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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-16) exists of draft-ietf-avtext-framemarking-04 ** Downref: Normative reference to an Experimental draft: draft-ietf-avtext-framemarking (ref. 'I-D.ietf-avtext-framemarking') == Outdated reference: A later version (-16) exists of draft-ietf-payload-vp9-03 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Payload Working Group J. Lennox 3 Internet-Draft D. Hong 4 Intended status: Standards Track Vidyo 5 Expires: November 9, 2017 J. Uberti 6 S. Holmer 7 M. Flodman 8 Google 9 May 8, 2017 11 The Layer Refresh Request (LRR) RTCP Feedback Message 12 draft-ietf-avtext-lrr-05 14 Abstract 16 This memo describes the RTCP Payload-Specific Feedback Message "Layer 17 Refresh Request" (LRR), which can be used to request a state refresh 18 of one or more substreams of a layered media stream. It also defines 19 its use with several RTP payloads for scalable media formats. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on November 9, 2017. 38 Copyright Notice 40 Copyright (c) 2017 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 56 2. Conventions, Definitions and Acronyms . . . . . . . . . . . . 2 57 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 58 3. Layer Refresh Request . . . . . . . . . . . . . . . . . . . . 5 59 3.1. Message Format . . . . . . . . . . . . . . . . . . . . . 5 60 3.2. Semantics . . . . . . . . . . . . . . . . . . . . . . . . 6 61 4. Usage with specific codecs . . . . . . . . . . . . . . . . . 7 62 4.1. H264 SVC . . . . . . . . . . . . . . . . . . . . . . . . 7 63 4.2. VP8 . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 64 4.3. H265 . . . . . . . . . . . . . . . . . . . . . . . . . . 9 65 5. Usage with different scalability transmission mechanisms . . 10 66 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 67 7. SDP Definitions . . . . . . . . . . . . . . . . . . . . . . . 10 68 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 69 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 70 9.1. Normative References . . . . . . . . . . . . . . . . . . 11 71 9.2. Informative References . . . . . . . . . . . . . . . . . 12 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 74 1. Introduction 76 This memo describes an RTCP [RFC3550] Payload-Specific Feedback 77 Message [RFC4585] "Layer Refresh Request" (LRR). It is designed to 78 allow a receiver of a layered media stream to request that one or 79 more of its substreams be refreshed, such that it can then be decoded 80 by an endpoint which previously was not receiving those layers, 81 without requiring that the entire stream be refreshed (as it would be 82 if the receiver sent a Full Intra Request (FIR); [RFC5104] see also 83 [RFC8082]). 85 The feedback message is applicable both to temporally and spatially 86 scaled streams, and to both single-stream and multi-stream 87 scalability modes. 89 2. Conventions, Definitions and Acronyms 91 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 92 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 93 document are to be interpreted as described in [RFC2119]. 95 2.1. Terminology 97 A "Layer Refresh Point" is a point in a scalable stream after which a 98 decoder, which previously had been able to decode only some (possibly 99 none) of the available layers of stream, is able to decode a greater 100 number of the layers. 102 For spatial (or quality) layers, layer refresh typically requires 103 that a spatial layer be encoded in a way that references only lower- 104 layer subpictures of the current picture, not any earlier pictures of 105 that spatial layer. Additionally, the encoder must promise that no 106 earlier pictures of that spatial layer will be used as reference in 107 the future. 