draft-ietf-payload-vp9-00.txt   draft-ietf-payload-vp9-01.txt 
Payload Working Group J. Uberti Payload Working Group J. Uberti
Internet-Draft S. Holmer Internet-Draft S. Holmer
Intended status: Standards Track M. Flodman Intended status: Standards Track M. Flodman
Expires: January 7, 2016 Google Expires: April 21, 2016 Google
J. Lennox J. Lennox
D. Hong D. Hong
Vidyo Vidyo
July 6, 2015 October 19, 2015
RTP Payload Format for VP9 Video RTP Payload Format for VP9 Video
draft-ietf-payload-vp9-00 draft-ietf-payload-vp9-01
Abstract Abstract
This memo describes an RTP payload format for the VP9 video codec. This memo describes an RTP payload format for the VP9 video codec.
The payload format has wide applicability, as it supports The payload format has wide applicability, as it supports
applications from low bit-rate peer-to-peer usage, to high bit-rate applications from low bit-rate peer-to-peer usage, to high bit-rate
video conferences. It includes provisions for temporal and spatial video conferences. It includes provisions for temporal and spatial
scalability. scalability.
Status of This Memo Status of This Memo
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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-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
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 January 7, 2016. This Internet-Draft will expire on April 21, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions, Definitions and Acronyms . . . . . . . . . . . . 2 2. Conventions, Definitions and Acronyms . . . . . . . . . . . . 2
3. Media Format Description . . . . . . . . . . . . . . . . . . 3 3. Media Format Description . . . . . . . . . . . . . . . . . . 3
4. Payload Format . . . . . . . . . . . . . . . . . . . . . . . 4 4. Payload Format . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. RTP Header Usage . . . . . . . . . . . . . . . . . . . . 4 4.1. RTP Header Usage . . . . . . . . . . . . . . . . . . . . 5
4.2. VP9 Payload Description . . . . . . . . . . . . . . . . . 6 4.2. VP9 Payload Description . . . . . . . . . . . . . . . . . 6
4.2.1. Scalability Structure (SS): . . . . . . . . . . . . . 10 4.2.1. Scalability Structure (SS): . . . . . . . . . . . . . 10
4.3. VP9 Payload Header . . . . . . . . . . . . . . . . . . . 12 4.3. VP9 Payload Header . . . . . . . . . . . . . . . . . . . 11
4.4. Frame Fragmentation . . . . . . . . . . . . . . . . . . . 12 4.4. Frame Fragmentation . . . . . . . . . . . . . . . . . . . 12
4.5. Examples of VP9 RTP Stream . . . . . . . . . . . . . . . 12 4.5. Examples of VP9 RTP Stream . . . . . . . . . . . . . . . 12
5. Using VP9 with RPSI and SLI Feedback . . . . . . . . . . . . 12 5. Using VP9 with RPSI and SLI Feedback . . . . . . . . . . . . 12
5.1. RPSI . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.1. RPSI . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.2. SLI . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.2. SLI . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.3. Example . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.3. Example . . . . . . . . . . . . . . . . . . . . . . . . . 13
6. Payload Format Parameters . . . . . . . . . . . . . . . . . . 15 6. Payload Format Parameters . . . . . . . . . . . . . . . . . . 15
6.1. Media Type Definition . . . . . . . . . . . . . . . . . . 15 6.1. Media Type Definition . . . . . . . . . . . . . . . . . . 15
6.2. SDP Parameters . . . . . . . . . . . . . . . . . . . . . 17 6.2. SDP Parameters . . . . . . . . . . . . . . . . . . . . . 17
6.2.1. Mapping of Media Subtype Parameters to SDP . . . . . 17 6.2.1. Mapping of Media Subtype Parameters to SDP . . . . . 17
6.2.2. Offer/Answer Considerations . . . . . . . . . . . . . 17 6.2.2. Offer/Answer Considerations . . . . . . . . . . . . . 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 17 7. Security Considerations . . . . . . . . . . . . . . . . . . . 17
8. Congestion Control . . . . . . . . . . . . . . . . . . . . . 18 8. Congestion Control . . . . . . . . . . . . . . . . . . . . . 18
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
10.1. Normative References . . . . . . . . . . . . . . . . . . 18 10.1. Normative References . . . . . . . . . . . . . . . . . . 18
10.2. Informative References . . . . . . . . . . . . . . . . . 19 10.2. Informative References . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
This memo describes an RTP payload specification applicable to the This memo describes an RTP payload specification applicable to the
transmission of video streams encoded using the VP9 video codec transmission of video streams encoded using the VP9 video codec
[I-D.grange-vp9-bitstream]. The format described in this document [I-D.grange-vp9-bitstream]. The format described in this document
can be used both in peer-to-peer and video conferencing applications. can be used both in peer-to-peer and video conferencing applications.
TODO: VP9 description. Please see [I-D.grange-vp9-bitstream]. TODO: VP9 description. Please see [I-D.grange-vp9-bitstream].
2. Conventions, Definitions and Acronyms 2. Conventions, Definitions and Acronyms
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
TODO: Cite terminology from [I-D.grange-vp9-bitstream].
3. Media Format Description 3. Media Format Description
The VP9 codec can maintain up to eight reference frames, of which up The VP9 codec can maintain up to eight reference frames, of which up
to three can be referenced or updated by any new frame. to three can be referenced or updated by any new frame.
VP9 also allows a reference frame to be resampled and used as a VP9 also allows a reference frame to be resampled and used as a
reference for another frame of a different resolution. This allows reference for another frame of a different resolution. This allows
internal resolution changes without requiring the use of key frames. internal resolution changes without requiring the use of key frames.
These features together enable an encoder to implement various forms These features together enable an encoder to implement various forms
skipping to change at page 3, line 32 skipping to change at page 3, line 34
frame to be encoded at different resolutions, whereas quality layers frame to be encoded at different resolutions, whereas quality layers
allow a frame to be encoded at the same resolution but at different allow a frame to be encoded at the same resolution but at different
qualities (and thus with different amounts of coding error). VP9 qualities (and thus with different amounts of coding error). VP9
supports quality layers as spatial layers without any resolution supports quality layers as spatial layers without any resolution
changes; hereinafter, the term "spatial layer" is used to represent changes; hereinafter, the term "spatial layer" is used to represent
both spatial and quality layers. both spatial and quality layers.
