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Informational                                             R. Pantos, Ed.
Internet-Draft                                                Apple Inc.
Intended status: Informational                              June 8, 2009
Expires: December 10, 2009


                          HTTP Live Streaming
                  draft-pantos-http-live-streaming-01

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.  This document may not be modified,
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   This Internet-Draft will expire on December 10, 2009.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
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   To the extent that this Informational Internet Draft contains one or
   more Code Components (see the IETF Trust's Legal Provisions Relating



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   to IETF Documents effective Feb. 15, 2009), such Code Components are
   exempt from and not subject to Section 4 of the Legal Provisions.

   Furthermore, this Informational Internet Draft is submitted as an RFC
   Editor Contribution and/or non-IETF Document (not as a Contribution,
   IETF Contribution, nor IETF Document) in accordance with BCP 78 and
   BCP 79.

Abstract

   This document describes a protocol for transmitting unbounded streams
   of multimedia data over HTTP.  It specifies the data format of the
   files and the actions to be taken by the server (sender) and the
   clients (receivers) of the streams.  It describes version 1.0 of this
   protocol.




































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Summary  . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  The Playlist file  . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  New Tags . . . . . . . . . . . . . . . . . . . . . . . . .  5
       3.1.1.  EXT-X-TARGETDURATION . . . . . . . . . . . . . . . . .  5
       3.1.2.  EXT-X-MEDIA-SEQUENCE . . . . . . . . . . . . . . . . .  5
       3.1.3.  EXT-X-KEY  . . . . . . . . . . . . . . . . . . . . . .  6
       3.1.4.  EXT-X-PROGRAM-DATE-TIME  . . . . . . . . . . . . . . .  6
       3.1.5.  EXT-X-ALLOW-CACHE  . . . . . . . . . . . . . . . . . .  6
       3.1.6.  EXT-X-ENDLIST  . . . . . . . . . . . . . . . . . . . .  7
       3.1.7.  EXT-X-STREAM-INF . . . . . . . . . . . . . . . . . . .  7
   4.  Media files  . . . . . . . . . . . . . . . . . . . . . . . . .  7
   5.  Key files  . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     5.1.  IV for AES-128 . . . . . . . . . . . . . . . . . . . . . .  8
   6.  Client/Server Actions  . . . . . . . . . . . . . . . . . . . .  8
     6.1.  Server Process . . . . . . . . . . . . . . . . . . . . . .  9
       6.1.1.  Sliding Window Playlists . . . . . . . . . . . . . . . 10
       6.1.2.  Encrypting media files . . . . . . . . . . . . . . . . 10
       6.1.3.  Providing variant streams  . . . . . . . . . . . . . . 11
     6.2.  Client Process . . . . . . . . . . . . . . . . . . . . . . 12
       6.2.1.  Loading the Playlist file  . . . . . . . . . . . . . . 12
       6.2.2.  Playing the Playlist file  . . . . . . . . . . . . . . 12
       6.2.3.  Reloading the Playlist file  . . . . . . . . . . . . . 13
       6.2.4.  Determining the next file to load  . . . . . . . . . . 13
       6.2.5.  Playing encrypted media files  . . . . . . . . . . . . 14
   7.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     7.1.  Simple Playlist file . . . . . . . . . . . . . . . . . . . 14
     7.2.  Sliding Window Playlist, using HTTPS . . . . . . . . . . . 15
     7.3.  Playlist file with encrypted media files . . . . . . . . . 15
     7.4.  Variant Playlist file  . . . . . . . . . . . . . . . . . . 15
   8.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 16
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 16
     11.2. Informative References . . . . . . . . . . . . . . . . . . 17
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 17












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1.  Introduction

   This document describes a protocol for transmitting unbounded streams
   of multimedia data over HTTP [RFC2616].  The protocol supports the
   encryption of media data, and the provision of alternate versions
   (e.g. bitrates) of a stream.  Media data can be transmitted soon
   after it is created, allowing it to be received in near real-time.

   External references that describe related standards such as HTTP are
   listed in Section 11.


2.  Summary

   A multimedia presentation is specified by a URI [RFC3986] to a
   Playlist file, which is an ordered list of additional URIs.  Each URI
   in the Playlist file refers to a media file which is a segment of a
   single contiguous stream.

   To play the stream, the client first obtains the Playlist file and
   then obtains and plays each media file in the Playlist.  It reloads
   the Playlist file as described in this document to discover
   additional segments.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].


