draft-ietf-avtext-framemarking-10.txt   draft-ietf-avtext-framemarking-11.txt 
Network Working Group M. Zanaty Network Working Group M. Zanaty
Internet-Draft E. Berger Internet-Draft E. Berger
Intended status: Standards Track S. Nandakumar Intended status: Standards Track S. Nandakumar
Expires: May 24, 2020 Cisco Systems Expires: February 5, 2021 Cisco Systems
November 21, 2019 August 4, 2020
Frame Marking RTP Header Extension Frame Marking RTP Header Extension
draft-ietf-avtext-framemarking-10 draft-ietf-avtext-framemarking-11
Abstract Abstract
This document describes a Frame Marking RTP header extension used to This document describes a Frame Marking RTP header extension used to
convey information about video frames that is critical for error convey information about video frames that is critical for error
recovery and packet forwarding in RTP middleboxes or network nodes. recovery and packet forwarding in RTP middleboxes or network nodes.
It is most useful when media is encrypted, and essential when the It is most useful when media is encrypted, and essential when the
middlebox or node has no access to the media decryption keys. It is middlebox or node has no access to the media decryption keys. It is
also useful for codec-agnostic processing of encrypted or unencrypted also useful for codec-agnostic processing of encrypted or unencrypted
media, while it also supports extensions for codec-specific media, while it also supports extensions for codec-specific
skipping to change at page 1, line 38 skipping to change at page 1, line 38
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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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 time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 24, 2020. This Internet-Draft will expire on February 5, 2021.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Key Words for Normative Requirements . . . . . . . . . . . . 4 2. Key Words for Normative Requirements . . . . . . . . . . . . 4
3. Frame Marking RTP Header Extension . . . . . . . . . . . . . 4 3. Frame Marking RTP Header Extension . . . . . . . . . . . . . 4
3.1. Short Extension for Non-Scalable Streams . . . . . . . . 4 3.1. Long Extension for Scalable Streams . . . . . . . . . . . 4
3.2. Long Extension for Scalable Streams . . . . . . . . . . . 5 3.2. Short Extension for Non-Scalable Streams . . . . . . . . 6
3.2.1. Layer ID Mappings for Scalable Streams . . . . . . . 7 3.3. Layer ID Mappings for Scalable Streams . . . . . . . . . 7
3.2.1.1. H265 LID Mapping . . . . . . . . . . . . . . . . 7 3.3.1. H265 LID Mapping . . . . . . . . . . . . . . . . . . 7
3.2.1.2. H264-SVC LID Mapping . . . . . . . . . . . . . . 8 3.3.2. H264-SVC LID Mapping . . . . . . . . . . . . . . . . 8
3.2.1.3. H264 (AVC) LID Mapping . . . . . . . . . . . . . 8 3.3.3. H264 (AVC) LID Mapping . . . . . . . . . . . . . . . 9
3.2.1.4. VP8 LID Mapping . . . . . . . . . . . . . . . . . 8 3.3.4. VP8 LID Mapping . . . . . . . . . . . . . . . . . . . 9
3.2.1.5. Future Codec LID Mapping . . . . . . . . . . . . 8 3.3.5. Future Codec LID Mapping . . . . . . . . . . . . . . 10
3.3. Signaling Information . . . . . . . . . . . . . . . . . . 9 3.4. Signaling Information . . . . . . . . . . . . . . . . . . 10
3.4. Usage Considerations . . . . . . . . . . . . . . . . . . 9 3.5. Usage Considerations . . . . . . . . . . . . . . . . . . 10
3.4.1. Relation to Layer Refresh Request (LRR) . . . . . . . 9 3.5.1. Relation to Layer Refresh Request (LRR) . . . . . . . 10
3.4.2. Scalability Structures . . . . . . . . . . . . . . . 10 3.5.2. Scalability Structures . . . . . . . . . . . . . . . 11
4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 4. Security Considerations . . . . . . . . . . . . . . . . . . . 11
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1. Normative References . . . . . . . . . . . . . . . . . . 10 7.1. Normative References . . . . . . . . . . . . . . . . . . 12
7.2. Informative References . . . . . . . . . . . . . . . . . 11 7.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
Many widely deployed RTP [RFC3550] topologies [RFC7667] used in Many widely deployed RTP [RFC3550] topologies [RFC7667] used in
modern voice and video conferencing systems include a centralized modern voice and video conferencing systems include a centralized
component that acts as an RTP switch. It receives voice and video component that acts as an RTP switch. It receives voice and video
streams from each participant, which may be encrypted using SRTP streams from each participant, which may be encrypted using SRTP
[RFC3711], or extensions that provide participants with private media [RFC3711], or extensions that provide participants with private media
[I-D.ietf-perc-private-media-framework] via end-to-end encryption [I-D.ietf-perc-private-media-framework] via end-to-end encryption
where the switch has no access to media decryption keys. The goal is where the switch has no access to media decryption keys. The goal is
skipping to change at page 3, line 31 skipping to change at page 3, line 31
switch typically needs some critical information about video frames switch typically needs some critical information about video frames
in order to start and stop forwarding streams. in order to start and stop forwarding streams.
