idnits 2.17.1 draft-ietf-xrblock-rtcp-xr-loss-conceal-07.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. 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 : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors 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 'SHALL not' in this paragraph: Equivalently, a concealed second is one in which some Loss-type concealment has occurred. Buffer adjustment-type concealment SHALL not cause Concealed Seconds to be incremented, with the following exception. An implementation MAY cause Concealed Seconds to be incremented for 'emergency' buffer adjustments made during talkspurts. -- The document date (July 8, 2013) is 3938 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) == Missing Reference: 'G.711' is mentioned on line 490, but not defined == Missing Reference: 'RFCXXXX' is mentioned on line 957, but not defined ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Audio/Video Transport Working Group A. Clark 3 Internet-Draft Telchemy 4 Intended status: Standards Track G. Zorn, Ed. 5 Expires: January 9, 2014 Network Zen 6 C. Bi 7 STTRI 8 Q. Wu, Ed. 9 Huawei 10 July 8, 2013 12 RTCP XR Report Block for Concealment metrics Reporting on Audio 13 Applications 14 draft-ietf-xrblock-rtcp-xr-loss-conceal-07.txt 16 Abstract 18 This document defines two RTCP XR Report Blocks that allows the 19 reporting of concealment metrics for audio applications of RTP. 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 January 9, 2014. 38 Copyright Notice 40 Copyright (c) 2013 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 1.1. Loss Concealment and Concealment Seconds Metrics 57 Reporting Block . . . . . . . . . . . . . . . . . . . . . 3 58 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 4 59 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 4 60 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 61 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 62 2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 5 63 2.2. Notations . . . . . . . . . . . . . . . . . . . . . . . . 5 64 3. Loss Concealment Block . . . . . . . . . . . . . . . . . . . . 6 65 3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 6 66 3.2. Definition of Fields in Loss Concealment Metrics Block . . 6 67 4. Concealment Seconds Block . . . . . . . . . . . . . . . . . . 11 68 4.1. Report Block Structure . . . . . . . . . . . . . . . . . . 11 69 4.2. Definition of Fields in Concealed Seconds Metrics Block . 12 70 5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 16 71 5.1. SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . 16 72 5.2. Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . 16 73 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 74 6.1. New RTCP XR Block Type values . . . . . . . . . . . . . . 17 75 6.2. New RTCP XR SDP Parameters . . . . . . . . . . . . . . . . 17 76 6.3. Contact information for registrations . . . . . . . . . . 17 77 7. Security Considerations . . . . . . . . . . . . . . . . . . . 18 78 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 19 79 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20 80 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21 81 10.1. Normative References . . . . . . . . . . . . . . . . . . . 21 82 10.2. Informative References . . . . . . . . . . . . . . . . . . 21 83 Appendix A. Metrics represented using RFC6390 Template . . . . . 22 84 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 29 85 B.1. draft-ietf-xrblock-rtcp-xr-loss-conceal-07 . . . . . . . . 29 86 B.2. draft-ietf-xrblock-rtcp-xr-loss-conceal-06 . . . . . . . . 29 87 B.3. draft-ietf-xrblock-rtcp-xr-loss-conceal-05 . . . . . . . . 29 88 B.4. draft-ietf-xrblock-rtcp-xr-loss-conceal-04 . . . . . . . . 29 89 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30 91 1. Introduction 93 1.1. Loss Concealment and Concealment Seconds Metrics Reporting Block 95 At any instant, the audio output at a receiver may be classified as 96 either 'normal' or 'concealed'. 'Normal' refers to playout of audio 97 payload received from the remote end, and also includes locally 98 generated signals such as announcements, tones and comfort noise. 99 Concealment refers to playout of locally-generated signals used to 100 mask the impact of network impairments or to reduce the audibility of 101 jitter buffer adaptations. 103 This draft defines two new concealment related block types to augment 104 those defined in [RFC3611] for use in a range of RTP applications. 105 These two block types extend packet loss concealment mechanism 106 defined in section 4.7.6 of RFC3611. 108 The first block type provides metrics for actions taken by the 109 receiver to mitigate the effect of packet loss and packet discard. 