorization R o o o o Authorization R o o o o
Bandwidth R - o - - Bandwidth R - o - -
Blocksize R - o - - Blocksize R - o - -
Connection o o o - Connection o o o - Content-
Content-Base R o o - - Base R o o - - Content-
Content-Base r o o - - Base r o o - - Content-
Content-Base 4xx o o o - Base 4xx o o o - Content-
Content-Encoding R r o o - - Encoding R r o o - - Content-
Content-Encoding r r o o - - Encoding r r o o - - Content-
Content-Encoding 4xx r o o o - Encoding 4xx r o o o - Content-
Content-Language R r o o - - Language R r o o - - Content-
Content-Language r r o o - - Language r r o o - - Content-
Content-Language 4xx r o o o - Language 4xx r o o o - Content-
Content-Length R r * * - - Length R r * * - - Content-
Content-Length r r * * - - Length r r * * - - Content-
Content-Length 4xx r * * * - Length 4xx r * * * - Content-
Content-Location R o o - - Location R o o - - Content-
Content-Location r o o - - Location r o o - - Content-
Content-Location 4xx o o o - Location 4xx o o o - Content-
Content-Type R * * - - Type R * * - - Content-
Content-Type r * * - - Type r * * - - Content-
Content-Type 4xx * * * - Type 4xx * * * -
CSeq Rc m m m m CSeq Rc m m m m
Date am o o o o Date am o o o o
From R r o o o o From R r o o o o
Host o o o o Host - - - - Last-
Last-Modified R r - - - - Modified R r - - - - Last-
Last-Modified r r o - - - Modified r r o - - -
Location 3rr o o o o Location 3rr o o o o
Location R - - m - Location R - - m - Proxy-
Proxy-Authenticate 407 amr m m m m Authenticate 407 amr m m m m Proxy-
Proxy-Require R ar o o o o Require R ar o o o o
Public 501 admr m* m* m* m* Public 501 admr m* m* m* m*
Range R - - o - Range R - - o -
Referer R o o o - Referer R o o o -
Require R o o o o Require R o o o o Retry-
Retry-After 3rr,503 o o - - After 3rr,503 o o - -
Scale - - - - Scale - - - -
Session R o o o m Session R o o o m
Session r c c o m Session r c c o m
Server R o o o o Server R o o o o
Server r o o - o Server r o o - o
Supported R o o o o
Supported r c c c c
Timestamp R o o o o Timestamp R o o o o
Timestamp c m m m m Timestamp c m m m m
Unsupported r c c c c Unsupported r c c c c User-
User-Agent R m* m* - m* Agent R m* m* - m* User-
User-Agent r - - m* - Agent r - - m* -
Vary r c c - - Vary r c c - -
Via R amr o o o o Via R amr o o o o
Via c dr m m m m Via c dr m m m m WWW-
WWW-Authenticate 401 m m m m Authenticate 401 m m m m
----------------------------------------------------- __________________________________________________
Header Where Proxy GPR SPR RDR PNG Header Where Proxy GPR SPR RDR PNG
Table 5: Overview of RTSP header fields related to methods GET_PARAM- Table 5: Overview of RTSP header fields related to methods
ETER, SET_PARAMETER,REDIRECT, and PING. GET_PARAMETER, SET_PARAMETER,REDIRECT, and PING.
13.2 Accept-Encoding
See [H14.3]
13.3 Accept-Language
See [H14.4]. Note that the language specified applies to the presen-
tation description and any reason phrases, not the media content.
13.4 Accept-Ranges
The Accept-Ranges response-header field allows the server to indicate
its acceptance of range requests and possible formats for a resource: |
Accept-Ranges = "Accept-Ranges" ":" acceptable-ranges ||
acceptable-ranges = 1#range-unit / "none" ||
range-unit = NPT / SMPTE / UTC / LIVE / extension-format ||
extension-format = token ||
This header has the same syntax as [H14.5]. However new range-units
are defined and byte-ranges SHALL NOT be used. Inclusion of any of
the three time formats indicates acceptance by the server for PLAY
and PAUSE requests with this format. Inclusion of the "LIVE" tag
indicates that the resource has LIVE properties. The headers value is
valid for the resource specified by the URI in the request, this
response corresponds to.
A server is RECOMMENDED to use this header in SETUP responses to
indicate to the client which range time formats the media supports.
The header SHOULD also be included in "456" responses which is a
result of use of unsupported range formats.
13.5 Allow
The Allow entity-header field lists the methods supported by the
resource identified by the request-URI. The purpose of this field is
to strictly inform the recipient of valid methods associated with the
resource. An Allow header field MUST be present in a 405 (Method Not
Allowed) response. See [H14.7] for syntax definition.
Example of use:
Allow: SETUP, PLAY, SET_PARAMETER
13.6 Authorization
See [H14.8]
13.7 Bandwidth
The Bandwidth request-header field describes the estimated bandwidth
available to the client, expressed as a positive integer and measured
in bits per second. The bandwidth available to the client may change
during an RTSP session, e.g., due to modem retraining.
Bandwidth = "Bandwidth" ":" 1*DIGIT
Example:
Bandwidth: 4000
13.8 Blocksize
The Blocksize request-header field is sent from the client to the
media server asking the server for a particular media packet size.
This packet size does not include lower-layer headers such as IP,
UDP, or RTP. The server is free to use a blocksize which is lower
than the one requested. The server MAY truncate this packet size to
the closest multiple of the minimum, media-specific block size, or
override it with the media-specific size if necessary. The block size
MUST be a positive decimal number, measured in octets. The server
only returns an error
(400) if the value is syntactically invalid.
Blocksize = "Blocksize" ":" 1*DIGIT
13.9 Cache-Control 13.9 Cache-Control
The Cache-Control general-header field is used to specify directives The Cache-Control general-header field is used to specify directives
that MUST be obeyed by all caching mechanisms along the that MUST be obeyed by all caching mechanisms along the
request/response chain. request/response chain.
Cache directives must be passed through by a proxy or gateway appli- Cache directives must be passed through by a proxy or gateway
cation, regardless of their significance to that application, since application, regardless of their significance to that application,
the directives may be applicable to all recipients along the since the directives may be applicable to all recipients along the
request/response chain. It is not possible to specify a cache-direc- request/response chain. It is not possible to specify a cache-
tive for a specific cache. directive for a specific cache.
Cache-Control should only be specified in a SETUP request and its Cache-Control should only be specified in a SETUP request and its
response. Note: Cache-Control does not govern the caching of response. Note: Cache-Control does not govern the caching of
responses as for HTTP, but rather of the stream identified by the responses as for HTTP, but rather of the stream identified by the
SETUP request. Responses to RTSP requests are not cacheable, except SETUP request. Responses to RTSP requests are not cacheable, except
for responses to DESCRIBE. for responses to DESCRIBE.
Cache-Control = "Cache-Control" ":" 1#cache-directive Cache-Control = "Cache-Control" ":" 1#cache-directive
cache-directive = cache-request-directive cache-directive = cache-request-directive
/ cache-response-directive / cache-response-directive
skipping to change at page 1, line 2760 skipping to change at page 65, line 10
cache-response-directive = "public" cache-response-directive = "public"
/ "private" / "private"
/ "no-cache" / "no-cache"
/ "no-transform" / "no-transform"
/ "must-revalidate" / "must-revalidate"
/ "proxy-revalidate" / "proxy-revalidate"
/ "max-age" "=" delta-seconds / "max-age" "=" delta-seconds
/ cache-extension / cache-extension
cache-extension = token [ "=" ( token / quoted-string ) ] cache-extension = token [ "=" ( token / quoted-string ) ]
delta-seconds = 1*DIGIT delta-seconds = 1*DIGIT
no-cache: Indicates that the media stream MUST NOT be cached any-
where. This allows an origin server to prevent caching even by
caches that have been configured to return stale responses to
client requests.
public: Indicates that the media stream is cacheable by any cache. no-cache: Indicates that the media stream MUST NOT be cached
anywhere. This allows an origin server to prevent caching
even by caches that have been configured to return stale
responses to client requests.
private: Indicates that the media stream is intended for a single public: Indicates that the media stream is cacheable by any
user and MUST NOT be cached by a shared cache. A private (non- cache.
shared) cache may cache the media stream.
no-transform: An intermediate cache (proxy) may find it useful to private: Indicates that the media stream is intended for a
convert the media type of a certain stream. A proxy might, for single user and MUST NOT be cached by a shared cache. A
example, convert between video formats to save cache space or private (non-shared) cache may cache the media stream.
to reduce the amount of traffic on a slow link. Serious opera-
tional problems may occur, however, when these transformations
have been applied to streams intended for certain kinds of
applications. For example, applications for medical imaging,
scientific data analysis and those using end-to-end authenti-
cation all depend on receiving a stream that is bit-for-bit
identical to the original entity-body. Therefore, if a
response includes the no-transform directive, an intermediate
cache or proxy MUST NOT change the encoding of the stream.
