draft-ietf-payload-vp9-01.txt   draft-ietf-payload-vp9-02.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: April 21, 2016 Google Expires: September 19, 2016 Google
J. Lennox J. Lennox
D. Hong D. Hong
Vidyo Vidyo
October 19, 2015 March 18, 2016
RTP Payload Format for VP9 Video RTP Payload Format for VP9 Video
draft-ietf-payload-vp9-01 draft-ietf-payload-vp9-02
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-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 21, 2016. This Internet-Draft will expire on September 19, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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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 . . . . . . . . . . . . 3
3. Media Format Description . . . . . . . . . . . . . . . . . . 3 3. Media Format Description . . . . . . . . . . . . . . . . . . 3
4. Payload Format . . . . . . . . . . . . . . . . . . . . . . . 4 4. Payload Format . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. RTP Header Usage . . . . . . . . . . . . . . . . . . . . 5 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 . . . . . . . . . . . . . . . . . . . 11 4.3. VP9 Payload Header . . . . . . . . . . . . . . . . . . . 12
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. Feedback Messages . . . . . . . . . . . . . . . . . . . . . . 12
5.1. RPSI . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.1. Reference Picture Selection Indication (RPSI) . . . . . . 12
5.2. SLI . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.2. Slice Loss Indication (SLI) . . . . . . . . . . . . . . . 13
5.3. Example . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.3. Full Intra Request (FIR) . . . . . . . . . . . . . . . . 13
6. Payload Format Parameters . . . . . . . . . . . . . . . . . . 15 5.4. Layer Refresh Request (LRR) . . . . . . . . . . . . . . . 14
6. Payload Format Parameters . . . . . . . . . . . . . . . . . . 14
6.1. Media Type Definition . . . . . . . . . . . . . . . . . . 15 6.1. Media Type Definition . . . . . . . . . . . . . . . . . . 15
6.2. SDP Parameters . . . . . . . . . . . . . . . . . . . . . 17 6.2. SDP Parameters . . . . . . . . . . . . . . . . . . . . . 16
6.2.1. Mapping of Media Subtype Parameters to SDP . . . . . 17 6.2.1. Mapping of Media Subtype Parameters to SDP . . . . . 16
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 . . . . . . . . . . . . . . . . . . . . . 17
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
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 . . . . . . . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
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].
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a lower spatial layer ID. This "inter-layer" dependency can result a lower spatial layer ID. This "inter-layer" dependency can result
in additional coding gain compared to the case where only traditional in additional coding gain compared to the case where only traditional
"inter-picture" dependency is used, where a frame depends on "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 and if inter-layer dependency is assumes that, within a super frame and if inter-layer dependency is
used, a spatial layer S frame can only depend on spatial layer S-1 used, a spatial layer S frame can only depend on spatial layer S-1
frame 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 previously 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?
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.
Given the D bit, a receiver only needs to additionally know the Given the D bit, a receiver only needs to additionally know the
inter-picture dependency structure for a given spatial layer frame in inter-picture dependency structure for a given spatial layer frame in
order to determine its decodability. Two modes of describing the order to determine its decodability. Two modes of describing the
inter-picture dependency structure are possible: "flexible mode" and inter-picture dependency structure are possible: "flexible mode" and
"non-flexible mode". An encoder can only switch between the two on "non-flexible mode". An encoder can only switch between the two on
the very first packet of a key frame with temporal layer ID equal to the very first packet of a key frame with temporal layer ID equal to
0. 0.
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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]. When P is set to zero, the T bit [I-D.ietf-avtext-lrr] message (see Section 5.4). When P is set to
(described below) MUST also be set to 0 (if present). 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
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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 M set. There is no mechanism for finer- with the RTP marker bit M set. There is no mechanism for finer-
grained 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. Feedback Messages
The VP9 payload descriptor defined in Section 4.2 above contains an
optional PictureID parameter. One use of this parameter is to enable
use of the reference picture selection index (RPSI) and slice loss
indication (SLI) RTCP feedback messages, both defined in [RFC4585].