110 Specifically, the first metric (On-Time Playout Duration) reports the 111 duration of normal playout of data which the receiver obtained from 112 the sender's stream. A second metric (Loss Concealment Duration) 113 reports the total time during which the receiver played out media 114 data which was manufactured locally, because the sender's data for 115 these periods was not available due to packet loss or discard. A 116 similar metric (Buffer Adjustment Concealment Duration) reports the 117 duration of playout of locally-manufactured data replacing data which 118 is unavailable due to adaptation of an adaptive de-jitter buffer. 119 Further metrics (Playout Interrupt Count and Mean Playout Interrupt 120 Size) report the number of times normal playout was interrupted, and 121 the mean duration of these interruptions. 123 Loss Concealment Duration and Buffer Adjustment Concealment Duration 124 are reported separately because buffer adjustment is typically 125 arranged to occur in silence periods so may have very little impact 126 on user experience, whilst loss concealment may occur at any time. 128 The second block type provides metrics for concealment seconds, which 129 are measured at the receiving end of the RTP stream. Specifically, 130 the first metric (Unimpaired Seconds) reports the number of whole 131 seconds occupied only with normal playout of data which the receiver 132 obtained from the sender's stream. The second metric (Concealed 133 Seconds) reports the number of whole seconds during which the 134 receiver played out any locally-generated media data. A third metric 135 (Severely Concealed Seconds) reports the number of whole seconds 136 during which the receiver played out locally-generated data for more 137 than SCS Threshold. 139 These metrics belongs to the class of transport-related terminal 140 metrics defined in [RFC6792]. 142 1.2. RTCP and RTCP XR Reports 144 The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] 145 defined an extensible structure for reporting using an RTCP Extended 146 Report (XR). This draft defines a new Extended Report block that 147 MUST be used as defined in [RFC3550] and [RFC3611]. 149 1.3. Performance Metrics Framework 151 The Performance Metrics Framework [RFC6390] provides guidance on the 152 definition and specification of performance metrics. The RTP 153 Monitoring Architectures [RFC6792] provides guideline for reporting 154 block format using RTCP XR. The Metrics Block described in this 155 document are in accordance with those guidelines. 157 1.4. Applicability 159 These metrics are applicable to audio applications of RTP and the 160 audio component of Audio/Video applications in which the packet loss 161 concealment machinery is contained at the receiving end to mitigate 162 the impact of network impairments to user's perception of media 163 quality. 165 2. Terminology 167 2.1. Standards Language 169 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 170 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 171 document are to be interpreted as described in RFC2119 [RFC2119]. 173 2.2. Notations 175 This report block makes use of binary fractions. The terminology 176 used is 178 Numeric formats S X:Y 180 where S indicates a two's complement signed representation, X 181 the number of bits prior to the decimal place and Y the number 182 of bits after the decimal place. 184 Hence 8:8 represents an unsigned number in the range 0.0 to 185 255.996 with a granularity of 0.0039. S7:8 would represent the 186 range -127.996 to +127.996. 0:16 represents a proper binary 187 fraction with range 189 0.0 to 1 - 1/65536 = 0.9999847 191 though note that use of flag values at the top of the numeric 192 range slightly reduces this upper limit. For example, if the 193 16- bit values 0xfffe and 0xffff are used as flags for "over- 194 range" and "unavailable" conditions, a 0:16 quantity has range 196 0.0 to 1 - 3/65536 = 0.9999542 198 3. Loss Concealment Block 200 The metrics block described here are intended to be used as described 201 in this section, in conjunction with information from the Measurement 202 Information block [RFC6776]. Instances of this Metrics Block refer 203 by Synchronization source (SSRC) to the separate auxiliary 204 Measurement Information block [RFC6776] which describes measurement 205 periods in use (see [RFC6776] section 4.2). This Metrics Block 206 relies on the measurement period in the Measurement Information block 207 indicating the span of the report and SHOULD be sent in the same 208 compound RTCP packet as the measurement information block. If the 209 measurement period is not received in the same compound RTCP packet 210 as this Metrics Block, this metrics block MUST be discarded. 