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Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- == There are 6 instances of lines with non-RFC6890-compliant IPv4 addresses in the document. If these are example addresses, they should be changed. -- The draft header indicates that this document updates RFC4788, but the abstract doesn't seem to mention this, which it should. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust Copyright Line does not match the current year == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: sendmode: A mode of EVRC-WB codec. Encoder can use this to signal its current mode of operation. Possible values are a comma separated list of modes from the set: 0,4,7 (see Table 2.5.1.2-1 [4]). 'sendmode' with value 0 signals wideband fixed rate (full or half rate, depending on the value of 'fixedrate' parameter) operation. 'sendmode' with value 4 signals narrowband fixed full rate operation. 'sendmode' with value 7 signals narrowband fixed half rate operation. 'fixedrate' parameter MUST not be present when 'sendmode' value is 4 or 7. Absence of this parameter signals mode 0. (Using the creation date from RFC4788, updated by this document, for RFC5378 checks: 2006-01-05) -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (May 19, 2007) is 6187 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. '3' -- Possible downref: Non-RFC (?) normative reference: ref. '4' ** Obsolete normative reference: RFC 4566 (ref. '7') (Obsoleted by RFC 8866) ** Obsolete normative reference: RFC 4288 (ref. '8') (Obsoleted by RFC 6838) -- Obsolete informational reference (is this intentional?): RFC 2326 (ref. '12') (Obsoleted by RFC 7826) Summary: 3 errors (**), 0 flaws (~~), 3 warnings (==), 11 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group H. Desineni 3 Internet-Draft Qualcomm 4 Updates: 4788 (if approved) Q. Xie 5 Intended status: Standards Track Motorola 6 Expires: November 20, 2007 May 19, 2007 8 RTP payload format for EVRC-WB codec and media subtype updates for 9 EVRC-B codec 10 draft-ietf-avt-rtp-evrc-wb-02.txt 12 Status of this Memo 14 By submitting this Internet-Draft, each author represents that any 15 applicable patent or other IPR claims of which he or she is aware 16 have been or will be disclosed, and any of which he or she becomes 17 aware will be disclosed, in accordance with Section 6 of BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt. 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html. 35 This Internet-Draft will expire on November 20, 2007. 37 Copyright Notice 39 Copyright (C) The IETF Trust (2007). 41 Abstract 43 This document specifies real-time transport protocol (RTP) payload 44 formats to be used for the EVRC wideband codec (EVRC-WB) and updates 45 the media type registrations for EVRC-B codec. Several media type 46 registrations are included for EVRC-WB RTP payload formats. In 47 addition, a file format is specified for transport of EVRC-WB speech 48 data in storage mode applications such as e-mail. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 54 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 5 55 4. EVRC-WB codec . . . . . . . . . . . . . . . . . . . . . . . . 6 56 5. RTP header usage . . . . . . . . . . . . . . . . . . . . . . . 7 57 6. Payload format . . . . . . . . . . . . . . . . . . . . . . . . 8 58 7. Congestion Control Considerations . . . . . . . . . . . . . . 9 59 8. Storage format for EVRC-WB Codec . . . . . . . . . . . . . . . 10 60 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 61 9.1. Media Type Registration . . . . . . . . . . . . . . . . . 11 62 9.1.1. Registration of Media Type EVRCWB . . . . . . . . . . 11 63 9.1.2. Registration of Media Type EVRCWB0 . . . . . . . . . . 13 64 9.1.3. Registration of Media Type EVRCWB1 . . . . . . . . . . 15 65 9.1.4. Updated Registration of Media Type EVRCB . . . . . . . 17 66 9.1.5. Updated Registration of Media Type EVRCB0 . . . . . . 19 67 10. EVRC-B RFC XXXX Interoperability with legacy EVRC-B (RFC 68 4788) implementations . . . . . . . . . . . . . . . . . . . . 22 69 11. Mapping EVRC-WB media type parameters into SDP . . . . . . . . 23 70 12. Mapping EVRC-B media type parameters into SDP . . . . . . . . 24 71 13. Offer-Answer Model Considerations for EVRC-WB . . . . . . . . 25 72 14. Offer-Answer Model Considerations for EVRC-B . . . . . . . . . 27 73 15. Declarative SDP Considerations . . . . . . . . . . . . . . . . 28 74 16. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 75 17. Security Considerations . . . . . . . . . . . . . . . . . . . 33 76 18. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 77 19. References . . . . . . . . . . . . . . . . . . . . . . . . . . 35 78 19.1. Normative References . . . . . . . . . . . . . . . . . . . 