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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-18) exists of draft-ietf-avtcore-rtp-circuit-breakers-15 -- Possible downref: Non-RFC (?) normative reference: ref. 'VC2' Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force J. Weaver 3 Internet-Draft BBC 4 Intended status: Standards Track June 9, 2016 5 Expires: December 11, 2016 7 RTP Payload Format for VC-2 HQ Profile Video 8 draft-weaver-payload-rtp-vc2hq-02 10 Abstract 12 This memo describes an RTP Payload format for the High Quality (HQ) 13 profile of SMPTE Standard ST 2042-1 known as VC-2. This document 14 describes the transport of HQ Profile VC-2 in RTP packets and has 15 applications for low-complexity, high-bandwidth streaming of both 16 lossless and lossy compressed video. 18 The HQ profile of VC-2 is intended for low latency video compression 19 (with latency potentially on the order of lines of video) at high 20 data rates (with compression ratios on the order of 2:1 or 4:1). 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on December 11, 2016. 39 Copyright Notice 41 Copyright (c) 2016 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Conventions, Definitions and Acronyms . . . . . . . . . . . . 3 58 3. Media Format Description . . . . . . . . . . . . . . . . . . 3 59 4. Payload format . . . . . . . . . . . . . . . . . . . . . . . 4 60 4.1. RTP Header Usage . . . . . . . . . . . . . . . . . . . . 8 61 4.2. Payload Header . . . . . . . . . . . . . . . . . . . . . 9 62 4.3. The Choice of Parse Codes (Informative) . . . . . . . . . 10 63 4.4. Payload Data . . . . . . . . . . . . . . . . . . . . . . 11 64 4.4.1. Reassembling the Data . . . . . . . . . . . . . . . . 11 65 5. Congestion Control Considerations . . . . . . . . . . . . . . 12 66 6. Payload Format Parameters . . . . . . . . . . . . . . . . . . 13 67 6.1. Media Type Definition . . . . . . . . . . . . . . . . . . 13 68 6.2. Mapping to SDP . . . . . . . . . . . . . . . . . . . . . 14 69 6.2.1. Offer/Answer Considerations . . . . . . . . . . . . . 14 70 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 71 8. Security Considerations . . . . . . . . . . . . . . . . . . . 14 72 9. RFC Editor Considerations . . . . . . . . . . . . . . . . . . 15 73 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 74 10.1. Normative References . . . . . . . . . . . . . . . . . . 15 75 10.2. Informative References . . . . . . . . . . . . . . . . . 16 76 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17 78 1. Introduction 80 This memo specifies an RTP payload format for the video coding 81 standard SMPTE ST 2042-1:2012 [VC2] also known as VC-2 83 The VC-2 codec is a wavelet-based codec intended primarily for 84 professional video use with high bit-rates and only low levels of 85 compression. It has been designed to be low-complexity, and 86 potentially have a very low latency through both encoder and decoder: 87 with some choices of parameters this latency may be as low as a few 88 lines of video. 90 The low level of complexity in the VC-2 codec allows for this low 91 latency operation but also means that it lacks many of the more 92 powerful compression techniques used in other codecs. As such it is 93 suitable for low compression ratios that produce coded data rates 94 around half to a quarter of that of uncompressed video, at a similar 95 visual quality. 97 The primary use for VC-2 is likely to be in professional video 98 production environments. 100 2. Conventions, Definitions and Acronyms 102 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 103 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 104 document are to be interpreted as described in RFC 2119 [RFC2119]. 106 3. Media Format Description 108 The VC-2 specification defines a VC-2 stream as being composed of one 109 or more sequences. Each sequence is independently decodable, 110 containing all of the needed parameters and metadata for configuring 111 the decoder. 113 Each Sequence consists of a series of 13-octet Parse Info headers and 114 variable length Data Units. The Sequence begins and ends with a 115 Parse Info header and each Data Unit is preceded by a Parse Info 116 Header. Data Units come in a variety of types, the most important 117 being the Sequence Header, which contains configuration data needed 118 by the decoder, and several types of Coded Picture, which contain the 119 coded data for the pictures themselves. Each picture represents a 120 frame in a progressively scanned video sequence or a field in an 121 interlaced video sequence. 