5.1. RPSI 5.1. Reference Picture Selection Indication (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
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point to point (unicast) communication. The use of RPSI for VP9 is point to point (unicast) communication. The use of RPSI for VP9 is
preferably combined with a special update pattern of the codec's two preferably combined with a special update pattern of the codec's two
special reference frames -- the golden frame and the altref frame -- special reference frames -- the golden frame and the altref frame --
in which they are updated in an alternating leapfrog fashion. When a in which they are updated in an alternating leapfrog fashion. When a
receiver has received and correctly decoded a golden or altref frame, receiver has received and correctly decoded a golden or altref frame,
and that frame had a PictureID in the payload descriptor, the and that frame had a PictureID in the payload descriptor, the
receiver can acknowledge this simply by sending an RPSI message back receiver can acknowledge this simply by sending an RPSI message back
to the sender. The message body (i.e., the "native RPSI bit string" to the sender. The message body (i.e., the "native RPSI bit string"
in [RFC4585]) is simply the PictureID of the received frame. in [RFC4585]) is simply the PictureID of the received frame.
5.2. SLI 5.2. Slice Loss Indication (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
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If the payload descriptor of the current frame does not have a If the payload descriptor of the current frame does not have a
PictureID, the receiver MAY send the last received PictureID+1 in the PictureID, the receiver MAY send the last received PictureID+1 in the
SLI message. The receiver MAY set the First parameter to 0, and the SLI message. The receiver MAY set the First parameter to 0, and the
Number parameter to the total number of macroblocks per frame, even Number parameter to the total number of macroblocks per frame, even
though only part of the frame is corrupted. When the sender receives though only part of the frame is corrupted. When the sender receives
an SLI message, it can make use of the knowledge from the latest an SLI message, it can make use of the knowledge from the latest
received RPSI message. Knowing that the last golden or altref frame received RPSI message. Knowing that the last golden or altref frame
was successfully received, it can encode the next frame with was successfully received, it can encode the next frame with
reference to that established reference. reference to that established reference.
5.3. Example 5.3. Full Intra Request (FIR)
TODO: this example is copied from the VP8 payload format The Full Intra Request (FIR) [RFC5104] RTCP feedback message allows a
specification, and has not been updated for VP9. It may be receiver to request a full state refresh of an encoded stream.
incorrect.
The use of RPSI and SLI is best illustrated in an example. In this Upon receipt of an FIR request, a VP9 sender MUST send a super frame
example, the encoder may not update the altref frame until the last with a keyframe for its spatial layer 0 layer frame, and then send
sent golden frame has been acknowledged with an RPSI message. If an frames without inter-picture prediction (P=0) for any higher layer
update is not received within some time, a new golden frame update is frames.
sent instead. Once the new golden frame is established and
acknowledged, the same rule applies when updating the altref frame.
+-------+-------------------+-------------------------+-------------+ 5.4. Layer Refresh Request (LRR)
| Event | Sender | Receiver | Established |
| | | | reference |
+-------+-------------------+-------------------------+-------------+
| 1000 | Send golden frame | | |
| | PictureID = 0 | | |
| | | | |
| | | Receive and decode | |
| | | golden frame | |
| | | | |
| 1001 | | Send RPSI(0) | |
| | | | |
| 1002 | Receive RPSI(0) | | golden |
| | | | |
| ... | (sending regular | | |
| | frames) | | |
| | | | |
| 1100 | Send altref frame | | |
| | PictureID = 100 | | |
| | | | |
| | | Altref corrupted or | golden |
| | | lost | |
| | | | |
| 1101 | | Send SLI(100) | golden |
| | | | |
| 1102 | Receive SLI(100) | | |
| | | | |
| 1103 | Send frame with | | |
| | reference to | | |
| | golden | | |
| | | | |
| | | Receive and decode | golden |
| | | frame (decoder state | |
| | | restored) | |
| | | | |
| ... | (sending regular | | |
| | frames) | | |
| | | | |
| 1200 | Send altref frame | | |
| | PictureID = 200 | | |
| | | | |
| | | Receive and decode | golden |
| | | altref frame | |
| | | | |
| 1201 | | Send RPSI(200) | |
| | | | |
| 1202 | Receive RPSI(200) | | altref |
| | | | |
| ... | (sending regular | | |
| | frames) | | |
| | | | |
| 1300 | Send golden frame | | |
| | PictureID = 300 | | |
| | | | |
| | | Receive and decode | altref |
| | | golden frame | |
| | | | |
| 1301 | | Send RPSI(300) | altref |
| | | | |
| 1302 | RPSI lost | | |
| | | | |
| 1400 | Send golden frame | | |
| | PictureID = 400 | | |
| | | | |
| | | Receive and decode | altref |
| | | golden frame | |
| | | | |
| 1401 | | Send RPSI(400) | |
| | | | |
| 1402 | Receive RPSI(400) | | golden |
+-------+-------------------+-------------------------+-------------+
Table 1: Example signaling between sender and receiver The Layer Refresh Request [I-D.ietf-avtext-lrr] allows a receiver to
request a single layer of a spatially or temporally encoded stream to
be refreshed, without necessarily affecting the stream's other
layers.