35 79 19.2. Informative References . . . . . . . . . . . . . . . . . . 35 80 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 36 81 Intellectual Property and Copyright Statements . . . . . . . . . . 37 83 1. Introduction 85 This document specifies the payload formats for packetization of 86 EVRC-WB encoded speech signals into the real-time transport protocol 87 (RTP).It defines support for the header-free, interleaved/bundled and 88 compact bundle packet formats for the EVRC-WB codec as well as 89 discontinuous transmission (DTX) support for EVRC-WB encoded speech 90 transported via RTP.EVRC-WB codec offers better speech quality than 91 EVRC and EVRC-B codecs. EVRC-WB belongs to the EVRC family of 92 codecs.This document also updates the media type registrations for 93 EVRC-B codec. 95 2. Conventions 97 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 98 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 99 document are to be interpreted as described in RFC 2119 [1]. 101 3. Background 103 EVRC-WB is a wideband extension of EVRC-B [3] speech codec developed 104 in 3GPP2 with support for discontinuous transmission (DTX). It 105 provides enhanced (wideband) voice quality. 107 EVRC-WB codec operates on 20 ms frames, and the default sampling rate 108 is 16 kHz. Input and output at 8 kHz sampling rate is also 109 supported. EVRC-WB modes are defined in [4]. EVRC-WB modes 4,7 are 110 interoperable with EVRC-B. EVRC-WB provides a standardized solution 111 for packetized voice applications that allow transitions between 112 narrowband and wideband telephony. The most important service 113 addressed is IP telephony. Target devices can be IP phones or VoIP 114 handsets, media gateways, voice messaging servers, etc. 116 4. EVRC-WB codec 118 EVRC-WB codec operates on 20 ms frames. It produces output frames of 119 one of the three different sizes: 171 bits, 80 bits or 16 bits. In 120 addition, there are two zero bit codec frame types: null frames and 121 erasure frames. The default sampling rate is 16 kHz. Input and 122 output at 8 kHz sampling rate is also supported. 124 The frame type values and size of the associated codec data frame are 125 listed in the table below: 127 Value Rate Total codec data frame size (in octets) 128 -------------------------------------------------------------------- 129 0 Blank 0 (0 bit) 130 1 1/8 2 (16 bits) 131 2 1/4 5 (40 bits; not valid for EVRC-WB) 132 3 1/2 10 (80 bits) 133 4 1 22 (171 bits; 5 bits padded at the end) 134 5 Erasure 0 (SHOULD NOT be transmitted by sender) 136 5. RTP header usage 138 The format of the RTP header is specified in RFC 3550 [5]. The 139 EVRC-WB payload formats (Section 6) use the fields of the RTP header 140 in a manner consistent with RFC 3550. 142 EVRC-WB has also the capability to operate with 8 kHz sampled input/ 143 output signals. The decoder does not require a priori knowledge 144 about the sampling rate of the original signal at the input of the 145 encoder. The decoder output can be at 8kHz or 16kHz regardless of 146 the sampling rate used at the encoder. Therefore, depending on the 147 implementation and the audio electro acoustic capabilities of the 148 devices, the input of the encoder and/or the output of the decoder 149 can be configured at 8 kHz; however, a 16 kHz RTP clock rate MUST 150 always be used. The RTP timestamp is increased by 320 for each 20 151 milliseconds. 153 The assignment of an RTP payload type for the payload formats 154 described in Section 6 is outside the scope of the document, and will 155 not be specified here. It is expected that the RTP profile under 156 which this payload format is being used will assign a payload type 157 for this codec or specify that the payload type is to be bound 158 dynamically (see Section 11). 160 6. Payload format 162 Three RTP packet formats are supported for the EVRC-WB codec - the 163 interleaved/bundled packet format, the header-free packet format and 164 the compact bundled packet format. For all these formats, the 165 operational details and capabilities, such as ToC, interleaving, DTX, 166 and bundling, of EVRC-WB are exactly the same as those of EVRC-B, as 167 defined in [3], except that the mode change request field in the ToC 168 MUST be interpreted according to the definition of the RATE_REDUC 169 parameter as defined in EVRC-WB [4]. 171 7. Congestion Control Considerations 173 Congestion control for RTP SHALL be used in accordance with RFC 3550 174 [5], and with any applicable RTP profile; e.g., RFC 3551 [9]. 176 Due to the header overhead, the number of frames encapsulated in each 177 RTP packet influences the overall bandwidth of the RTP stream. 