This payload format specification defines how such temporal and This payload format specification defines how such temporal and
spatial scalability layers can be described and communicated. spatial scalability layers can be described and communicated.
Temporal and spatial scalability layers are associated with non-
negative integer IDs. The lowest layer of either type has an ID of
0.
Layers are designed (and MUST be encoded) such that if any layer, and Layers are designed (and MUST be encoded) such that if any layer, and
all higher layers, are removed from the bitstream along any of the all higher layers, are removed from the bitstream along any of the
two dimensions, the remaining bitstream is still correctly decodable. two dimensions, the remaining bitstream is still correctly decodable.
For terminology, this document uses the term "layer frame" to refer For terminology, this document uses the term "layer frame" to refer
to a single encoded VP9 frame for a particular resolution/quality, to a single encoded VP9 frame for a particular resolution/quality,
and "super frame" to refer to all the representations (layer frames) and "super frame" to refer to all the representations (layer frames)
at a single instant in time. A super frame thus consists of one or at a single instant in time. A super frame thus consists of one or
more layer frames, encoding different spatial layers. more layer frames, encoding different spatial layers.
Within a super frame, a layer frame with spatial layer ID equal to S, Within a super frame, a layer frame with spatial layer ID equal to S,
where S > 0, can depend on a frame with a lower spatial layer ID. where S > 0, can depend on a layer frame of the same super frame with
This "inter-layer" dependency results in additional coding gain to a lower spatial layer ID. This "inter-layer" dependency can result
the traditional "inter-picture" dependency, where a frame depends on in additional coding gain compared to the case where only traditional
"inter-picture" dependency is used, where a frame depends on
previously coded frame in time. For simplicity, this payload format previously coded frame in time. For simplicity, this payload format
assumes that, within a super frame if inter-layer dependency is used, assumes that, within a super frame and if inter-layer dependency is
a spatial layer S frame can only depend on spatial layer S-1 frame used, a spatial layer S frame can only depend on spatial layer S-1
when S > 0. Additionally, if inter-picture dependency is used, frame when S > 0. Additionally, if inter-picture dependency is used,
spatial layer S frame is assumed to only depend on prevously coded spatial layer S frame is assumed to only depend on previously coded
spatial layer S frame. spatial layer S frame.
TODO: Describe how simulcast can be supported? TODO: Describe how simulcast can be supported?
Given above simplifications for inter-layer and inter-picture Given above simplifications for inter-layer and inter-picture
dependencies, a flag (the D bit described below) is used to indicate dependencies, a flag (the D bit described below) is used to indicate
whether a spatial layer S frame depends on spatial layer S-1 frame. whether a spatial layer S frame depends on spatial layer S-1 frame.
Then a receiver only needs to know the inter-picture dependency Given the D bit, a receiver only needs to additionally know the
structure for a given spatial layer frame in order to determine its inter-picture dependency structure for a given spatial layer frame in
decodability. Two modes of describing the inter-picture dependency order to determine its decodability. Two modes of describing the
structure are possible: "flexible mode" and "non-flexible mode". An inter-picture dependency structure are possible: "flexible mode" and
encoder can only switch between the two on the very first packet of a "non-flexible mode". An encoder can only switch between the two on
key frame with temporal layer ID equal to 0. the very first packet of a key frame with temporal layer ID equal to
0.
In flexible mode, each packet can contain up to 3 reference indices, In flexible mode, each packet can contain up to 3 reference indices,
which identifies all frames referenced by the frame transmitted in which identify all frames referenced by the frame transmitted in the
the current packet for inter-picture prediction. This (along with current packet for inter-picture prediction. This (along with the D
the D bit) enables a receiver to identify if a frame is decodable or bit) enables a receiver to identify if a frame is decodable or not
not and helps it understand the temporal layer structure so that it and helps it understand the temporal layer structure. Since this is
can drop packets as it sees fit. Since this is signaled in each signaled in each packet it makes it possible to have very flexible
packet it makes it possible to have very flexible temporal layer temporal layer hierarchies and patterns which are changing
hierarchies and patterns which are changing dynamically. dynamically.
In non-flexible mode, the inter-picture dependency (the reference In non-flexible mode, the inter-picture dependency (the reference
indices) of a group of frames (GOF) MUST be pre-specified as part of indices) of a group of frames (GOF) MUST be pre-specified as part of
the scalability structure (SS) data. In this mode, each packet will the scalability structure (SS) data. In this mode, each packet MUST
have an index to refer to one of the described frames, from which the have an index to refer to one of the described frames in the GOF,
frames referenced by the frame transmitted in the current packet for from which the frames referenced by the frame transmitted in the
inter-picture prediction can be identified. current packet for inter-picture prediction can be identified.
The SS data can also be used to specify the resolution of each The SS data can also be used to specify the resolution of each
spatial layer present in the VP9 stream. spatial layer present in the VP9 stream for both flexible and non-
flexible modes.
4. Payload Format 4. Payload Format
This section describes how the encoded VP9 bitstream is encapsulated This section describes how the encoded VP9 bitstream is encapsulated
in RTP. To handle network losses usage of RTP/AVPF [RFC4585] is in RTP. To handle network losses usage of RTP/AVPF [RFC4585] is
RECOMMENDED. All integer fields in the specifications are encoded as RECOMMENDED. All integer fields in the specifications are encoded as
unsigned integers in network octet order. unsigned integers in network octet order.