123 The first Data Unit in a Sequence as produced by an encoder is always 124 a Sequence Header, but sequences can be joined in the middle, so this 125 should not be assumed. 127 The High Quality (HQ) profile for VC-2 restricts the types of parse 128 info headers which may appear in the Sequence to only: 130 o Sequence Headers, 132 o High Quality Pictures, 134 o Auxiliary Data, 136 o Padding Data, and 138 o End of Sequence. 140 At time of writing there is currently no definition for the use of 141 Auxiliary Data in VC-2, and Padding Data is required to be ignored by 142 all receivers. 144 Each High Quality Picture data unit contains a set of parameters for 145 the picture followed by a series of coded Slices, each representing a 146 rectangular region of the transformed picture. Slices within a 147 picture may vary in coded length, but all represent the same shape 148 and size of rectangle in the picture. 150 4. Payload format 152 Since there is no definition for the use of Auxiliary Data Units and 153 Padding Data Units are defined by the VC-2 spec to be ignored by all 154 decoders this specification only covers the transport of Sequence 155 Headers, High Quality Pictures, and (optionally) End of Sequence 156 headers. 158 Since Sequence Headers and End of Sequence Headers are always small 159 they can easily be encapsulated in a single RTP packet each, but 160 since High Quality Pictures are usually much larger than the MTU of 161 most networks they require fragmentation into multiple packets. 163 For this reason this document defines four types of RTP packets in a 164 VC-2 media stream: one which carries the VC-2 Sequence Header 165 (Figure 1), one which carries the picture fragment containing the 166 VC-2 Transform Parameters for a Picture (Figure 2), one which carries 167 a picture fragment containing VC-2 Coded Slices (Figure 3) for a 168 picture, and one which signals the end of a VC-2 Sequence (Figure 4). 170 These four packet-types can be distinguished by the fact that they 171 use different codes in the "PC" field, except for the two types of 172 packet fragment which both use the same value in PC but have 173 different values in the "No. of slices" field. 175 The choices of PC codes is explained in more detail in a following 176 informative section (Section 4.3). 178 0 1 2 3 179 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 1 180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 181 | V |P|X| CC |M| PT | Sequence Number | 182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 183 | Time Stamp | 184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 185 | SSRC | 186 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 187 | contributing source (CSRC) identifiers | 188 | .... | 189 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 190 | Optional Extension Header | 191 | .... | 192 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 193 | Extended Sequence Number | Reserved | PC = 0x00 | 194 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 195 . . 196 . Variable Length Coded Sequence Header . 197 . . 198 +---------------------------------------------------------------+ 200 Figure 1: RTP Payload Format For Sequence Header 202 0 1 2 3 203 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 1 204 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 205 | V |P|X| CC |M| PT | Sequence Number | 206 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 207 | Time Stamp | 208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 209 | SSRC | 210 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 211 | contributing source (CSRC) identifiers | 212 | .... | 213 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 214 | Optional Extension Header | 215 | .... | 216 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 217 | Extended Sequence Number | Reserved |I|F| PC = 0xEC | 218 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 219 | Picture Number | 220 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 221 | Slice Prefix Bytes | Slice Size Scaler | 222 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 223 | Fragment Length | No. of Slices = 0 | 224 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 225 . . 226 . Variable Length Coded Transform Parameters . 227 . . 