rfc9626.original   rfc9626.txt 
Network Working Group M. Zanaty Internet Engineering Task Force (IETF) M. Zanaty
Internet-Draft E. Berger Request for Comments: 9626 E. Berger
Intended status: Experimental S. Nandakumar Category: Experimental S. Nandakumar
Expires: 5 September 2024 Cisco Systems ISSN: 2070-1721 Cisco Systems
4 March 2024 August 2024
Video Frame Marking RTP Header Extension Video Frame Marking RTP Header Extension
draft-ietf-avtext-framemarking-16
Abstract Abstract
This document describes a Video Frame Marking RTP header extension This document describes a Video Frame Marking RTP header extension
used to convey information about video frames that is critical for used to convey information about video frames that is critical for
error recovery and packet forwarding in RTP middleboxes or network error recovery and packet forwarding in RTP middleboxes or network
nodes. It is most useful when media is encrypted, and essential when nodes. It is most useful when media is encrypted and essential when
the middlebox or node has no access to the media decryption keys. It the middlebox or node has no access to the media decryption keys. It
is also useful for codec-agnostic processing of encrypted or is also useful for codec-agnostic processing of encrypted or
unencrypted media, while it also supports extensions for codec- unencrypted media, while it also supports extensions for codec-
specific information. specific information.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This document is not an Internet Standards Track specification; it is
provisions of BCP 78 and BCP 79. published for examination, experimental implementation, and
evaluation.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document defines an Experimental Protocol for the Internet
and may be updated, replaced, or obsoleted by other documents at any community. This document is a product of the Internet Engineering
time. It is inappropriate to use Internet-Drafts as reference Task Force (IETF). It represents the consensus of the IETF
material or to cite them other than as "work in progress." community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG). Not
all documents approved by the IESG are candidates for any level of
Internet Standard; see Section 2 of RFC 7841.
This Internet-Draft will expire on 5 September 2024. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9626.
Copyright Notice Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction
2. Key Words for Normative Requirements . . . . . . . . . . . . 4 2. Requirements Language
3. Frame Marking RTP Header Extension . . . . . . . . . . . . . 4 3. Frame Marking RTP Header Extension
3.1. Long Extension for Scalable Streams . . . . . . . . . . . 5 3.1. Long Extension for Scalable Streams
3.2. Short Extension for Non-Scalable Streams . . . . . . . . 7 3.2. Short Extension for Non-scalable Streams
3.3. Layer ID Mappings for Scalable Streams . . . . . . . . . 7 3.3. LID Mappings for Scalable Streams
3.3.1. VP9 LID Mapping . . . . . . . . . . . . . . . . . . . 8 3.3.1. VP9 LID Mapping
3.3.2. H265 LID Mapping . . . . . . . . . . . . . . . . . . 8 3.3.2. H265 LID Mapping
3.3.3. H264-SVC LID Mapping . . . . . . . . . . . . . . . . 9 3.3.3. H264 Scalable Video Coding (SVC) LID Mapping
3.3.4. H264 (AVC) LID Mapping . . . . . . . . . . . . . . . 10 3.3.4. H264 Advanced Video Coding (AVC) LID Mapping
3.3.5. VP8 LID Mapping . . . . . . . . . . . . . . . . . . . 10 3.3.5. VP8 LID Mapping
3.3.6. Future Codec LID Mapping . . . . . . . . . . . . . . 11 3.3.6. Future Codec LID Mapping
3.4. Signaling Information . . . . . . . . . . . . . . . . . . 11 3.4. Signaling Information
3.5. Usage Considerations . . . . . . . . . . . . . . . . . . 11 3.5. Usage Considerations
3.5.1. Relation to Layer Refresh Request (LRR) . . . . . . . 12 3.5.1. Relation to Layer Refresh Request (LRR)
3.5.2. Scalability Structures . . . . . . . . . . . . . . . 12 3.5.2. Scalability Structures
4. Security Considerations and Privacy Considerations . . . . . 12 4. Security and Privacy Considerations
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 5. IANA Considerations
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 6. References
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 6.1. Normative References
7.1. Normative References . . . . . . . . . . . . . . . . . . 14 6.2. Informative References
7.2. Informative References . . . . . . . . . . . . . . . . . 14 Acknowledgements
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 Authors' Addresses
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 Secure
[RFC3711], or extensions that provide participants with private media Real-time Transport Protocol (SRTP) [RFC3711] or extensions that
[RFC8871] via end-to-end encryption where the switch has no access to provide participants with private media [RFC8871] via end-to-end
media decryption keys. The goal is to provide a set of streams back encryption where the switch has no access to media decryption keys.
to the participants which enable them to render the right media The goal is to provide a set of streams back to the participants,
content. In a simple video configuration, for example, the goal will which enable them to render the right media content. For example, in
be that each participant sees and hears just the active speaker. In a simple video configuration, the goal will be that each participant
that case, the goal of the switch is to receive the voice and video sees and hears just the active speaker. In that case, the goal of
streams from each participant, determine the active speaker based on the switch is to receive the voice and video streams from each
energy in the voice packets, possibly using the client-to-mixer audio participant, determine the active speaker based on energy in the
level RTP header extension [RFC6464], and select the corresponding voice packets, possibly using the client-to-mixer audio level RTP
video stream for transmission to participants; see Figure 1. header extension [RFC6464], and select the corresponding video stream
for transmission to participants; see Figure 1.