4.1. RTP Header Usage 4.1. RTP Header Usage
The general RTP payload format for VP9 is depicted below. The general RTP payload format for VP9 is depicted below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V=2|P|X| CC |M| PT | sequence number | |V=2|P|X| CC |M| PT | sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| timestamp | | timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| synchronization source (SSRC) identifier | | synchronization source (SSRC) identifier |
skipping to change at page 5, line 18 skipping to change at page 5, line 21
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V=2|P|X| CC |M| PT | sequence number | |V=2|P|X| CC |M| PT | sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| timestamp | | timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| synchronization source (SSRC) identifier | | synchronization source (SSRC) identifier |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| contributing source (CSRC) identifiers | | contributing source (CSRC) identifiers |
| .... | | .... |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| VP9 payload descriptor (integer #bytes) | | VP9 payload descriptor (integer #octets) |
: : : :
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : VP9 pyld hdr | | | : VP9 pyld hdr | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| | | |
+ | + |
: Bytes 2..N of VP9 payload : : Bytes 2..N of VP9 payload :
| | | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : OPTIONAL RTP padding | | : OPTIONAL RTP padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The VP9 payload descriptor and VP9 payload header will be described The VP9 payload descriptor and VP9 payload header will be described
in the next section. OPTIONAL RTP padding MUST NOT be included in Section 4.2 and Section 4.3. OPTIONAL RTP padding MUST NOT be
unless the P bit is set. included unless the P bit is set. The figure specifically shows the
format for the first packet in a frame. Subsequent packets will not
contain the VP9 payload header, and will have later octets in the
frame payload.
Figure 1 Figure 1
Marker bit (M): MUST be set to 1 for the final packet of the highest Marker bit (M): MUST be set to 1 for the final packet of the highest
spatial layer frame (the final packet of the super frame), and 0 spatial layer frame (the final packet of the super frame), and 0
otherwise. Unless spatial scalability is in use for this super otherwise. Unless spatial scalability is in use for this super
frame, this will have the same value as the E bit described below. frame, this will have the same value as the E bit described below.
Note that a MANE MUST set this value to 1 for the target spatial Note this bit MUST be set to 1 for the target spatial layer frame
layer frame when shaping out higher spatial layers. if a stream is being rewritten to remove higher spatial layers.
Payload Type (TP): In line with the policy in Section 3 of
[RFC3551], applications using the VP9 RTP payload profile MUST
assign a dynamic payload type number to be used in each RTP
session and provide a mechanism to indicate the mapping. See
Section 6.2 for the mechanism to be used with the Session
Description Protocol (SDP) [RFC4566].
Timestamp: The RTP timestamp indicates the time when the input frame Timestamp: The RTP timestamp indicates the time when the input frame
was sampled, at a clock rate of 90 kHz. If the input frame is was sampled, at a clock rate of 90 kHz. If the input frame is
encoded with multiple layer frames, all of the layer frames of the encoded with multiple layer frames, all of the layer frames of the
super frame MUST have the same timestamp. super frame MUST have the same timestamp.
Sequence number: The sequence numbers are monotonically increasing The remaining RTP Fixed Header Fields (V, P, X, CC, sequence number,
in order of the encoded bitstream. SSRC and CSRC identifiers) are used as specified in Section 5.1 of
[RFC3550].
The remaining RTP header fields are used as specified in [RFC3550].
4.2. VP9 Payload Description 4.2. VP9 Payload Description
In flexible mode (with the F bit below set to 1), The first octets In flexible mode (with the F bit below set to 1), The first octets
after the RTP header are the VP9 payload descriptor, with the after the RTP header are the VP9 payload descriptor, with the
following structure. following structure.
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|I|P|L|F|B|E|V|-| (REQUIRED) |I|P|L|F|B|E|V|-| (REQUIRED)
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
I: |M| PICTURE ID | (RECOMMENDED) I: |M| PICTURE ID | (REQUIRED)
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
M: | EXTENDED PID | (RECOMMENDED) M: | EXTENDED PID | (RECOMMENDED)
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
L: | T |U| S |D| (CONDITIONALLY RECOMMENDED) L: | T |U| S |D| (CONDITIONALLY RECOMMENDED)
+-+-+-+-+-+-+-+-+ -\ +-+-+-+-+-+-+-+-+ -\
P,F: | P_DIFF |X|N| (CONDITIONALLY RECOMMENDED) . P,F: | P_DIFF |N| (CONDITIONALLY REQUIRED) - up to 3 times
+-+-+-+-+-+-+-+-+ . - up to 3 times
X: |EXTENDED P_DIFF| (OPTIONAL) .
+-+-+-+-+-+-+-+-+ -/ +-+-+-+-+-+-+-+-+ -/
V: | SS | V: | SS |
| .. | | .. |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
Figure 2 Figure 2
In non-flexible mode (with the F bit below set to 0), The first In non-flexible mode (with the F bit below set to 0), The first
octets after the RTP header are the VP9 payload descriptor, with the octets after the RTP header are the VP9 payload descriptor, with the
following structure. following structure.
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|I|P|L|F|B|E|V|-| (REQUIRED) |I|P|L|F|B|E|V|-| (REQUIRED)
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
I: |M| PICTURE ID | (RECOMMENDED) I: |M| PICTURE ID | (RECOMMENDED)
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
M: | EXTENDED PID | (RECOMMENDED) M: | EXTENDED PID | (RECOMMENDED)
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
L: |GOF_IDX| S |D| (CONDITIONALLY RECOMMENDED) L: | T |U| S |D| (CONDITIONALLY RECOMMENDED)
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| TL0PICIDX | (CONDITIONALLY REQUIRED) | TL0PICIDX | (CONDITIONALLY REQUIRED)
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
V: | SS | V: | SS |
| .. | | .. |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
Figure 3 Figure 3
I: Picture ID (PID) present. When set to one, the OPTIONAL PID MUST I: Picture ID (PID) present. When set to one, the OPTIONAL PID MUST
be present after the mandatory first octet and specified as below. be present after the mandatory first octet and specified as below.
Otherwise, PID MUST NOT be present. Otherwise, PID MUST NOT be present.
P: Inter-picture predicted layer frame. When set to zero, the layer P: Inter-picture predicted layer frame. When set to zero, the layer
frame does not utilize inter-picture prediction. In this case, frame does not utilize inter-picture prediction. In this case,
up-switching to current spatial layer's frame is possible from up-switching to current spatial layer's frame is possible from
directly lower spatial layer frame. P SHOULD also be set to zero directly lower spatial layer frame. P SHOULD also be set to zero
when encoding a layer synchronization frame in response to an LRR when encoding a layer synchronization frame in response to an LRR
[I-D.lennox-avtext-lrr]. [I-D.lennox-avtext-lrr]. When P is set to zero, the T bit
(described below) MUST also be set to 0 (if present).