o Because of inter-frame dependencies, it should ideally switch o Because of inter-frame dependencies, it should ideally switch
video streams at a point where the first frame from the new video streams at a point where the first frame from the new
speaker can be decoded by recipients without prior frames, e.g speaker can be decoded by recipients without prior frames, e.g
switch on an intra-frame. switch on an intra-frame.
o In many cases, the switch may need to drop frames in order to o In many cases, the switch may need to drop frames in order to
realize congestion control techniques, and needs to know which realize congestion control techniques, and needs to know which
frames can be dropped with minimal impact to video quality. frames can be dropped with minimal impact to video quality.
o For scalable streams with dependent layers, the switch may need to
selectively forward specific layers to specific recipients due to
recipient bandwidth or decoder limits.
o Furthermore, it is highly desirable to do this in a payload o Furthermore, it is highly desirable to do this in a payload
format-agnostic way which is not specific to each different video format-agnostic way which is not specific to each different video
codec. Most modern video codecs share common concepts around codec. Most modern video codecs share common concepts around
frame types and other critical information to make this codec- frame types and other critical information to make this codec-
agnostic handling possible. agnostic handling possible.
o It is also desirable to be able to do this for SRTP without o It is also desirable to be able to do this for SRTP without
requiring the video switch to decrypt the packets. SRTP will requiring the video switch to decrypt the packets. SRTP will
encrypt the RTP payload format contents and consequently this data encrypt the RTP payload format contents and consequently this data
is not usable for the switching function without decryption, which is not usable for the switching function without decryption, which
may not even be possible in the case of end-to-end encryption of may not even be possible in the case of end-to-end encryption of
skipping to change at page 4, line 41 skipping to change at page 4, line 41
original source packet. Such provisions SHALL be followed to recover original source packet. Such provisions SHALL be followed to recover
the Frame Marking RTP header extension of the original source packet. the Frame Marking RTP header extension of the original source packet.
Source packet frame markings may be useful when generating Redundancy Source packet frame markings may be useful when generating Redundancy
RTP Streams; for example, the I and D bits can be used to generate RTP Streams; for example, the I and D bits can be used to generate
extra or no redundancy, respectively, and redundancy schemes with extra or no redundancy, respectively, and redundancy schemes with
source blocks can align source block boundaries with Independent source blocks can align source block boundaries with Independent
frame boundaries as marked by the I bit. frame boundaries as marked by the I bit.