178 Packing more frames in each RTP packet can reduce the number of 179 packets sent and hence the header overhead, at the expense of 180 increased delay and reduced error robustness. 182 8. Storage format for EVRC-WB Codec 184 The storage format is used for storing EVRC-WB encoded speech frames, 185 e.g., as a file or e-mail attachment. 187 The file begins with a magic number to identify the vocoder that is 188 used. The magic number for EVRC-WB corresponds to the ASCII 189 character string "#!EVCWB\n", i.e., "0x23 0x21 0x45 0x56 0x43 0x57 190 0x42 0x0A". 192 The codec data frames are stored in consecutive order, with a single 193 TOC entry field, extended to one octet, prefixing each codec data 194 frame. The ToC field is extended to one octet by setting the four 195 most significant bits of the octet to zero. For example, a ToC value 196 of 4 (a full-rate frame) is stored as 0x04. See Section 4 for the 197 mapping from frame type to ToC value. 199 Speech frames lost in transmission and non-received frames MUST be 200 stored as erasure frames (ToC value of 5) to maintain synchronization 201 with the original media. 203 9. IANA Considerations 205 This document updates EVRCB, EVRCB0 media subtypes defined in RFC 206 4788 [2] and adds new EVRC-WB media subtypes. 208 [-- RFC Editor: Please replace all instances of "RFC XXXX" in this 209 document with the RFC number of this document prior to IANA 210 registration and RFC publication, and remove this note.] 212 [-- RFC Editor:Please add media subtypes "EVRCWB","EVRCWB0", and 213 "EVRCWB1" to the IANA registry for "RTP Payload Format media types" 214 at http://www.iana.org/assignments/rtp-parameters, and remove this 215 note.] 217 9.1. Media Type Registration 219 Following the guidelines in RFC 4288 [8], this section registers new 220 media subtypes for EVRC-WB and updates EVRCB, EVRCB0 media subtypes 221 defined in RFC 4788 [2]. 223 9.1.1. Registration of Media Type EVRCWB 225 Type name: audio 227 Subtype names: EVRCWB 229 Required parameters: none 231 Optional parameters: 233 mode-set-recv: A subset of EVRC-WB modes. Possible values are a 234 comma separated list of modes from the set: 0,4,7 (see Table 235 2.5.1.2-1 [4]). A decoder can use this to signal an encoder to limit 236 its modes to the specified subset. Absence of this parameter signals 237 the mode set {0,4,7}. 239 sendmode: A mode of EVRC-WB codec. Encoder can use this to signal 240 its current mode of operation. Possible values are 0,4,7 (see Table 241 2.5.1.2-1 [4]). Absence of this parameter signals mode 0. 243 ptime: see RFC 4566 [7]. 245 maxptime: The maximum amount of media which can be encapsulated in 246 each packet, expressed as time in milliseconds. The time MUST be 247 calculated as the sum of the time the media present in the packet 248 represents. The time SHOULD be a multiple of the duration of a 249 single codec data frame (20 msec). If not signaled, the default 250 maxptime value MUST be 200 milliseconds. 252 maxinterleave: Maximum number for interleaving length (field LLL in 253 the Interleaving Octet). The interleaving lengths used in the entire 254 session MUST NOT exceed this maximum value. If not signaled, the 255 maxinterleave length MUST be 5. 257 silencesupp: see Section 6.1 in [2] 259 dtxmax: see Section 6.1 in [2] 261 dtxmin: see Section 6.1 in [2] 263 hangover: see Section 6.1 in [2] 265 Encoding considerations: 267 This media type is framed binary data (see RFC 4288, Section 4.8) and 268 is defined for transfer of EVRC-WB encoded data via RTP using the 269 Interleaved/Bundled packet format specified in RFC 3558 [10]. 271 Security considerations: See Section 17 of RFC XXXX. 273 Interoperability considerations: none 275 Published specification: 277 The EVRC-WB vocoder is specified in 3GPP2 C.S0014-C [4]. Transfer 278 method with Interleaved/Bundled packet format via RTP is specified in 279 RFC 3558 and RFC XXXX. 281 3GPP2 C.S0050-B, 3GPP2 File Formats for Multimedia Services. 283 3GPP2 specifications are publicly accessible at http://www.3gpp2.org 285 Applications that use this media type: 287 It is expected that many VoIP applications (as well as mobile 288 applications) will use this type. 290 Additional information: 292 The following information applies for storage format only. 294 Magic number: #!EVCWB\n (see Section 8 of RFC XXXX) 296 File extensions: evw, EVW 298 Macintosh file type code: none 299 Object identifier or OID: none 301 EVRC-WB speech frames may also be stored in the file format "3g2" 302 defined in 3GPP2 C.S0050-B, which is identified using the media types 303 "audio/3gpp2" or "video/3gpp2" registered by RFC4393. 