L: Layer indices present. When set to one, the one or two octets L: Layer indices present. When set to one, the one or two octets
following the mandatory first octet and the PID (if present) is as following the mandatory first octet and the PID (if present) is as
described by "Layer indices" below. If the F bit (described described by "Layer indices" below. If the F bit (described
below) is set to 1 (indicating flexible mode), then only one octet below) is set to 1 (indicating flexible mode), then only one octet
is present for the layer indices. Otherwise if the F bit is set is present for the layer indices. Otherwise if the F bit is set
to 0 (indicating non-flexible mode), then two octets are present to 0 (indicating non-flexible mode), then two octets are present
for the layer indices. for the layer indices.
F: Flexible mode. F set to one indicates flexible mode and if the P F: Flexible mode. F set to one indicates flexible mode and if the P
bit is also set to one, then the octets following the mandatory bit is also set to one, then the octets following the mandatory
first octet, the PID, and layer indices (if present) are as first octet, the PID, and layer indices (if present) are as
described by "Reference indices" below. This MUST only be set to described by "Reference indices" below. This MUST only be set to
one if the I bit is also set to one; if the I bit is set to zero, 1 if the I bit is also set to one; if the I bit is set to zero,
then this MUST also be set to zero and ignored by receivers. The then this MUST also be set to zero and ignored by receivers. The
value of this F bit CAN ONLY CHANGE on the very first packet of a value of this F bit CAN ONLY CHANGE on the very first packet of a
key picture. This is a packet with the P bit equal to zero, S or key picture. This is a packet with the P bit equal to zero, S or
D bit (described below) equal to zero, B bit (described below) D bit (described below) equal to zero, and B bit (described below)
equal to 1, and temporal layer ID equal to 0. equal to 1.
B: Start of a layer frame. MUST be set to 1 if the first payload B: Start of a layer frame. MUST be set to 1 if the first payload
octet of the RTP packet is the beginning of a new VP9 layer frame, octet of the RTP packet is the beginning of a new VP9 layer frame,
and MUST NOT be 1 otherwise. Note that this layer frame might not and MUST NOT be 1 otherwise. Note that this layer frame might not
be the very first layer frame of a super frame. be the very first layer frame of a super frame.
E: End of a layer frame. MUST be set to 1 for the final RTP packet E: End of a layer frame. MUST be set to 1 for the final RTP packet
of a VP9 layer frame, and 0 otherwise. This enables a decoder to of a VP9 layer frame, and 0 otherwise. This enables a decoder to
finish decoding the layer frame, where it otherwise may need to finish decoding the layer frame, where it otherwise may need to
wait for the next packet to explicitly know that the layer frame wait for the next packet to explicitly know that the layer frame
skipping to change at page 8, line 41 skipping to change at page 8, line 42
M: The most significant bit of the first octet is an extension flag. M: The most significant bit of the first octet is an extension flag.
The field MUST be present if the I bit is equal to one. If set, The field MUST be present if the I bit is equal to one. If set,
the PID field MUST contain 15 bits; otherwise, it MUST contain 7 the PID field MUST contain 15 bits; otherwise, it MUST contain 7
bits. See PID below. bits. See PID below.
Picture ID (PID): Picture ID represented in 7 or 15 bits, depending Picture ID (PID): Picture ID represented in 7 or 15 bits, depending
on the M bit. This is a running index of the pictures. The field on the M bit. This is a running index of the pictures. The field
MUST be present if the I bit is equal to one. If M is set to MUST be present if the I bit is equal to one. If M is set to
zero, 7 bits carry the PID; else if M is set to one, 15 bits carry zero, 7 bits carry the PID; else if M is set to one, 15 bits carry
the PID. The sender may choose between 7 or 15 bits index. The the PID in network byte order. The sender may choose between a 7-
PID SHOULD start on a random number, and MUST wrap after reaching or 15-bit index. The PID SHOULD start on a random number, and
the maximum ID. The receiver MUST NOT assume that the number of MUST wrap after reaching the maximum ID. The receiver MUST NOT
bits in PID stay the same through the session. assume that the number of bits in PID stay the same through the
session.
In the non-flexible mode (when the F bit is set to 0), this PID is
used as an index to the GOF specified in the SS data bleow. In
this mode, the PID of the key frame corresponds to the very first
specified frame in the GOF. Then subsequent PIDs are mapped to
subsequently specified frames in the GOF (modulo N_G, specified in
the SS data below), respectively.
Layer indices: This information is optional but recommended whenever Layer indices: This information is optional but recommended whenever
encoding with layers. In the flexible mode (when the F bit is set encoding with layers. For both flexible and non-flexible modes,
to 1), one octet is used to specify a layer frame's temporal layer one octet is used to specify a layer frame's temporal layer ID (T)
ID (T) and spatial layer ID (S) as shown in Figure 2. and spatial layer ID (S) as shown both in Figure 2 and Figure 3.
Additionally, a bit (U) is used to indcate that the current frame Additionally, a bit (U) is used to indicate that the current frame
is a "switching up point" frame. Another bit (D) is used to is a "switching up point" frame. Another bit (D) is used to
indicate whether inter-layer prediction is used for the current indicate whether inter-layer prediction is used for the current
layer frame. layer frame.
In the non-flexible mode (when the F bit is set to 0), two octets In the non-flexible mode (when the F bit is set to 0), another
are used as depicted in Figure 3. Like the flexible mode, the octet is used to represent temporal layer 0 index (TL0PICIDX), as
first byte contains the spatial layer ID and the D bit. Unlike depicted in Figure 3. The TL0PICIDX is present so that all
the flexible mode, instead of the T and U fields, a group of minimally required frames - the base temporal layer frames - can
frames index (GOF_IDX) is specified, which can be used to obtain be tracked.
the values of T and U fields from the scalable structure (SS) data
described below. An additional octet to represent the temporal
layer 0 index, TL0PICIDX, is present so that all minimally
required frames can be tracked.