Unlike HTTP, RTSP does not provide for partial transformation
at this point, e.g., allowing translation into a different
language.
only-if-cached: In some cases, such as times of extremely poor net- no-transform: An intermediate cache (proxy) may find it useful
work connectivity, a client may want a cache to return only to convert the media type of a certain stream. A proxy
those media streams that it currently has stored, and not to might, for example, convert between video formats to save
receive these from the origin server. To do this, the client cache space or to reduce the amount of traffic on a slow
may include the only-if-cached directive in a request. If it link. Serious operational problems may occur, however, when
receives this directive, a cache SHOULD either respond using a these transformations have been applied to streams intended
cached media stream that is consistent with the other con- for certain kinds of applications. For example,
straints of the request, or respond with a 504 (Gateway Time- applications for medical imaging, scientific data analysis
out) status. However, if a group of caches is being operated and those using end-to-end authentication all depend on
as a unified system with good internal connectivity, such a receiving a stream that is bit-for-bit identical to the
request MAY be forwarded within that group of caches. original entity-body. Therefore, if a response includes the
no-transform directive, an intermediate cache or proxy MUST
NOT change the encoding of the stream. Unlike HTTP, RTSP
does not provide for partial transformation at this point,
e.g., allowing translation into a different language.
max-stale: Indicates that the client is willing to accept a media only-if-cached: In some cases, such as times of extremely poor
stream that has exceeded its expiration time. If max-stale is network connectivity, a client may want a cache to return
assigned a value, then the client is willing to accept a only those media streams that it currently has stored, and
response that has exceeded its expiration time by no more than not to receive these from the origin server. To do this,
the specified number of seconds. If no value is assigned to the client may include the only-if-cached directive in a
max-stale, then the client is willing to accept a stale request. If it receives this directive, a cache SHOULD
response of any age. either respond using a cached media stream that is
consistent with the other constraints of the request, or
respond with a 504 (Gateway Timeout) status. However, if a
group of caches is being operated as a unified system with
good internal connectivity, such a request MAY be forwarded
within that group of caches.
min-fresh: Indicates that the client is willing to accept a media max-stale: Indicates that the client is willing to accept a
stream whose freshness lifetime is no less than its current media stream that has exceeded its expiration time. If
age plus the specified time in seconds. That is, the client max-stale is assigned a value, then the client is willing
wants a response that will still be fresh for at least the to accept a response that has exceeded its expiration time
specified number of seconds. by no more than the specified number of seconds. If no
value is assigned to max-stale, then the client is willing
to accept a stale response of any age.
must-revalidate: When the must-revalidate directive is present in a min-fresh: Indicates that the client is willing to accept a
SETUP response received by a cache, that cache MUST NOT use media stream whose freshness lifetime is no less than its
the entry after it becomes stale to respond to a subsequent current age plus the specified time in seconds. That is,
request without first revalidating it with the origin server. the client wants a response that will still be fresh for at
That is, the cache must do an end-to-end revalidation every least the specified number of seconds.
time, if, based solely on the origin server's Expires, the
cached response is stale.)
proxy-revalidate: The proxy-revalidate directive has the same mean- must-revalidate: When the must-revalidate directive is present
ing as the must-revalidate directive, except that it does not in a SETUP response received by a cache, that cache MUST
apply to non-shared user agent caches. It can be used on a NOT use the entry after it becomes stale to respond to a
response to an authenticated request to permit the user's subsequent request without first revalidating it with the
cache to store and later return the response without needing origin server. That is, the cache must do an end-to-end
to revalidate it (since it has already been authenticated once revalidation every time, if, based solely on the origin
by that user), while still requiring proxies that service many server's Expires, the cached response is stale.)
users to revalidate each time (in order to make sure that each
user has been authenticated). Note that such authenticated
responses also need the public cache control directive in
order to allow them to be cached at all.
max-age: When an intermediate cache is forced, by means of a max- proxy-revalidate: The proxy-revalidate directive has the same
age=0 directive, to revalidate its own cache entry, and the meaning as the must-revalidate directive, except that it
client has supplied its own validator in the request, the sup- does not apply to non-shared user agent caches. It can be
plied validator might differ from the validator currently used on a response to an authenticated request to permit
stored with the cache entry. In this case, the cache MAY use the user's cache to store and later return the response
either validator in making its own request without affecting without needing to revalidate it (since it has already been
semantic transparency. authenticated once by that user), while still requiring
proxies that service many users to revalidate each time (in
order to make sure that each user has been authenticated).
Note that such authenticated responses also need the public
cache control directive in order to allow them to be cached
at all.
However, the choice of validator might affect performance. The max-age: When an intermediate cache is forced, by means of a
best approach is for the intermediate cache to use its own max-age=0 directive, to revalidate its own cache entry, and
validator when making its request. If the server replies with the client has supplied its own validator in the request,
304 (Not Modified), then the cache can return its now vali- the supplied validator might differ from the validator
dated copy to the client with a 200 (OK) response. If the currently stored with the cache entry. In this case, the
server replies with a new entity and cache validator, however, cache MAY use either validator in making its own request
the intermediate cache can compare the returned validator with without affecting semantic transparency.
the one provided in the client's request, using the strong
comparison function. If the client's validator is equal to the However, the choice of validator might affect performance.
origin server's, then the intermediate cache simply returns The best approach is for the intermediate cache to use its
304 (Not Modified). Otherwise, it returns the new entity with own validator when making its request. If the server
a 200 (OK) response. replies with 304 (Not Modified), then the cache can return
its now validated copy to the client with a 200 (OK)
response. If the server replies with a new entity and cache
validator, however, the intermediate cache can compare the
returned validator with the one provided in the client's
request, using the strong comparison function. If the
client's validator is equal to the origin server's, then
the intermediate cache simply returns 304 (Not Modified).
Otherwise, it returns the new entity with a 200 (OK)
response.
13.10 Connection 13.10 Connection
See [H14.10]. The use of the connection option "close" in RTSP mes- See [H14.10]. The use of the connection option "close" in RTSP
sages SHOULD be limited to error messages when the server is unable messages SHOULD be limited to error messages when the server is
to recover and therefore see it necessary to close the connection. unable to recover and therefore see it necessary to close the
The reason is that the client shall have the choice of continue using connection. The reason is that the client shall have the choice of
a connection indefinitely as long as it sends valid messages. continue using a connection indefinitely as long as it sends valid
messages.
13.11 Content-Base 13.11 Content-Base
The Content-Base entity-header field may be used to specify the base The Content-Base entity-header field may be used to specify the base
URI for resolving relative URLs within the entity. URI for resolving relative URLs within the entity.
Content-Base = "Content-Base" ":" absoluteURI Content-Base = "Content-Base" ":" absoluteURI
If no Content-Base field is present, the base URI of an entity is If no Content-Base field is present, the base URI of an entity is
defined either by its Content-Location (if that Content-Location URI defined either by its Content-Location (if that Content-Location URI
skipping to change at page 1, line 2907 skipping to change at page 68, line 21
See [H14.17]. Note that the content types suitable for RTSP are See [H14.17]. Note that the content types suitable for RTSP are
likely to be restricted in practice to presentation descriptions and likely to be restricted in practice to presentation descriptions and
parameter-value types. parameter-value types.
13.17 CSeq 13.17 CSeq
The CSeq general-header field specifies the sequence number for an The CSeq general-header field specifies the sequence number for an
RTSP request-response pair. This field MUST be present in all RTSP request-response pair. This field MUST be present in all
requests and responses. For every RTSP request containing the given requests and responses. For every RTSP request containing the given
sequence number, the corresponding response will have the same num- sequence number, the corresponding response will have the same
ber. Any retransmitted request must contain the same sequence number number. Any retransmitted request must contain the same sequence
as the original (i.e. the sequence number is not incremented for number as the original (i.e. the sequence number is not incremented
retransmissions of the same request). For each new RTSP request the for retransmissions of the same request). For each new RTSP request
CSeq value SHALL be incremented by one. The initial sequence number the CSeq value SHALL be incremented by one. The initial sequence
MAY be any number. Each sequence number series is unique between each number MAY be any number. Each sequence number series is unique
requester and responder, i.e. the client has one series for its between each requester and responder, i.e. the client has one series
request to a server and the server has another when sending request for its request to a server and the server has another when sending
to the client. Each requester and responder is identified with its request to the client. Each requester and responder is identified
network address. with its network address.
CSeq = "Cseq" ":" 1*DIGIT CSeq = "Cseq" ":" 1*DIGIT
13.18 Date 13.18 Date
See [H14.18]. An RTSP message containing a body MUST include a Date See [H14.18]. An RTSP message containing a body MUST include a Date
header if the sending host has a clock. Servers SHOULD include a Date header if the sending host has a clock. Servers SHOULD include a Date
header in all other RTSP messages. header in all other RTSP messages.
13.19 Expires 13.19 Expires
The Expires entity-header field gives a date and time after which the The Expires entity-header field gives a date and time after which the
description or media-stream should be considered stale. The interpre- description or media-stream should be considered stale. The
tation depends on the method: interpretation depends on the method:
DESCRIBE response: The Expires header indicates a date and time DESCRIBE response: The Expires header indicates a date and time
after which the description should be considered stale. after which the description should be considered stale.
A stale cache entry may not normally be returned by a cache (either a A stale cache entry may not normally be returned by a cache (either a
proxy cache or an user agent cache) unless it is first validated with proxy cache or an user agent cache) unless it is first validated with
the origin server (or with an intermediate cache that has a fresh the origin server (or with an intermediate cache that has a fresh
copy of the entity). See section 14 for further discussion of the copy of the entity). See section 14 for further discussion of the
expiration model. expiration model.
skipping to change at page 1, line 2976 skipping to change at page 69, line 44
time in the future on a media stream that otherwise would by default time in the future on a media stream that otherwise would by default
be non-cacheable indicates that the media stream is cacheable, unless be non-cacheable indicates that the media stream is cacheable, unless
indicated otherwise by a Cache-Control header field (Section 13.9). indicated otherwise by a Cache-Control header field (Section 13.9).
13.20 From 13.20 From
See [H14.22]. See [H14.22].
13.21 Host 13.21 Host
The Host HTTP request header field [H14.23] is not needed for RTSP. The Host HTTP request header field [H14.23] is not needed for RTSP, |
It should be silently ignored if sent. and SHALL NOT be sent. It SHALL be silently ignored if received.
13.22 If-Match 13.22 If-Match
See [H14.24]. See [H14.24].
The If-Match request-header field is especially useful for ensuring The If-Match request-header field is especially useful for ensuring
the integrity of the presentation description, in both the case where the integrity of the presentation description, in both the case where
it is fetched via means external to RTSP (such as HTTP), or in the it is fetched via means external to RTSP (such as HTTP), or in the
case where the server implementation is guaranteeing the integrity of case where the server implementation is guaranteeing the integrity of
the description between the time of the DESCRIBE message and the the description between the time of the DESCRIBE message and the
skipping to change at page 1, line 3021 skipping to change at page 71, line 4
which the origin server believes the presentation description or which the origin server believes the presentation description or
media stream was last modified. See [H14.29]. For the methods media stream was last modified. See [H14.29]. For the methods
DESCRIBE, the header field indicates the last modification date and DESCRIBE, the header field indicates the last modification date and
time of the description, for SETUP that of the media stream. time of the description, for SETUP that of the media stream.