3.  The Playlist file

   Playlists MUST be Extended M3U Playlist files [M3U].  This document
   extends the M3U file format by defining additional tags.

   An M3U Playlist is a text file that consists of individual lines.
   Lines are terminated by either a single LF character or a CR
   character followed by an LF character.  Each line is a URI, a blank,
   or starts with the comment character '#'.  URIs identify media files
   to be played.  Blank lines are ignored.

   Lines that start with the comment character '#' are either comments
   or tags.  Tags begin with #EXT.  All other lines that begin with '#'
   are comments and SHOULD be ignored.

   Implementations SHOULD produce Playlist files encoded in UTF-8
   [RFC3629].  URIs to such Playlist files SHOULD end in .m3u8 and/or
   have the MIME type [RFC2046] application/x-mpegURL.




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   The Extended M3U file format defines two tags: EXTM3U and EXTINF.  An
   Extended M3U file is distinguished from a basic M3U file by its first
   line, which MUST be #EXTM3U.

   EXTINF is a record marker that describes the media file identified by
   the URI that follows it.  Each media file URI MUST be preceded by an
   EXTINF tag.  Its format is:

   #EXTINF:<duration>,<title>

   "duration" is an integer that specifies the duration of the media
   file in seconds.  Durations SHOULD be rounded to the nearest integer.
   The remainder of the line following the comma is the title of the
   media file.

3.1.  New Tags

   This document defines seven new tags: EXT-X-TARGETDURATION, EXT-X-
   MEDIA-SEQUENCE, EXT-X-KEY, EXT-X-PROGRAM-DATE-TIME, EXT-X-ALLOW-
   CACHE, EXT-X-STREAM-INF, and EXT-X-ENDLIST.

3.1.1.  EXT-X-TARGETDURATION

   The EXT-X-TARGETDURATION tag indicates the approximate duration of
   the next media file that will be added to the main presentation.  It
   MUST appear in the Playlist file.  Its format is:

   #EXT-X-TARGETDURATION:<seconds>

   The actual duration of the media file MAY differ slightly from the
   target duration.

3.1.2.  EXT-X-MEDIA-SEQUENCE

   Each media file URI in a Playlist has a unique sequence number.  The
   sequence number of a URI is equal to the sequence number of the URI
   that preceded it plus one.  The EXT-X-MEDIA-SEQUENCE tag indicates
   the sequence number of the first URI that appears in a Playlist file.
   Its format is:

   #EXT-X-MEDIA-SEQUENCE:<number>

   If the Playlist file does not contain an EXT-X-MEDIA-SEQUENCE tag
   then the sequence number of the first URI in the playlist SHALL be
   considered to be 1.

   See Section 6.2.1 and Section 6.2.4 for information on handling the
   EXT-X-MEDIA-SEQUENCE tag.



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3.1.3.  EXT-X-KEY

   Media files MAY be encrypted.  The EXT-X-KEY tag provides information
   necessary to decrypt media files that follow it.  Its format is:

   #EXT-X-KEY:METHOD=<method>[,URI="<URI>"]

   The METHOD parameter specifies the encryption method.  The URI
   parameter, if present, specifies how to obtain the key.

   Version 1.0 of the protocol defines two encryption methods: NONE and
   AES-128.  An encryption method of NONE means that media files are not
   encrypted.

   An encryption method of AES-128 means that media files are encrypted
   using the Advanced Encryption Standard [AES_128] with a 128-bit key
   and PKCS7 padding [RFC3852].

   A new EXT-X-KEY supersedes any prior EXT-X-KEY.

   If no EXT-X-KEY tag is present then media files are not encrypted.

   See Section 5 for the format of the key file, and Section 5.1,
   Section 6.1.2 and Section 6.2.5 for additional information on media
   file encryption.