In this document, an "RTP switch" is used as a common short term for In this document, an "RTP switch" is used as shorthand for the terms
the terms "switching RTP mixer", "source projecting middlebox", "switching RTP mixer", "source projecting middlebox", "source
"source forwarding unit/middlebox" and "video switching MCU" as forwarding unit/middlebox" and "video switching Multipoint Control
discussed in [RFC7667]. Unit (MCU)", as discussed in [RFC7667].
+---+ +------------+ +---+ +---+ +------------+ +---+
| A |<---->| |<---->| B | | A |<---->| |<---->| B |
+---+ | | +---+ +---+ | | +---+
| RTP | | RTP |
+---+ | Switch | +---+ +---+ | Switch | +---+
| C |<---->| |<---->| D | | C |<---->| |<---->| D |
+---+ +------------+ +---+ +---+ +------------+ +---+
Figure 1: RTP switch Figure 1: RTP Switch
In order to properly support switching of video streams, the RTP In order to properly support the switching of video streams, the RTP
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.
* Because of inter-frame dependencies, it should ideally switch * 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.
* In many cases, the switch may need to drop frames in order to * 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 it needs to know which
frames can be dropped with minimal impact to video quality. frames can be dropped with minimal impact to video quality.
* For scalable streams with dependent layers, the switch may need to * For scalable streams with dependent layers, the switch may need to
selectively forward specific layers to specific recipients due to selectively forward specific layers to specific recipients due to
recipient bandwidth or decoder limits. recipient bandwidth or decoder limits.
Furthermore, it is highly desirable to do this in a payload format- Furthermore, it is highly desirable to do this in a payload format-
agnostic way which is not specific to each different video codec. agnostic way that is not specific to each different video codec.
Most modern video codecs share common concepts around frame types and Most modern video codecs share common concepts around frame types and
other critical information to make this codec-agnostic handling other critical information to make this codec-agnostic handling
possible. possible.
It is also desirable to be able to do this for SRTP without requiring It is also desirable to be able to do this for SRTP without requiring
the video switch to decrypt the packets. SRTP will encrypt the RTP the video switch to decrypt the packets. SRTP will encrypt the RTP
payload format contents and consequently this data is not usable for payload format contents; consequently, this data is not usable for
the switching function without decryption, which may not even be the switching function without decryption, which may not even be
possible in the case of end-to-end encryption of private media possible in the case of end-to-end encryption of private media
[RFC8871]. [RFC8871].
By providing meta-information about the RTP streams outside the By providing meta-information about the RTP streams outside the
encrypted media payload, an RTP switch can do codec-agnostic encrypted media payload, an RTP switch can do codec-agnostic
selective forwarding without decrypting the payload. This document selective forwarding without decrypting the payload. This document
specifies the necessary meta-information in an RTP header extension. specifies the necessary meta-information in an RTP header extension.
2. Key Words for Normative Requirements 2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Frame Marking RTP Header Extension 3. Frame Marking RTP Header Extension
This specification uses RTP header extensions as defined in This specification uses RTP header extensions as defined in
[RFC8285]. A subset of meta-information from the video stream is [RFC8285]. A subset of meta-information from the video stream is
provided as an RTP header extension to allow an RTP switch to do provided as an RTP header extension to allow an RTP switch to do
generic selective forwarding of video streams encoded with generic selective forwarding of video streams encoded with
potentially different video codecs. potentially different video codecs.
The Frame Marking RTP header extension is encoded using the one-byte The Frame Marking RTP header extension is encoded using the one-byte
header or two-byte header as described in [RFC8285]. The one-byte header or two-byte header as described in [RFC8285]. The one-byte
header format is used for examples in this memo. The two-byte header header format is used for examples in this document. The two-byte
format is used when other two-byte header extensions are present in header format is used when other two-byte header extensions are
the same RTP packet, since mixing one-byte and two-byte extensions is present in the same RTP packet since mixing one-byte and two-byte
not possible in the same RTP packet. extensions is not possible in the same RTP packet.