13.25 Location 13.25 Location
See [H14.30]. See [H14.30].
13.26 Proxy-Authenticate 13.26 Proxy-Authenticate
See [H14.33]. See [H14.33].
13.27 Proxy-Require 13.27 Proxy-Require
The Proxy-Require request-header field is used to indicate proxy-sen- The Proxy-Require request-header field is used to indicate proxy- |
sitive features that MUST be supported by the proxy. Any Proxy- sensitive features that MUST be supported by the proxy. Any Proxy- |
Require header features that are not supported by the proxy MUST be Require header features that are not supported by the proxy MUST be |
negatively acknowledged by the proxy to the client using the Unsup- negatively acknowledged by the proxy to the client using the |
ported header. Servers should treat this field identically to the Unsupported header. Any feature tag included in the Proxy-Require |
Require field, i.e. the Proxy-Require requirements does also apply to does not apply to the server. To ensure that a feature is supported |
the server. by both proxies and servers the tag must be included in also a |
Require header.
See Section 13.32 for more details on the mechanics of this message See Section 13.32 for more details on the mechanics of this message
and a usage example. and a usage example.
Proxy-Require = "Proxy-Require" ":" 1#feature-tag Proxy-Require = "Proxy-Require" ":" 1#feature-tag |
Example of use: Example of use: |
Proxy-Require: play.basic, con.persistent Proxy-Require: play.basic |
13.28 Public 13.28 Public
The Public response-header field lists the set of methods supported The Public response-header field lists the set of methods supported
by the server. The purpose of this field is strictly to inform the by the server. The purpose of this field is strictly to inform the
recipient of the capabilities of the server regarding unusual meth- recipient of the capabilities of the server regarding unusual
ods. The methods listed may or may not be applicable to the Request- methods. The methods listed may or may not be applicable to the
URI; the Allow header field (section 14.7) MAY be used to indicate Request-URI; the Allow header field (section 14.7) MAY be used to
methods allowed for a particular URI. indicate methods allowed for a particular URI.
Public = "Public" ":" 1#method Public = "Public" ":" 1#method
Example of use: Example of use:
Public: OPTIONS, SETUP, PLAY, PAUSE, TEARDOWN Public: OPTIONS, SETUP, PLAY, PAUSE, TEARDOWN
This header field applies only to the server directly connected to This header field applies only to the server directly connected to the
the client (i.e., the nearest neighbor in a chain of connections). client (i.e., the nearest neighbor in a chain of connections). If the
If the response passes through a proxy, the proxy MUST either remove response passes through a proxy, the proxy MUST either remove the Public
the Public header field or replace it with one applicable to its own header field or replace it with one applicable to its own capabilities.
capabilities.
13.29 Range 13.29 Range
The Range request and response header field specifies a range of The Range request and response header field specifies a range of
time. The range can be specified in a number of units. This specifi- time. The range can be specified in a number of units. This
cation defines the smpte (Section 3.4), npt (Section 3.5), and clock specification defines the smpte (Section 3.4), npt (Section 3.5), and
(Section 3.6) range units. Within RTSP, byte ranges [H14.35.1] are | clock (Section 3.6) range units. Within RTSP, byte ranges [H14.35.1]
normally not meaningful. The header MAY contain a time parameter in | are normally not meaningful. The header MAY contain a time parameter
UTC, specifying the time at which the operation is to be made | in UTC, specifying the time at which the operation is to be made
effective. This functionality SHALL only be used with the REDIRECT | effective. This functionality SHALL only be used with the REDIRECT
method. Servers supporting the Range header MUST understand the NPT method. Servers supporting the Range header MUST understand the NPT
range format and SHOULD understand the SMPTE range format. The Range range format and SHOULD understand the SMPTE range format. The Range
response header indicates what range of time is actually being response header indicates what range of time is actually being
played. If the Range header is given in a time format that is not played. If the Range header is given in a time format that is not
understood, the recipient should return 501 (Not Implemented). understood, the recipient should return 501 (Not Implemented).
Ranges are half-open intervals, including the first point, but Ranges are half-open intervals, including the first point, but
excluding the second point. In other words, a range of A-B starts excluding the second point. In other words, a range of A-B starts
exactly at time A, but stops just before B. Only the start time of a exactly at time A, but stops just before B. Only the start time of a
media unit such as a video or audio frame is relevant. As an example, media unit such as a video or audio frame is relevant. As an example,
skipping to change at page 1, line 3097 skipping to change at page 72, line 43
would exclude the frame at 10.08. would exclude the frame at 10.08.
Range = "Range" ":" 1#ranges-specifier [ ";" "time" "=" utc-time ] Range = "Range" ":" 1#ranges-specifier [ ";" "time" "=" utc-time ]
ranges-specifier = npt-range / utc-range / smpte-range ranges-specifier = npt-range / utc-range / smpte-range
Example: Example:
Range: clock=19960213T143205Z-;time=19970123T143720Z Range: clock=19960213T143205Z-;time=19970123T143720Z
The notation is similar to that used for the HTTP/1.1 [26] The notation is similar to that used for the HTTP/1.1 [26]
byte-range header. It allows clients to select an excerpt from byte-range header. It allows clients to select an excerpt
the media object, and to play from a given point to the end as from the media object, and to play from a given point to
well as from the current location to a given point. The start the end as well as from the current location to a given
of playback can be scheduled for any time in the future, point. The start of playback can be scheduled for any time
although a server may refuse to keep server resources for in the future, although a server may refuse to keep server
extended idle periods. resources for extended idle periods.
By default, range intervals increase, where the second point is By default, range intervals increase, where the second point is
larger than the first point. larger than the first point.
Example: Example:
Range: npt=10-15 Range: npt=10-15
However, range intervals can also decrease if the Scale header (see However, range intervals can also decrease if the Scale header (see
section 13.34) indicates a negative scale value. For example, this section 13.34) indicates a negative scale value. For example, this
skipping to change at page 1, line 3155 skipping to change at page 74, line 19
13.32 Require 13.32 Require
The Require request-header field is used by clients or servers to The Require request-header field is used by clients or servers to
ensure that the other end-point supports features that are required ensure that the other end-point supports features that are required
in respect to this request. It can also be used to query if the in respect to this request. It can also be used to query if the
other end-point supports certain features, however the use of the other end-point supports certain features, however the use of the
Supported (Section 13.38) is much more effective in this purpose. Supported (Section 13.38) is much more effective in this purpose.
The server MUST respond to this header by using the Unsupported The server MUST respond to this header by using the Unsupported
header to negatively acknowledge those feature-tags which are NOT header to negatively acknowledge those feature-tags which are NOT
supported. The response SHALL use the error code 551 (Option Not Sup- supported. The response SHALL use the error code 551 (Option Not
ported). This header does not apply to proxies, for the same Supported). This header does not apply to proxies, for the same
functionality in respect to proxies see, header Proxy-Require (Sec- functionality in respect to proxies see, header Proxy-Require
tion 13.27). (Section 13.27).
This is to make sure that the client-server interaction will This is to make sure that the client-server interaction
proceed without delay when all features are understood by both will proceed without delay when all features are understood
sides, and only slow down if features are not understood (as by both sides, and only slow down if features are not
in the example below). For a well-matched client-server pair, understood (as in the example below). For a well-matched
the interaction proceeds quickly, saving a round-trip often client-server pair, the interaction proceeds quickly,
required by negotiation mechanisms. In addition, it also saving a round-trip often required by negotiation
removes state ambiguity when the client requires features that mechanisms. In addition, it also removes state ambiguity
the server does not understand. when the client requires features that the server does not
understand.
Require = "Require" ":" feature-tag *("," feature-tag) Require = "Require" ":" feature-tag *("," feature-tag)
Example: Example:
C->S: SETUP rtsp://server.com/foo/bar/baz.rm RTSP/1.0 C->S: SETUP rtsp://server.com/foo/bar/baz.rm RTSP/1.0
CSeq: 302 CSeq: 302
Require: funky-feature Require: funky-feature
Funky-Parameter: funkystuff Funky-Parameter: funkystuff
skipping to change at page 1, line 3192 skipping to change at page 75, line 13
C->S: SETUP rtsp://server.com/foo/bar/baz.rm RTSP/1.0 C->S: SETUP rtsp://server.com/foo/bar/baz.rm RTSP/1.0
CSeq: 303 CSeq: 303
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 303 CSeq: 303
In this example, "funky-feature" is the feature-tag which indicates In this example, "funky-feature" is the feature-tag which indicates
to the client that the fictional Funky-Parameter field is required. to the client that the fictional Funky-Parameter field is required.
The relationship between "funky-feature" and Funky-Parameter is not The relationship between "funky-feature" and Funky-Parameter is not
communicated via the RTSP exchange, since that relationship is an communicated via the RTSP exchange, since that relationship is an
immutable property of "funky-feature" and thus should not be trans- immutable property of "funky-feature" and thus should not be
mitted with every exchange. transmitted with every exchange.
Proxies and other intermediary devices SHOULD ignore features that Proxies and other intermediary devices SHOULD ignore features that
are not understood in this field. If a particular extension requires are not understood in this field. If a particular extension requires
that intermediate devices support it, the extension should be tagged that intermediate devices support it, the extension should be tagged
in the Proxy-Require field instead (see Section 13.27). in the Proxy-Require field instead (see Section 13.27).
13.33 RTP-Info 13.33 RTP-Info
The RTP-Info response-header field is used to set RTP-specific param- The RTP-Info response-header field is used to set RTP-specific
eters in the PLAY response. For streams using RTP as transport proto- parameters in the PLAY response. For streams using RTP as transport
col the RTP-Info header SHALL be part of a 200 response to PLAY. protocol the RTP-Info header SHALL be part of a 200 response to PLAY.