3.1.4.  EXT-X-PROGRAM-DATE-TIME

   The EXT-X-PROGRAM-DATE-TIME tag associates the beginning of the next
   media file with an absolute date and/or time.  The date/time
   representation is ISO/IEC 8601:2004 [ISO_8601] and SHOULD indicate a
   time zone.  For example:

   #EXT-X-PROGRAM-DATE-TIME:<YYYY-MM-DDThh:mm:ssZ>

3.1.5.  EXT-X-ALLOW-CACHE

   The EXT-X-ALLOW-CACHE tag indicates whether the client MAY cache
   downloaded media files for later replay.  Its format is:

   #EXT-X-ALLOW-CACHE:<YES|NO>










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3.1.6.  EXT-X-ENDLIST

   The EXT-X-ENDLIST tag indicates that no more media files will be
   added to the Playlist file.  Its format is:

   #EXT-X-ENDLIST

3.1.7.  EXT-X-STREAM-INF

   The EXT-X-STREAM-INF tag indicates that the next URI in the Playlist
   file identifies another Playlist file.  Its format is:

   #EXT-X-STREAM-INF:[attribute=value][,attribute=value]*
   <URI>

   The following attributes are defined for the EXT-X-STREAM-INF tag:

   BANDWIDTH=<n>

   where n is an approximate upper bound of the stream bitrate,
   expressed as a number of bits per second.

   PROGRAM-ID=<i>

   where i is a number that uniquely identifies a particular
   presentation within the scope of the Playlist file.

   A Playlist file MAY contain multiple EXT-X-STREAM-INF URIs with the
   same PROGRAM-ID to describe variant streams of the same presentation.

   CODECS="[format][,format]*"

   where each format specifies a media sample type that is present in a
   media file in the Playlist file.

   Valid format identifiers are those in the ISO File Format Name Space
   defined by RFC 4281 [RFC4281].


4.  Media files

   Each media file URI in a Playlist file MUST identify a media file
   which is a segment of the overall presentation.  Each media file MUST
   be formatted as an MPEG-2 Transport Stream, an MPEG-2 Program Stream,
   or an MPEG-2 audio elementary stream [ISO_13818].  All media files in
   a presentation MUST have the same format.

   Transport Stream files MUST contain a single MPEG-2 Program.  There



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   SHOULD be a Program Association Table and a Program Map Table at the
   start of each file.  A file that contains video SHOULD have at least
   one key frame and enough information to completely initialize a video
   decoder.

   Clients SHOULD be prepared to handle multiple tracks of a particular
   type (e.g. audio or video) by choosing a reasonable subset.  Clients
   MUST ignore private streams inside Transport Streams that they do not
   recognize.

   The encoding parameters for samples within a stream inside a media
   file and between corresponding streams across multiple media files
   SHOULD remain consistent.  However clients SHOULD deal with encoding
   changes as they are encountered, for example by scaling video content
   to accomodate a resolution change.


5.  Key files

   An EXT-X-KEY tag with the URI parameter identifies a Key file.  A Key
   file contains the cipher key that MUST be used to decrypt subsequent
   media files in the Playlist.

   The AES-128 encryption method uses 16-octet keys.  The format of the
   Key file is simply a packed array of these 16 octets in binary
   format.

5.1.  IV for AES-128

   128-bit AES requires the same 16-octet Initialization Vector (IV) to
   be supplied when encrypting and decrypting.  Varying this IV
   increases the strength of the cipher.

   When using the encryption METHOD AES-128, implementations SHALL use
   the sequence number of the media file as the IV when encrypting or
   decrypting media files.  The big-endian binary representation of the
   sequence number SHALL be placed in a 16-octet buffer and padded (on
   the left) with zeros.


6.  Client/Server Actions

   This section describes how the server generates the Playlist and
   media files and how the client should download and play them.







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6.1.  Server Process

   The production of the MPEG-2 stream is outside the scope of this
   document, which simply presumes a source of a continuous stream
   containing the main presentation.

   The server MUST divide the stream into individual media files whose
   duration is approximately equal.  The server SHOULD attempt to divide
   the stream at points that support effective decode of individual
   media files, e.g. on packet and key frame boundaries.

   The server MUST create a URI for each media file that will allow its
   clients to obtain the file.

   The server MUST create a Playlist file.  The Playlist file MUST
   conform to the format described in Section 3.  A URI for each media
   file that the server wishes to make available MUST appear in the
   Playlist in the order in which it is to be played.  The entire media
   file MUST be available to clients if its URI is in the Playlist file.

   The Playlist file MUST contain an EXT-X-TARGETDURATION tag.  It MUST
   indicate the approximate duration of the next media file to be added
   to the main presentation.  This value MUST remain constant for the
   entire presentation.  A typical target duration is 10 seconds.

   The server MUST create a URI for the Playlist file that will allow
   its clients to obtain the file.

   Changes to the Playlist file MUST be made atomically from the point
   of view of the clients.

   Every media file URI in a Playlist MUST be prefixed with an EXTINF
   tag indicating the approximate duration of the media file.