A frame, in the context of this specification, is the set of RTP A frame, in the context of this specification, is the set of RTP
packets with the same RTP timestamp from a specific RTP packets with the same RTP timestamp from a specific RTP
synchronization source (SSRC). synchronization source (SSRC). A frame within a layer is the set of
RTP packets with the same RTP timestamp, SSRC, Temporal ID (TID), and
3.1. Short Extension for Non-Scalable Streams Layer ID (LID).
The following RTP header extension is RECOMMENDED for non-scalable
streams. It MAY also be used for scalable streams if the sender has
limited or no information about stream scalability. The ID is
assigned per [RFC8285], and the length is encoded as L=0 which
indicates 1 octet of data.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID=? | L=0 |S|E|I|D|0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The following information are extracted from the media payload and
sent in the Frame Marking RTP header extension.
o S: Start of Frame (1 bit) - MUST be 1 in the first packet in a
frame; otherwise MUST be 0.
o E: End of Frame (1 bit) - MUST be 1 in the last packet in a frame;
otherwise MUST be 0. SHOULD match the RTP header marker bit in
payload formats with such semantics for marking end of frame.
o I: Independent Frame (1 bit) - MUST be 1 for frames that can be
decoded independent of temporally prior frames, e.g. intra-frame,
VPX keyframe, H.264 IDR [RFC6184], H.265 IDR/CRA/BLA/RAP
[RFC7798]; otherwise MUST be 0.
o D: Discardable Frame (1 bit) - MUST be 1 for frames the sender
knows can be discarded, and still provide a decodable media
stream; otherwise MUST be 0.
o The remaining (4 bits) - are reserved/fixed values and not used
for non-scalable streams; they MUST be set to 0 upon transmission
and ignored upon reception.
3.2. Long Extension for Scalable Streams 3.1. Long Extension for Scalable Streams
The following RTP header extension is RECOMMENDED for scalable The following RTP header extension is RECOMMENDED for scalable
streams. It MAY also be used for non-scalable streams, in which case streams. It MAY also be used for non-scalable streams, in which case
TID, LID and TL0PICIDX MUST be 0 or omitted. The ID is assigned per TID, LID and TL0PICIDX MUST be 0 or omitted. The ID is assigned per
[RFC8285], and the length is encoded as L=2 which indicates 3 octets [RFC8285], and the length is encoded as L=2 which indicates 3 octets
of data when nothing is omitted, or L=1 for 2 octets when TL0PICIDX of data when nothing is omitted, or L=1 for 2 octets when TL0PICIDX
is omitted, or L=0 for 1 octet when both LID and TL0PICIDX are is omitted, or L=0 for 1 octet when both LID and TL0PICIDX are
omitted. omitted.
0 1 2 3 0 1 2 3
skipping to change at page 6, line 28 skipping to change at page 5, line 30
The following information are extracted from the media payload and The following information are extracted from the media payload and
sent in the Frame Marking RTP header extension. sent in the Frame Marking RTP header extension.
o S: Start of Frame (1 bit) - MUST be 1 in the first packet in a o S: Start of Frame (1 bit) - MUST be 1 in the first packet in a
frame within a layer; otherwise MUST be 0. frame within a layer; otherwise MUST be 0.
o E: End of Frame (1 bit) - MUST be 1 in the last packet in a frame o E: End of Frame (1 bit) - MUST be 1 in the last packet in a frame
within a layer; otherwise MUST be 0. Note that the RTP header within a layer; otherwise MUST be 0. Note that the RTP header
marker bit MAY be used to infer the last packet of the highest marker bit MAY be used to infer the last packet of the highest
enhancement layer, in payload formats with such semantics. enhancement layer, in payload formats with such semantics.
o I: Independent Frame (1 bit) - MUST be 1 for frames that can be o I: Independent Frame (1 bit) - MUST be 1 for a frame within a
decoded independent of temporally prior frames, e.g. intra-frame, layer that can be decoded independent of temporally prior frames,
VPX keyframe, H.264 IDR [RFC6184], H.265 IDR/CRA/BLA/RAP e.g. intra-frame, VPX keyframe, H.264 IDR [RFC6184], H.265
[RFC7798]; otherwise MUST be 0. Note that this bit only signals IDR/CRA/BLA/RAP [RFC7798]; otherwise MUST be 0. Note that this
temporal independence, so it can be 1 in spatial or quality bit only signals temporal independence, so it can be 1 in spatial
enhancement layers that depend on temporally co-located layers but or quality enhancement layers that depend on temporally co-located
not temporally prior frames. layers but not temporally prior frames.