305 Person & email address to contact for further information: 307 Harikishan Desineni 309 Intended usage: COMMON 311 Restrictions on usage: 313 This media type may be used with RTP framing (RFC 3550 [6]) and as a 314 storage format. When used with RTP, the procedures in Section 6 MUST 315 be followed. In all other contexts, the storage format defined in 316 Section 8 MAY be used. 318 Author: 320 Harikishan Desineni 322 Change controller: 324 IETF Audio/Video Transport working group delegated from the IESG. 326 9.1.2. Registration of Media Type EVRCWB0 328 Type name: audio 330 Subtype names: EVRCWB0 332 Required parameters: 334 Optional parameters: 336 mode-set-recv: A subset of EVRC-WB modes. Possible values are a 337 comma separated list of modes from the set: 0,4,7 (see Table 338 2.5.1.2-1 [4]). A decoder can use this to signal an encoder to limit 339 its modes to the specified subset. Absence of this parameter signals 340 the mode set {0,4,7}. 342 sendmode: A mode of EVRC-WB codec. Encoder can use this to signal 343 its current mode of operation. Possible values are 0,4,7 (see Table 344 2.5.1.2-1 [4]). Absence of this parameter signals mode 0. 346 ptime: see RFC 4566 [7]. 348 silencesupp: see Section 6.1 in [2] 350 dtxmax: see Section 6.1 in [2] 352 dtxmin: see Section 6.1 in [2] 354 hangover: see Section 6.1 in [2] 356 Encoding considerations: 358 This media type is framed binary data (see RFC 4288, Section 4.8) and 359 is defined for transfer of EVRC-WB encoded data via RTP using the 360 Header-Free packet format specified in RFC 3558. 362 Security considerations: See Section 17 of RFC XXXX. 364 Interoperability considerations: none 366 Published specification: 368 The EVRC-WB vocoder is specified in 3GPP2 C.S0014-C [4]. Transfer 369 method with header free packet format via RTP is specified in RFC 370 3558 and RFC XXXX. 372 3GPP2 C.S0050-B, 3GPP2 File Formats for Multimedia Services. 374 3GPP2 specifications are publicly accessible at http://www.3gpp2.org 376 Applications that use this media type: 378 It is expected that many VoIP applications (as well as mobile 379 applications) will use this type. 381 Additional information: 383 The following information applies for storage format only. 385 Magic number: #!EVCWB\n (see Section 8 of RFC XXXX) 387 File extensions: evw, EVW 389 Macintosh file type code: none 391 Object identifier or OID: none 393 EVRC-WB speech frames may also be stored in the file format "3g2" 394 defined in 3GPP2 C.S0050-B, which is identified using the media types 395 "audio/3gpp2" or "video/3gpp2" registered by RFC4393. 397 Person & email address to contact for further information: 399 Harikishan Desineni 401 Intended usage: COMMON 403 Restrictions on usage: 405 This media type may be used with RTP framing (RFC 3550) and as a 406 storage format. When used with RTP, the procedures in Section 6 MUST 407 be followed. In all other contexts, the storage format defined in 408 Section 8 MAY be used. 410 Author: 412 Harikishan Desineni 414 Change controller: 416 IETF Audio/Video Transport working group delegated from the IESG. 418 9.1.3. Registration of Media Type EVRCWB1 420 Type name: audio 422 Subtype names: EVRCWB1 424 Required parameters: 426 Optional parameters: 428 mode-set-recv: A subset of EVRC-WB modes. Possible values are a 429 comma separated list of modes from the set: 0,4,7 (see Table 430 2.5.1.2-1 [4]). A decoder can use this to signal an encoder to limit 431 its modes to the specified subset. Value of 0 signals the support 432 for wideband fixed rate (full or half rate, depending on the value of 433 'fixedrate' parameter). Value of 4 signals narroband fixed full 434 rate. Value of 7 signals narrowband fixed half rate. Absence of 435 this parameter signals mode 0. 437 sendmode: A mode of EVRC-WB codec. Encoder can use this to signal 438 its current mode of operation. Possible values are a comma separated 439 list of modes from the set: 0,4,7 (see Table 2.5.1.2-1 [4]). 440 'sendmode' with value 0 signals wideband fixed rate (full or half 441 rate, depending on the value of 'fixedrate' parameter) operation. 442 'sendmode' with value 4 signals narrowband fixed full rate operation. 443 'sendmode' with value 7 signals narrowband fixed half rate operation. 444 'fixedrate' parameter MUST not be present when 'sendmode' value is 4 445 or 7. Absence of this parameter signals mode 0. 447 ptime: see RFC 4566 [7]. 449 maxptime: The maximum amount of media which can be encapsulated in 450 each packet, expressed as time in milliseconds. The time MUST be 451 calculated as the sum of the time the media present in the packet 452 represents. The time SHOULD be an integer multiple of the duration 453 of a single codec data frame (20 msec). If not signaled, the default 454 maxptime value MUST be 200 milliseconds. 456 fixedrate: Indicates the EVRC-WB rate of the session while in single 457 rate operation. Valid values include: 0.5 and 1, where a value of 458 0.5 indicates the 1/2 rate while a value of 1 indicates the full 459 rate. If this parameter is not present, 1/2 rate is assumed. 