The RTP-Info response-header field is used to set RTP-specific param- The RTP-Info response-header field is used to set RTP-specific
eters in the PLAY response. These parameters correspond to the syn- parameters in the PLAY response. These parameters correspond to the
chronization source identified by the ssrc parameter of the Transport synchronization source identified by the ssrc parameter of the
response header in the SETUP reponse. For streams using RTP as trans- Transport response header in the SETUP reponse. For streams using RTP
port protocol the RTP-Info header SHALL be part of a 200 response to as transport protocol the RTP-Info header SHALL be part of a 200
PLAY. response to PLAY.
url: Indicates the stream URL which for which the following RTP url: Indicates the stream URL which for which the following RTP
parameters correspond, this URL MUST be the same used in the parameters correspond, this URL MUST be the same used in
SETUP request for this media stream. Any relative URL SHALL the SETUP request for this media stream. Any relative URL
use the request URL as base URL. SHALL use the request URL as base URL.
seq: Indicates the sequence number of the first packet of the seq: Indicates the sequence number of the first packet of the
stream. This allows clients to gracefully deal with packets stream. This allows clients to gracefully deal with packets
when seeking. The client uses this value to differentiate when seeking. The client uses this value to differentiate
packets that originated before the seek from packets that packets that originated before the seek from packets that
originated after the seek. originated after the seek.
rtptime: Indicates the RTP timestamp corresponding to the time rtptime: Indicates the RTP timestamp corresponding to the time
value in the Range response header. (Note: For aggregate con- value in the Range response header. (Note: For aggregate
trol, a particular stream may not actually generate a packet control, a particular stream may not actually generate a
for the Range time value returned or implied. Thus, there is packet for the Range time value returned or implied. Thus,
no guarantee that the packet with the sequence number indi- there is no guarantee that the packet with the sequence
cated by seq actually has the timestamp indicated by rtptime.) number indicated by seq actually has the timestamp
The client uses this value to calculate the mapping of RTP indicated by rtptime.) The client uses this value to
time to NPT. calculate the mapping of RTP time to NPT.
A mapping from RTP timestamps to NTP timestamps (wall A mapping from RTP timestamps to NTP timestamps (wall
clock) is available via RTCP. However, this information clock) is available via RTCP. However, this
is not sufficient to generate a mapping from RTP times- information is not sufficient to generate a mapping
tamps to NPT. Furthermore, in order to ensure that this from RTP timestamps to NPT. Furthermore, in order to
information is available at the necessary time (immedi- ensure that this information is available at the
ately at startup or after a seek), and that it is deliv- necessary time (immediately at startup or after a
ered reliably, this mapping is placed in the RTSP control seek), and that it is delivered reliably, this mapping
channel. is placed in the RTSP control channel.
In order to compensate for drift for long, uninterrupted pre- In order to compensate for drift for long, uninterrupted
sentations, RTSP clients should additionally map NPT to NTP, presentations, RTSP clients should additionally map NPT to
using initial RTCP sender reports to do the mapping, and later NTP, using initial RTCP sender reports to do the mapping,
reports to check drift against the mapping. and later reports to check drift against the mapping.
Additionally, the RTP-Info header parameter fields only apply to a Additionally, the RTP-Info header parameter fields only apply to a |
single SSRC within a stream (the SSRC reported in the transport single SSRC within a stream (the SSRC reported in the transport |
response header; see section 13.40). If there are multiple synchro- response header; see section 13.40). If there are multiple |
nization sources present within a RTP session, RTCP must be used to synchronization sources (SSRCs) present within a RTP session, RTCP |
map RTP and NTP timestamps for those sources, for both synchroniza- must be used to map RTP and NTP timestamps for those sources, for |
tion and drift-checking. both synchronization and drift-checking.
Syntax: Syntax:
RTP-Info = "RTP-Info" ":" 1#rtsp-info-spec RTP-Info = "RTP-Info" ":" 1#rtsp-info-spec
rtsp-info-spec = stream-url 1*parameter rtsp-info-spec = stream-url 1*parameter
stream-url = quoted-url / unquoted-url stream-url = quoted-url / unquoted-url
unquoted-url = "url" "=" safe-url unquoted-url = "url" "=" safe-url
quoted-url = "url" "=" <"> needquote-url <"> quoted-url = "url" "=" <"> needquote-url <">
safe-url = url safe-url = url
needquote-url = url //That contains ; or , needquote-url = url //That contains ; or ,
skipping to change at page 1, line 3282 skipping to change at page 77, line 12
absoluteURI and relativeURI are defined in RFC 2396 [22] with RFC absoluteURI and relativeURI are defined in RFC 2396 [22] with RFC
2732 [30] applied. 2732 [30] applied.
Example: Example:
RTP-Info: url=rtsp://foo.com/bar.avi/streamid=0;seq=45102, RTP-Info: url=rtsp://foo.com/bar.avi/streamid=0;seq=45102,
url=rtsp://foo.com/bar.avi/streamid=1;seq=30211 url=rtsp://foo.com/bar.avi/streamid=1;seq=30211
13.34 Scale 13.34 Scale
A scale value of 1 indicates normal play at the normal forward view- A scale value of 1 indicates normal play at the normal forward
ing rate. If not 1, the value corresponds to the rate with respect to viewing rate. If not 1, the value corresponds to the rate with
normal viewing rate. For example, a ratio of 2 indicates twice the respect to normal viewing rate. For example, a ratio of 2 indicates
normal viewing rate ("fast forward") and a ratio of 0.5 indicates twice the normal viewing rate ("fast forward") and a ratio of 0.5
half the normal viewing rate. In other words, a ratio of 2 has normal indicates half the normal viewing rate. In other words, a ratio of 2
play time increase at twice the wallclock rate. For every second of has normal play time increase at twice the wallclock rate. For every
elapsed (wallclock) time, 2 seconds of content will be delivered. A second of elapsed (wallclock) time, 2 seconds of content will be
negative value indicates reverse direction. delivered. A negative value indicates reverse direction.
Unless requested otherwise by the Speed parameter, the data rate Unless requested otherwise by the Speed parameter, the data rate
SHOULD not be changed. Implementation of scale changes depends on the SHOULD not be changed. Implementation of scale changes depends on the
server and media type. For video, a server may, for example, deliver server and media type. For video, a server may, for example, deliver
only key frames or selected key frames. For audio, it may time-scale only key frames or selected key frames. For audio, it may time-scale
the audio while preserving pitch or, less desirably, deliver frag- the audio while preserving pitch or, less desirably, deliver
ments of audio. fragments of audio.
The server should try to approximate the viewing rate, but may The server should try to approximate the viewing rate, but may
restrict the range of scale values that it supports. The response restrict the range of scale values that it supports. The response
MUST contain the actual scale value chosen by the server. MUST contain the actual scale value chosen by the server.
If the server does not implement the possibility to scale, it will If the server does not implement the possibility to scale, it will
not return a Scale header. A server supporting Scale operations for not return a Scale header. A server supporting Scale operations for
PLAY SHALL indicate this with the use of the "play.scale" feature- PLAY SHALL indicate this with the use of the "play.scale" feature-
tags. tags.
skipping to change at page 1, line 3322 skipping to change at page 78, line 9
Example of playing in reverse at 3.5 times normal rate: Example of playing in reverse at 3.5 times normal rate:
Scale: -3.5 Scale: -3.5
Range: npt=15-10 Range: npt=15-10
13.35 Speed 13.35 Speed
The Speed request-header field requests the server to deliver data to The Speed request-header field requests the server to deliver data to
the client at a particular speed, contingent on the server's ability the client at a particular speed, contingent on the server's ability
and desire to serve the media stream at the given speed. Implementa- and desire to serve the media stream at the given speed.
tion by the server is OPTIONAL. The default is the bit rate of the Implementation by the server is OPTIONAL. The default is the bit rate
stream. of the stream.
The parameter value is expressed as a decimal ratio, e.g., a value of The parameter value is expressed as a decimal ratio, e.g., a value of
2.0 indicates that data is to be delivered twice as fast as normal. A 2.0 indicates that data is to be delivered twice as fast as normal. A
speed of zero is invalid. All speeds may not be possible to support. speed of zero is invalid. All speeds may not be possible to support.
Therefore the actual used speed MUST be included in the response. Therefore the actual used speed MUST be included in the response.
The lack of a response header is indication of lack of support from The lack of a response header is indication of lack of support from
the server of this functionality. Support of the speed functionality the server of this functionality. Support of the speed functionality
are indicated by the "play.speed" feature-tag. are indicated by the "play.speed" feature-tag.
Speed = "Speed" ":" 1*DIGIT [ "." *DIGIT ] Speed = "Speed" ":" 1*DIGIT [ "." *DIGIT ]
Example: Example:
Speed: 2.5 Speed: 2.5
Use of this field changes the bandwidth used for data delivery. It is Use of this field changes the bandwidth used for data delivery. It is |
meant for use in specific circumstances where preview of the presen- meant for use in specific circumstances where preview of the |
tation at a higher or lower rate is necessary. Implementors should presentation at a higher or lower rate is necessary. Implementors |
keep in mind that bandwidth for the session may be negotiated before- should keep in mind that bandwidth for the session may be negotiated |
hand (by means other than RTSP), and therefore re-negotiation may be beforehand (by means other than RTSP), and therefore re-negotiation |
necessary. When data is delivered over UDP, it is highly recommended may be necessary. When data is delivered over UDP, it is highly |
that means such as RTCP be used to track packet loss rates. If the recommended that means such as RTCP be used to track packet loss |
data transport is performed over public best-effort networks the rates. If the data transport is performed over public best-effort |
sender is responsible for performing congestion control of the networks the sender SHOULD perform congestion control of the |
stream. This MAY result in that the communicated speed is impossible stream(s). This can result in that the communicated speed is |
to maintain. impossible to maintain.
13.36 Server 13.36 Server
See [H14.38], however the header syntax is here corrected. See [H14.38], however the header syntax is here corrected.