212 3.1. Report Block Structure 214 Loss Concealment Metrics Block 216 0 1 2 3 217 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 218 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 219 | BT=NLC | I |plc| rsv. | block length=5 | 220 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 221 | SSRC of Source | 222 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 223 | On-time Playout Duration | 224 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 225 | Loss Concealment Duration | 226 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 227 | Buffer Adjustment Concealment Duration | 228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 229 | Playout Interrupt Count | Reserved. | 230 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 231 | Mean Playout Interrupt Size | 232 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 234 Figure 1: Report Block Structure 236 3.2. Definition of Fields in Loss Concealment Metrics Block 238 Block type (BT): 8 bits 240 A Loss Concealment Metrics Report Block is identified by the 241 constant NLC. 243 [Note to RFC Editor: please replace NLC with the IANA provided 244 RTCP XR block type for this block.] 246 Interval Metric flag (I): 2 bit 248 This field is used to indicate whether the Loss Concealment 249 metrics are Sampled, Interval or Cumulative metrics: 251 I=10: Interval Duration - the reported value applies to the 252 most recent measurement interval duration between successive 253 metrics reports. 255 I=11: Cumulative Duration - the reported value applies to the 256 accumulation period characteristic of cumulative measurements. 258 I=01: Sampled Value - the reported value is a sampled 259 instantaneous value. 261 In this document, Loss Concealment Metrics can only be measured 262 over definite intervals, and cannot be sampled. Also, the value 263 I=00 is reserved for future use. Senders MUST NOT use the values 264 I=00 or I=01. If a block is received with I=00 or I=01, the 265 receiver MUST discard the block. 267 Packet Loss Concealment Method (plc): 2 bits 269 This field is used to identify the packet loss concealment method 270 in use at the receiver, according to the following code: 272 bits 014-015 274 0 = silence insertion 276 1 = simple replay, no attenuation 278 2 = simple replay, with attenuation 280 3 = enhancement 282 Other values reserved 284 Note that the enhancement method (plc =3 )for packet loss 285 concealment offers an improved audio quality and or a better 286 robustness against packet losses [G.711] and is equivalent to 287 enhanced in section 4.7.1 of [RFC3611], 289 Reserved (resv): 4 bits 291 These bits are reserved. They MUST be set to zero by senders and 292 ignored by receivers (See [RFC6709] section 4.2). 294 block length: 16 bits 296 The length of this report block in 32-bit words, minus one. For 297 the Loss Concealment Block, the block length is equal to 5. 299 SSRC of source: 32 bits 301 As defined in Section 4.1 of [RFC3611]. 303 On-time Playout Duration: 32 bits 305 'On-time' playout is the uninterrupted, in-sequence playout of 306 valid decoded audio information originating from the remote 307 endpoint. This includes comfort noise during periods of remote 308 talker silence, if VAD [VAD] is used, and locally generated or 309 regenerated tones and announcements. 311 An equivalent definition is that on-time playout is playout of any 312 signal other than those used for concealment. 314 On-time playout duration is expressed in units of 1/65536 seconds 315 and MUST include both speech and silence intervals, whether VAD is 316 used or not. 318 If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE 319 MUST be reported to indicate an over-range measurement. If the 320 measurement is unavailable, the value 0xFFFFFFFF MUST be reported. 322 Loss Concealment Duration: 32 bits 324 The duration, expressed in units of 1/65536 seconds, of audio 325 playout corresponding to Loss-type concealment. 327 Loss-type concealment is reactive insertion or deletion of samples 328 in the audio playout stream due to effective frame loss at the 329 audio decoder. "Effective frame loss" is the event in which a 330 frame of coded audio is simply not present at the audio decoder 331 when required. In this case, substitute audio samples are 332 generally formed, at the decoder or elsewhere, to reduce audible 333 impairment. 335 If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE 336 MUST be reported to indicate an over-range measurement. If the 337 measurement is unavailable, the value 0xFFFFFFFF MUST be reported. 339 Buffer Adjustment Concealment Duration: 32 bits 341 The duration, expressed in units of 1/65536 seconds, of audio 342 playout corresponding to Buffer Adjustment-type concealment, if 343 known. 