461 silencesupp: see Section 6.1 in [2] 463 dtxmax: see Section 6.1 in [2] 465 dtxmin: see Section 6.1 in [2] 467 hangover: see Section 6.1 in [2] 469 Encoding considerations: 471 This media type is framed binary data (see RFC 4288, Section 4.8) and 472 is defined for transfer of EVRC-WB encoded data via RTP using the 473 compact bundle packet format specified in RFC 4788. 475 Security considerations: See Section 17 of RFC XXXX. 477 Interoperability considerations: none 479 Published specification: 481 The EVRC-WB vocoder is specified in 3GPP2 C.S0014-C. Transfer method 482 with compact bundled packet format via RTP is specified in RFC 4788 483 and RFC XXXX. 485 3GPP2 C.S0050-B, 3GPP2 File Formats for Multimedia Services. 487 3GPP2 specifications are publicly accessible at http://www.3gpp2.org 489 Applications that use this media type: 491 It is expected that many VoIP applications (as well as mobile 492 applications) will use this type. 494 Additional information: 496 The following information applies for storage format only. 498 Magic number: #!EVCWB\n (see Section 8 of RFC XXXX) 500 File extensions: evw, EVW 502 Macintosh file type code: none 504 Object identifier or OID: none 506 EVRC-WB speech frames may also be stored in the file format "3g2" 507 defined in 3GPP2 C.S0050-B, which is identified using the media types 508 "audio/3gpp2" or "video/3gpp2" registered by RFC 4393. 510 Person & email address to contact for further information: 512 Harikishan Desineni 514 Intended usage: COMMON 516 Restrictions on usage: 518 This media type may be used with RTP framing (RFC 3550 [6]) and as a 519 storage format. When used with RTP, the procedures in Section 6 MUST 520 be followed. In all other contexts, the storage format defined in 521 Section 8 MAY be used. 523 Author: 525 Harikishan Desineni 527 Change controller: 529 IETF Audio/Video Transport working group delegated from the IESG. 531 9.1.4. Updated Registration of Media Type EVRCB 533 Type name: audio 535 Subtype names: EVRCB 537 Required parameters: none 539 Optional parameters: 541 recvmode: A mode of EVRC-B codec. A decoder can use this to signal 542 an encoder to operate in the specified mode. Possible values are a 543 comma separated list of modes from the set: 0..7 (see encoder 544 operating point column in Table 2-6 [3]). 546 sendmode: A mode of EVRC-B codec. An encoder can use this to signal 547 its current mode of operation. Possible values are a comma separated 548 list of modes from the set: 0..7 (see encoder operating point column 549 in Table 2-6 [3]). 551 ptime: see RFC 4566 553 maxptime: The maximum amount of media which can be encapsulated in 554 each packet, expressed as time in milliseconds. The time MUST be 555 calculated as the sum of the time the media present in the packet 556 represents. The time SHOULD be a multiple of the duration of a 557 single codec data frame (20 msec). If not signaled, the default 558 maxptime value MUST be 200 milliseconds. 560 maxinterleave: Maximum number for interleaving length (field LLL in 561 the Interleaving Octet). The interleaving lengths used in the entire 562 session MUST NOT exceed this maximum value. If not signaled, the 563 maxinterleave length MUST be 5. 565 silencesupp: see Section 6.1 for definition. If this parameter is 566 not present, the default value 1 MUST be assumed. 568 dtxmax: see Section 6.1 of [2] 570 dtxmin: see Section 6.1 of [2] 572 hangover: see Section 6.1 of [2] 574 Encoding considerations: 576 This media type is framed binary data (see RFC 4288, Section 4.8) and 577 is defined for transfer of EVRC-B encoded data via RTP using the 578 Interleaved/Bundled packet format specified in RFC 3558. 580 Security considerations: See Section 9 of RFC 4788. 582 Interoperability considerations: none 584 Published specification: 586 The EVRC-B vocoder is specified in 3GPP2 C.S0014-B. Transfer method 587 with Interleaved/Bundled packet format via RTP is specified in RFC 588 3558,RFC XXXX and RFC 4788. 590 Applications that use this media type: 592 It is expected that many VoIP applications (as well as mobile 593 applications) will use this type. 595 Additional information: The following information applies for storage 596 format only. Magic number: #!EVRC-B\n (see Section 5 of RFC 4788) 597 File extensions: evb, EVB Macintosh file type code: none Object 598 identifier or OID: none 600 Person & email address to contact for further information: 602 Harikishan Desineni 604 Intended usage: COMMON 606 Restrictions on usage: 608 This media type depends on RTP framing, and hence is only defined for 609 transfer via RTP (RFC 3550). Transfer within other framing protocols 610 is not defined at this time. 612 Author: 614 Qiaobing Xie / Harikishan Desineni 616 Change controller: 618 IETF Audio/Video Transport working group delegated from the IESG. 620 9.1.5. Updated Registration of Media Type EVRCB0 622 Type name: audio 624 Subtype names: EVRCB0 626 Required parameters: none 628 Optional parameters: 630 recvmode: A mode of EVRC-B codec. A decoder can use this to signal 631 an encoder to operate in the specified mode. Possible values are a 632 comma separated list of modes from the set: 0..7 (see encoder 633 operating point column in Table 2-6 [3]). 