This extension is only specified for Source (not Redundancy) RTP This extension is only specified for Source (not Redundancy) RTP
Streams [RFC7656] that carry video payloads. It is not specified for Streams [RFC7656] that carry video payloads. It is not specified for
audio payloads, nor is it specified for Redundancy RTP Streams. The audio payloads, nor is it specified for Redundancy RTP Streams. The
(separate) specifications for Redundancy RTP Streams often include (separate) specifications for Redundancy RTP Streams often include
provisions for recovering any header extensions that were part of the provisions for recovering any header extensions that were part of the
original source packet. Such provisions can be followed to recover original source packet. Such provisions can 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 (Independent Frame) and D RTP Streams; for example, the I (Independent Frame) and D
(Discardable Frame) bits, defined in Section 3.1, can be used to (Discardable Frame) bits, defined in Section 3.1, can be used to
generate extra or no redundancy, respectively, and redundancy schemes generate extra or no redundancy, respectively, and redundancy schemes
with source blocks can align source block boundaries with independent with 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). A frame within a layer is the set of Synchronization Source (SSRC). A frame within a layer is the set of
RTP packets with the same RTP timestamp, SSRC, Temporal ID (TID), and RTP packets with the same RTP timestamp, SSRC, Temporal ID (TID), and
Layer ID (LID). Layer ID (LID).
3.1. 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 the TID, LID, and TL0PICIDX MUST be 0 or omitted. The ID is assigned
[RFC8285], and the length is encoded as L=2 which indicates 3 octets per [RFC8285]. The length is encoded as follows:
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 * L=2 to indicate 3 octets of data when nothing is omitted,
omitted.
* L=1 for 2 octets when TL0PICIDX is omitted, or
* L=0 for 1 octet when both the LID and TL0PICIDX are omitted.
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 | LID | TL0PICIDX | | ID=? | L=2 |S|E|I|D|B| TID | LID | TL0PICIDX |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
or or
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID=? | L=1 |S|E|I|D|B| TID | LID | (TL0PICIDX omitted) | ID=? | L=1 |S|E|I|D|B| TID | LID | (TL0PICIDX omitted)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
or or
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID=? | L=0 |S|E|I|D|B| TID | (LID and TL0PICIDX omitted) | ID=? | L=0 |S|E|I|D|B| TID | (LID and TL0PICIDX omitted)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The following information are extracted from the media payload and The following information is extracted from the media payload and
sent in the Frame Marking RTP header extension. sent in the Frame Marking RTP header extension.
* S: Start of Frame (1 bit) - MUST be 1 in the first packet in a S: Start of Frame (1 bit)
frame within a layer; otherwise MUST be 0. MUST be 1 in the first packet in a frame within a layer;
* E: End of Frame (1 bit) - MUST be 1 in the last packet in a frame otherwise, MUST be 0.
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
enhancement layer, in payload formats with such semantics.
* I: Independent Frame (1 bit) - MUST be 1 for a frame within a
layer 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. Note that this
bit only signals temporal independence, so it can be 1 in spatial
or quality enhancement layers that depend on temporally co-located
layers but not temporally prior frames.
* D: Discardable Frame (1 bit) - MUST be 1 for a frame within a
layer the sender knows can be discarded, and still provide a
decodable media stream; otherwise MUST be 0.
* B: Base Layer Sync (1 bit) - When TID is not 0, this MUST be 1 if
the sender knows this frame within a layer only depends on the
base temporal layer; otherwise MUST be 0. When TID is 0 or if no
scalability is used, this MUST be 0.
* TID: Temporal ID (3 bits) - Identifies the temporal layer/sub- E: End of Frame (1 bit)
layer encoded, starting with 0 for the base layer, and increasing MUST be 1 in the last packet in a frame within a layer; otherwise,
with higher temporal fidelity. If no scalability is used, this MUST be 0. Note that the RTP header marker bit MAY be used to
MUST be 0. It is implicitly 0 in the short extension format. infer the last packet of the highest enhancement layer in payload
* LID: Layer ID (8 bits) - Identifies the spatial and quality layer formats with such semantics.
encoded, starting with 0 for the base layer, and increasing with
higher fidelity. If no scalability is used, this MUST be 0 or
omitted to reduce length. When omitted, TL0PICIDX MUST also be
omitted. It is implicitly 0 in the short extension format or when
omitted in the long extension format.
* 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.
When TID is not 0 or LID is not 0, this indicates a dependency on
the given index, such that this frame within this layer depends on
the frame with this label in the layer with TID 0 and LID 0. If
no scalability is used, or the cyclic counter is unknown, this
MUST be omitted to reduce length. Note that 0 is a valid index
value for TL0PICIDX.