345 If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE 346 MUST be reported to indicate an over-range measurement. If the 347 measurement is unavailable, the value 0xFFFFFFFF MUST be reported. 349 Buffer Adjustment-type concealment is proactive or controlled 350 insertion or deletion of samples in the audio playout stream due 351 to jitter buffer adaptation, re-sizing or re-centering decisions 352 within the endpoint. 354 Because this insertion is controlled, rather than occurring 355 randomly in response to losses, it is typically less audible than 356 loss-type concealment. For example, jitter buffer adaptation 357 events may be constrained to occur during periods of talker 358 silence, in which case only silence duration is affected, or 359 sophisticated time-stretching methods for insertion/deletion 360 during favorable periods in active speech may be employed. 362 Concealment events which cannot be classified as Buffer 363 Adjustment-type MUST be classified as Loss-type. 365 Playout Interrupt Count: 16 bits 367 The number of interruptions to normal playout which occurred 368 during the reporting period. 370 If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be 371 reported to indicate an over-range measurement. If the 372 measurement is unavailable, the value 0xFFFF MUST be reported. 374 Reserved (resv): 16 bits 376 These bits are reserved. They MUST be set to zero by senders and 377 ignored by receivers (See [RFC6709] section 4.2). 379 Mean Playout Interrupt Size: 32 bits 381 The mean duration, expressed in units of 1/65536 seconds, of 382 interruptions to normal playout which occurred during the 383 reporting period. 385 If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be 386 reported to indicate an over-range measurement. If the 387 measurement is unavailable, the value 0xFFFF MUST be reported. 389 4. Concealment Seconds Block 391 This sub-block described here is intended to be used as described in 392 this section, in conjunction with information from the Measurement 393 Information block [RFC6776] and provides a description of potentially 394 audible impairments due to lost and discarded packets at the 395 endpoint, expressed on a time basis analogous to a traditional PSTN 396 T1/E1 errored seconds metric. Instances of this Metrics Block refer 397 by Synchronization source (SSRC) to the separate auxiliary 398 Measurement Information block [RFC6776] which describes measurement 399 periods in use (see [RFC6776] section 4.2). This Metrics Block 400 relies on the measurement period in the Measurement Information block 401 indicating the span of the report and SHOULD be sent in the same 402 compound RTCP packet as the measurement information block. If the 403 measurement period is not received in the same compound RTCP packet 404 as this Metrics Block, this metrics block MUST be discarded. 406 The following metrics are based on successive one second intervals as 407 declared by a RTP clock. This RTP clock does NOT need to be 408 synchronized to any external time reference. The starting time of 409 this clock is unspecified. Note that this implies that the same loss 410 pattern could result in slightly different count values, depending on 411 where the losses occur relative to the particular one-second 412 demarcation points. For example, two loss events occurring 50ms 413 apart could result in either one concealed second or two, depending 414 on the particular one second boundaries used. 416 The seconds in this sub-block are not necessarily calendar seconds. 417 At the tail end of a session, periods of time of less than one second 418 shall be incorporated into these counts if they exceed 500ms and 419 shall be disregarded if they are less than 500ms. 421 4.1. Report Block Structure 423 Concealed Seconds Metrics Block 425 0 1 2 3 426 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 1 427 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 428 | BT=NCS | I |plc|Rserved| block length=4 | 429 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 430 | SSRC of Source | 431 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 432 | Unimpaired Seconds | 433 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 434 | Concealed Seconds | 435 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 436 | Severely Concealed Seconds | RESERVED | SCS Threshold | 437 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 439 Figure 2: Report Block Structure 441 4.2. Definition of Fields in Concealed Seconds Metrics Block 443 Block type (BT): 8 bits 445 A Concealed Seconds Metrics Report Block is identified by the 446 constant NCS. 448 [Note to RFC Editor: please replace NCS with the IANA provided 449 RTCP XR block type for this block.] 