Server = "Server" ":" ( product / comment ) *(SP (product / comment)) Server = "Server" ":" ( product / comment ) *(SP (product / comment))
13.37 Session 13.37 Session
The Session request-header and response-header field identifies an |
RTSP session. An RTSP session is created by the server as a result of |
a successful SETUP request and in the response the session identifier |
is given to the client. The RTSP session exist until destroyed by a |
TEARDOWN or timed out by the server. |
The Session request-header and response-header field identifies an The session identifier is chosen by the server (see Section 3.3) and |
RTSP session started by the media server in a SETUP response and con- MUST be returned in the SETUP response. Once a client receives a |
cluded by TEARDOWN on the presentation URL. The session identifier is session identifier, it SHALL be included in any request related to |
chosen by the media server (see Section 3.3) and MUST be returned in that session. This means that the Session header MUST be included in |
the SETUP response. Once a client receives a Session identifier, it a request using the following methods: PLAY, PAUSE, PING, and |
MUST return it for any request related to that session. TEARDOWN, and MAY be included in SETUP, OPTIONS, SET_PARAMETER, |
GET_PARAMETER, and REDIRECT, and SHALL NOT be included in DESCRIBE. |
In a RTSP response the session header SHALL be included in methods, |
SETUP, PING, PLAY, and PAUSE, and MAY be included in methods, |
TEARDOWN, and REDIRECT, and if included in the request of the |
following methods it SHALL also be included in the response, OPTIONS, |
GET_PARAMETER, and SET_PARAMETER, and SHALL NOT be included in |
DESCRIBE. |
Note that RFC 2326 servers and client may in some cases not include |
or return a Session header when expected according to the above text. |
Any client or server is RECOMMENDED to be forgiving of this error if |
possible (which it is in many cases).
Session = "Session" ":" session-id [ ";" "timeout" "=" delta-seconds ] Session = "Session" ":" session-id [ ";" "timeout" "=" delta-seconds ]
The timeout parameter is only allowed in a response header. The The timeout parameter MAY be included in a response, and SHALL NOT be |
server uses it to indicate to the client how long the server is pre- included in requests. The server uses it to indicate to the client |
pared to wait between RTSP commands or other signs of life before how long the server is prepared to wait between RTSP commands or |
closing the session due to lack of activity (see Section A). The other signs of life before closing the session due to lack of |
timeout is measured in seconds, with a default of 60 seconds (1 activity (see below and Section A). The timeout is measured in |
minute). seconds, with a default of 60 seconds (1 minute). |
The mechanisms for showing liveness of the client is, any RTSP mes- The mechanisms for showing liveness of the client is, any RTSP |
sage with a Session header, or a RTCP message. It is RECOMMENDED that request with a Session header, if RTP & RTCP is used an RTCP message, |
a client does not wait to the last second of the timeout before try- or through any other used media protocol capable of indicating |
ing to send a liveness message. Even for RTSP messages using reliable liveness of the RTSP client. It is RECOMMENDED that a client does not |
protocols, such as TCP, the message may take some time to arrive wait to the last second of the timeout before trying to send a |
safely at the receiver. To show liveness between RTSP request with liveness message. The RTSP message may be lost or when using reliable |
other effects, the following mechanisms can be used, in descending protocols, such as TCP, the message may take some time to arrive |
order of preference: safely at the receiver. To show liveness between RTSP request issued |
to accomplish other things, the following mechanisms can be used, in |
descending order of preference: |
RTCP: Is used to report transport statistics and SHALL also work as RTCP: If RTP is used for media transport RTCP SHOULD be used. If |
keep alive. The server can determine the client by used net- RTCP is used to report transport statistics, it SHALL also |
work address and port together with the fact that the client work as keep alive. The server can determine the client by |
is reporting on the servers SSRC(s). A downside of using RTCP used network address and port together with the fact that |
is that it gives lower statistical guarantees to reach the the client is reporting on the servers SSRC(s). A downside |
server. However that probability is so little that it can be of using RTCP is that it only gives statistical guarantees |
ignored in most cases. For example, a session with 60 seconds to reach the server. However that probability is so low |
timeout and enough bitrate assigned to the RTCP messages, so that it can be ignored in most cases. For example, a |
the client sends a message on average every 5 seconds. That session with 60 seconds timeout and enough bitrate assigned |
session have for a network with 5 % packet loss the probabil- to RTCP messages to send a message from client to server on |
ity to not get a liveness sign over to the server in the time- average every 5 seconds. That client have for a network |
out interval is 2.4*E-16. In sessions with shorter timeout with 5 % packet loss, the probability to fail showing |
times, or much higher packet loss, or small RTCP bandwidths liveness sign in that session within the timeout interval |
SHOULD use any of the mechanisms below. of 2.4*E-16. In sessions with shorter timeout times, or |
much higher packet loss, or small RTCP bandwidths SHOULD |
also use any of the mechanisms below. |
PING: The use of the PING method is the best of the RTSP based PING: The use of the PING method is the best of the RTSP based |
methods. It has no other effects than updating the timeout methods. It has no other effects than updating the timeout |
timer. In that way it will be a minimal message, that also timer. In that way it will be a minimal message, that also |
does not cause any extra processing for the server. The down- does not cause any extra processing for the server. The |
side is that it may not be implemented. A client SHOULD use a downside is that it may not be implemented. A client SHOULD |
OPTIONS request to verify support of the PING at the server. use a OPTIONS request to verify support of the PING at the |
It is possible to detect support by sending a PING to the server. It is also possible to detect support by sending a |
server. If a 200 (OK) message is received the server supports PING to the server. If a 200 (OK) message is received the |
it. In case a 501 (Not Implemented) is received it does not server supports it. In case a 501 (Not Implemented) is |
support PING and there is no meaning in continue trying. Also received it does not support PING and there is no meaning |
the reception of a error message will also mean that the live- in continue trying. Also the reception of a error message |
ness timer is not updated. will also mean that the liveness timer has not been |
updated. |
SET_PARAMETER: When using SET_PARAMETER for keep alive, no body SET_PARAMETER: When using SET_PARAMETER for keep alive, no body |
SHOULD be included. This method is basically as good as PING, SHOULD be included. This method is basically as good as |
however the implementation support of the method is today lim- PING, however the implementation support of the method is |
ited. The same considerations as for PING apply regarding today limited. The same considerations as for PING apply |
checking of support in server and proxies. regarding checking of support in server and proxies. |
OPTIONS: This method does also work. However it causes the server OPTIONS: This method does also work. However it causes the |
to perform unnecessary processing and result in bigger server to perform unnecessary processing and result in |
responses than necessary for the task. The reason for this is bigger responses than necessary for the task. The reason |
that the Public is always included creating overhead. for this is that the Public is always included creating |
overhead. |
Note that a session identifier identifies an RTSP session across Note that a session identifier identifies an RTSP session across |
transport sessions or connections. Control messages for more than one transport sessions or connections. RTSP requests for a given session |
RTSP URL may be sent within a single RTSP session. Hence, it is pos- can use different URIs (Presentation and media URIs). Note, that |
sible that clients use the same session for controlling many streams there are restrictions depending on the session which URIs that are |
constituting a presentation, as long as all the streams come from the acceptable for a given method. However, multiple "user" sessions for |
same server. (See example in Section 15). However, multiple "user" the same URI from the same client will require use of different |
sessions for the same URL from the same client MUST use different session identifiers. |
session identifiers.
The session identifier is needed to distinguish several deliv- The session identifier is needed to distinguish several |
ery requests for the same URL coming from the same client. delivery requests for the same URL coming from the same |
client. |
The response 454 (Session Not Found) is returned if the session iden- The response 454 (Session Not Found) SHALL be returned if the session |
tifier is invalid. identifier is invalid.
13.38 Supported 13.38 Supported
The Supported header field enumerates all the extensions supported by The Supported header field enumerates all the extensions supported by
the client or server. When offered in a request, the receiver MUST the client or server. When offered in a request, the receiver MUST
respond with its corresponding Supported header. respond with its corresponding Supported header.
The Supported header field contains a list of feature-tags, described The Supported header field contains a list of feature-tags, described
in Section 3.7, that are understood by the client or server. | in Section 3.7, that are understood by the client or server.
Supported = "Supported" ":" [feature-tag *("," feature-tag)] || Supported = "Supported" ":" [feature-tag *("," feature-tag)]
Example: | Example:
C->S: OPTIONS rtsp://example.com/ RTSP/1.0 | C->S: OPTIONS rtsp://example.com/ RTSP/1.0
Supported: foo, bar, blech | Supported: foo, bar, blech
S->C: RTSP/1.0 200 OK | S->C: RTSP/1.0 200 OK
Supported: bar, blech, baz | Supported: bar, blech, baz
13.39 Timestamp 13.39 Timestamp
The Timestamp general-header field describes when the client sent the The Timestamp general-header field describes when the client sent the
request to the server. The value of the timestamp is of significance request to the server. The value of the timestamp is of significance
only to the client and may use any timescale. The server MUST echo only to the client and may use any timescale. The server MUST echo
the exact same value and MAY, if it has accurate information about the exact same value and MAY, if it has accurate information about
this, add a floating point number indicating the number of seconds this, add a floating point number indicating the number of seconds
that has elapsed since it has received the request. The timestamp is that has elapsed since it has received the request. The timestamp is
used by the client to compute the round-trip time to the server so used by the client to compute the round-trip time to the server so
that it can adjust the timeout value for retransmissions. It also that it can adjust the timeout value for retransmissions. It also
resolves retransmission ambiguities for unreliable transport of RTSP. resolves retransmission ambiguities for unreliable transport of RTSP.
Timestamp = "Timestamp" ":" *(DIGIT) [ "." *(DIGIT) ] [ delay ] Timestamp = "Timestamp" ":" *(DIGIT) [ "." *(DIGIT) ] [ delay ]
delay = *(DIGIT) [ "." *(DIGIT) ] delay = *(DIGIT) [ "." *(DIGIT) ]
13.40 Transport 13.40 Transport
The Transport request- and response- header field indicates which The Transport request- and response- header field indicates which
transport protocol is to be used and configures its parameters such transport protocol is to be used and configures its parameters such
as destination address, compression, multicast time-to-live and des- as destination address, compression, multicast time-to-live and
tination port for a single stream. It sets those values not already destination port for a single stream. It sets those values not
determined by a presentation description. already determined by a presentation description.
Transports are comma separated, listed in order of preference. Transports are comma separated, listed in order of preference.
Parameters may be added to each transport, separated by a semicolon. Parameters may be added to each transport, separated by a semicolon.