   The server MAY associate an absolute date and time with a media file
   by prefixing its URI with an EXT-X-PROGRAM-DATE-TIME tag.  The value
   of the date and time is arbitrary.

   If the Playlist contains the final media file of the presentation
   then the Playlist file MUST contain the EXT-X-ENDLIST tag.

   If the server wishes to remove an entire presentation, it MUST make
   the Playlist file unavailable to clients.  It SHOULD ensure that all
   media files in the Playlist file remain available to clients for at
   least the duration of the Playlist file at the time of removal.






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6.1.1.  Sliding Window Playlists

   The server MAY limit the availability of media files to those which
   have been most recently added to the Playlist.  To do so the Playlist
   file MUST ALWAYS contain exactly one EXT-X-MEDIA-SEQUENCE tag.  Its
   value MUST be incremented by 1 for every media file URI that is
   removed from the Playlist file.

   Media file URIs MUST be removed from the Playlist file in the order
   in which they were added.

   When the server removes a media file URI from the Playlist, the media
   file MUST remain available to clients for a period of time equal to
   the duration of the media file plus the duration of the longest
   Playlist file in which the media file has appeared.  The duration of
   a Playlist file is the sum of the durations of the media files within
   it.

   If a server plans to remove a media file, it SHOULD ensure that an
   HTTP Expires header reflects the planned time-to-live when it is
   delivered to clients.

   The server MUST maintain at least three main presentation media files
   in the Playlist at all times unless the EXT-X-ENDLIST tag is present.

6.1.2.  Encrypting media files

   If media files are to be encrypted the server MUST define a URI which
   will allow authorized clients to obtain a Key file containing a
   decryption key.  The Key file MUST conform to the format described in
   Section 5.

   The server MAY set the Expires header in the key response to indicate
   that the key may be cached.

   If the encryption METHOD is AES-128, AES-128 CBC encyption SHALL be
   applied to individual media files.  The entire file MUST be
   encrypted.  Cipher Block Chaining MUST NOT be applied across media
   files.  The sequence number of the media file MUST be used as the IV
   as described in Section 5.1.

   The server MUST encrypt every media file in a Playlist using the
   method specified by the EXT-X-KEY tag that most immediately precedes
   its URI in the Playlist file.  Media files preceded by an EXT-X-KEY
   tag whose METHOD is NONE, or not preceded by any EXT-X-KEY tag, MUST
   NOT be encrypted.

   The URI of every EXT-X-KEY tag must be distinct from the URI of every



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   other EXT-X-KEY tag that appears or has appeared in the Playlist
   file, unless its METHOD is NONE.  An EXT-X-KEY tag with a METHOD of
   NONE MUST NOT contain a URI parameter.

   The server MUST NOT remove an EXT-X-KEY tag from the Playlist file if
   the Playlist file contains a URI to a media file encrypted with that
   key.

6.1.3.  Providing variant streams

   A server MAY offer multiple Playlist files to provide different
   encodings of the same presentation.  If it does so it SHOULD provide
   a variant Playlist file that lists each variant stream to allow
   clients to switch between encodings dynamically.

   Variant Playlists MUST contain an EXT-X-STREAM-INF tag for each
   variant stream.  Each EXT-X-STREAM-INF tag for the same presentation
   MUST have the same PROGRAM-ID attribute value.  The PROGRAM-ID value
   for each presentation MUST be unique within the variant Playlist.

   If an EXT-X-STREAM-INF tag contains the CODECS attribute, the
   attribute value MUST include every format defined by [RFC4281] that
   is present in any media file that appears or will appear in the
   Playlist file.

   The server MUST meet the following constraints when producing variant
   streams:

      Each variant stream MUST consist of the same content, including
      content which is not part of the main presentation.

      The server MUST make the same period of content available for all
      variant streams, within an accuracy of the smallest target
      duration of the streams.

      Matching content in variant streams MUST have matching timestamps.
      This allows clients to synchronize the streams.

      Elementary Audio Stream files MUST signal the timestamp of the
      first sample in the file by prepending an ID3 PRIV tag [ID3] with
      an owner identifier of
      "com.apple.streaming.transportStreamTimestamp".  The binary data
      MUST be a 33-bit MPEG-2 Program Elementary Stream timestamp
      expressed as a big-endian eight-octet number.

   In addition, all variant streams SHOULD contain the same encoded
   audio bitstream.  This allows clients to switch between streams
   without audible glitching.