The T and S fields, whether obtained directly or indirectly from The T and S fields indicate the temporal and spatial layers and
the SS data, indicate the temporal and spatial layers and can help can help middleboxes and and endpoints quickly identify which
MCUs measure bitrates per layer and can help them make a quick layer a packet belongs to.
decision on whether to relay a packet or not. They can also help
receivers determine what layers they are currently decoding.
T: The temporal layer ID of current frame. This field is only T: The temporal layer ID of current frame. In the case of non-
present in the flexible mode (F = 1). flexible mode, if PID is mapped to a frame in a specified GOF,
then the value of T MUST match the corresponding T value of the
mapped frame in the GOF.
U: Switching up point. This bit is only present in the flexible U: Switching up point. If this bit is set to 1 for the current
mode (F = 1). If this bit is set to 1 for the current frame frame with temporal layer ID equal to T, then "switch up" to a
with temporal layer ID equal to T, then "switch up" to a higher higher frame rate is possible as subsequent higher temporal
frame rate is possible as subsequent higher temporal layer layer frames will not depend on any frame before the current
frames will not depend on any frame before the current frame frame (in coding time) with temporal layer ID greater than T.
(in coding time) with temporal layer ID greater than T.
S: The spatial layer ID of current frame. Note that frames with S: The spatial layer ID of current frame. Note that frames with
spatial layer S > 0 may be dependent on decoded spatial layer spatial layer S > 0 may be dependent on decoded spatial layer
S-1 frame within the same super frame. S-1 frame within the same super frame.
D: Inter-layer dependency used. MUST be set to one if current D: Inter-layer dependency used. MUST be set to one if current
spatial layer S frame depends on spatial layer S-1 frame of the spatial layer S frame depends on spatial layer S-1 frame of the
same super frame. MUST only be set to zero if current spatial same super frame. MUST only be set to zero if current spatial
layer S frame does not depend on spatial layer S-1 frame of the layer S frame does not depend on spatial layer S-1 frame of the
same super frame. For the base layer frame with S equal to 0, same super frame. For the base layer frame with S equal to 0,
this D bit MUST be set to zero. this D bit MUST be set to zero.
GOF_IDX: An index to a frame in the group of frames (GOF)
described by the SS data. This field is only present in the
non-flexible mode (F = 0). In this mode, the SS data SHOULD
have been received and the temporal characteristics of each
frame must have been speficied as group of frames in the SS
data (see the description of "Scalability structure" below).
Here, the values of the T and the U fields are derived from the
SS data. Additionally, the frame's inter-picture dependecy can
also be obtained from the SS data. In the case no SS data has
been received or the received SS data does not specify GOF (N_G
is set to 0), then GOF_IDX MUST be ignored and the stream is
assumed to have no temporal hierarchy with both T and U equal
to 0.
TL0PICIDX: 8 bits temporal layer zero index. TL0PICIDX is only TL0PICIDX: 8 bits temporal layer zero index. TL0PICIDX is only
present in the non-flexible mode (F = 0). This is a running present in the non-flexible mode (F = 0). This is a running
index for the temporal base layer frames, i.e., the frames with index for the temporal base layer frames, i.e., the frames with
temporal layer ID (TID) set to 0. If TID is larger than 0, T set to 0. If T is larger than 0, TL0PICIDX indicates which
TL0PICIDX indicates which temporal base layer frame the current temporal base layer frame the current frame depends on.
frame depends on. TL0PICIDX MUST be incremented when TID is 0. TL0PICIDX MUST be incremented when T is equal to 0. The index
The index SHOULD start on a random number, and MUST restart at SHOULD start on a random number, and MUST restart at 0 after
0 after reaching the maximum number 255. reaching the maximum number 255.
Reference indices: These bytes are optional, but recommended when
encoding with temporal layers in the flexible mode. When P and F
are both set to one, then at least one reference index has to be
specified as below. Additional reference indices (total of up to
3 reference indices are allowed) may be specified using the N bit
below. When either P or F is set to zero, then no reference index
is specified.
P_DIFF: The reference index specified as the relative PID from Reference indices: When P and F are both set to one, indicating a
the current frame. For example, when P_DIFF=3 on a packet non-key frame in flexible mode, then at least one reference index
containing the frame with PID 112 means that the frame refers has to be specified as below. Additional reference indices (total
back to the frame with PID 109. This calculation is done of up to 3 reference indices are allowed) may be specified using
modulo the size of the PID field, i.e., either 7 or 15 bits. the N bit below. When either P or F is set to zero, then no
For most layer structures a 6-bit relative PID will be enough; reference index is specified.
however, the X bit can be used to refer to older frames.
X: 1 if this layer index has an extended P_DIFF. P_DIFF: The reference index (in 7 bits) specified as the relative
PID from the current frame. For example, when P_DIFF=3 on a
packet containing the frame with PID 112 means that the frame
refers back to the frame with PID 109. This calculation is
done modulo the size of the PID field, i.e., either 7 or 15
bits.
N: 1 if there is additional P_DIFF following the current P_DIFF. N: 1 if there is additional P_DIFF following the current P_DIFF.
4.2.1. Scalability Structure (SS): 4.2.1. Scalability Structure (SS):
The scalability structure (SS) data describes the resolution of each The scalability structure (SS) data describes the resolution of each
layer frame within a super frame as well as the inter-picture layer frame within a super frame as well as the inter-picture
dependencies for a group of frames (GOF). If the VP9 payload dependencies for a group of frames (GOF). If the VP9 payload
descriptor's "V" bit is set, the SS data is present in the position descriptor's "V" bit is set, the SS data is present in the position
indicated in Figure 2 and Figure 3. indicated in Figure 2 and Figure 3.
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
V: | N_S |Y| N_G | V: | N_S |Y|G|-|-|-|
+-+-+-+-+-+-+-+-+ -\ +-+-+-+-+-+-+-+-+ -\
Y: | WIDTH | (OPTIONAL) . Y: | WIDTH | (OPTIONAL) .
+ + . + + .
| | (OPTIONAL) . | | (OPTIONAL) .