109 In a layer refresh, however, other layers than the ones requested for 110 refresh may still maintain dependency on earlier content of the 111 stream. This is the difference between a layer refresh and a Full 112 Intra Request [RFC5104]. This minimizes the coding overhead of 113 refresh to only those parts of the stream that actually need to be 114 refreshed at any given time. 116 An illustration of spatial layer refresh of an enhancement layer is 117 shown below. 119 ... <-- S1 <-- S1 S1 <-- S1 <-- ... 120 | | | | 121 \/ \/ \/ \/ 122 ... <-- S0 <-- S0 <-- S0 <-- S0 <-- ... 124 1 2 3 4 126 Figure 1 128 In Figure 1, frame 3 is a layer refresh point for spatial layer S1; a 129 decoder which had previously only been decoding spatial layer S0 130 would be able to decode layer S1 starting at frame 3. 132 An illustration of spatial layer refresh of a base layer is shown 133 below. 135 ... <-- S1 <-- S1 <-- S1 <-- S1 <-- ... 136 | | | | 137 \/ \/ \/ \/ 138 ... <-- S0 <-- S0 S0 <-- S0 <-- ... 140 1 2 3 4 142 Figure 2 144 In Figure 2, frame 3 is a layer refresh point for spatial layer S0; a 145 decoder which had previously not been decoding the stream at all 146 could decode layer S0 starting at frame 3. 148 For temporal layers, layer refresh requires that the layer be 149 "temporally nested", i.e. use as reference only earlier frames of a 150 lower temporal layer, not any earlier frames of this temporal layer, 151 and also promise that no future frames of this temporal layer will 152 reference frames of this temporal layer before the refresh point. In 153 many cases, the temporal structure of the stream will mean that all 154 frames are temporally nested, in which case decoders will have no 155 need to send LRR messages for the stream. 157 An illustration of temporal layer refresh is shown below. 159 ... <----- T1 <------ T1 T1 <------ ... 160 / / / 161 |_ |_ |_ 162 ... <-- T0 <------ T0 <------ T0 <------ T0 <--- ... 164 1 2 3 4 5 6 7 166 Figure 3 168 In Figure 3, frame 6 is a layer refresh point for temporal layer T1; 169 a decoder which had previously only been decoding temporal layer T0 170 would be able to decode layer T1 starting at frame 6. 172 An illustration of an inherently temporally nested stream is shown 173 below. 175 T1 T1 T1 176 / / / 177 |_ |_ |_ 178 ... <-- T0 <------ T0 <------ T0 <------ T0 <--- ... 180 1 2 3 4 5 6 7 182 Figure 4 184 In Figure 4, the stream is temporally nested in its ordinary 185 structure; a decoder receiving layer T0 can begin decoding layer T1 186 at any point. 188 3. Layer Refresh Request 190 A layer refresh frame can be requested by sending a Layer Refresh 191 Request (LRR), which is an Real-Time Transport Control Protocol 192 (RTCP) [RFC3550] payload-specific feedback message [RFC4585] asking 193 the encoder to encode a frame which makes it possible to upgrade to a 194 higher layer. The LRR contains one or two tuples, indicating the 195 layer the decoder wants to upgrade to, and (optionally) the currently 196 highest layer the decoder can decode. 198 The specific format of the tuples, and the mechanism by which a 199 receiver recognizes a refresh frame, is codec-dependent. Usage for 200 several codecs is discussed in Section 4. 202 LRR follows the model of the Full Intra Request (FIR) 203 [RFC5104](Section 3.5.1) for its retransmission, reliability, and use 204 in multipoint conferences. 206 The LRR message is identified by RTCP packet type value PT=PSFB and 207 FMT=TBD. The FCI field MUST contain one or more LRR entries. Each 208 entry applies to a different media sender, identified by its SSRC. 210 [NOTE TO RFC Editor: Please replace "TBD" with the IANA-assigned 211 payload-specific feedback number.] 213 3.1. Message Format 215 The Feedback Control Information (FCI) for the Layer Refresh Request 216 consists of one or more FCI entries, the content of which is depicted 217 in Figure 5. The length of the LRR feedback message MUST be set to 218 2+3*N, where N is the number of FCI entries. 