635 sendmode: A mode of EVRC-B codec. An encoder can use this to signal 636 its current mode of operation. Possible values are a comma separated 637 list of modes from the set: 0..7 (see encoder operating point column 638 in Table 2-6 [3]). 640 silencesupp: see Section 6.1 for definition. If this parameter is 641 not present, the default value 1 MUST be assumed. 643 dtxmax: see Section 6.1 of [2] 645 dtxmin: see Section 6.1 of [2] 647 hangover: see Section 6.1 of [2] 649 Encoding considerations: 651 This media type is framed binary data (see RFC 4288, Section 4.8) and 652 is defined for transfer of EVRC-B encoded data via RTP using the 653 Header-Free packet format specified in RFC 3558. 655 Security considerations: See Section 9 of RFC 4788. 657 Interoperability considerations: none 659 Published specification: 661 The EVRC-B vocoder is specified in 3GPP2 C.S0014-B. Transfer method 662 with Header-Free packet format via RTP is specified in RFC 3558, RFC 663 4788 and RFC XXXX. 665 Applications that use this media type: 667 It is expected that many VoIP applications (as well as mobile 668 applications) will use this type. 670 Additional information: none 672 Person & email address to contact for further information: 674 Harikishan Desineni 676 Intended usage: COMMON 678 Restrictions on usage: 680 This media type depends on RTP framing, and hence is only defined for 681 transfer via RTP (RFC 3550). Transfer within other framing protocols 682 is not defined at this time. 684 Author: 686 Qiaobing Xie / Harikishan Desineni 688 Change controller: 690 IETF Audio/Video Transport working group delegated from the IESG. 692 10. EVRC-B RFC XXXX Interoperability with legacy EVRC-B (RFC 4788) 693 implementations 695 This document adds new optional parameters "recvmode" and "sendmode" 696 to the original EVRC-B payload subtypes "EVRCB" and "EVRCB0" defined 697 in RFC 4788. The existing RFC 4788 implementations will not send 698 these parameters in SDP and will ignore if they are received. This 699 will allow interoperability between RFC 4788 and RFC XXXX 700 implementations of EVRC-B. For an example offer and answer exchange, 701 see Section 16. 703 11. Mapping EVRC-WB media type parameters into SDP 705 Information carried in the media type specification has a specific 706 mapping to fields in the Session Description Protocol (SDP) [7], 707 which is commonly used to describe RTP sessions. When SDP is used to 708 specify sessions employing EVRC-WB encoded speech, the mapping is as 709 follows. 711 The media type ("audio") goes in SDP "m=" as the media name. 713 o The media subtype ("EVRCWB", "EVRCWB0" or "EVRCWB1") goes in SDP 714 "a=rtpmap" as the encoding name. 716 o The optional parameters "ptime" and "maxptime" (for subtypes 717 EVRCWB, EVRCWB1) go in the SDP "a=ptime" and "a=maxptime" 718 attributes, respectively. 720 o Any remaining parameters (for subtypes EVRCWB, EVRCWB0 and 721 EVRCWB1) go in the SDP "a=fmtp" attribute by copying them from the 722 media type string as a semicolon separated list of parameter=value 723 pairs. 725 12. Mapping EVRC-B media type parameters into SDP 727 The optional parameters "recvmode" and "sendmode" (for subtypes EVRCB 728 and EVRCB0) go in the SDP "a=fmtp" attribute by copying them directly 729 from the media type string. 731 13. Offer-Answer Model Considerations for EVRC-WB 733 The following considerations apply when using SDP offer-answer 734 procedures [6] to negotiate the use of EVRC-WB payload in RTP: 736 o Since EVRC-WB is an extension of EVRC-B, the offerer SHOULD 737 announce EVRC-B support in its "m=audio" line, with EVRC-WB as the 738 preferred codec. This will allow interoperability with an 739 answerer which supports only EVRC-B. 741 Below is an example of such an offer: 743 m=audio 55954 RTP/AVP 98 99 744 a=rtpmap:98 EVRCWB0/16000 745 a=rtpmap:99 EVRCB0/8000 746 a=fmtp:98 mode-set-recv=0,4;sendmode=0 747 a=fmtp:99 recvmode=0 sendmode=4 749 If the answerer supports EVRC-WB then the answerer can keep the 750 payload type 98 in its answer and the conversation can be done 751 using EVRC-WB. Else, if the answerer supports only EVRC-B then 752 the answerer will leave only the payload type 99 in its answer and 753 the conversation will be done using EVRC-B. 755 An example answer for the above offer: 757 m=audio 55954 RTP/AVP 98 758 a=rtpmap:98 EVRCWB0/16000 759 a=fmtp:98 mode-set-recv=4;sendmode=4 761 o "mode-set-recv" is a uni-directional receive only parameter. 