+-+-+-+-+-+-+-+-+ . - N_S + 1 times +-+-+-+-+-+-+-+-+ . - N_S + 1 times
| HEIGHT | (OPTIONAL) . | HEIGHT | (OPTIONAL) .
+ + . + + .
| | (OPTIONAL) . | | (OPTIONAL) .
+-+-+-+-+-+-+-+-+ -/ -\ +-+-+-+-+-+-+-+-+ -/ -\
G: | N_G | (OPTIONAL)
+-+-+-+-+-+-+-+-+ -\
N_G: | T |U| R |-|-| (OPTIONAL) . N_G: | T |U| R |-|-| (OPTIONAL) .
+-+-+-+-+-+-+-+-+ -\ . - N_G + 1 times +-+-+-+-+-+-+-+-+ -\ . - N_G times
| P_DIFF | (OPTIONAL) . - R times . | P_DIFF | (OPTIONAL) . - R times .
+-+-+-+-+-+-+-+-+ -/ -/ +-+-+-+-+-+-+-+-+ -/ -/
Figure 4 Figure 4
N_S: N_S + 1 indicates the number of spatial layers present in the N_S: N_S + 1 indicates the number of spatial layers present in the
VP9 stream. VP9 stream.
Y: Each spatial layer's frame resolution present. When set to one, Y: Each spatial layer's frame resolution present. When set to one,
the OPTIONAL WIDTH (2 octets) and HEIGHT (2 octets) MUST be the OPTIONAL WIDTH (2 octets) and HEIGHT (2 octets) MUST be
present for each layer frame. Otherwise, the resolution MUST NOT present for each layer frame. Otherwise, the resolution MUST NOT
be present. be present.
N_G: N_G + 1 indicates the number of frames in a GOF. If N_G is G: GOF description present flag.
greater than 0, then the SS data allows the inter-picture
dependency structure of the VP9 stream to be pre-declared, rather
than indicating it on the fly with every packet. If N_G is
greater than 0, then for N_G + 1 pictures in the GOF, each frame's
temporal layer ID (T), switch up point (U), and the R reference
indices (P_DIFFs) are specified.
N_G=0 indicates that either there is only one temporal layer or no -: Bit reserved for future use. MUST be set to zero and MUST be
fixed inter-picture dependency information is present going ignored by the receiver.
forward in the bitstream.
N_G: N_G indicates the number of frames in a GOF. If N_G is greater
than 0, then the SS data allows the inter-picture dependency
structure of the VP9 stream to be pre-declared, rather than
indicating it on the fly with every packet. If N_G is greater
than 0, then for N_G pictures in the GOF, each frame's temporal
layer ID (T), switch up point (U), and the R reference indices
(P_DIFFs) are specified.
The very first frame specified in the GOF MUST have T set to 0.
G set to 0 or N_G set to 0 indicates that either there is only one
temporal layer or no fixed inter-picture dependency information is
present going forward in the bitstream.
Note that for a given super frame, all layer frames follow the Note that for a given super frame, all layer frames follow the
same inter-picture dependency structure. However, the frame rate same inter-picture dependency structure. However, the frame rate
of each spatial layer can be different from each other and this of each spatial layer can be different from each other and this
can be controlled with the use of the D bit described above. The can be controlled with the use of the D bit described above. The
specified dependency structure in the SS data MUST be for the specified dependency structure in the SS data MUST be for the
highest frame rate layer. highest frame rate layer.
In a scalable stream sent with a fixed pattern, the SS data SHOULD be In a scalable stream sent with a fixed pattern, the SS data SHOULD be
included in the first packet of every key frame. This is a packet included in the first packet of every key frame. This is a packet
with P bit equal to zero, S or D bit equal to zero, B bit equal to 1, with P bit equal to zero, S or D bit equal to zero, and B bit equal
and temporal layer ID (TID) equal to 0. The SS data SHOULD also be to 1. The SS data MUST only be changed on the frame that corresponds
included in the first packet of the first frame in which the SS to the very first frame specified in the previous SS data's GOF (if
changes. If the SS data is included in a frame with TID not equal to the previous SS data's N_G was greater than 0).
0, it MUST also be repeated in the first packet of the first frame
with a lower TID, until TID equals to 0.
4.3. VP9 Payload Header 4.3. VP9 Payload Header
TODO: need to describe VP9 payload header. TODO: need to describe VP9 payload header.
4.4. Frame Fragmentation 4.4. Frame Fragmentation
VP9 frames are fragmented into packets, in RTP sequence number order, VP9 frames are fragmented into packets, in RTP sequence number order,
beginning with a packet with the B bit set, and ending with a packet beginning with a packet with the B bit set, and ending with a packet
with the RTP marker bit set. There is no mechanism for finer-grained with the RTP marker bit M set. There is no mechanism for finer-
access to parts of a VP9 frame. grained access to parts of a VP9 frame.
4.5. Examples of VP9 RTP Stream 4.5. Examples of VP9 RTP Stream
TODO TODO
5. Using VP9 with RPSI and SLI Feedback 5. Using VP9 with RPSI and SLI Feedback
The VP9 payload descriptor defined in Section 4.2 above contains an The VP9 payload descriptor defined in Section 4.2 above contains an
optional PictureID parameter. One use of this parameter is included optional PictureID parameter. One use of this parameter is to enable
to enable use of reference picture selection index (RPSI) and slice use of the reference picture selection index (RPSI) and slice loss
loss indication (SLI), both defined in [RFC4585]. indication (SLI) RTCP feedback messages, both defined in [RFC4585].
5.1. RPSI 5.1. RPSI
TODO: Update to indicate which frame within the picture. TODO: Update to indicate which frame within the picture.
The reference picture selection index is a payload-specific feedback The reference picture selection index is a payload-specific feedback
message defined within the RTCP-based feedback format. The RPSI message defined within the RTCP-based feedback format. The RPSI
message is generated by a receiver and can be used in two ways. message is generated by a receiver and can be used in two ways.