228 +---------------------------------------------------------------+ 230 Figure 2: RTP Payload Format For Transform Parameters 232 0 1 2 3 233 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 1 234 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 235 | V |P|X| CC |M| PT | Sequence Number | 236 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 237 | Time Stamp | 238 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 239 | SSRC | 240 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 241 | contributing source (CSRC) identifiers | 242 | .... | 243 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 244 | Optional Extension Header | 245 | .... | 246 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 247 | Extended Sequence Number | Reserved |I|F| PC = 0xEC | 248 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 249 | Picture Number | 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 251 | Slice Prefix Bytes | Slice Size Scaler | 252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 253 | Fragment Length | No. of Slices | 254 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 255 | Slice Offset X | Slice Offset Y | 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 257 . . 258 . Coded Slices . 259 . . 260 +---------------------------------------------------------------+ 262 Figure 3: RTP Payload Format For Slices 264 0 1 2 3 265 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 1 266 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 267 | V |P|X| CC |M| PT | Sequence Number | 268 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 269 | Time Stamp | 270 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 271 | SSRC | 272 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 273 | contributing source (CSRC) identifiers | 274 | .... | 275 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 276 | Optional Extension Header | 277 | .... | 278 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 279 | Extended Sequence Number | Reserved | PC = 0x10 | 280 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 282 Figure 4: RTP Payload Format For End of Sequence 284 4.1. RTP Header Usage 286 The fields of the RTP header have the following additional notes on 287 their useage: 289 Marker Bit (M): 1 bit The marker bit MUST be set on any packet which 290 contains the final slice in a coded picture and MUST NOT be set 291 otherwise. 293 Payload Type (PT): 7 bits A dynamically allocated payload type field 294 that designates the payload as VC-2 coded video. 296 Sequence Number: 16 bits Because the data rate of VC-2 coded streams 297 can often be very high, in the order of gigabits rather than 298 megabits per second, the standard 16-bit RTP sequence number 299 can cycle very quickly. For this reason the sequence number is 300 extneded to 32-bits, and this field MUST holds the low-order 301 16-bits of this value. 303 Timestamp: 32 bits If the packet contains transform parameters or 304 coded slice data for a coded picture then the timestamp 305 corresponds to the sampling instant of the coded picture. A 306 90kHz clock SHOULD be used. A single RTP packet MUST NOT 307 contain coded data for more than one coded picture, so there is 308 no ambiguity here. 310 A sequence header packet SHOULD have the same timestamp as the 311 next picture which will follow it in the stream. An End of 312 Sequence packet SHOULD have the same timestamp as the previous 313 picture which appeared in the stream. 315 The remaining RTP header fields are used as specified in RTP 316 [RFC3550]. 318 4.2. Payload Header 320 The fields of the extended headers are defined as follows: 322 Extended Sequence Number: 16 bits MUST Contain the high-order 323 16-bits of the 32-bit packet sequence number, a number which 324 increments with each packet. This is needed since the high 325 data rates of VC2 sequences mean that it is highly likely that 326 the 16-bit sequence number will roll-over too frequently to be 327 of use for stream synchronisation. 329 I: 1 bit SHOULD be set to 1 if the packet contains coded picture 330 paramaters or slice data from a field in an interlaced frame, 331 and to 0 otherwise. 333 F: 1 bit SHOULD be set to 1 if the packet contains coded picture 334 paramaters or slice data from the second field of an interlaced 335 frame, and to 0 otherwise. 337 Parse Code (PC): 8 bits Contains a Parse Code which MUST be the 338 value indicated for the type of data in the packet. 340 Picture Number: 32 bits MUST contain the Picture Number for the 341 coded picture this packet contains data for, as described in 342 Section 12.1 of the VC-2 specification [VC2]. 