763 o "sendmode" is a uni-directional send only parameter. 765 o Using "sendmode", a sender can signal its current mode of 766 operation. Note that a receiver may receive RTP media well before 767 the arrival of SDP with 'sendmode' parameter. 769 o An offerer can use "mode-set-recv" to request that the remote 770 sender's encoder be limited to the list of modes signaled in 771 "mode-set-recv". A remote sender MAY ignore "mode-set-recv" 772 requests. 774 o The parameters "maxptime" and "ptime" will in most cases not 775 affect interoperability, however the setting of the parameters can 776 affect the performance of the application. The SDP offer-answer 777 handling of the "ptime" parameter is described in RFC3264 [6]. 778 The "maxptime" parameter MUST be handled in the same way. 780 o For a sendonly stream, "mode-set-recv" parameter is not useful and 781 SHOULD NOT be used. 783 o For a recvonly stream, "sendmode" parameter is not useful and 784 SHOULD NOT be used. 786 o When using EVRCWB1, the entire session MUST use the same fixed 787 rate and mode (0-Wideband or 4,7-Narrowband). 789 o For additional rules which MUST be followed while negotiating DTX 790 parameters, see Section 6.8 in [2]. 792 o Any unknown parameter in an SDP offer MUST be ignored by the 793 receiver and MUST NOT be included in the SDP answer. 795 14. Offer-Answer Model Considerations for EVRC-B 797 See Section 6.8 of [2] for offer-answer usage of EVRC-B. The 798 following are several additional considerations for EVRC-B. 800 o "recvmode" is a uni-directional receive only parameter. 802 o "sendmode" is a uni-directional send only parameter. 804 o Using "recvmode", a receiver can signal the remote sender to 805 operate its encoder in the specified mode. A remote sender MAY 806 ignore "recvmode" requests. 808 o Using "sendmode", a sender can signal its current mode of 809 operation. Note that a receiver may receive RTP media well before 810 the arrival of SDP with 'sendmode' parameter. 812 o For a sendonly stream, "recvmode" parameter is not useful and 813 SHOULD NOT be used. 815 o For a recvonly stream, "sendmode" parameter is not useful and 816 SHOULD NOT be used. 818 15. Declarative SDP Considerations 820 For declarative use of SDP in SAP [11] and RTSP [12] , the following 821 considerations apply: 823 o Any "maxptime" and "ptime" values should be selected with care to 824 ensure that the session's participants can achieve reasonable 825 performance. 827 o The payload format configuration parameters are all declarative 828 and a participant MUST use the configuration(s) that is provided 829 for the session. More than one configuration may be provided if 830 necessary by declaring multiple RTP payload types, however the 831 number of types should be kept small. For declarative examples, 832 see Section 16 834 16. Examples 836 Some example SDP session descriptions utilizing EVRC-WB and EVRC-B 837 encodings follow. In these examples, long a=fmtp lines are folded to 838 meet the column width constraints of this document. The backslash 839 ("\") at the end of a line and the carriage return that follows it 840 should be ignored. Note that media subtype names are case- 841 insensitive. Parameter names are case-insensitive both in media 842 types and in the mapping to the SDP a=fmtp attribute. 844 Example usage of EVRCWB: 846 m=audio 49120 RTP/AVP 97 98 847 a=rtpmap:97 EVRCWB/16000 848 a=rtpmap:98 EVRCB0/8000 849 a=fmtp:97 mode-set-recv=0,4;sendmode=0 850 a=fmtp:98 recvmode=0 sendmode=0 851 a=maxptime:120 853 Example usage of EVRCWB0: 855 m=audio 49120 RTP/AVP 97 98 856 a=rtpmap:97 EVRCWB0/16000 857 a=rtpmap:98 EVRCB0/8000 858 a=fmtp:97 mode-set-recv=0,4;sendmode=0 859 a=fmtp:98 recvmode=0 sendmode=0 861 Example SDP answer from a media gateway requesting a terminal to 862 limit its encoder operation to EVRC-WB mode 4. 