The layer information contained in TID and LID convey useful aspects I: Independent Frame (1 bit)
of the layer structure that can be utilized in selective forwarding. MUST be 1 for a frame within a layer that can be decoded
independent of temporally prior frames, e.g., intra-frame, VPX
keyframe, H.264 Instantaneous Decoding Refresh (IDR) [RFC6184], or
H.265 IDR / Clean Random Access (CRA) / Broken Link Access (BLA) /
Random Access Point (RAP) [RFC7798]; otherwise, MUST be 0. Note
that this bit only signals temporal independence, so it can be 1
in spatial or quality enhancement layers that depend on temporally
co-located layers but not temporally prior frames.
D: Discardable Frame (1 bit)
MUST be 1 for a frame within a layer the sender knows can be
discarded and still provide a decodable media stream; otherwise,
MUST be 0.
B: Base Layer Sync (1 bit)
When the TID is not 0, this MUST be 1 if the sender knows this
frame within a layer only depends on the base temporal layer;
otherwise, MUST be 0. When the TID is 0 or if no scalability is
used, this MUST be 0.
TID: Temporal ID (3 bits)
Identifies the temporal layer/sub-layer encoded, starting with 0
for the base layer and increasing with higher temporal fidelity.
If no scalability is used, this MUST be 0. It is implicitly 0 in
the short extension format.
LID: Layer ID (8 bits)
Identifies the spatial and quality layer encoded, starting with 0
for the base layer and increasing with higher fidelity. If no
scalability is used, this MUST be 0 or omitted to reduce length.
When the LID is omitted, TL0PICIDX MUST also be omitted. It is
implicitly 0 in the short extension format or when omitted in the
long extension format.
TL0PICIDX: Temporal Layer 0 Picture Index (8 bits)
When the TID is 0 and the LID is 0, this is a cyclic counter
labeling base layer frames. When the TID is not 0 or the LID is
not 0, the indication is that a dependency on the given index,
such that this frame within this layer depends on the frame with
this label in the layer with a TID 0 and LID 0. If no scalability
is used, or the cyclic counter is unknown, TL0PICIDX MUST be
omitted to reduce length. Note that 0 is a valid index value for
TL0PICIDX.
The layer information contained in the TID and LID convey useful
aspects of the layer structure that can be utilized in selective
forwarding.
Without further information about the layer structure, these TID/LID Without further information about the layer structure, these TID/LID
identifiers can only be used for relative priority of layers and identifiers can only be used for relative priority of layers and
implicit dependencies between layers. They convey a layer hierarchy implicit dependencies between layers. They convey a layer hierarchy
with TID=0 and LID=0 identifying the base layer. Higher values of with TID = 0 and LID = 0 identifying the base layer. Higher values
TID identify higher temporal layers with higher frame rates. Higher of TID identify higher temporal layers with higher frame rates.
values of LID identify higher spatial and/or quality layers with Higher values of LID identify higher spatial and/or quality layers
higher resolutions and/or bitrates. Implicit dependencies between with higher resolutions and/or bitrates. Implicit dependencies
layers assume that a layer with a given TID/LID MAY depend on 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 a layer or layers with the same or lower TID/LID, but they MUST NOT
layer(s) with higher TID/LID. depend on a layer or layers with higher TID/LID.
With further information, for example, possible future RTCP SDES With further information, for example, possible future RTCP source
items that convey full layer structure information, it may be description (SDES) items that convey full layer structure
possible to map these TIDs and LIDs to specific absolute frame rates, information, it may be possible to map these TIDs and LIDs to
resolutions and bitrates, as well as explicit dependencies between specific absolute frame rates, resolutions, bitrates, and explicit
layers. Such additional layer information may be useful for dependencies between layers. Such additional layer information may
forwarding decisions in the RTP switch, but is beyond the scope of be useful for forwarding decisions in the RTP switch but is beyond
this memo. The relative layer information is still useful for many the scope of this memo. The relative layer information is still
selective forwarding decisions even without such additional layer useful for many selective forwarding decisions, even without such
information. additional layer information.
3.2. Short Extension for Non-Scalable Streams 3.2. Short Extension for Non-scalable Streams
The following RTP header extension is RECOMMENDED for non-scalable The following RTP header extension is RECOMMENDED for non-scalable
streams. It is identical to the shortest form of the extension for streams. It is identical to the shortest form of the extension for
scalable streams, except the last four bits (B and TID) are replaced 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 with zeros. It MAY also be used for scalable streams if the sender
has limited or no information about stream scalability. The ID is has limited or no information about stream scalability. The ID is
assigned per [RFC8285], and the length is encoded as L=0 which assigned per [RFC8285]; the length is encoded as L=0, which indicates
indicates 1 octet of data. 1 octet of data.
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 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| | ID=? | L=0 |S|E|I|D|0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The following information are extracted from the media payload and The following information is extracted from the media payload and
sent in the Frame Marking RTP header extension. sent in the Frame Marking RTP header extension.