Either it can signal a preferred reference picture when a loss has Either it can signal a preferred reference picture when a loss has
been detected by the decoder -- preferably then a reference that the been detected by the decoder -- preferably then a reference that the
decoder knows is perfect -- or, it can be used as positive feedback decoder knows is perfect -- or, it can be used as positive feedback
information to acknowledge correct decoding of certain reference information to acknowledge correct decoding of certain reference
pictures. The positive feedback method is useful for VP9 used as pictures. The positive feedback method is useful for VP9 used for
unicast. The use of RPSI for VP9 is preferably combined with a point to point (unicast) communication. The use of RPSI for VP9 is
special update pattern of the codec's two special reference frames -- preferably combined with a special update pattern of the codec's two
the golden frame and the altref frame -- in which they are updated in special reference frames -- the golden frame and the altref frame --
an alternating leapfrog fashion. When a receiver has received and in which they are updated in an alternating leapfrog fashion. When a
correctly decoded a golden or altref frame, and that frame had a receiver has received and correctly decoded a golden or altref frame,
PictureID in the payload descriptor, the receiver can acknowledge and that frame had a PictureID in the payload descriptor, the
this simply by sending an RPSI message back to the sender. The receiver can acknowledge this simply by sending an RPSI message back
message body (i.e., the "native RPSI bit string" in [RFC4585]) is to the sender. The message body (i.e., the "native RPSI bit string"
simply the PictureID of the received frame. in [RFC4585]) is simply the PictureID of the received frame.
5.2. SLI 5.2. SLI
TODO: Update to indicate which frame within the picture. TODO: Update to indicate which frame within the picture.
The slice loss indication is another payload-specific feedback The slice loss indication is another payload-specific feedback
message defined within the RTCP-based feedback format. The SLI message defined within the RTCP-based feedback format. The SLI
message is generated by the receiver when a loss or corruption is message is generated by the receiver when a loss or corruption is
detected in a frame. The format of the SLI message is as follows detected in a frame. The format of the SLI message is as follows
[RFC4585]: [RFC4585]:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| First | Number | PictureID | | First | Number | PictureID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5 Figure 5
Here, First is the macroblock address (in scan order) of the first Here, First is the macroblock address (in scan order) of the first
lost block and Number is the number of lost blocks. PictureID is the lost block and Number is the number of lost blocks, as defined in
six least significant bits of the codec-specific picture identifier [RFC4585]. PictureID is the six least significant bits of the codec-
in which the loss or corruption has occurred. For VP9, this codec- specific picture identifier in which the loss or corruption has
specific identifier is naturally the PictureID of the current frame, occurred. For VP9, this codec-specific identifier is naturally the
as read from the payload descriptor. If the payload descriptor of PictureID of the current frame, as read from the payload descriptor.
the current frame does not have a PictureID, the receiver MAY send If the payload descriptor of the current frame does not have a
the last received PictureID+1 in the SLI message. The receiver MAY PictureID, the receiver MAY send the last received PictureID+1 in the
set the First parameter to 0, and the Number parameter to the total SLI message. The receiver MAY set the First parameter to 0, and the
number of macroblocks per frame, even though only parts of the frame Number parameter to the total number of macroblocks per frame, even
is corrupted. When the sender receives an SLI message, it can make though only part of the frame is corrupted. When the sender receives
use of the knowledge from the latest received RPSI message. Knowing an SLI message, it can make use of the knowledge from the latest
that the last golden or altref frame was successfully received, it received RPSI message. Knowing that the last golden or altref frame
can encode the next frame with reference to that established was successfully received, it can encode the next frame with
reference. reference to that established reference.
5.3. Example 5.3. Example
TODO: this example is copied from the VP8 payload format TODO: this example is copied from the VP8 payload format
specification, and has not been updated for VP9. It may be specification, and has not been updated for VP9. It may be
incorrect. incorrect.
The use of RPSI and SLI is best illustrated in an example. In this The use of RPSI and SLI is best illustrated in an example. In this
example, the encoder may not update the altref frame until the last example, the encoder may not update the altref frame until the last
sent golden frame has been acknowledged with an RPSI message. If an sent golden frame has been acknowledged with an RPSI message. If an
skipping to change at page 15, line 43 skipping to change at page 15, line 32
Note that the scheme is robust to loss of the feedback messages. If Note that the scheme is robust to loss of the feedback messages. If
the RPSI is lost, the sender will try to update the golden (or the RPSI is lost, the sender will try to update the golden (or
altref) again after a while, without releasing the established altref) again after a while, without releasing the established
reference. Also, if an SLI is lost, the receiver can keep sending reference. Also, if an SLI is lost, the receiver can keep sending
SLI messages at any interval allowed by the RTCP sending timing SLI messages at any interval allowed by the RTCP sending timing
restrictions as specified in [RFC4585], as long as the picture is restrictions as specified in [RFC4585], as long as the picture is
corrupted. corrupted.
6. Payload Format Parameters 6. Payload Format Parameters
This payload format has two required parameters. This payload format has two optional parameters.
6.1. Media Type Definition 6.1. Media Type Definition
This registration is done using the template defined in [RFC6838] and This registration is done using the template defined in [RFC6838] and
following [RFC4855]. following [RFC4855].
Type name: video Type name: video
Subtype name: VP9 Subtype name: VP9
Required parameters: Required parameters: None.
These parameters MUST be used to signal the capabilities of a
receiver implementation. These parameters MUST NOT be used for Optional parameters:
any other purpose. These parameters are used to signal the capabilities of a receiver
implementation. If the implementation is willing to receive
media, both parameters MUST be provided. These parameters MUST
NOT be used for any other purpose.
max-fr: The value of max-fr is an integer indicating the maximum max-fr: The value of max-fr is an integer indicating the maximum
frame rate in units of frames per second that the decoder is frame rate in units of frames per second that the decoder is
capable of decoding. capable of decoding.
max-fs: The value of max-fs is an integer indicating the maximum max-fs: The value of max-fs is an integer indicating the maximum
frame size in units of macroblocks that the decoder is capable frame size in units of macroblocks that the decoder is capable
of decoding. of decoding.