o D: Discardable Frame (1 bit) - MUST be 1 for frames the sender o D: Discardable Frame (1 bit) - MUST be 1 for a frame within a
knows can be discarded, and still provide a decodable media layer the sender knows can be discarded, and still provide a
stream; otherwise MUST be 0. decodable media stream; otherwise MUST be 0.
o B: Base Layer Sync (1 bit) - When TID is not 0, this MUST be 1 if o B: Base Layer Sync (1 bit) - When TID is not 0, this MUST be 1 if
the sender knows this frame only depends on the base temporal the sender knows this frame within a layer only depends on the
layer; otherwise MUST be 0. When TID is 0 or if no scalability is base temporal layer; otherwise MUST be 0. When TID is 0 or if no
used, this MUST be 0. scalability is used, this MUST be 0.
o TID: Temporal ID (3 bits) - The base temporal layer starts with 0, o TID: Temporal ID (3 bits) - Identifies the temporal layer/sub-
and increases with 1 for each higher temporal layer/sub-layer. If layer encoded, starting with 0 for the base layer, and increasing
no scalability is used, this MUST be 0. It is implicitly 0 in the with higher temporal fidelity. If no scalability is used, this
short extension format. MUST be 0. It is implicitly 0 in the short extension format.
o LID: Layer ID (8 bits) - Identifies the spatial and quality layer o LID: Layer ID (8 bits) - Identifies the spatial and quality layer
encoded, starting with 0 and increasing with higher fidelity. If encoded, starting with 0 for the base layer, and increasing with
no scalability is used, this MUST be 0 or omitted to reduce higher fidelity. If no scalability is used, this MUST be 0 or
length. When omitted, TL0PICIDX MUST also be omitted. It is omitted to reduce length. When omitted, TL0PICIDX MUST also be
implicitly 0 in the short extension format or when omitted in the omitted. It is implicitly 0 in the short extension format or when
long extension format. omitted in the long extension format.
o TL0PICIDX: Temporal Layer 0 Picture Index (8 bits) - When TID is 0 o TL0PICIDX: Temporal Layer 0 Picture Index (8 bits) - When TID is 0
and LID is 0, this is a cyclic counter labeling base layer frames. and LID is 0, this is a cyclic counter labeling base layer frames.
When TID is not 0 or LID is not 0, this indicates a dependency on When TID is not 0 or LID is not 0, this indicates a dependency on
the given index, such that this frame in this layer depends on the the given index, such that this frame within this layer depends on
frame with this label in the layer with TID 0 and LID 0. If no the frame with this label in the layer with TID 0 and LID 0. If
scalability is used, or the cyclic counter is unknown, this MUST no scalability is used, or the cyclic counter is unknown, this
be omitted to reduce length. Note that 0 is a valid index value MUST be omitted to reduce length. Note that 0 is a valid index
for TL0PICIDX. value for TL0PICIDX.
The layer information contained in TID and LID convey useful aspects The layer information contained in TID and LID convey useful aspects
of the layer structure that can be utilized in selective forwarding. of the layer structure that can be utilized in selective forwarding.
Without further information about the layer structure, these
identifiers can only be used for relative priority of layers. They Without further information about the layer structure, these TID/LID
convey a layer hierarchy with TID=0 and LID=0 identifying the base identifiers can only be used for relative priority of layers and
layer. Higher values of TID identify higher temporal layers with implicit dependencies between layers. They convey a layer hierarchy
higher frame rates. Higher values of LID identify higher spatial with TID=0 and LID=0 identifying the base layer. Higher values of
and/or quality layers with higher resolutions and/or bitrates. TID identify higher temporal layers with higher frame rates. Higher
values of LID identify higher spatial and/or quality layers with
higher resolutions and/or bitrates. Implicit dependencies between
layers assume that a layer with a given TID/LID MAY depend on
layer(s) with the same or lower TID/LID, but MUST NOT depend on
layer(s) with higher TID/LID.