* S: Start of Frame (1 bit) - MUST be 1 in the first packet in a S: Start of Frame (1 bit)
frame; otherwise MUST be 0. MUST be 1 in the first packet in a frame; otherwise, MUST be 0.
* 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.
* 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.
* 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.
* 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 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.
This section maps the specific Layer ID information contained in I: Independent Frame (1 bit)
specific scalable codecs to the generic LID and TID fields. MUST be 1 for frames that can be decoded independent of temporally
prior frames, e.g., intra-frame, VPX keyframe, H.264 IDR
[RFC6184], or H.265 IDR/CRA/BLA/IRAP [RFC7798]; otherwise, MUST be
0.
Note that non-scalable streams have no Layer ID information and thus D: Discardable Frame (1 bit)
no mappings. MUST be 1 for frames the sender knows can be discarded and still
provide a decodable media stream; otherwise, MUST be 0.
The remaining (4 bits)
These 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. LID Mappings for Scalable Streams
This section maps the specific Layer ID (LID) information contained
in specific scalable codecs to the generic LID and TID fields.
Note that non-scalable streams have no LID information; thus, they
have no mappings.
3.3.1. VP9 LID Mapping 3.3.1. VP9 LID Mapping
The VP9 [I-D.ietf-payload-vp9] Spatial Layer ID (SID, 3 bits) and The VP9 [RFC9628] Spatial Layer ID (SID, 3 bits) and Temporal Layer
Temporal Layer ID (TID, 3 bits) in the VP9 payload descriptor are ID (TID, 3 bits) in the VP9 payload descriptor are mapped to the
mapped to the generic LID and TID fields in the header extension as generic LID and TID fields in the header extension as shown in the
shown in the following figure. following figure.
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| SID | TL0PICIDX | | ID=? | L=2 |S|E|I|D|B| TID |0|0|0|0|0| SID | TL0PICIDX |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The S bit MUST match the B bit in the VP9 payload descriptor. The S bit MUST match the B bit in the VP9 payload descriptor.
The E bit MUST match the E bit in the VP9 payload descriptor. The E bit MUST match the E bit in the VP9 payload descriptor.
The I bit MUST match the inverse of the P bit in the VP9 payload The I bit MUST match the inverse of the P bit in the VP9 payload
descriptor. descriptor.
The D bit MUST be 1 if the refresh_frame_flags in the VP9 payload The D bit MUST be 1 if the refresh_frame_flags in the VP9 payload
uncompressed header are all 0, otherwise it MUST be 0. uncompressed header are all 0; otherwise, it MUST be 0.
The B bit MUST be 0 if TID is 0; otherwise, if TID is not 0, it MUST The B bit MUST be 0 if the TID is 0; if the TID is not 0, it MUST
match the U bit in the VP9 payload descriptor. Note: When using match the U bit in the VP9 payload descriptor. Note: when using
temporally nested scalability structures as recommended in temporally nested scalability structures as recommended in
Section 3.5.2, the B bit and VP9 U bit will always be 1 if TID is not Section 3.5.2, the B bit and VP9 U bit will always be 1 if the TID is
0, since it is always possible to switch up to a higher temporal not 0 since it is always possible to switch up to a higher temporal
layer in such nested structures. layer in such nested structures.
TID, SID and TL0PICIDX MUST match the correspondingly named fields in The TID, SID, and TL0PICIDX MUST match the correspondingly named
the VP9 payload descriptor, with SID aligned in the least significant fields in the VP9 payload descriptor, with SID aligned in the least
3 bits of the 8-bit LID field and zeros in the most significant 5 significant 3 bits of the 8-bit LID field and zeros in the most
bits. significant 5 bits.
3.3.2. H265 LID Mapping 3.3.2. H265 LID Mapping
The H265 [RFC7798] LayerID (6 bits) and TID (3 bits) from the NAL The H265 [RFC7798] LayerID (6 bits), and TID (3 bits) from the
unit header are mapped to the generic LID and TID fields in the Network Abstraction Layer (NAL) unit header are mapped to the generic
header extension as shown in the following figure. LID and TID fields in the header extension as shown in the following
figure.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The S and E bits MUST match the correspondingly named bits in The S and E bits MUST match the correspondingly named bits in
PACI:PHES:TSCI payload structures. PACI:PHES:TSCI payload structures.
The I bit MUST be 1 when the NAL unit type is 16-23 (inclusive) or The I bit MUST be 1 when the NAL unit type is 16-23 (inclusive) or
32-34 (inclusive), or an aggregation packet or fragmentation unit 32-34 (inclusive), or an aggregation packet or fragmentation unit
encapsulating any of these types, otherwise it MUST be 0. These encapsulating any of these types; otherwise, it MUST be 0. These
ranges cover intra (IRAP) frames as well as critical parameter sets ranges cover intra (IRAP) frames as well as critical parameter sets
(VPS, SPS, PPS). (Video Parameter Set (VPS), Sequence Parameter Set (SPS), Picture
Parameter Set (PPS)).