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6.2.  Client Process

   How the client obtains the URI to the Playlist file is outside the
   scope of this document; it is presumed to have done so.

   The client MUST obtain the Playlist file from the URI.  If the
   Playlist file so obtained is a variant Playlist, the client MUST
   obtain the Playlist file from the variant Playlist.

   This document does not specify the treatment of variant streams by
   clients.

6.2.1.  Loading the Playlist file

   Every time a Playlist file is loaded or reloaded from the Playlist
   URI:

      The client SHOULD check that the Playlist file begins with #EXTM3U
      and refuse to continue if it does not.  The client SHOULD ignore
      any tags it does not recognize.

      The client MUST determine the next media file to load as described
      in Section 6.2.4.

   If the Playlist contains the EXT-X-MEDIA-SEQUENCE tag, the client
   SHOULD assume that each media file in it will become unavailable at
   the time that the Playlist file was loaded plus the duration of the
   Playlist file.  The duration of a Playlist file is the sum of the
   durations of the media files within it.

6.2.2.  Playing the Playlist file

   The client SHALL choose which media file to play first from the
   Playlist when playback starts.  If the Playlist file contains the
   EXT-X-ENDLIST tag, any file in the Playlist MAY be played first.  If
   the EXT-X-ENDLIST tag is not present, any file except for the last
   and second-to-last files in the Playlist MAY be played first.

   Once the first media file to play has been chosen, subsequent media
   files in the Playlist MUST be loaded in the order that they appear
   and played in the order that they are loaded.

   The client SHOULD attempt to load media files in advance of when they
   will be required for uninterrupted playback to compensate for
   temporary variations in latency and throughput.

   If the Playlist file contains the EXT-X-ALLOW-CACHE tag and its value
   is NO, the client MUST NOT cache downloaded media files after they



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   have been played.  Otherwise the client MAY cache downloaded media
   files indefinitely for later replay.

   The client MAY use the value of the EXT-X-PROGRAM-DATE-TIME tag to
   display the program origination time to the user.  If the value
   includes time zone information the client SHALL take it into account,
   but if it does not the client MUST NOT infer an originating time
   zone.

   The client MUST NOT depend upon the correctness or the consistency of
   the value of the EXT-X-PROGRAM-DATE-TIME tag.

6.2.3.  Reloading the Playlist file

   The client MUST periodically reload the Playlist file unless it
   contains the EXT-X-ENDLIST tag.

   However the client MUST NOT attempt to reload the Playlist file more
   frequently than specified by this section.

   When a client loads a Playlist file for the first time or reloads a
   Playlist file and finds that it has changed since the last time it
   was loaded, the client MUST wait for a period of time before
   attempting to reload the Playlist file again.  This period is called
   the initial minimum reload delay.  It is measured from the time that
   the client began loading the Playlist file.

   The initial minimum reload delay is the duration of the last media
   file in the Playlist or 3 times the target duration, whichever is
   less.  Media file duration is specified by the EXTINF tag.

   If the client reloads a Playlist file and finds that it has not
   changed then it MUST wait for a period of time before retrying.  The
   minimum delay is three times the target duration or a multiple of the
   initial minimum reload delay, whichever is less.  This multiple is
   0.5 for the first attempt, 1.5 for the second, and 3.0 thereafter.

6.2.4.  Determining the next file to load

   The client MUST examine the Playlist file every time it is loaded or
   reloaded to determine the next media file to load.

   The first file to load MUST be the file that the client has chosen to
   play first, as described in Section 6.2.2.

   If the first file to be played has been loaded and the Playlist file
   does not contain the EXT-X-MEDIA-SEQUENCE tag then the client MUST
   verify that the current Playlist file contains the URI of the last



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   loaded media file at the offset it was originally found at, halting
   playback if it does not.  The next media file to load MUST be the
   first media file URI following the last-loaded URI in the Playlist.

   If the first file to be played has been loaded and the Playlist file
   contains the EXT-X-MEDIA-SEQUENCE tag then the next media file to
   load SHALL be the one with the lowest sequence number that is greater
   than the sequence number of the last media file loaded.

6.2.5.  Playing encrypted media files

   If a Playlist file contains an EXT-X-KEY tag that specifies a Key
   file URI, the client MUST obtain that key file and use the key inside
   it to decrypt all media files following the EXT-X-KEY tag until
   another EXT-X-KEY tag is encountered.