The Transport header field MAY also be used to change certain trans- The Transport header field MAY also be used to change certain
port parameters. A server MAY refuse to change parameters of an transport parameters. A server MAY refuse to change parameters of an
existing stream. existing stream.
The server MAY return a Transport response-header field in the The server MAY return a Transport response-header field in the
response to indicate the values actually chosen. response to indicate the values actually chosen.
A Transport request header field MAY contain a list of transport A Transport request header field MAY contain a list of transport
options acceptable to the client, in the form of multiple transport- options acceptable to the client, in the form of multiple
spec entries. In that case, the server MUST return the single option transportspec entries. In that case, the server MUST return the
(transport-spec) which was actually chosen. single option (transport-spec) which was actually chosen.
A transport-spec transport option may only contain one of any given A transport-spec transport option may only contain one of any given
parameter within it. Parameters may be given in any order. Addition- parameter within it. Parameters may be given in any order.
ally, it may only contain the unicast or multicast transport parame- Additionally, it may only contain the unicast or multicast transport
ter. parameter.
The Transport header field is restricted to describing a sin- The Transport header field is restricted to describing a
gle media stream. (RTSP can also control multiple streams as a single media stream. (RTSP can also control multiple
single entity.) Making it part of RTSP rather than relying on streams as a single entity.) Making it part of RTSP rather
a multitude of session description formats greatly simplifies than relying on a multitude of session description formats
designs of firewalls. greatly simplifies designs of firewalls.
The syntax for the transport specifier is The syntax for the transport specifier is
transport/profile/lower-transport. transport/profile/lower-transport.
The default value for the "lower-transport" parameters is specific to The default value for the "lower-transport" parameters is specific to
the profile. For RTP/AVP, the default is UDP. the profile. For RTP/AVP, the default is UDP.
Below are the configuration parameters associated with transport: Below are the configuration parameters associated with transport:
General parameters: General parameters:
unicast / multicast: This parameter is a mutually exclusive indica- unicast / multicast: This parameter is a mutually exclusive
tion of whether unicast or multicast delivery will be indication of whether unicast or multicast delivery will be
attempted. One of the two values MUST be specified. Clients attempted. One of the two values MUST be specified. Clients
that are capable of handling both unicast and multicast trans- that are capable of handling both unicast and multicast
mission MUST indicate such capability by including two full transmission MUST indicate such capability by including two
transport-specs with separate parameters for each. full transport-specs with separate parameters for each.
destination: The address of the stream recipient to which a stream destination: The address of the stream recipient to which a
will be sent. The client originating the RTSP request may stream will be sent. The client originating the RTSP
specify the destination address of the stream recipient with request may specify the destination address of the stream
the destination parameter. When the destination field is spec- recipient with the destination parameter. When the
ified, the recipient may be a different party than the origi- destination field is specified, the recipient may be a
nator of the request. To avoid becoming the unwitting perpe- different party than the originator of the request. To
trator of a remote-controlled denial-of-service attack, a avoid becoming the unwitting perpetrator of a remote-
server SHOULD authenticate the client originating the request controlled denial-of-service attack, a server SHOULD
and SHOULD log such attempts before allowing the client to authenticate the client originating the request and SHOULD
direct a media stream to a recipient address not chosen by the log such attempts before allowing the client to direct a
server. While, this is particularly important if RTSP commands media stream to a recipient address not chosen by the
are issued via UDP, implementations cannot rely on TCP as server. While, this is particularly important if RTSP
reliable means of client identification by itself either. commands are issued via UDP, implementations cannot rely on
TCP as reliable means of client identification by itself
either.
The server SHOULD NOT allow the destination field to be set The server SHOULD NOT allow the destination field to be set
unless a mechanism exists in the system to authorize the unless a mechanism exists in the system to authorize the
request originator to direct streams to the recipient. It is request originator to direct streams to the recipient. It
preferred that this authorization be performed by the recipi- is preferred that this authorization be performed by the
ent itself and the credentials passed along to the server. recipient itself and the credentials passed along to the
However, in certain cases, such as when recipient address is a server. However, in certain cases, such as when recipient
multicast group, or when the recipient is unable to communi- address is a multicast group, or when the recipient is
cate with the server in an out-of-band manner, this may not be unable to communicate with the server in an out-of-band
possible. In these cases server may chose another method such manner, this may not be possible. In these cases server may
as a server-resident authorization list to ensure that the chose another method such as a server-resident
request originator has the proper credentials to request authorization list to ensure that the request originator
stream delivery to the recipient. has the proper credentials to request stream delivery to
the recipient.
This parameter SHALL NOT be used when src_addr and dst_addr is | This parameter SHALL NOT be used when src_addr and dst_addr |
used in a transport declaration. IPv6 addresses are RECOM- | is used in a transport declaration. For IPv6 addresses it |
MENDED to be given as fully qualified domain to make it back- | is RECOMMENDED that they be given as fully qualified domain |
wards compatible with RFC 2326 implementations. | to make it backwards compatible with RFC 2326 |
implementations.
source: If the source address for the stream is different than can | source: If the source address for the stream is different than
be derived from the RTSP endpoint address (the server in play- | can be derived from the RTSP endpoint address (the server
back), the source address SHOULD be specified. To maintain | in playback), the source address SHOULD be specified. To
backwards compatibility with RFC 2326, any IPv6 host's address | maintain backwards compatibility with RFC 2326, any IPv6
must be given as a fully qualified domain name. This | host's address must be given as a fully qualified domain
parameter SHALL NOT be used when src_addr and dst_addr is used | name. This parameter SHALL NOT be used when src_addr and
in a transport declaration. dst_addr is used in a transport declaration.
This information may also be available through SDP. How- This information may also be available through SDP.
ever, since this is more a feature of transport than However, since this is more a feature of transport
media initialization, the authoritative source for this than media initialization, the authoritative source
information should be in the SETUP response. for this information should be in the SETUP response.
layers: The number of multicast layers to be used for this media layers: The number of multicast layers to be used for this media
stream. The layers are sent to consecutive addresses starting stream. The layers are sent to consecutive addresses
at the destination address. starting at the destination address.
dest_addr: A general destination address parameter that can contain | dest_addr: A general destination address parameter that can
one or more address and port pair. For each combination of | contain one or more address and port pair. For each
Protocol/Profile/Lower Transport the interpretation of the | combination of Protocol/Profile/Lower Transport the
address or addresses needs to be defined. The client or server | interpretation of the address or addresses needs to be
SHALL NOT use this parameter unless both client and server has | defined. The client or server SHALL NOT use this parameter
shown support. This parameter MUST be supported by client and | unless both client and server has shown support. This
servers that implements this specification. Support is indi- | parameter MUST be supported by client and servers that
cated by the use of the feature-tag "play.basic". This parame- | implements this specification. Support is indicated by the
ter SHALL NOT be used in the same transport specification as | use of the feature-tag "play.basic". This parameter SHALL
any of the parameters "destination", "source", "port", | NOT be used in the same transport specification as any of
"client_port", and "server_port". | the parameters "destination", "source", "port",
"client_port", and "server_port".
The same security consideration that are given for the "Desti- | The same security consideration that are given for the
nation" parameter does also applies to this parameter. This | "Destination" parameter does also applies to this
parameter can be used for redirecting traffic to recipient not | parameter. This parameter can be used for redirecting
desiring the media traffic. | traffic to recipient not desiring the media traffic.
src_addr: A General source address parameter that can contain one | src_addr: A General source address parameter that can contain
or more address and port pair. For each combination of Proto- | one or more address and port pair. For each combination of
col/Profile/Lower Transport the interpretation of the address | Protocol/Profile/Lower Transport the interpretation of the
or addresses needs to be defined. The client or server SHALL | address or addresses needs to be defined. The client or
NOT use this parameter unless both client and server has shown | server SHALL NOT use this parameter unless both client and
support. This parameter MUST be supported by client and | server has shown support. This parameter MUST be supported
servers that implements this specification. Support is indi- | by client and servers that implements this specification.
cated by the use the feature-tag "play.basic". This parameter | Support is indicated by the use the feature-tag
SHALL NOT be used in the same transport specification as any | "play.basic". This parameter SHALL NOT be used in the same
of the parameters "destination", "source", "port", | transport specification as any of the parameters
"client_port", and "server_port". | "destination", "source", "port", "client_port", and
"server_port".
The address or addresses indicated in the src_addr parameter | The address or addresses indicated in the src_addr
SHOULD be used both for sending and receiving of the media | parameter SHOULD be used both for sending and receiving of
streams data packet. The main reasons are two: First by send- | the media streams data packet. The main reasons are two:
ing from the indicated ports the source address will be known | First by sending from the indicated ports the source
by the receiver of the packet. Secondly, in the presence of | address will be known by the receiver of the packet.
NATs some traversal mechanism requires either knowledge from | Secondly, in the presence of NATs some traversal mechanism
which address and port a packet flow is coming, or having the | requires either knowledge from which address and port a
possibility to send data to the sender port. packet flow is coming, or having the possibility to send
data to the sender port.
mode: The mode parameter indicates the methods to be supported for mode: The mode parameter indicates the methods to be supported
this session. Valid values are PLAY and RECORD. If not pro- for this session. Valid values are PLAY and RECORD. If not
vided, the default is PLAY. The RECORD value was defined in provided, the default is PLAY. The RECORD value was
RFC 2326 and is deprecated in this specification. defined in RFC 2326 and is deprecated in this
specification.
append: The append parameter was used together with RECORD and is append: The append parameter was used together with RECORD and
now deprecated. is now deprecated.
interleaved: The interleaved parameter implies mixing the media interleaved: The interleaved parameter implies mixing the media
stream with the control stream in whatever protocol is being stream with the control stream in whatever protocol is
used by the control stream, using the mechanism defined in being used by the control stream, using the mechanism
Section 11.11. The argument provides the channel number to be defined in Section 11.11. The argument provides the channel
used in the $ statement and MUST be present. This parameter number to be used in the $ statement and MUST be present.