The D bit MUST be 1 when the NAL unit type is 0, 2, 4, 6, 8, 10, 12, 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 14, 38, or an aggregation packet or fragmentation unit encapsulating
encapsulating only these types, otherwise it MUST be 0. These ranges only these types; otherwise, it MUST be 0. These ranges cover non-
cover non-reference frames as well as filler data. reference frames as well as filler data.
The B bit can not be determined reliably from simple inspection of The B bit cannot be determined reliably from simple inspection of
payload headers, and therefore is determined by implementation- payload headers; therefore, it is determined by implementation-
specific means. For example, internal codec interfaces may provide specific means. For example, internal codec interfaces may provide
information to set this reliably. information to set this reliably.
TID and LayerID MUST match the correspondingly named fields in the The TID and LayerID MUST match the correspondingly named fields in
H265 NAL unit header, with LayerID aligned in the least significant 6 the H265 NAL unit header, with LayerID aligned in the least
bits of the 8-bit LID field and zeros in the most significant 2 bits. significant 6 bits of the 8-bit LID field and zeros in the most
significant 2 bits.
3.3.3. H264-SVC LID Mapping 3.3.3. H264 Scalable Video Coding (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 correspondingly named bits in The S, E, I, and D bits MUST match the correspondingly named bits in
PACSI payload structures. Payload Content Scalability Information (PACSI) payload structures.
The I bit MUST be 1 when the NAL unit type is 5, 7, 8, 13, or 15, or The I bit MUST be 1 when the NAL unit type is 5, 7, 8, 13, 15, or an
an aggregation packet or fragmentation unit encapsulating any of aggregation packet or fragmentation unit encapsulating any of these
these types, otherwise it MUST be 0. These ranges cover intra (IDR) types; otherwise, it MUST be 0. These ranges cover intra (IDR)
frames as well as critical parameter sets (SPS/PPS variants). 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 The D bit MUST be 1 when the NAL unit header Network Remote
aggregation packet or fragmentation unit encapsulating only NAL units Identification (NRI) field is 0, or an aggregation packet or
with NRI=0, otherwise it MUST be 0. The NRI=0 condition signals non- fragmentation unit encapsulating only NAL units with NRI=0;
reference frames. 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 The B bit cannot be determined reliably from simple inspection of
payload headers, and therefore is determined by implementation- payload headers; therefore, it is determined by implementation-
specific means. For example, internal codec interfaces may provide specific means. For example, internal codec interfaces may provide
information to set this reliably. 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.3.4. H264 (AVC) LID Mapping 3.3.4. H264 Advanced Video Coding (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 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, the timestamp in the prior RTP sequence number from the same SSRC;
otherwise it MUST be 0. otherwise, it MUST be 0.
The E bit MUST match the M bit in the RTP header. 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 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 aggregation packet or fragmentation unit encapsulating any of these
types, otherwise it MUST be 0. These ranges cover intra (IDR) frames types; otherwise, it MUST be 0. These ranges cover intra (IDR)
as well as critical parameter sets (SPS/PPS). 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 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 aggregation packet or fragmentation unit encapsulating only NAL units
with NRI=0, otherwise it MUST be 0. The NRI=0 condition signals non- with NRI=0; otherwise, it MUST be 0. The NRI=0 condition signals
reference frames. non-reference frames.
The B bit can not be determined reliably from simple inspection of The B bit cannot be determined reliably from simple inspection of
payload headers, and therefore is determined by implementation- payload headers; therefore, it is determined by implementation-
specific means. For example, internal codec interfaces may provide specific means. For example, internal codec interfaces may provide
information to set this reliably. 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.3.5. VP8 LID Mapping 3.3.5. 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 The S bit MUST match the correspondingly named bit in the VP8 payload
descriptor when PID=0, otherwise it MUST be 0. descriptor when PID=0; otherwise, it MUST be 0.
The E bit MUST match the M bit in the RTP header. 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 The I bit MUST match the inverse of the P bit in the VP8 payload
header. header.
The D bit MUST match the N bit in the VP8 payload descriptor. 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. Note: The B bit MUST match the Y bit in the VP8 payload descriptor. Note:
When using temporally nested scalability structures as recommended in when using temporally nested scalability structures as recommended in
Section 3.5.2, the B bit and VP8 Y bit will always be 1 if TID is not Section 3.5.2, the B bit and VP8 Y bit will always be 1 if the TID is
0, since it is always possible to switch up to a higher temporal not 0 since it is always possible to switch up to a higher temporal
layer in such nested structures. layer in such nested structures.