   If the encryption METHOD is AES-128, AES-128 CBC decryption SHALL be
   applied to individual media files.  The entire file MUST be
   decrypted.  Cipher Block Chaining MUST NOT be applied across media
   files.  The sequence number of the media file MUST be used as the IV
   as described in Section 5.1.

   If the encryption METHOD is NONE, the client MUST treat all media
   files following the EXT-X-KEY tag as cleartext (not encrypted) until
   another EXT-X-KEY tag is encountered.


7.  Examples

   This section contains several example Playlist files.

7.1.  Simple Playlist file

   #EXTM3U
   #EXT-X-TARGETDURATION:10
   #EXTINF:5220,
   http://media.example.com/entire.ts
   #EXT-X-ENDLIST













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7.2.  Sliding Window Playlist, using HTTPS

   #EXTM3U
   #EXT-X-TARGETDURATION:8
   #EXT-X-MEDIA-SEQUENCE:2680

   #EXTINF:8,
   https://priv.example.com/fileSequence2680.ts
   #EXTINF:8,
   https://priv.example.com/fileSequence2681.ts
   #EXTINF:8,
   https://priv.example.com/fileSequence2682.ts

7.3.  Playlist file with encrypted media files

   #EXTM3U
   #EXT-X-MEDIA-SEQUENCE:7794
   #EXT-X-TARGETDURATION:15

   #EXT-X-KEY:METHOD=AES-128,URI="https://priv.example.com/key.php?r=52"

   #EXTINF:15,
   http://media.example.com/fileSequence7794.ts
   #EXTINF:15,
   http://media.example.com/fileSequence7795.ts
   #EXTINF:15,
   http://media.example.com/fileSequence7796.ts

   #EXT-X-KEY:METHOD=AES-128,URI="https://priv.example.com/key.php?r=53"

   #EXTINF:15,
   http://media.example.com/fileSequence7797.ts

7.4.  Variant Playlist file

   #EXTM3U
   #EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=1280000
   http://example.com/low.m3u8
   #EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=2560000
   http://example.com/mid.m3u8
   #EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=7680000
   http://example.com/hi.m3u8
   #EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=65000,CODECS="mp4a.40.5"
   http://example.com/audio-only.m3u8







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8.  Contributors

   Significant contributions to the design of this protocol were made by
   Jim Batson, David Biderman, Bill May, Roger Pantos, and Alan Tseng.


9.  IANA Considerations

   This memo includes no request to IANA.


10.  Security Considerations

   Since the protocol relies primarily on HTTP for transport, most of
   the same security considerations apply.  See section 15 of RFC 2616
   [RFC2616].

   Media file parsers are typically subject to "fuzzing" attacks.
   Clients should take care when parsing files received from a server so
   that non-compliant files are rejected.


11.  References

11.1.  Normative References

   [AES_128]  U.S. Department of Commerce/National Institute of
              Standards and Technology, "Advanced Encryption Standard
              (AES), FIPS PUB 197", November 2001, <http://
              csrc.nist.gov/publications/fips/fips197/fips-197.pdf>.

   [ISO_13818]
              International Organization for Standardization, "ISO/IEC
              International Standard 13818; Generic coding of moving
              pictures and associated audio information", November 1994,
              <http://www.iso.org/iso/catalogue_detail?csnumber=44169>.

   [ISO_8601]
              International Organization for Standardization, "ISO/IEC
              International Standard 8601:2004; Data elements and
              interchange formats -- Information interchange --
              Representation of dates and times", December 2004,
              <http://www.iso.org/iso/catalogue_detail?csnumber=40874>.

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              November 1996.




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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [RFC3852]  Housley, R., "Cryptographic Message Syntax (CMS)",
              RFC 3852, July 2004.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC4281]  Gellens, R., Singer, D., and P. Frojdh, "The Codecs
              Parameter for "Bucket" Media Types", RFC 4281,
              November 2005.

11.2.  Informative References

   [ID3]      ID3.org, "The ID3 audio file data tagging format",
              <http://www.id3.org/Developer_Information>.

   [M3U]      Nullsoft, Inc., "The M3U Playlist format, originally
              invented for the Winamp media player",
              <http://wikipedia.org/wiki/M3U>.


Author's Address

   Roger Pantos (editor)
   Apple Inc.
   Cupertino, California
   United States

   Email: http-live-streaming-review@group.apple.com












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