With further information, for example, possible future RTCP SDES With further information, for example, possible future RTCP SDES
items that convey full layer structure information, it may be items that convey full layer structure information, it may be
possible to map these TIDs and LIDs to specific frame rates, possible to map these TIDs and LIDs to specific absolute frame rates,
resolutions and bitrates. Such additional layer information may be resolutions and bitrates, as well as explicit dependencies between
useful for forwarding decisions in the RTP switch, but is beyond the layers. Such additional layer information may be useful for
scope of this memo. The relative layer information is still useful forwarding decisions in the RTP switch, but is beyond the scope of
for many selective forwarding decisions even without such additional this memo. The relative layer information is still useful for many
layer information. selective forwarding decisions even without such additional layer
information.
3.2.1. Layer ID Mappings for Scalable Streams 3.2. Short Extension for Non-Scalable Streams
The following RTP header extension is RECOMMENDED for non-scalable
streams. It is identical to the shortest form of the extension for
scalable streams, except the last four bits (B and TID) are replaced
with zeros. It MAY also be used for scalable streams if the sender
has limited or no information about stream scalability. The ID is
assigned per [RFC8285], and the length is encoded as L=0 which
indicates 1 octet of data.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID=? | L=0 |S|E|I|D|0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The following information are extracted from the media payload and
sent in the Frame Marking RTP header extension.
o S: Start of Frame (1 bit) - MUST be 1 in the first packet in a
frame; otherwise MUST be 0.
o E: End of Frame (1 bit) - MUST be 1 in the last packet in a frame;
otherwise MUST be 0. SHOULD match the RTP header marker bit in
payload formats with such semantics for marking end of frame.
o I: Independent Frame (1 bit) - MUST be 1 for frames that can be
decoded independent of temporally prior frames, e.g. intra-frame,
VPX keyframe, H.264 IDR [RFC6184], H.265 IDR/CRA/BLA/IRAP
[RFC7798]; otherwise MUST be 0.
o D: Discardable Frame (1 bit) - MUST be 1 for frames the sender
knows can be discarded, and still provide a decodable media
stream; otherwise MUST be 0.
o The remaining (4 bits) - are reserved/fixed values and not used
for non-scalable streams; they MUST be set to 0 upon transmission
and ignored upon reception.
3.3. Layer ID Mappings for Scalable Streams
This section maps the specific Layer ID information contained in This section maps the specific Layer ID information contained in
specific scalable codecs to the generic LID and TID fields. specific scalable codecs to the generic LID and TID fields.
Note that non-scalable streams have no Layer ID information and thus Note that non-scalable streams have no Layer ID information and thus
no mappings. no mappings.
3.2.1.1. H265 LID Mapping 3.3.1. H265 LID Mapping
The following shows the H265 [RFC7798] LayerID (6 bits) and TID (3 The following shows the H265 [RFC7798] LayerID (6 bits) and TID (3
bits) from the NAL unit header mapped to the generic LID and TID bits) from the NAL unit header mapped to the generic LID and TID
fields. fields.
The I bit MUST be 1 when the NAL unit type is 16-23 (inclusive), The S and E bits MUST match the correspondingly named bits in
otherwise it MUST be 0. PACI:PHES:TSCI payload structures.
The S and E bits MUST match the corresponding bits in PACI:PHES:TSCI The I bit MUST be 1 when the NAL unit type is 16-23 (inclusive) or
payload structures. 32-34 (inclusive), or an aggregation packet or fragmentation unit
encapsulating any of these types, otherwise it MUST be 0. These
ranges cover intra (IRAP) frames as well as critical parameter sets
(VPS, SPS, PPS).
The D bit MUST be 1 when the NAL unit type is 0, 2, 4, 6, 8, 10, 12,
14, or 38, or an aggregation packet or fragmentation unit
encapsulating only these types, otherwise it MUST be 0. These ranges
cover non-reference frames as well as filler data.