TID and TL0PICIDX MUST match the correspondingly named fields in the The TID and TL0PICIDX MUST match the correspondingly named fields in
VP8 payload descriptor. 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.3.6. Future Codec LID Mapping 3.3.6. Future Codec LID Mapping
The RTP payload format specification for future video codecs SHOULD The RTP payload format specification for future video codecs SHOULD
skipping to change at page 11, line 51 skipping to change at line 544
3.5. 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 dependencies 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 that a media
source to generate a switching point by sending Full Intra Request source generate a switching point by sending Full Intra Request (RTCP
(RTCP FIR) as defined in [RFC5104], for example. FIR) as defined in [RFC5104], for example.
3.5.1. 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) [RFC9627] RTCP
[I-D.ietf-avtext-lrr] RTCP feedback message to upgrade to a higher feedback message to upgrade to a higher layer in scalable encodings.
layer in scalable encodings. The TID/LID values and formats used in The TID/LID values and formats used in LRR messages MUST correspond
LRR messages MUST correspond to the same values and formats specified to the same values and formats specified in Section 3.1.
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.
3.5.2. 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
structures, and it is NOT RECOMMENDED for other (more complex or structures, and it is NOT RECOMMENDED for other (more complex or
irregular) scalability structures. irregular) scalability structures.
4. Security Considerations and Privacy Considerations 4. Security and Privacy 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 and optionally encrypted header extensions are authenticated and optionally encrypted
[RFC9335]. When unencrypted header extensions are used, some [RFC9335]. When unencrypted header extensions are used, some
metadata is exposed and visible to middle boxes on the network path, metadata is exposed and visible to middleboxes on the network path,
while encrypted media data and metadata in encrypted header while encrypted media data and metadata in encrypted header
extensions are not exposed. extensions are not exposed.
The primary utility of this specification is for RTP switches to make The primary utility of this specification is for RTP switches to make
proper media forwarding decisions. RTP switches are the SRTP peers proper media forwarding decisions. RTP switches are the SRTP peers
of endpoints, so they can access encrypted header extensions, but not of endpoints, so they can access encrypted header extensions, but not
end-to-end encrypted private media payloads. Other middle boxes on end-to-end encrypted private media payloads. Other middleboxes on
the network path can only access unencrypted header extensions, since the network path can only access unencrypted header extensions since
they are not SRTP peers. they are not SRTP peers.
RTP endpoints which negotiate this extension should consider whether RTP endpoints that negotiate this extension should consider whether:
this video frame marking metadata needs to be exposed to the SRTP
peer only, in which case the header extension can be encrypted; or
whether other middle boxes on the network path also need this
metadata, for example, to optimize packet drop decisions that
minimize media quality impacts, in which case the header extension
can be unencrypted, if the endpoint accepts the potential privacy
leakage of this metadata. For example, it would be possible to
determine keyframes and their frequency in unencrypted header
extensions. This information can often be obtained via statistical
analysis of encrypted data. For example, keyframes are usually much
larger than other frames, so frame size alone can leak this in the
absence of any unencrypted metadata. However, unencrypted metadata
provides a reliable signal rather than a statistical probability; so
endpoints should take that into consideration to balance the privacy
leakage risk against the potential benefit of optimized media
delivery when deciding whether to negotiate and encrypt this header
extension.
5. Acknowledgements * this video frame marking metadata needs to be exposed to the SRTP
peer only, in which case the header extension can be encrypted; or
Many thanks to Bernard Aboba, Jonathan Lennox, Stephan Wenger, Dale * other middleboxes on the network path also need this metadata, for
Worley, and Magnus Westerlund for their inputs. example, to optimize packet drop decisions that minimize media
quality impacts, in which case the header extension can be
unencrypted, if the endpoint accepts the potential privacy leakage
of this metadata.
6. IANA Considerations For example, it would be possible to determine keyframes and their
frequency in unencrypted header extensions. This information can
often be obtained via statistical analysis of encrypted data. For
example, keyframes are usually much larger than other frames, so
frame size alone can leak this in the absence of any unencrypted
metadata. However, unencrypted metadata provides a reliable signal
rather than a statistical probability; so endpoints should take that
into consideration to balance the privacy leakage risk against the
potential benefit of optimized media delivery when deciding whether
to negotiate and encrypt this header extension.
This document defines a new extension URI to the RTP Compact 5. IANA Considerations
HeaderExtensions sub-registry of the Real-Time Transport Protocol
(RTP) Parameters registry, according to the following data: This document defines a new extension URI listed in the "RTP Compact
Header Extensions" subregistry of the "Real-Time Transport Protocol
(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
Reference: RFC XXXX Reference: RFC 9626
Note to RFC Editor: please replace RFC XXXX with the number of this
RFC.