220 0 1 2 3 221 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 1 222 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 223 | SSRC | 224 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 225 | Seq nr. |C| Payload Type| Reserved | 226 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 227 | RES | TTID| TLID | RES | CTID| CLID (opt) | 228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 230 Figure 5 232 SSRC (32 bits) The SSRC value of the media sender that is requested 233 to send a layer refresh point. 235 Seq nr. (8 bits) Command sequence number. The sequence number space 236 is unique for each pairing of the SSRC of command source and the 237 SSRC of the command target. The sequence number SHALL be 238 increased by 1 modulo 256 for each new command. A repetition 239 SHALL NOT increase the sequence number. The initial value is 240 arbitrary. 242 C (1 bit) A flag bit indicating whether the "Current Layer Index" 243 field is present in the FCI. If this bit is false, the sender of 244 the LRR message is requesting refresh of all layers up to and 245 including the target layer. 247 Payload Type (7 bits) The RTP payload type for which the LRR is 248 being requested. This gives the context in which the target layer 249 index is to be interpreted. 251 Reserved (RES) (16 bits / 5 bits / 5 bits) All bits SHALL be set to 252 0 by the sender and SHALL be ignored on reception. 254 Target Temporal Layer ID (TTID) (3 bits) The temporal ID of the 255 target layer for which the receiver wishes a refresh point. 257 Target Layer ID (TLID) (8 bits) The layer ID of the target spatial 258 or quality layer for which the receiver wishes a refresh point. 259 Its format is dependent on the payload type field. 261 Current Temporal Layer ID (CTID) (3 bits) If C is 1, the ID of the 262 current temporal layer being decoded by the receiver. This 263 message is not requesting refresh of layers at or below this 264 layer. If C is 0, this field SHALL be set to 0 by the sender and 265 SHALL be ignored on reception. 267 Current Layer ID (CLID) (8 bits) If C is 1, the layer ID of the 268 current spatial or quality layer being decoded by the receiver. 269 This message is not requesting refresh of layers at or below this 270 layer. If C is 0, this field SHALL be set to 0 by the sender and 271 SHALL be ignored on reception. 273 Note: the syntax of the TTID, TLID, CTID, and CLID fields match, by 274 design, the TID and LID fields in [I-D.ietf-avtext-framemarking]. 276 3.2. Semantics 278 Within the common packet header for feedback messages (as defined in 279 section 6.1 of [RFC4585]), the "SSRC of packet sender" field 280 indicates the source of the request, and the "SSRC of media source" 281 is not used and SHALL be set to 0. The SSRCs of the media senders to 282 which the LRR command applies are in the corresponding FCI entries. 284 A LRR message MAY contain requests to multiple media senders, using 285 one FCI entry per target media sender. 287 Upon reception of LRR, the encoder MUST send a decoder refresh point 288 (see section Section 2.1) as soon as possible. 290 The sender MUST consider congestion control as outlined in section 5 291 of [RFC5104], which MAY restrict its ability to send a layer refresh 292 point quickly. 294 4. Usage with specific codecs 296 In order for LRR to be used with a scalable codec, the format of the 297 target layer and current target layer fields needs to be specified 298 for that codec's RTP packetization. New RTP packetization 299 specifications for scalable codecs SHOULD define how this is done. 300 (The VP9 payload [I-D.ietf-payload-vp9], for instance, has done so.) 301 If the payload also specifies how it is used with the Frame Marking 302 RTP Header Extension [I-D.ietf-avtext-framemarking], the syntax MUST 303 be defined in the same manner as the TID and LID fields in that 304 header. 306 4.1. H264 SVC 308 H.264 SVC [RFC6190] defines temporal, dependency (spatial), and 309 quality scalability modes. 311 +---------------+---------------+ 312 |0|1|2|3|4|5|6|7|0|1|2|3|4|5|6|7| 313 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 314 | RES | TID |R| DID | QID | 315 +---------------+---------------+ 317 Figure 6 319 Figure 6 shows the format of the layer index field for H.264 SVC 320 streams. The "R" and "RES" fields MUST be set to 0 on transmission 321 and ignored on reception. See [RFC6190] Section 1.1.3 for details on 322 the DID, QID, and TID fields. 