451 Interval Metric flag (I): 2 bit 453 This field is used to indicate whether the Concealment Seconds 454 Metrics are Sampled, Interval or Cumulative metrics: 456 I=10: Interval Duration - the reported value applies to the 457 most recent measurement interval duration between successive 458 metrics reports. 460 I=11: Cumulative Duration - the reported value applies to the 461 accumulation period characteristic of cumulative measurements. 463 I=01: Sampled Value - the reported value is a sampled 464 instantaneous value. 466 In this document, Concealment Seconds Metrics can only be measured 467 over definite intervals, and cannot be sampled. Also, the value 468 I=00 is reserved for future use. Senders MUST NOT use the values 469 I=00 or I=01. If a block is received with I=00 or I=01, the 470 receiver MUST discard the block. 472 Packet Loss Concealment Method (plc): 2 bits 474 This field is used to identify the packet loss concealment method 475 in use at the receiver, according to the following code: 477 bits 014-015 478 0 = silence insertion 480 1 = simple replay, no attenuation 482 2 = simple replay, with attenuation 484 3 = enhancement 486 Other values reserved 488 Note that the enhancement method (plc =3) for packet loss 489 concealment offers an improved audio quality and or a better 490 robustness against packet losses [G.711] and is equivalent to 491 enhanced in section 4.7.1 of [RFC3611], 493 Reserved (resv): 4 bits 495 These bits are reserved. They MUST be set to zero by senders and 496 ignored by receivers (See [RFC6709] section 4.2). 498 Block Length: 16 bits 500 The length of this report block in 32-bit words, minus one. For 501 the Concealment Seconds Block, the block length is equal to 4. 503 SSRC of source: 32 bits 505 As defined in Section 4.1 of [RFC3611]. 507 Unimpaired Seconds: 32 bits 509 A count of the number of unimpaired Seconds that have occurred. 511 An unimpaired Second is defined as a continuous period of one 512 second during which no frame loss or discard due to late arrival 513 has occurred. Every second in a session must be classified as 514 either OK or Concealed. 516 Normal playout of comfort noise or other silence concealment 517 signal during periods of talker silence, if VAD is used, shall be 518 counted as unimpaired seconds. 520 If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE 521 MUST be reported to indicate an over-range measurement. If the 522 measurement is unavailable, the value 0xFFFFFFFF MUST be reported. 524 Concealed Seconds: 32 bits 526 A count of the number of Concealed Seconds that have occurred. 528 A Concealed Second is defined as a continuous period of one second 529 during which any frame loss or discard due to late arrival has 530 occurred. 532 Equivalently, a concealed second is one in which some Loss-type 533 concealment has occurred. Buffer adjustment-type concealment 534 SHALL not cause Concealed Seconds to be incremented, with the 535 following exception. An implementation MAY cause Concealed 536 Seconds to be incremented for 'emergency' buffer adjustments made 537 during talkspurts. 539 Loss-type concealment is reactive insertion or deletion of samples 540 in the audio playout stream due to effective frame loss at the 541 audio decoder. "Effective frame loss" is the event in which a 542 frame of coded audio is simply not present at the audio decoder 543 when required. In this case, substitute audio samples are 544 generally formed, at the decoder or elsewhere, to reduce audible 545 impairment. 547 Buffer Adjustment-type concealment is proactive or controlled 548 insertion or deletion of samples in the audio playout stream due 549 to jitter buffer adaptation, re-sizing or re-centering decisions 550 within the endpoint. 552 Because this insertion is controlled, rather than occurring 553 randomly in response to losses, it is typically less audible than 554 loss-type concealment. For example, jitter buffer adaptation 555 events may be constrained to occur during periods of talker 556 silence, in which case only silence duration is affected, or 557 sophisticated time-stretching methods for insertion/deletion 558 during favorable periods in active speech may be employed. For 559 these reasons, buffer adjustment-type concealment MAY be exempted 560 from inclusion in calculations of Concealed Seconds and Severely 561 Concealed Seconds. 