7. References 6. References
7.1. Normative References 6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
skipping to change at page 14, line 43 skipping to change at line 669
[RFC7741] Westin, P., Lundin, H., Glover, M., Uberti, J., and F. [RFC7741] Westin, P., Lundin, H., Glover, M., Uberti, J., and F.
Galligan, "RTP Payload Format for VP8 Video", RFC 7741, Galligan, "RTP Payload Format for VP8 Video", RFC 7741,
DOI 10.17487/RFC7741, March 2016, DOI 10.17487/RFC7741, March 2016,
<https://www.rfc-editor.org/info/rfc7741>. <https://www.rfc-editor.org/info/rfc7741>.
[RFC7798] Wang, Y.-K., Sanchez, Y., Schierl, T., Wenger, S., and M. [RFC7798] Wang, Y.-K., Sanchez, Y., Schierl, T., Wenger, S., and M.
M. Hannuksela, "RTP Payload Format for High Efficiency M. Hannuksela, "RTP Payload Format for High Efficiency
Video Coding (HEVC)", RFC 7798, DOI 10.17487/RFC7798, Video Coding (HEVC)", RFC 7798, DOI 10.17487/RFC7798,
March 2016, <https://www.rfc-editor.org/info/rfc7798>. March 2016, <https://www.rfc-editor.org/info/rfc7798>.
7.2. Informative References 6.2. Informative References
[RFC7656] Lennox, J., Gross, K., Nandakumar, S., Salgueiro, G., and [RFC7656] Lennox, J., Gross, K., Nandakumar, S., Salgueiro, G., and
B. Burman, Ed., "A Taxonomy of Semantics and Mechanisms B. Burman, Ed., "A Taxonomy of Semantics and Mechanisms
for Real-Time Transport Protocol (RTP) Sources", RFC 7656, for Real-Time Transport Protocol (RTP) Sources", RFC 7656,
DOI 10.17487/RFC7656, November 2015, DOI 10.17487/RFC7656, November 2015,
<https://www.rfc-editor.org/info/rfc7656>. <https://www.rfc-editor.org/info/rfc7656>.
[RFC7667] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 7667, [RFC7667] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 7667,
DOI 10.17487/RFC7667, November 2015, DOI 10.17487/RFC7667, November 2015,
<https://www.rfc-editor.org/info/rfc7667>. <https://www.rfc-editor.org/info/rfc7667>.
skipping to change at page 15, line 40 skipping to change at line 712
[RFC8871] Jones, P., Benham, D., and C. Groves, "A Solution [RFC8871] 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)", RFC 8871, DOI 10.17487/RFC8871, Conferencing (PERC)", RFC 8871, DOI 10.17487/RFC8871,
January 2021, <https://www.rfc-editor.org/info/rfc8871>. January 2021, <https://www.rfc-editor.org/info/rfc8871>.
[RFC9335] Uberti, J., Jennings, C., and S. Murillo, "Completely [RFC9335] Uberti, J., Jennings, C., and S. Murillo, "Completely
Encrypting RTP Header Extensions and Contributing Encrypting RTP Header Extensions and Contributing
Sources", RFC 9335, DOI 10.17487/RFC9335, January 2023, Sources", RFC 9335, DOI 10.17487/RFC9335, January 2023,
<https://www.rfc-editor.org/info/rfc9335>. <https://www.rfc-editor.org/info/rfc9335>.
[I-D.ietf-avtext-lrr] [RFC9627] 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", Work in Progress, Internet-Draft, draft-ietf- Message", RFC 9627, DOI 10.17487/RFC9627, August 2024,
avtext-lrr-07, 2 July 2017, <https://www.rfc-editor.org/info/rfc9627>.
<https://datatracker.ietf.org/doc/html/draft-ietf-avtext-
lrr-07>.
[I-D.ietf-payload-vp9] [RFC9628] Uberti, J., Holmer, S., Flodman, M., Hong, D., and J.
Uberti, J., Holmer, S., Flodman, M., Hong, D., and J. Lennox, "RTP Payload Format for VP9 Video", RFC 9628,
Lennox, "RTP Payload Format for VP9 Video", Work in DOI 10.17487/RFC9628, August 2024,
Progress, Internet-Draft, draft-ietf-payload-vp9-16, 10 <https://www.rfc-editor.org/info/rfc9628>.
June 2021, <https://datatracker.ietf.org/doc/html/draft-
ietf-payload-vp9-16>. Acknowledgements
Many thanks to Bernard Aboba, Jonathan Lennox, Stephan Wenger, Dale
Worley, and Magnus Westerlund for their inputs.
Authors' Addresses Authors' Addresses
Mo Zanaty Mo Zanaty
Cisco Systems Cisco Systems
170 West Tasman Drive 170 West Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
United States of America United States of America
Email: mzanaty@cisco.com Email: mzanaty@cisco.com
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