324 A dependency or quality layer refresh of a given layer in H.264 SVC 325 can be identified by the "I" bit (idr_flag) in the extended NAL unit 326 header, present in NAL unit types 14 (prefix NAL unit) and 20 (coded 327 scalable slice). Layer refresh of the base layer can also be 328 identified by its NAL unit type of its coded slices, which is "5" 329 rather than "1". A dependency or quality layer refresh is complete 330 once this bit has been seen on all the appropriate layers (in 331 decoding order) above the current layer index (if any, or beginning 332 from the base layer if not) through the target layer index. 334 Note that as the "I" bit in a PACSI header is set if the 335 corresponding bit is set in any of the aggregated NAL units it 336 describes; thus, it is not sufficient to identify layer refresh when 337 NAL units of multiple dependency or quality layers are aggregated. 339 In H.264 SVC, temporal layer refresh information can be determined 340 from various Supplemental Encoding Information (SEI) messages in the 341 bitstream. 343 Whether an H.264 SVC stream is scalably nested can be determined from 344 the Scalability Information SEI message's temporal_id_nesting flag. 345 If this flag is set in a stream's currently applicable Scalability 346 Information SEI, receivers SHOULD NOT send temporal LRR messages for 347 that stream, as every frame is implicitly a temporal layer refresh 348 point. (The Scalability Information SEI message may also be 349 available in the signaling negotiation of H.264 SVC, as the sprop- 350 scalability-info parameter.) 352 If a stream's temporal_id_nesting flag is not set, the Temporal Level 353 Switching Point SEI message identifies temporal layer switching 354 points. A temporal layer refresh is satisfied when this SEI message 355 is present in a frame with the target layer index, if the message's 356 delta_frame_num refers to a frame with the requested current layer 357 index. (Alternately, temporal layer refresh can also be satisfied by 358 a complete state refresh, such as an IDR.) Senders which support 359 receiving LRR for non-temporally-nested streams MUST insert Temporal 360 Level Switching Point SEI messages as appropriate. 362 4.2. VP8 364 The VP8 RTP payload format [RFC7741] defines temporal scalability 365 modes. It does not support spatial scalability. 367 +---------------+---------------+ 368 |0|1|2|3|4|5|6|7|0|1|2|3|4|5|6|7| 369 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 370 | RES | TID | RES | 371 +---------------+---------------+ 373 Figure 7 375 Figure 7 shows the format of the layer index field for VP8 streams. 376 The "RES" fields MUST be set to 0 on transmission and be ignored on 377 reception. See [RFC7741] Section 4.2 for details on the TID field. 379 A VP8 layer refresh point can be identified by the presence of the 380 "Y" bit in the VP8 payload header. When this bit is set, this and 381 all subsequent frames depend only on the current base temporal layer. 382 On receipt of an LRR for a VP8 stream, A sender which supports LRR 383 MUST encode the stream so it can set the Y bit in a packet whose 384 temporal layer is at or below the target layer index. 386 Note that in VP8, not every layer switch point can be identified by 387 the Y bit, since the Y bit implies layer switch of all layers, not 388 just the layer in which it is sent. Thus the use of LRR with VP8 can 389 result in some inefficiency in transmision. However, this is not 390 expected to be a major issue for temporal structures in normal use. 392 4.3. H265 394 The initial version of the H.265 payload format [RFC7798] defines 395 temporal scalability, with protocol elements reserved for spatial or 396 other scalability modes (which are expected to be defined in a future 397 version of the specification). 