344 The sender MUST send at least one transform parameters packet 345 for each coded picture and MAY include more than one as long as 346 they contain identical data. The sender MUST NOT send a packet 347 from a new picture until all the coded data from the current 348 picture has been sendt. 350 If the receiver does not receive a transform parameters packet 351 for a picture then it MAY assume that the parameters are 352 unchanged since the last picture, or MAY discard the picture. 354 Slice Prefix Bytes: 16 bits MUST contain the Slice Prefix Bytes 355 value for the coded picture this packet contains data for, as 356 described in Section 12.3.4 of the VC-2 specification [VC2]. 358 In the VC-2 specification this value is not restricted to 16 359 bits, but in practice this is unlikely to ever be too large. 361 Slice Size Scaler: 16 bits MUST contain the Slice Size Scaler value 362 for the coded picture this packet contains data for, as 363 described in Section 12.3.4 of the VC-2 specification [VC2]. 365 In the VC-2 specification this value is not restricted to 16 366 bits, but in practice this is unlikely to ever be too large. 368 Fragment Length: 16 bits Contains the number of bytes of data 369 contained in the coded payload section of this packet. 371 No. of Slices: 16 bits Contains the number of coded slices contained 372 in this packet, which MUST be 0 for a packet containing 373 transform parameters. In a packet containing coded slices this 374 number MUST be the number of whole slices contained in the 375 packet, and the packet MUST NOT contain any partial slices. 377 Slice Offset X: 16 bits Indicates the X coordinate of the first 378 slice in this packet, in slices, starting from the top left 379 corner of the picture. 381 Slice Offset Y: 16 bits Indicates the Y coordinate of the first 382 slice in this packet, in slices, starting from the top left 383 corner of the picture. 385 4.3. The Choice of Parse Codes (Informative) 387 The "PC" field in the packets is used to carry the Parse Code which 388 identifies the type of content in the packet. For Sequence Header 389 and End of Sequence packets this code matches the value of the Parse 390 Code used to identify those data units in a VC-2 stream, as defined 391 in the VC-2 specification, and each packet contains the entire such 392 data unit. 394 For coded picture data, however, this is not possible because VC-2 395 coded picture data units are too large to fit conveniently into a 396 packet on most transports. Rather than use the Parse Code for the 397 picture, even though only a fragment of it is present, it was decided 398 to create a new parse code which would indicate a fragment of a 399 picture. 401 In compliance with the VC-2 specification this new choice of Parse 402 Code preserves the meaning of all the bits given meanings in 403 Section 10.4.1.1 of the VC-2 specification, but sets an additional 404 bit, bit 2, which was reserved for future expansion in that 405 specification. In this adaptation approach bit 2 now takes on the 406 meaning of "Picture Fragment". 408 +----------+-----------+---------------------+---------------+ 409 | PC (hex) | Binary | Description | Origin | 410 +----------+-----------+---------------------+---------------+ 411 | 0x00 | 0000 0000 | Sequence Header | VC-2 Spec | 412 | 0x10 | 0001 0000 | End of Sequence | VC-2 Spec | 413 +----------+-----------+---------------------+---------------+ 414 | 0xEC | 1110 1100 | HQ Picture Fragment | This document | 415 +----------+-----------+---------------------+---------------+ 417 Figure 5: Parse Codes and Meanings 419 4.4. Payload Data 421 For the Sequence Header packet type (PC = 0x00) the payload data MUST 422 be the coded sequence header exactly as it appears in the VC-2 423 Sequence. 425 For the Transform Parameters packet type (PC = 0xEC and No. Slices = 426 0) the payload data MUST be all the data which appears in the VC-2 427 High Quality Picture Data Unit after the end of the Parse Info Header 428 but before the start of the first coded slice. 430 For the Picture Fragment packet type (PC = 0xEC and No. Slices > 0) 431 the payload data MUST be a specified number of coded slices in the 432 same order that they appear in the VC-2 stream. Which slices appear 433 in the packet is identified using the Slice Offset X and Slice Offset 434 Y fields in the payload header. 