The B bit can not be determined reliably from simple inspection of
payload headers, and therefore is determined by implementation-
specific means. For example, internal codec interfaces may provide
information to set this reliably.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID=? | L=2 |S|E|I|D|B| TID |0|0| LayerID | TL0PICIDX | | ID=? | L=2 |S|E|I|D|B| TID |0|0| LayerID | TL0PICIDX |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2.1.2. H264-SVC LID Mapping 3.3.2. H264-SVC LID Mapping
The following shows H264-SVC [RFC6190] Layer encoding information (3 The following shows H264-SVC [RFC6190] Layer encoding information (3
bits for spatial/dependency layer, 4 bits for quality layer and 3 bits for spatial/dependency layer, 4 bits for quality layer and 3
bits for temporal layer) mapped to the generic LID and TID fields. bits for temporal layer) mapped to the generic LID and TID fields.
The S, E, I and D bits MUST match the corresponding bits in PACSI The S, E, I and D bits MUST match the correspondingly named bits in
payload structures. PACSI payload structures.
The I bit MUST be 1 when the NAL unit type is 5, 7, 8, 13, or 15, or
an aggregation packet or fragmentation unit encapsulating any of
these types, otherwise it MUST be 0. These ranges cover intra (IDR)
frames as well as critical parameter sets (SPS/PPS variants).
The D bit MUST be 1 when the NAL unit header NRI field is 0, or an
aggregation packet or fragmentation unit encapsulating only NAL units
with NRI=0, otherwise it MUST be 0. The NRI=0 condition signals non-
reference frames.
The B bit can not be determined reliably from simple inspection of
payload headers, and therefore is determined by implementation-
specific means. For example, internal codec interfaces may provide
information to set this reliably.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID=? | L=2 |S|E|I|D|B| TID |0| DID | QID | TL0PICIDX | | ID=? | L=2 |S|E|I|D|B| TID |0| DID | QID | TL0PICIDX |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2.1.3. H264 (AVC) LID Mapping 3.3.3. H264 (AVC) LID Mapping
The following shows the header extension for H264 (AVC) [RFC6184] The following shows the header extension for H264 (AVC) [RFC6184]
that contains only temporal layer information. that contains only temporal layer information.
The S bit MUST be 1 when the timestamp in the RTP header differs from
the timestamp in the prior RTP sequence number from the same SSRC,
otherwise it MUST be 0.
The E bit MUST match the M bit in the RTP header.
The I bit MUST be 1 when the NAL unit type is 5, 7, or 8, or an
aggregation packet or fragmentation unit encapsulating any of these
types, otherwise it MUST be 0. These ranges cover intra (IDR) frames
as well as critical parameter sets (SPS/PPS).
The D bit MUST be 1 when the NAL unit header NRI field is 0, or an
aggregation packet or fragmentation unit encapsulating only NAL units
with NRI=0, otherwise it MUST be 0. The NRI=0 condition signals non-
reference frames.
The B bit can not be determined reliably from simple inspection of
payload headers, and therefore is determined by implementation-
specific means. For example, internal codec interfaces may provide
information to set this reliably.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID=? | L=2 |S|E|I|D|B| TID |0|0|0|0|0|0|0|0| TL0PICIDX | | ID=? | L=2 |S|E|I|D|B| TID |0|0|0|0|0|0|0|0| TL0PICIDX |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2.1.4. VP8 LID Mapping 3.3.4. VP8 LID Mapping
The following shows the header extension for VP8 [RFC7741] that The following shows the header extension for VP8 [RFC7741] that
contains only temporal layer information. contains only temporal layer information.
The S bit MUST match the correspondingly named bit in the VP8 payload
descriptor when PID=0, otherwise it MUST be 0.
The E bit MUST match the M bit in the RTP header.
The I bit MUST match the inverse of the P bit in the VP8 payload
header.
The D bit MUST match the N bit in the VP8 payload descriptor.