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 |0|1|2|3|4|5|6|7|0|1|2|3|4|5|6|7|
altref) again after a while, without releasing the established +-------------+-----------------+
reference. Also, if an SLI is lost, the receiver can keep sending | T |R| S | RES |
SLI messages at any interval allowed by the RTCP sending timing +-------------+-----------------+
restrictions as specified in [RFC4585], as long as the picture is
corrupted. Figure 6
Figure 6 shows the format of LRR's layer index field for VP9 streams.
This is designed to follow the same layout as the "L" byte of the VP9
payload header, which carries the stream's layer information. The
"R" and "RES" fields MUST be set to 0 on transmission and ingnored on
reception. See Section 4.2 for details on the T and S fields.
Identification of a layer refresh frame can be derived from the
reference IDs of each frame by backtracking the dependency chain
until reaching a point where only decodable frames are being
referenced. Therefore it's recommended for both the flexible and the
non-flexible mode that, when upgrade frames are being encoded in
response to a LRR, those packets should contain layer indices and the
reference fields so that the decoder or an MCU can make this
derivation.
Example:
LRR {1,0}, {2,1} is sent by an MCU when it is currently relaying
{1,0} to a receiver and which wants to upgrade to {2,1}. In response
the encoder should encode the next frames in layers {1,1} and {2,1}
by only referring to frames in {1,0}, or {0,0}.
In the non-flexible mode, periodic upgrade frames can be defined by
the layer structure of the SS, thus periodic upgrade frames can be
automatically identified by the picture ID.
6. Payload Format Parameters 6. Payload Format Parameters
This payload format has two optional 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].
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10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.grange-vp9-bitstream] [I-D.grange-vp9-bitstream]
Grange, A. and H. Alvestrand, "A VP9 Bitstream Overview", Grange, A. and H. Alvestrand, "A VP9 Bitstream Overview",
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.ietf-avtext-lrr]
Lennox, J., Hong, D., Uberti, J., Holmer, S., and M. Lennox, J., Hong, D., Uberti, J., Holmer, S., and M.
Flodman, "The Layer Refresh Request (LRR) RTCP Feedback Flodman, "The Layer Refresh Request (LRR) RTCP Feedback
Message", draft-lennox-avtext-lrr-00 (work in progress), Message", draft-ietf-avtext-lrr-01 (work in progress),
March 2015. October 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, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997, RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <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, DOI 10.17487/RFC3550, Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <http://www.rfc-editor.org/info/rfc3550>. July 2003, <http://www.rfc-editor.org/info/rfc3550>.
skipping to change at page 19, line 29 skipping to change at page 18, line 44
[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, DOI Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, DOI
10.17487/RFC4585, July 2006, 10.17487/RFC4585, July 2006,
<http://www.rfc-editor.org/info/rfc4585>. <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, DOI 10.17487/RFC4855, February 2007, Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,
<http://www.rfc-editor.org/info/rfc4855>. <http://www.rfc-editor.org/info/rfc4855>.
[RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
"Codec Control Messages in the RTP Audio-Visual Profile
with Feedback (AVPF)", RFC 5104, DOI 10.17487/RFC5104,
February 2008, <http://www.rfc-editor.org/info/rfc5104>.
[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, DOI 10.17487/RFC6838, January 2013, 6838, DOI 10.17487/RFC6838, January 2013,
<http://www.rfc-editor.org/info/rfc6838>. <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,
DOI 10.17487/RFC3551, July 2003, DOI 10.17487/RFC3551, July 2003,
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