436 For the End of Sequence packet type (PC = 0x10) there is no payload 437 data. 439 4.4.1. Reassembling the Data 441 0 1 2 3 442 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 1 443 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 444 | 0x42 | 0x42 | 0x43 | 0x44 | 445 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 446 | Parse Code | Next Parse Offset 447 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 448 | Prev Parse Offset 449 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 450 | 451 +-+-+-+-+-+-+-+-+ 453 Figure 6: VC-2 Parse Info Header 455 To reassemble the data in the RTP packets into a valid VC-2 sequence 456 the receiver SHOULD: 458 o Take the data from each packet with a Parse Code of 0x00 and 459 prepend a valid VC-2 Parse Info header (Figure 6) with the same 460 parse code to it. The resulting sequence header parse info header 461 and data unit MUST be included in the output stream before any 462 coded pictures which followed it in the RTP stream unless an 463 identical sequence header has already been included, and MAY be 464 repeated at any point that results in a valid VC-2 stream. 466 o Take the data from each packet with a Parse Code of 0xEC and No. 467 of Slices set to 0 (which together indicates that this packet 468 contains the transform parameters for a coded picture) and prepend 469 a valid VC-2 Parse Info header (Figure 6) followed by the picture 470 number to it with the parse code 0xE8, then take the data from 471 each subsequent packet with parse code 0xEC and the same picture 472 number and append it to the end of this data unit. When all the 473 packets for a particular picture have been received (which is 474 indicated by the marker bit) the picture MUST be included in the 475 output stream, although a copy of the most recent Sequence Header 476 MAY be included immediately before it (and MUST be so if not 477 alrerady included in the current sequence). 479 o Once a data unit has been assembled, whether a Sequence Header or 480 a Coded Picture, the next parse offset and previous parse offset 481 values in its parse info header should be filled with the offset 482 between the start of the header and the start of the next or 483 previous. 485 o An End of Sequence parse info header MAY be inserted when a packet 486 with parse code set to 0x10 is encountered, or at any other time 487 that is allowed in a valid VC-2 stream. After an End of Sequence 488 parse info header is included in the output stream either the 489 stream must end or it MUST be followed by a Sequence Header 490 indicating the start of a new sequence. 492 5. Congestion Control Considerations 494 Congestion control for RTP SHALL be used in accordance with RFC 3550 495 [RFC3550], and with any applicable RTP profile; e.g., RFC 3551 496 [RFC3551]. An additional requirement if best-effort service is being 497 used is: users of this payload format MUST monitor packet loss to 498 ensure that the packet loss rate is within acceptable parameters. 499 Circuit Breakers [I-D.ietf-avtcore-rtp-circuit-breakers] is an update 500 to RTP [RFC3550] that defines criteria for when one is required to 501 stop sending RTP Packet Streams. The circuit breakers is to be 502 implemented and followed. 504 6. Payload Format Parameters 506 This RTP payload format is identified using the video/vc2 media type 507 which is registered in accordance with RFC 4855 [RFC4855] and using 508 the template of RFC 6838 [RFC6838]. 510 6.1. Media Type Definition 512 Type name: 514 video 516 Subtype name: 518 vc2 520 Required parameters: 522 rate: The RTP timestamp clock rate. Applications using this 523 payload format SHOULD use a value of 90000. 525 profile: The VC-2 profile in use, the only currently allowed value 526 is "HQ". 528 Optional parameters: N/A 530 Encoding considerations: 532 This media type is framed and binary, see section 4.8 in RFC6838 533 [RFC6838]. 535 Security considerations: 537 Please see security consideration in RFCXXXX 539 Interoperability considerations: N/A 541 Published specification: 543 "VC-2 Video Compression", SMPTE Standard ST 2042-1 [VC2] 545 Applications that use this media type: 547 Video Communication. 549 Additional information: N/A 551 Person & email address to contact for further information: 553 james.barrett@bbc.co.uk 555 Intended usage: 557 COMMON 559 Restrictions on usage: 561 This media type depends on RTP framing, and hence is only defined 562 for transfer via RTP [RFC3550]. Transport within other framing 563 protocols is not defined at this time. 565 Author: 567 Change controller: 569 IETF Payload working group delegated from the IESG. 571 Provisional registration? (standards tree only): 573 No 575 (Any other information that the author deems interesting may be added 576 below this line.) 578 6.2. Mapping to SDP 580 The mapping of the above defined payload format media type and its 581 parameters SHALL be done according to Section 3 of RFC 4855 582 [RFC4855]. 