MAY be specified as a range, e.g., interleaved=4-5 in cases This parameter MAY be specified as a range, e.g.,
where the transport choice for the media stream requires it, interleaved=4-5 in cases where the transport choice for the
e.g. for RTP with RTCP. The channel number given in the media stream requires it, e.g. for RTP with RTCP. The
request are only a guidance from the client to the server on channel number given in the request are only a guidance
what channel number(s) to use. The server MAY set any valid from the client to the server on what channel number(s) to
channel number in the response. The declared channel(s) are use. The server MAY set any valid channel number in the
bi-directional, so both end-parties MAY send data on the given response. The declared channel(s) are bi-directional, so
channel. One example of such usage is the second channel used both end-parties MAY send data on the given channel. One
for RTCP, where both server and client sends RTCP packets on example of such usage is the second channel used for RTCP,
the same channel. where both server and client sends RTCP packets on the same
channel.
This allows RTP/RTCP to be handled similarly to the way This allows RTP/RTCP to be handled similarly to the
that it is done with UDP, i.e., one channel for RTP and way that it is done with UDP, i.e., one channel for
the other for RTCP. RTP and the other for RTCP.
Multicast-specific: Multicast-specific:
ttl: multicast time-to-live. ttl: multicast time-to-live.
RTP-specific: RTP-specific:
These parameters are MAY only be used if the media transport protocol These parameters are MAY only be used if the media transport protocol
is RTP. is RTP.
port: This parameter provides the RTP/RTCP port pair for a multi- port: This parameter provides the RTP/RTCP port pair for a
cast session. It is should be specified as a range, e.g., multicast session. It is should be specified as a range,
port=3456-3457 e.g., port=3456-3457
client_port: This parameter provides the unicast RTP/RTCP port pair |
on the client where media data and control information is to |
be sent. It is specified as a range, e.g., port=3456-3457 is |
used in a transport declaration. |
server_port: This parameter provides the unicast RTP/RTCP port pair | client_port: This parameter provides the unicast RTP/RTCP port
on the server where media data and control information is to | pair on the client where media data and control information
be sent. It is specified as a range, e.g., port=3456-3457 is | is to be sent. It is specified as a range, e.g.,
used in a transport declaration. port=3456-3457 is used in a transport declaration.
ssrc: The ssrc parameter, if included in a SETUP response, indi- server_port: This parameter provides the unicast RTP/RTCP port
cates the RTP SSRC [23] value that will be used by the media pair on the server where media data and control information
server for RTP packets within the stream. It is expressed as is to be sent. It is specified as a range, e.g.,
an eight digit hexadecimal value. If the server does not act port=3456-3457 is used in a transport declaration.
as a synchronization source for stream data (for instance,
server is a translator, reflector, etc.) the value will be the
"packet sender's SSRC" that would have been used in the RTCP
Receiver Reports generated by the server, regardless of
whether the server actually generates RTCP RRs. If there are
multiple sources within the stream, the ssrc parameter only
indicates the value for a single synchronization source. Other
sources must be deduced from the actual RTP/RTCP stream.
The functionality of specifying the ssrc parameter in a SETUP ssrc: The ssrc parameter, if included in a SETUP response,
request is deprecated as it is incompatible with the specifi- indicates the RTP SSRC [23] value that will be used by the
cation of RTP in RFC 1889. If the parameter is included in the media server for RTP packets within the stream. It is
transport header of a SETUP request, the server MAY ignore the expressed as an eight digit hexadecimal value. If the
it, and choose an appropriate SSRC for the stream. It MAY set server does not act as a synchronization source for stream
the ssrc parameter in the transport header of the response. data (for instance, server is a translator, reflector,
etc.) the value will be the "packet sender's SSRC" that
would have been used in the RTCP Receiver Reports generated
by the server, regardless of whether the server actually
generates RTCP RRs. If there are multiple sources within
the stream, the ssrc parameter only indicates the value for
a single synchronization source. Other sources must be
deduced from the actual RTP/RTCP stream.
Transport = "Transport" ":" 1#transport-spec || The functionality of specifying the ssrc parameter in a
transport-spec = transport-id *parameter || SETUP request is deprecated as it is incompatible with the
transport-id = transport-protocol "/" profile ["/" lower-transport]|| specification of RTP in RFC 3550. If the parameter is
; no LWS is allowed inside transport-id || included in the transport header of a SETUP request, the
transport-protocol = "RTP" / token || server MAY ignore it, and choose an appropriate SSRC for
profile = "AVP" / token || the stream. The server MAY set the ssrc parameter in the
lower-transport = "TCP" / "UDP" / token || transport header of the response.
parameter = ";" ( "unicast" / "multicast" ) ||
/ ";" "source" "=" host ||
/ ";" "destination" [ "=" host ] ||
/ ";" "interleaved" "=" channel [ "-" channel ]||
/ ";" "append" ||
/ ";" "ttl" "=" ttl ||
/ ";" "layers" "=" 1*DIGIT ||
/ ";" "port" "=" port-spec ||
/ ";" "client_port" "=" port-spec ||
/ ";" "server_port" "=" port-spec ||
/ ";" "ssrc" "=" ssrc ||
/ ";" "mode" "=" mode-spec ||
/ ";" "dest_addr" "=" addr-list ||
/ ";" "src_addr" "=" addr-list ||
/ ";" trn-parameter-extension ||
port-spec = port [ "-" port ] ||
trn-parameter-extension = par-name "=" trn-par-value ||
par-name = token ||
trn-par-value = *unreserved ||
ttl = 1*3(DIGIT) ||
ssrc = 8*8(HEX) ||
channel = 1*3(DIGIT) ||
mode-spec = <"> 1#mode <"> / mode ||
mode = "PLAY" / "RECORD" / token ||
addr-list = host-port *("/" host-port) ||
host-port = host [":" port] ||
host = see chapter 16 ||
port = see chapter 16 ||
The combination of transport protocol, profile and lower transport | Transport = "Transport" ":" 1#transport-spec
needs to be defined. A number of combinations are defined in the | transport-spec = transport-id *parameter
transport-id = transport-protocol "/" profile ["/" lower-transport]
; no LWS is allowed inside transport-id
transport-protocol = "RTP" / token
profile = "AVP" / token
lower-transport = "TCP" / "UDP" / token
parameter = ";" ( "unicast" / "multicast" )
/ ";" "source" "=" host
/ ";" "destination" [ "=" host ]
/ ";" "interleaved" "=" channel [ "-" channel ]
/ ";" "append"
/ ";" "ttl" "=" ttl
/ ";" "layers" "=" 1*DIGIT
/ ";" "port" "=" port-spec
/ ";" "client_port" "=" port-spec
/ ";" "server_port" "=" port-spec
/ ";" "ssrc" "=" ssrc
/ ";" "mode" "=" mode-spec
/ ";" "dest_addr" "=" addr-list
/ ";" "src_addr" "=" addr-list
/ ";" trn-parameter-extension
port-spec = port [ "-" port ]
trn-parameter-extension = par-name "=" trn-par-value
par-name = token
trn-par-value = *unreserved
ttl = 1*3(DIGIT)
ssrc = 8*8(HEX)
channel = 1*3(DIGIT)
mode-spec = <"> 1#mode <"> / mode
mode = "PLAY" / "RECORD" / token
addr-list = quoted-host-port *("/" quoted-host-port)
quoted-host-port = <"> host [":" port]<">
host = see chapter 16
port = see chapter 16
The combination of transport protocol, profile and lower transport
needs to be defined. A number of combinations are defined in the
appendix B. appendix B.
Below is a usage example, showing a client advertising the capability Below is a usage example, showing a client advertising the capability
to handle multicast or unicast, preferring multicast. Since this is a to handle multicast or unicast, preferring multicast. Since this is a
unicast-only stream, the server responds with the proper transport unicast-only stream, the server responds with the proper transport
parameters for unicast. parameters for unicast.
C->S: SETUP rtsp://example.com/foo/bar/baz.rm RTSP/1.0 C->S: SETUP rtsp://example.com/foo/bar/baz.rm RTSP/1.0
CSeq: 302 CSeq: 302
Transport: RTP/AVP;multicast;mode="PLAY", Transport: RTP/AVP;multicast;mode="PLAY",
skipping to change at page 1, line 3741 skipping to change at page 88, line 7
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 302 CSeq: 302
Date: 23 Jan 1997 15:35:06 GMT Date: 23 Jan 1997 15:35:06 GMT
Session: 47112344 Session: 47112344
Transport: RTP/AVP;unicast;client_port=3456-3457; Transport: RTP/AVP;unicast;client_port=3456-3457;
server_port=6256-6257;mode="PLAY" server_port=6256-6257;mode="PLAY"
13.41 Unsupported 13.41 Unsupported
The Unsupported response-header field lists the features not sup- The Unsupported response-header field lists the features not
ported by the server. In the case where the feature was specified via supported by the server. In the case where the feature was specified
the Proxy-Require field (Section 13.27), if there is a proxy on the via the Proxy-Require field (Section 13.27), if there is a proxy on
path between the client and the server, the proxy MUST send a the path between the client and the server, the proxy MUST send a
response message with a status code of 551 (Option Not Supported). response message with a status code of 551 (Option Not Supported).
The request SHALL NOT be forwarded. The request SHALL NOT be forwarded.
See Section 13.32 for a usage example. See Section 13.32 for a usage example.
Unsupported = "Unsupported" ":" feature-tag *("," feature-tag) Unsupported = "Unsupported" ":" feature-tag *("," feature-tag)
13.42 User-Agent 13.42 User-Agent
See [H14.43] for explanation, however the syntax is clarified due to See [H14.43] for explanation, however the syntax is clarified due to
skipping to change at page 1, line 3775 skipping to change at page 88, line 41
13.44 Via 13.44 Via
See [H14.45]. See [H14.45].
13.45 WWW-Authenticate 13.45 WWW-Authenticate
See [H14.47]. See [H14.47].