The B bit MUST match the Y bit in the VP8 payload descriptor.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID=? | L=2 |S|E|I|D|B| TID |0|0|0|0|0|0|0|0| TL0PICIDX | | ID=? | L=2 |S|E|I|D|B| TID |0|0|0|0|0|0|0|0| TL0PICIDX |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2.1.5. Future Codec LID Mapping 3.3.5. Future Codec LID Mapping
The RTP payload format specification for future video codecs SHOULD The RTP payload format specification for future video codecs SHOULD
include a section describing the LID mapping and TID mapping for the include a section describing the LID mapping and TID mapping for the
codec. For example, the LID/TID mapping for the VP9 codec is codec. For example, the LID/TID mapping for the VP9 codec is
described in the VP9 RTP Payload Format [I-D.ietf-payload-vp9]. described in the VP9 RTP Payload Format [I-D.ietf-payload-vp9].
3.3. Signaling Information 3.4. Signaling Information
The URI for declaring this header extension in an extmap attribute is The URI for declaring this header extension in an extmap attribute is
"urn:ietf:params:rtp-hdrext:framemarking". It does not contain any "urn:ietf:params:rtp-hdrext:framemarking". It does not contain any
extension attributes. extension attributes.
An example attribute line in SDP: An example attribute line in SDP:
a=extmap:3 urn:ietf:params:rtp-hdrext:framemarking a=extmap:3 urn:ietf:params:rtp-hdrext:framemarking
3.4. Usage Considerations 3.5. Usage Considerations
The header extension values MUST represent what is already in the RTP The header extension values MUST represent what is already in the RTP
payload. payload.
When an RTP switch needs to discard a received video frame due to When an RTP switch needs to discard a received video frame due to
congestion control considerations, it is RECOMMENDED that it congestion control considerations, it is RECOMMENDED that it
preferably drop frames marked with the D (Discardable) bit set, or preferably drop frames marked with the D (Discardable) bit set, or
the highest values of TID and LID, which indicate the highest the highest values of TID and LID, which indicate the highest
temporal and spatial/quality enhancement layers, since those temporal and spatial/quality enhancement layers, since those
typically have fewer dependenices on them than lower layers. typically have fewer dependenices on them than lower layers.
When an RTP switch wants to forward a new video stream to a receiver, When an RTP switch wants to forward a new video stream to a receiver,
it is RECOMMENDED to select the new video stream from the first it is RECOMMENDED to select the new video stream from the first
switching point with the I (Independent) bit set in all spatial switching point with the I (Independent) bit set in all spatial
layers and forward the same. An RTP switch can request a media layers and forward the same. An RTP switch can request a media
source to generate a switching point by sending Full Intra Request source to generate a switching point by sending Full Intra Request
(RTCP FIR) as defined in [RFC5104], for example. (RTCP FIR) as defined in [RFC5104], for example.
3.4.1. Relation to Layer Refresh Request (LRR) 3.5.1. Relation to Layer Refresh Request (LRR)
Receivers can use the Layer Refresh Request (LRR) Receivers can use the Layer Refresh Request (LRR)
[I-D.ietf-avtext-lrr] RTCP feedback message to upgrade to a higher [I-D.ietf-avtext-lrr] RTCP feedback message to upgrade to a higher
layer in scalable encodings. The TID/LID values and formats used in layer in scalable encodings. The TID/LID values and formats used in
LRR messages MUST correspond to the same values and formats specified LRR messages MUST correspond to the same values and formats specified
in Section 3.2. in Section 3.1.
Because frame marking can only be used with temporally-nested Because frame marking can only be used with temporally-nested
streams, temporal-layer LRR refreshes are unnecessary for frame- streams, temporal-layer LRR refreshes are unnecessary for frame-
marked streams. Other refreshes can be detected based on the I bit marked streams. Other refreshes can be detected based on the I bit
being set for the specific spatial layers. being set for the specific spatial layers.