563 However, an implementation SHOULD include buffer-type concealment 564 in counts of Concealed Seconds and Severely Concealed Seconds if 565 the event occurs at an 'inopportune' moment, with an emergency or 566 large, immediate adaptation during active speech, or for 567 unsophisticated adaptation during speech without regard for the 568 underlying signal, in which cases the assumption of low-audibility 569 cannot hold. In other words, jitter buffer adaptation events 570 which may be presumed to be audible SHOULD be included in 571 Concealed Seconds and Severely Concealed Seconds counts. 573 Concealment events which cannot be classified as Buffer 574 Adjustment- type MUST be classified as Loss-type. 576 For clarification, the count of Concealed Seconds MUST include the 577 count of Severely Concealed Seconds. 579 If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE 580 MUST be reported to indicate an over-range measurement. If the 581 measurement is unavailable, the value 0xFFFFFFFF MUST be reported. 583 Severely Concealed Seconds: 16 bits 585 A count of the number of Severely Concealed Seconds. 587 A Severely Concealed Second is defined as a non-overlapping period 588 of one second during which the cumulative amount of time that has 589 been subject to frame loss or discard due to late arrival, exceeds 590 the SCS Threshold. 592 If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be 593 reported to indicate an over-range measurement. If the 594 measurement is unavailable, the value 0xFFFF MUST be reported. 596 Reserved: 8 bits 598 These bits are reserved. They MUST be set to zero by senders and 599 ignored by receivers (See [RFC6709] section 4.2). 601 SCS Threshold: 8 bits 603 The SCS Threshold is defined as the percentage of packets 604 corresponding to lost or discarded frames that must occur within a 605 one second period in order for the second to be classified as a 606 Severely Concealed Second. This is expressed in numeric format 607 0:8 and hence can represent a range of 0.1 to 25.5 percent loss or 608 discard. 610 A default threshold of 5% effective frame loss (50ms effective 611 frame loss ) per second is suggested. 613 5. SDP Signaling 615 [RFC3611] defines the use of SDP (Session Description Protocol) 616 [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used 617 without prior signaling. 619 5.1. SDP rtcp-xr-attrib Attribute Extension 621 This section augments the SDP attribute "rtcp-xr" [RFC3611] by 622 providing two additional values of "xr-format" to signal the use of 623 two report blocks defined in this document. 625 xr-format =/ xr-conceal-block 626 / xr-conc-sec-block 628 xr-conceal-block = "loss-conceal" 629 xr-conc-sec-block = "conc-sec" ["=" thresh] 631 thresh = 1*DIGIT ; threshold for SCS (ms) 632 DIGIT = %x30-39 634 5.2. Offer/Answer Usage 636 When SDP is used in offer-answer context, the SDP Offer/Answer usage 637 defined in [RFC3611] applies. Note that "thresh" is declared by the 638 offer. 640 6. IANA Considerations 642 New block types for RTCP XR are subject to IANA registration. For 643 general guidelines on IANA considerations for RTCP XR, refer to 644 [RFC3611]. 646 6.1. New RTCP XR Block Type values 648 This document assigns two block type values in the IANA "RTP Control 649 Protocol Extended Reports (RTCP XR) Block Type Registry ": 651 Name: LCB 652 Long Name: Loss Concealment Block 653 Value 654 Reference: Section 3.1 656 Name: CSB 657 Long Name: Concealment Seconds Block 658 Value 659 Reference: Section 4.1 661 [Note to RFC Editor: please replace and with the RTCP XR 662 block type assigned by IANA for this block.] 664 6.2. New RTCP XR SDP Parameters 666 This document also registers two new parameters in the "RTP Control 667 Protocol Extended Reports (RTCP XR) Session Description Protocol 668 (SDP) Parameters Registry": 670 o "loss-conceal" 672 o "conc-sec" 674 6.3. Contact information for registrations 676 The contact information for the registrations is: 678 Qin Wu (sunseawq@huawei.com) 679 101 Software Avenue, Yuhua District 680 Nanjing, Jiangsu 210012 681 China 683 7. Security Considerations 685 It is believed that this proposed RTCP XR report block introduces no 686 new security considerations beyond those described in [RFC3611]. 687 This block does not provide per-packet statistics so the risk to 688 confidentiality documented in Section 7, paragraph 3 of [RFC3611] 689 does not apply. 691 8. Contributors 693 Geoff Hunt wrote the initial draft of this document. 695 9. Acknowledgements 697 The authors gratefully acknowledge reviews and feedback provided by 698 Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin Connor, 699 Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert Higashi, 700 Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith Lantz, 701 Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, Ravi 702 Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada. 704 10. References 706 10.1. Normative References 708 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 709 Requirement Levels", March 1997. 