399 +---------------+---------------+ 400 |0|1|2|3|4|5|6|7|0|1|2|3|4|5|6|7| 401 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 402 | RES | TID |RES| LayerId | 403 +---------------+---------------+ 405 Figure 8 407 Figure 8 shows the format of the layer index field for H.265 streams. 408 The "RES" fields MUST be set to 0 on transmission and ignored on 409 reception. See [RFC7798] Section 1.1.4 for details on the LayerId 410 and TID fields. 412 H.265 streams signal whether they are temporally nested, using the 413 vps_temporal_id_nesting_flag in the Video Parameter Set (VPS), and 414 the sps_temporal_id_nesting_flag in the Sequence Parameter Set (SPS). 415 If this flag is set in a stream's currently applicable VPS or SPS, 416 receivers SHOULD NOT send temporal LRR messages for that stream, as 417 every frame is implicitly a temporal layer refresh point. 419 If a stream's sps_temporal_id_nesting_flag is not set, the NAL unit 420 types 2 to 5 inclusively identify temporal layer switching points. A 421 layer refresh to any higher target temporal layer is satisfied when a 422 NAL unit type of 4 or 5 with TID equal to 1 more than current TID is 423 seen. Alternatively, layer refresh to a target temporal layer can be 424 incrementally satisfied with NAL unit type of 2 or 3. In this case, 425 given current TID = TO and target TID = TN, layer refresh to TN is 426 satisfied when NAL unit type of 2 or 3 is seen for TID = T1, then TID 427 = T2, all the way up to TID = TN. During this incremental process, 428 layer refresh to TN can be completely satisfied as soon as a NAL unit 429 type of 2 or 3 is seen. 431 Of course, temporal layer refresh can also be satisfied whenever any 432 Intra Random Access Point (IRAP) NAL unit type (with values 16-23, 433 inclusively) is seen. An IRAP picture is similar to an IDR picture 434 in H.264 (NAL unit type of 5 in H.264) where decoding of the picture 435 can start without any older pictures. 437 In the (future) H.265 payloads that support spatial scalability, a 438 spatial layer refresh of a specific layer can be identified by NAL 439 units with the requested layer ID and NAL unit types between 16 and 440 21 inclusive. A dependency or quality layer refresh is complete once 441 NAL units of this type have been seen on all the appropriate layers 442 (in decoding order) above the current layer index (if any, or 443 beginning from the base layer if not) through the target layer index. 445 5. Usage with different scalability transmission mechanisms 447 Several different mechanisms are defined for how scalable streams can 448 be transmitted in RTP. The RTP Taxonomy [RFC7656] Section 3.7 449 defines three mechanisms: Single RTP Stream on a Single Media 450 Transport (SRST), Multiple RTP Streams on a Single Media Transport 451 (MRST), and Multiple RTP Streams on Multiple Media Transports (MRMT). 453 The LRR message is applicable to all these mechanisms. For MRST and 454 MRMT mechanisms, the "media source" field of the LRR FCI is set to 455 the SSRC of the RTP stream containing the layer indicated by the 456 Current Layer Index (if "C" is 1), or the stream containing the base 457 encoded stream (if "C" is 0). For MRMT, it is sent on the RTP 458 session on which this stream is sent. On receipt, the sender MUST 459 refresh all the layers requested in the stream, simultaneously in 460 decode order. 462 6. Security Considerations 464 All the security considerations of FIR feedback packets [RFC5104] 465 apply to LRR feedback packets as well. Additionally, media senders 466 receiving LRR feedback packets MUST validate that the payload types 467 and layer indices they are receiving are valid for the stream they 468 are currently sending, and discard the requests if not. 470 7. SDP Definitions 472 Section 7 of [RFC5104] defines SDP procedures for indicating and 473 negotiating support for codec control messages (CCM) in SDP. This 474 document extends this with a new codec control command, "lrr", which 475 indicates support of the Layer Refresh Request (LRR). 