14 Caching 14 Caching
In HTTP, response-request pairs are cached. RTSP differs signifi- | In HTTP, response-request pairs are cached. RTSP differs
cantly in that respect. Responses are not cacheable, with the excep- | significantly in that respect. Responses are not cacheable, with the
tion of the presentation description returned by DESCRIBE. (Since the | exception of the presentation description returned by DESCRIBE.
responses for anything but DESCRIBE and GET_PARAMETER do not return | (Since the responses for anything but DESCRIBE and GET_PARAMETER do
any data, caching is not really an issue for these requests.) How- | not return any data, caching is not really an issue for these
ever, it is desirable for the continuous media data, typically deliv- | requests.) However, it is desirable for the continuous media data,
ered out-of-band with respect to RTSP, to be cached, as well as the | typically delivered out-of-band with respect to RTSP, to be cached,
session description. as well as the session description.
On receiving a SETUP or PLAY request, a proxy ascertains whether it On receiving a SETUP or PLAY request, a proxy ascertains whether it
has an up-to-date copy of the continuous media content and its has an up-to-date copy of the continuous media content and its
description. It can determine whether the copy is up-to-date by description. It can determine whether the copy is up-to-date by
issuing a SETUP or DESCRIBE request, respectively, and comparing the issuing a SETUP or DESCRIBE request, respectively, and comparing the
Last-Modified header with that of the cached copy. If the copy is not Last-Modified header with that of the cached copy. If the copy is not
up-to-date, it modifies the SETUP transport parameters as appropriate up-to-date, it modifies the SETUP transport parameters as appropriate
and forwards the request to the origin server. Subsequent control and forwards the request to the origin server. Subsequent control
commands such as PLAY or PAUSE then pass the proxy unmodified. The commands such as PLAY or PAUSE then pass the proxy unmodified. The
proxy delivers the continuous media data to the client, while possi- proxy delivers the continuous media data to the client, while
bly making a local copy for later reuse. The exact behavior allowed possibly making a local copy for later reuse. The exact behavior
to the cache is given by the cache-response directives described in allowed to the cache is given by the cache-response directives
Section 13.9. A cache MUST answer any DESCRIBE requests if it is cur- described in Section 13.9. A cache MUST answer any DESCRIBE requests
rently serving the stream to the requestor, as it is possible that if it is currently serving the stream to the requestor, as it is
low-level details of the stream description may have changed on the possible that low-level details of the stream description may have
origin-server. changed on the origin-server.
Note that an RTSP cache, unlike the HTTP cache, is of the "cut- Note that an RTSP cache, unlike the HTTP cache, is of the "cut-
through" variety. Rather than retrieving the whole resource from the through" variety. Rather than retrieving the whole resource from the
origin server, the cache simply copies the streaming data as it origin server, the cache simply copies the streaming data as it
passes by on its way to the client. Thus, it does not introduce addi- passes by on its way to the client. Thus, it does not introduce
tional latency. additional latency.
To the client, an RTSP proxy cache appears like a regular media To the client, an RTSP proxy cache appears like a regular media
server, to the media origin server like a client. Just as an HTTP server, to the media origin server like a client. Just as an HTTP
cache has to store the content type, content language, and so on for cache has to store the content type, content language, and so on for
the objects it caches, a media cache has to store the presentation the objects it caches, a media cache has to store the presentation
description. Typically, a cache eliminates all transport-references description. Typically, a cache eliminates all transport-references
(that is, multicast information) from the presentation description, (that is, multicast information) from the presentation description,
since these are independent of the data delivery from the cache to since these are independent of the data delivery from the cache to
the client. Information on the encodings remains the same. If the the client. Information on the encodings remains the same. If the
cache is able to translate the cached media data, it would create a cache is able to translate the cached media data, it would create a
skipping to change at page 1, line 3828 skipping to change at page 89, line 49
15 Examples 15 Examples
The following examples refer to stream description formats that are The following examples refer to stream description formats that are
not standards, such as RTSL. The following examples are not to be not standards, such as RTSL. The following examples are not to be
used as a reference for those formats. used as a reference for those formats.
15.1 Media on Demand (Unicast) 15.1 Media on Demand (Unicast)
Client C requests a movie from media servers A (audio.example.com ) Client C requests a movie from media servers A (audio.example.com )
and V (video.example.com ). The media description is stored on a web and V (video.example.com ). The media description is stored on a web
server W. The media description contains descriptions of the presen- server W. The media description contains descriptions of the
tation and all its streams, including the codecs that are available, presentation and all its streams, including the codecs that are
dynamic RTP payload types, the protocol stack, and content informa- available, dynamic RTP payload types, the protocol stack, and content
tion such as language or copyright restrictions. It may also give an information such as language or copyright restrictions. It may also
indication about the timeline of the movie. give an indication about the timeline of the movie.
In this example, the client is only interested in the last part of In this example, the client is only interested in the last part of
the movie. the movie.
C->W: GET /twister.sdp HTTP/1.1 C->W: GET /twister.sdp HTTP/1.1
Host: www.example.com Host: www.example.com
Accept: application/sdp Accept: application/sdp
W->C: HTTP/1.0 200 OK W->C: HTTP/1.0 200 OK
Date: 23 Jan 1997 15:35:06 GMT Date: 23 Jan 1997 15:35:06 GMT
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V->C: RTSP/1.0 200 OK V->C: RTSP/1.0 200 OK
CSeq: 3 CSeq: 3
Even though the audio and video track are on two different servers, Even though the audio and video track are on two different servers,
and may start at slightly different times and may drift with respect and may start at slightly different times and may drift with respect
to each other, the client can synchronize the two using standard RTP to each other, the client can synchronize the two using standard RTP
methods, in particular the time scale contained in the RTCP sender methods, in particular the time scale contained in the RTCP sender
reports. reports.
15.2 Streaming of a Container file 15.2 Streaming of a Container file
For purposes of this example, a container file is a storage entity in For purposes of this example, a container file is a storage entity in
which multiple continuous media types pertaining to the same end-user which multiple continuous media types pertaining to the same end-user
presentation are present. In effect, the container file represents an presentation are present. In effect, the container file represents an
RTSP presentation, with each of its components being RTSP streams. RTSP presentation, with each of its components being RTSP streams.
Container files are a widely used means to store such presentations. Container files are a widely used means to store such presentations.
While the components are transported as independent streams, it is While the components are transported as independent streams, it is
desirable to maintain a common context for those streams at the desirable to maintain a common context for those streams at the
server end. server end.
This enables the server to keep a single storage handle open This enables the server to keep a single storage handle
easily. It also allows treating all the streams equally in open easily. It also allows treating all the streams
case of any prioritization of streams by the server. equally in case of any prioritization of streams by the
server.
It is also possible that the presentation author may wish to prevent It is also possible that the presentation author may wish to prevent
selective retrieval of the streams by the client in order to preserve selective retrieval of the streams by the client in order to preserve
the artistic effect of the combined media presentation. Similarly, in the artistic effect of the combined media presentation. Similarly, in
such a tightly bound presentation, it is desirable to be able to con- such a tightly bound presentation, it is desirable to be able to
trol all the streams via a single control message using an aggregate control all the streams via a single control message using an
URL. aggregate URL.
The following is an example of using a single RTSP session to control The following is an example of using a single RTSP session to control
multiple streams. It also illustrates the use of aggregate URLs. multiple streams. It also illustrates the use of aggregate URLs.
Client C requests a presentation from media server M. The movie is Client C requests a presentation from media server M. The movie is
stored in a container file. The client has obtained an RTSP URL to stored in a container file. The client has obtained an RTSP URL to
the container file. the container file.
C->M: DESCRIBE rtsp://example.com/twister RTSP/1.0 C->M: DESCRIBE rtsp://example.com/twister RTSP/1.0
CSeq: 1 CSeq: 1
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instance, the aggregate URL may not be used for SETUP and one control instance, the aggregate URL may not be used for SETUP and one control
message is required per stream to set up transport parameters. message is required per stream to set up transport parameters.
This keeps the syntax of the Transport header simple and This keeps the syntax of the Transport header simple and
allows easy parsing of transport information by firewalls. allows easy parsing of transport information by firewalls.
15.3 Single Stream Container Files 15.3 Single Stream Container Files
Some RTSP servers may treat all files as though they are "container Some RTSP servers may treat all files as though they are "container
files", yet other servers may not support such a concept. Because of files", yet other servers may not support such a concept. Because of
this, clients SHOULD use the rules set forth in the session descrip- this, clients SHOULD use the rules set forth in the session
tion for request URLs, rather than assuming that a consistent URL may description for request URLs, rather than assuming that a consistent
always be used throughout. Here's an example of how a multi-stream URL may always be used throughout. Here's an example of how a multi-
server might expect a single-stream file to be served: stream server might expect a single-stream file to be served:
C->S DESCRIBE rtsp://foo.com/test.wav RTSP/1.0 C->S DESCRIBE rtsp://foo.com/test.wav RTSP/1.0
Accept: application/x-rtsp-mh, application/sdp Accept: application/x-rtsp-mh, application/sdp
CSeq: 1 CSeq: 1
S->C RTSP/1.0 200 OK S->C RTSP/1.0 200 OK
CSeq: 1 CSeq: 1
Content-base: rtsp://foo.com/test.wav/ Content-base: rtsp://foo.com/test.wav/
Content-type: application/sdp Content-type: application/sdp
Content-length: 48 Content-length: 48
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"a" / "b" / "c" / "d" / "e" / "f" "a" / "b" / "c" / "d" / "e" / "f"
escape = "%" hex hex escape = "%" hex hex
reserved = ";" / "/" / "?" / ":" / "@" / "&" / "=" reserved = ";" / "/" / "?" / ":" / "@" / "&" / "="
unreserved = alpha / digit / safe / extra unreserved = alpha / digit / safe / extra
xchar = unreserved / reserved / escape xchar = unreserved / reserved / escape
16.2 RTSP Protocol Definition 16.2 RTSP Protocol Definition
16.2.1 Message Syntax 16.2.1 Message Syntax
generRTSP-message= st=rtRequest / Response ; RTSP/1.0 messages RTSP-message = Request / Response ; RTSP/1.0 messages
generic-message = start-line
*(message-header CRLF) *(message-header CRLF)
CRLF CRLF
[ message-body ] [ message-body ]
start-line = Request-Line / Status-Line start-line = Request-Line / Status-Line