864 m=audio 49120 RTP/AVP 97 865 a=rtpmap:97 EVRCWB0/16000 866 a=fmtp:97 mode-set-recv=4;sendmode=4 868 Example usage of EVRCWB1: 870 m=audio 49120 RTP/AVP 97 98 871 a=rtpmap:97 EVRCWB1/16000 872 a=fmtp:97 mode-set-recv=4;sendmode=4 873 a=maxptime:100 875 Example usage of EVRCWB with DTX with silencesupp=1: 877 m=audio 49120 RTP/AVP 97 98 878 a=rtpmap:97 EVRCWB/16000 879 a=rtpmap:98 EVRCB0/8000 880 a=fmtp:97 silencesupp=1;dtxmax=32;dtxmin=12;hangover=1 \ 881 mode-set-recv=0,4; sendmode=0 882 a=fmtp:98 recvmode=0 sendmode=0 883 a=maxptime:120 885 Examples usage of EVRCWB with DTX with silencesupp=0: 887 m=audio 49120 RTP/AVP 97 98 888 a=rtpmap:97 EVRCWB/16000 889 a=rtpmap:98 EVRCB0/8000 890 a=fmtp:97 silencesupp=0;dtxmax=32;dtxmin=12;hangover=1 \ 891 mode-set-recv=0,4;sendmode=0 892 a=fmtp:98 recvmode=0 sendmode=0 893 a=maxptime:120 895 Example usage of EVRCB: 897 m=audio 49120 RTP/AVP 97 898 a=rtpmap:97 EVRCB/8000 899 a=fmtp:97 recvmode=0 sendmode=4 900 a=maxptime:120 902 Example usage of EVRCB0: 904 m=audio 49120 RTP/AVP 97 905 a=rtpmap:97 EVRCB0/8000 906 a=fmtp:97 recvmode=0 sendmode=4 908 Example offer answer exchange between EVRC-WB and 909 legacy EVRC-B (RFC 4788): 911 Offer: 913 m=audio 55954 RTP/AVP 98 99 914 a=rtpmap:98 EVRCWB0/16000 915 a=rtpmap:99 EVRCB0/8000 916 a=fmtp:98 mode-set-recv=0,4;sendmode=0 917 a=fmtp:99 recvmode=0 sendmode=0 919 Answer: 921 m=audio 55954 RTP/AVP 99 922 a=rtpmap:99 EVRCB0/8000 924 Example offer answer exchange between EVRC-WB and 925 updated EVRC-B (RFC XXXX): 927 Offer: 929 m=audio 55954 RTP/AVP 98 99 930 a=rtpmap:98 EVRCWB0/16000 931 a=rtpmap:99 EVRCB0/8000 932 a=fmtp:98 mode-set-recv=0,4; sendmode=0 933 a=fmtp:99 recvmode=0 sendmode=0 935 Answer: 937 m=audio 55954 RTP/AVP 99 938 a=rtpmap:99 EVRCB0/8000 939 a=fmtp:99 recvmode=0 sendmode=4 941 In the above example, note that the answerer has chosen 942 to send in mode 4 even though the offerer was willing to 943 receive in mode 0. 'recvmode' is a receiver's preference 944 but the sender can send in a different mode. 946 Example offer answer exchanges for interoperability between 947 legacy (RFC XXXX) and updated EVRC-B(RFC 4788) implementations: 949 Offer from an offer which supports updated EVRC-B (RFC XXXX) 950 implementation: 952 m=audio 55954 RTP/AVP 99 953 a=rtpmap:99 EVRCB0/8000 954 a=fmtp:99 recvmode=0 sendmode=4 956 Answer from an answerer which supports only 957 legacy EVRC-B (RFC 4788) implementation: 959 m=audio 55954 RTP/AVP 99 960 a=rtpmap:99 EVRCB0/8000 962 Offer from an offer which supports only 963 legacy EVRC-B (RFC 4788) implementation: 965 m=audio 55954 RTP/AVP 99 966 a=rtpmap:99 EVRCB0/8000 968 Answer from an answerer which supports updated 969 EVRC-B (RFC XXXX) implementation: 971 m=audio 55954 RTP/AVP 99 972 a=rtpmap:99 EVRCB0/8000 973 a=fmtp:99 recvmode=0 sendmode=4 975 17. Security Considerations 977 Implementations using the payload defined in this specification are 978 subject to the security considerations discussed in RFC3558 [10], 979 RFC3550 [5], and any appropriate profile (for example RFC3551 [9]). 980 This payload does not specify any different security services. 982 18. Changes 984 This document updates RFC 4788 and the updates are summarized below: 986 o Added new media type attribute "sendmode" to media sub-types EVRCB 987 and EVRCB0. This attribute can be used to signal EVRC-B encoder's 988 current mode of operation. 990 o Added new media type attribute "recvmode" to media sub-types EVRCB 991 and EVRCB0. This attribute can be used to signal EVRC-B decoder's 992 preferred operating mode to a remote sender. 994 19. References 996 19.1. Normative References 998 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 999 Levels", BCP 14, RFC 2119, March 1997. 1001 [2] Xie, Q., "Enhancements to RTP Payload Formats for EVRC Family 1002 Codecs", RFC 4788, January 2007. 1004 [3] "Enhanced Variable Rate Codec, Speech Service Option 3 and 68 1005 for Wideband Spread Spectrum Digital Systems", 3GPP2 C.S0014-B 1006 v1.0 , May 2006. 1008 [4] "Enhanced Variable Rate Codec, Speech Service Option 3,68 and 1009 70 for Wideband Spread Spectrum Digital Systems", 3GPP2 1010 C.S0014-C v1.0 , October 2006. 1012 [5] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 1013 Applications", STD 64, RFC 3550, March 1997. 1015 [6] Rosenberg, J., "An Offer/Answer Model with Session Description 1016 Protocol (SDP)", RFC 3264, June 2002. 1018 [7] Handley, M., "SDP: Session Description Protocol", RFC 4566, 1019 July 2006. 1021 [8] Freed, N., "Media Type Specifications and Registration 1022 Procedures", BCP 13, RFC 4288, December 2005. 1024 19.2. Informative References 1026 [9] Schulzrinne, H., "RTP Profile for Audio and Video Conferences 1027 with Minimal Control", STD 65, RFC 3551, July 2003. 1029 [10] Li, A., "RTP Payload Format for Enhanced Variable Rate Codecs 1030 (EVRC) and Selectable Mode Vocoders (SMV)", RFC 3558, 1031 July 2003. 1033 [11] Handley, M., "Session Announcement Protocol", RFC 2974, 1034 October 2000. 1036 [12] Schulzrinne, H., "Real Time Streaming Protocol (RTSP)", 1037 RFC 2326, April 1998. 1039 Authors' Addresses 1041 Harikishan Desineni 1042 Qualcomm 1043 5775 Morehouse Drive 1044 San Diego, CA 92126 1045 USA 1047 Phone: +1 858 845 8996 1048 Email: hd@qualcomm.com 1049 URI: http://www.qualcomm.com 1051 Qiaobing Xie 1052 Motorola 1053 1501 W. 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