477 Figure 9 gives a formal Augmented Backus-Naur Form (ABNF) [RFC5234] 478 showing this grammar extension, extending the grammar defined in 479 [RFC5104]. 481 rtcp-fb-ccm-param =/ SP "lrr" ; Layer Refresh Request 483 Figure 9: Syntax of the "lrr" ccm 485 The Offer-Answer considerations defined in [RFC5104] Section 7.2 486 apply. 488 8. IANA Considerations 490 This document defines a new entry to the "Codec Control Messages" 491 subregistry of the "Session Description Protocol (SDP) Parameters" 492 registry, according to the following data: 494 Value name: lrr 496 Long name: Layer Refresh Request Command 498 Usable with: ccm 500 Reference: RFC XXXX 502 This document also defines a new entry to the "FMT Values for PSFB 503 Payload Types" subregistry of the "Real-Time Transport Protocol (RTP) 504 Parameters" registry, according to the following data: 506 Name: LRR 508 Long Name: Layer Refresh Request Command 510 Value: TBD 512 Reference: RFC XXXX 514 9. References 516 9.1. Normative References 518 [I-D.ietf-avtext-framemarking] 519 Berger, E., Nandakumar, S., and M. Zanaty, "Frame Marking 520 RTP Header Extension", draft-ietf-avtext-framemarking-04 521 (work in progress), March 2017. 523 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 524 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ 525 RFC2119, March 1997, 526 . 528 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 529 Jacobson, "RTP: A Transport Protocol for Real-Time 530 Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, 531 July 2003, . 533 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 534 "Extended RTP Profile for Real-time Transport Control 535 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, DOI 536 10.17487/RFC4585, July 2006, 537 . 539 [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman, 540 "Codec Control Messages in the RTP Audio-Visual Profile 541 with Feedback (AVPF)", RFC 5104, DOI 10.17487/RFC5104, 542 February 2008, . 544 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 545 Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/ 546 RFC5234, January 2008, 547 . 549 [RFC6190] Wenger, S., Wang, Y., Schierl, T., and A. Eleftheriadis, 550 "RTP Payload Format for Scalable Video Coding", RFC 6190, 551 DOI 10.17487/RFC6190, May 2011, 552 . 554 [RFC7741] Westin, P., Lundin, H., Glover, M., Uberti, J., and F. 555 Galligan, "RTP Payload Format for VP8 Video", RFC 7741, 556 DOI 10.17487/RFC7741, March 2016, 557 . 559 [RFC7798] Wang, Y., Sanchez, Y., Schierl, T., Wenger, S., and M. 560 Hannuksela, "RTP Payload Format for High Efficiency Video 561 Coding (HEVC)", RFC 7798, DOI 10.17487/RFC7798, March 562 2016, . 564 9.2. Informative References 566 [I-D.ietf-payload-vp9] 567 Uberti, J., Holmer, S., Flodman, M., Lennox, J., and D. 568 Hong, "RTP Payload Format for VP9 Video", draft-ietf- 569 payload-vp9-03 (work in progress), March 2017. 571 [RFC7656] Lennox, J., Gross, K., Nandakumar, S., Salgueiro, G., and 572 B. Burman, Ed., "A Taxonomy of Semantics and Mechanisms 573 for Real-Time Transport Protocol (RTP) Sources", RFC 7656, 574 DOI 10.17487/RFC7656, November 2015, 575 . 577 [RFC8082] Wenger, S., Lennox, J., Burman, B., and M. Westerlund, 578 "Using Codec Control Messages in the RTP Audio-Visual 579 Profile with Feedback with Layered Codecs", RFC 8082, DOI 580 10.17487/RFC8082, March 2017, 581 . 583 Authors' Addresses 585 Jonathan Lennox 586 Vidyo, Inc. 587 433 Hackensack Avenue 588 Seventh Floor 589 Hackensack, NJ 07601 590 US 592 Email: jonathan@vidyo.com 594 Danny Hong 595 Vidyo, Inc. 596 433 Hackensack Avenue 597 Seventh Floor 598 Hackensack, NJ 07601 599 US 601 Email: danny@vidyo.com 603 Justin Uberti 604 Google, Inc. 605 747 6th Street South 606 Kirkland, WA 98033 607 USA 609 Email: justin@uberti.name 610 Stefan Holmer 611 Google, Inc. 612 Kungsbron 2 613 Stockholm 111 22 614 Sweden 616 Email: holmer@google.com 618 Magnus Flodman 619 Google, Inc. 620 Kungsbron 2 621 Stockholm 111 22 622 Sweden 624 Email: mflodman@google.com