584 6.2.1. Offer/Answer Considerations 586 All parameters are declarative. 588 7. IANA Considerations 590 This memo requests that IANA registers video/vc2 as specified in 591 Section 6.1. The media type is also requested to be added to the 592 IANA registry for "RTP Payload Format MIME types" 593 (http://www.iana.org/assignments/rtp-parameters). 595 8. Security Considerations 597 RTP packets using the payload format defined in this specification 598 are subject to the security considerations discussed in the RTP 599 specification [RFC3550] , and in any applicable RTP profile such as 600 RTP/AVP [RFC3551], RTP/AVPF [RFC4585], RTP/SAVP [RFC3711] or RTP/ 601 SAVPF [RFC5124]. However, as "Securing the RTP Protocol Framework: 602 Why RTP Does Not Mandate a Single Media Security Solution" [RFC7202] 603 discusses, it is not an RTP payload format's responsibility to 604 discuss or mandate what solutions are used to meet the basic security 605 goals like confidentiality, integrity and source authenticity for RTP 606 in general. This responsibility lays on anyone using RTP in an 607 application. They can find guidance on available security mechanisms 608 and important considerations in Options for Securing RTP Sessions 609 [RFC7201]. Applications SHOULD use one or more appropriate strong 610 security mechanisms. The rest of this security consideration section 611 discusses the security impacting properties of the payload format 612 itself. 614 This RTP payload format and its media decoder do not exhibit any 615 significant non-uniformity in the receiver-side computational 616 complexity for packet processing, and thus are unlikely to pose a 617 denial-of-service threat due to the receipt of pathological data. 618 Nor does the RTP payload format contain any active content. 620 9. RFC Editor Considerations 622 Note to RFC Editor: This section may be removed after carrying out 623 all the instructions of this section. 625 RFCXXXX is to be replaced by the RFC number this specification 626 receives when published. 628 10. References 630 10.1. Normative References 632 [I-D.ietf-avtcore-rtp-circuit-breakers] 633 Perkins, C. and V. Varun, "Multimedia Congestion Control: 634 Circuit Breakers for Unicast RTP Sessions", draft-ietf- 635 avtcore-rtp-circuit-breakers-15 (work in progress), April 636 2016. 638 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 639 Requirement Levels", BCP 14, RFC 2119, 640 DOI 10.17487/RFC2119, March 1997, 641 . 643 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 644 Jacobson, "RTP: A Transport Protocol for Real-Time 645 Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, 646 July 2003, . 648 [RFC3551] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and 649 Video Conferences with Minimal Control", STD 65, RFC 3551, 650 DOI 10.17487/RFC3551, July 2003, 651 . 653 [RFC4855] Casner, S., "Media Type Registration of RTP Payload 654 Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007, 655 . 657 [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type 658 Specifications and Registration Procedures", BCP 13, 659 RFC 6838, DOI 10.17487/RFC6838, January 2013, 660 . 662 [VC2] SMPTE, "VC-2 Video Compression", SMPTE Standard ST 2042-1, 663 2012, . 666 10.2. Informative References 668 [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. 669 Norrman, "The Secure Real-time Transport Protocol (SRTP)", 670 RFC 3711, DOI 10.17487/RFC3711, March 2004, 671 . 673 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 674 "Extended RTP Profile for Real-time Transport Control 675 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, 676 DOI 10.17487/RFC4585, July 2006, 677 . 679 [RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for 680 Real-time Transport Control Protocol (RTCP)-Based Feedback 681 (RTP/SAVPF)", RFC 5124, DOI 10.17487/RFC5124, February 682 2008, . 684 [RFC7201] Westerlund, M. and C. Perkins, "Options for Securing RTP 685 Sessions", RFC 7201, DOI 10.17487/RFC7201, April 2014, 686 . 688 [RFC7202] Perkins, C. and M. Westerlund, "Securing the RTP 689 Framework: Why RTP Does Not Mandate a Single Media 690 Security Solution", RFC 7202, DOI 10.17487/RFC7202, April 691 2014, . 693 Author's Address 695 James P. Weaver 696 BBC 698 Email: james.barrett@bbc.co.uk