3.4.2. Scalability Structures 3.5.2. Scalability Structures
The LID and TID information is most useful for fixed scalability The LID and TID information is most useful for fixed scalability
structures, such as nested hierarchical temporal layering structures, structures, such as nested hierarchical temporal layering structures,
where each temporal layer only references lower temporal layers or where each temporal layer only references lower temporal layers or
the base temporal layer. The LID and TID information is less useful, the base temporal layer. The LID and TID information is less useful,
or even not useful at all, for complex, irregular scalability or even not useful at all, for complex, irregular scalability
structures that do not conform to common, fixed patterns of inter- structures that do not conform to common, fixed patterns of inter-
layer dependencies and referencing structures. Therefore it is layer dependencies and referencing structures. Therefore it is
RECOMMENDED to use LID and TID information for RTP switch forwarding RECOMMENDED to use LID and TID information for RTP switch forwarding
decisions only in the case of temporally nested scalability decisions only in the case of temporally nested scalability
skipping to change at page 10, line 29 skipping to change at page 11, line 36
4. Security Considerations 4. Security Considerations
In the Secure Real-Time Transport Protocol (SRTP) [RFC3711], RTP In the Secure Real-Time Transport Protocol (SRTP) [RFC3711], RTP
header extensions are authenticated but usually not encrypted. When header extensions are authenticated but usually not encrypted. When
header extensions are used some of the payload type information are header extensions are used some of the payload type information are
exposed and visible to middle boxes. The encrypted media data is not exposed and visible to middle boxes. The encrypted media data is not
exposed, so this is not seen as a high risk exposure. exposed, so this is not seen as a high risk exposure.
5. Acknowledgements 5. Acknowledgements
Many thanks to Bernard Aboba, Jonathan Lennox, Stephan Wenger, and Many thanks to Bernard Aboba, Jonathan Lennox, Stephan Wenger, Dale
Dale Worley for their inputs. Worley, and Magnus Westerlund for their inputs.
6. IANA Considerations 6. IANA Considerations
This document defines a new extension URI to the RTP Compact This document defines a new extension URI to the RTP Compact
HeaderExtensions sub-registry of the Real-Time Transport Protocol HeaderExtensions sub-registry of the Real-Time Transport Protocol
(RTP) Parameters registry, according to the following data: (RTP) Parameters registry, according to the following data:
Extension URI: urn:ietf:params:rtp-hdrext:framemarkinginfo Extension URI: urn:ietf:params:rtp-hdrext:framemarkinginfo
Description: Frame marking information for video streams Description: Frame marking information for video streams
Contact: mzanaty@cisco.com Contact: mzanaty@cisco.com
skipping to change at page 11, line 44 skipping to change at page 12, line 48
7.2. Informative References 7.2. Informative References
[I-D.ietf-avtext-lrr] [I-D.ietf-avtext-lrr]
Lennox, J., Hong, D., Uberti, J., Holmer, S., and M. Lennox, J., Hong, D., Uberti, J., Holmer, S., and M.
Flodman, "The Layer Refresh Request (LRR) RTCP Feedback Flodman, "The Layer Refresh Request (LRR) RTCP Feedback
Message", draft-ietf-avtext-lrr-07 (work in progress), Message", draft-ietf-avtext-lrr-07 (work in progress),
July 2017. July 2017.
[I-D.ietf-payload-vp9] [I-D.ietf-payload-vp9]
Uberti, J., Holmer, S., Flodman, M., Lennox, J., and D. Uberti, J., Holmer, S., Flodman, M., Hong, D., and J.
Hong, "RTP Payload Format for VP9 Video", draft-ietf- Lennox, "RTP Payload Format for VP9 Video", draft-ietf-
payload-vp9-07 (work in progress), July 2019. payload-vp9-10 (work in progress), July 2020.
[I-D.ietf-perc-private-media-framework] [I-D.ietf-perc-private-media-framework]
Jones, P., Benham, D., and C. Groves, "A Solution Jones, P., Benham, D., and C. Groves, "A Solution
Framework for Private Media in Privacy Enhanced RTP Framework for Private Media in Privacy Enhanced RTP
Conferencing (PERC)", draft-ietf-perc-private-media- Conferencing (PERC)", draft-ietf-perc-private-media-
framework-12 (work in progress), June 2019. framework-12 (work in progress), June 2019.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
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