The decoder is capable of decoding this frame size as long as The decoder is capable of decoding this frame size as long as
skipping to change at page 17, line 51 skipping to change at page 17, line 45
a=fmtp:98 max-fr=30; max-fs=3600; a=fmtp:98 max-fr=30; max-fs=3600;
6.2.2. Offer/Answer Considerations 6.2.2. Offer/Answer Considerations
TODO: Update this for VP9 TODO: Update this for VP9
7. Security Considerations 7. Security Considerations
RTP packets using the payload format defined in this specification RTP packets using the payload format defined in this specification
are subject to the security considerations discussed in the RTP are subject to the security considerations discussed in the RTP
specification [RFC3550], and in any applicable RTP profile. The main specification [RFC3550], and in any applicable RTP profile such as
security considerations for the RTP packet carrying the RTP payload RTP/AVP [RFC3551], RTP/AVPF [RFC4585], RTP/SAVP [RFC3711], or RTP/
format defined within this memo are confidentiality, integrity and SAVPF [RFC5124]. SAVPF [RFC5124]. However, as "Securing the RTP
source authenticity. Confidentiality is achieved by encryption of Protocol Framework: Why RTP Does Not Mandate a Single Media Security
the RTP payload. Integrity of the RTP packets through suitable Solution" [RFC7202] discusses, it is not an RTP payload format's
cryptographic integrity protection mechanism. Cryptographic system responsibility to discuss or mandate what solutions are used to meet
may also allow the authentication of the source of the payload. A the basic security goals like confidentiality, integrity and source
suitable security mechanism for this RTP payload format should authenticity for RTP in general. This responsibility lays on anyone
provide confidentiality, integrity protection and at least source using RTP in an application. They can find guidance on available
authentication capable of determining if an RTP packet is from a security mechanisms in Options for Securing RTP Sessions [RFC7201].
member of the RTP session or not. Note that the appropriate Applications SHOULD use one or more appropriate strong security
mechanism to provide security to RTP and payloads following this memo mechanisms. The rest of this security consideration section
may vary. It is dependent on the application, the transport, and the discusses the security impacting properties of the payload format
signaling protocol employed. Therefore a single mechanism is not itself.
sufficient, although if suitable the usage of SRTP [RFC3711] is
recommended. This RTP payload format and its media decoder do not This RTP payload format and its media decoder do not exhibit any
exhibit any significant non-uniformity in the receiver-side significant non-uniformity in the receiver-side computational
computational complexity for packet processing, and thus are unlikely complexity for packet processing, and thus are unlikely to pose a
to pose a denial-of-service threat due to the receipt of pathological denial-of-service threat due to the receipt of pathological data.
data. Nor does the RTP payload format contain any active content. Nor does the RTP payload format contain any active content.
8. Congestion Control 8. Congestion Control
Congestion control for RTP SHALL be used in accordance with RFC 3550 Congestion control for RTP SHALL be used in accordance with RFC 3550
[RFC3550], and with any applicable RTP profile; e.g., RFC 3551 [RFC3550], and with any applicable RTP profile; e.g., RFC 3551
[RFC3551]. The congestion control mechanism can, in a real-time [RFC3551]. The congestion control mechanism can, in a real-time
encoding scenario, adapt the transmission rate by instructing the encoding scenario, adapt the transmission rate by instructing the
encoder to encode at a certain target rate. Media aware network encoder to encode at a certain target rate. Media aware network
elements MAY use the information in the VP9 payload descriptor in elements MAY use the information in the VP9 payload descriptor in
Section 4.2 to identify non-reference frames and discard them in Section 4.2 to identify non-reference frames and discard them in
skipping to change at page 19, line 12 skipping to change at page 19, line 6
draft-grange-vp9-bitstream-00 (work in progress), February draft-grange-vp9-bitstream-00 (work in progress), February
2013. 2013.
[I-D.lennox-avtext-lrr] [I-D.lennox-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-lennox-avtext-lrr-00 (work in progress), Message", draft-lennox-avtext-lrr-00 (work in progress),
March 2015. March 2015.
[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, March 1997. Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[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, July 2003. Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <http://www.rfc-editor.org/info/rfc3550>.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <http://www.rfc-editor.org/info/rfc4566>.
[RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
"Extended RTP Profile for Real-time Transport Control "Extended RTP Profile for Real-time Transport Control
Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, DOI
2006. 10.17487/RFC4585, July 2006,
<http://www.rfc-editor.org/info/rfc4585>.
[RFC4855] Casner, S., "Media Type Registration of RTP Payload [RFC4855] Casner, S., "Media Type Registration of RTP Payload
Formats", RFC 4855, February 2007. Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,
<http://www.rfc-editor.org/info/rfc4855>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13, RFC Specifications and Registration Procedures", BCP 13, RFC
6838, January 2013. 6838, DOI 10.17487/RFC6838, January 2013,
<http://www.rfc-editor.org/info/rfc6838>.
10.2. Informative References 10.2. Informative References
[RFC3551] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and [RFC3551] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and
Video Conferences with Minimal Control", STD 65, RFC 3551, Video Conferences with Minimal Control", STD 65, RFC 3551,
July 2003. DOI 10.17487/RFC3551, July 2003,
<http://www.rfc-editor.org/info/rfc3551>.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)", Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, March 2004. RFC 3711, DOI 10.17487/RFC3711, March 2004,
<http://www.rfc-editor.org/info/rfc3711>.
[RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for
Real-time Transport Control Protocol (RTCP)-Based Feedback
(RTP/SAVPF)", RFC 5124, DOI 10.17487/RFC5124, February
2008, <http://www.rfc-editor.org/info/rfc5124>.
[RFC7201] Westerlund, M. and C. Perkins, "Options for Securing RTP
Sessions", RFC 7201, DOI 10.17487/RFC7201, April 2014,
<http://www.rfc-editor.org/info/rfc7201>.
[RFC7202] Perkins, C. and M. Westerlund, "Securing the RTP
Framework: Why RTP Does Not Mandate a Single Media
Security Solution", RFC 7202, DOI 10.17487/RFC7202, April
2014, <http://www.rfc-editor.org/info/rfc7202>.
Authors' Addresses Authors' Addresses
Justin Uberti Justin Uberti
Google, Inc. Google, Inc.
747 6th Street South 747 6th Street South
Kirkland, WA 98033 Kirkland, WA 98033
USA USA
Email: justin@uberti.name Email: justin@uberti.name
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