711 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 712 Applications", RFC 3550, July 2003. 714 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 715 Protocol Extended Reports (RTCP XR)", November 2003. 717 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 718 Description Protocol", July 2006. 720 [RFC6776] Wu, Q., "Measurement Identity and information Reporting 721 using SDES item and XR Block", RFC 6776, August 2012. 723 10.2. Informative References 725 [RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric 726 Development", RFC 6390, October 2011. 728 [RFC6709] Carpenter, B., Aboba, B., and S. Cheshire, "Design 729 Considerations for Protocol Extensions", RFC 6709, 730 September 2012. 732 [RFC6792] Hunt, G., "Monitoring Architectures for RTP", RFC 6792, 733 November 2012. 735 [VAD] "http://en.wikipedia.org/wiki/Voice_activity_detection". 737 Appendix A. Metrics represented using RFC6390 Template 739 RFC EDITOR NOTE: please change XXXX in [RFCXXXX] by the new RFC 740 number, when assigned. 742 a. On-time Playout Duration Metric 744 * Metric Name: On-time Playout Duration 746 * Metric Description: 'On-time' playout is the uninterrupted, 747 in-sequence playout of valid decoded audio information 748 originating from the remote endpoint. On-time playout 749 Duration is playout duration of any signal other than those 750 used for concealment 752 * Method of Measurement or Calculation: See section 3. 2, On- 753 time Playout Duration definition [RFCXXXX]. 755 * Units of Measurement: See section 3.2, On-time Playout 756 Duration definition [RFCXXXX]. 758 * Measurement Point(s) with Potential Measurement Domain: See 759 section 1.1, 3rd paragraph [RFCXXXX]. 761 * Measurement Timing: See section 3, 1st paragraph [RFCXXXX] for 762 measurement timing and section 3.2 [RFCXXXX] for Interval 763 Metric flag. 765 * Use and applications: See section 1.4 [RFCXXXX]. 767 * Reporting model: See RFC3611. 769 b. Loss Concealment Duration Metric 771 * Metric Name: Loss Concealment Duration 772 * Metric Description: The duration of audio playout 773 corresponding to Loss-type concealment. 775 * Method of Measurement or Calculation: See section 3.2, Loss 776 Concealment Duration definition [RFCXXXX]. 778 * Units of Measurement: See section 3.2, Loss Concealment 779 Duration definition [RFCXXXX]. 781 * Measurement Point(s) with Potential Measurement Domain: See 782 section 1.1, 3rd paragraph [RFCXXXX]. 784 * Measurement Timing: See section 3, 1st paragraph [RFCXXXX] for 785 measurement timing and section 3. 2 [RFCXXXX] for Interval 786 Metric flag. 788 * Use and applications: See section 1.4 [RFCXXXX]. 790 * Reporting model: See RFC3611. 792 c. Buffer Adjustment Concealment Duration Metric 794 * Metric Name: Buffer Adjustment Concealment Duration 796 * Metric Description: The duration of audio playout 797 corresponding to Buffer Adjustment-type concealment. 799 * Method of Measurement or Calculation: See section 3. 2, Buffer 800 Adjustment Concealment Duration definition [RFCXXXX]. 802 * Units of Measurement: See section 3.2, Buffer Adjustment 803 Concealment Duration definition [RFCXXXX]. 805 * Measurement Point(s) with Potential Measurement Domain: See 806 section 1.1, 3rd paragraph [RFCXXXX]. 808 * Measurement Timing: See section 3, 1st paragraph [RFCXXXX] for 809 measurement timing and section 3.2 [RFCXXXX] for Interval 810 Metric flag. 812 * Use and applications: See section 1.4 [RFCXXXX]. 814 * Reporting model: See RFC3611. 816 d. Playout Interrupt Count Metric 818 * Metric Name: Playout Interrupt Count 820 * Metric Description: The number of interruptions to normal 821 playout which occurred during the reporting period. 823 * Method of Measurement or Calculation: See section 3. 2, 824 Playout Interrupt Count definition [RFCXXXX]. 826 * Units of Measurement: See section 3.2, Playout Interrupt Count 827 definition [RFCXXXX]. 829 * Measurement Point(s) with Potential Measurement Domain: See 830 section 1.1, 3rd paragraph [RFCXXXX]. 832 * Measurement Timing: See section 3, 1st paragraph [RFCXXXX] for 833 measurement timing and section 3.2 [RFCXXXX] for Interval 834 Metric flag. 836 * Use and applications: See section 1.4 [RFCXXXX]. 838 * Reporting model: See RFC3611. 840 e. Mean Playout Interrupt Size Metric 841 * Metric Name: Mean Playout Interrupt Size 843 * Metric Description: The mean duration of interruptions to 844 normal playout which occurred during the reporting period. 846 * Method of Measurement or Calculation: See section 3. 2, 847 Playout Interrupt Count definition [RFCXXXX]. 849 * Units of Measurement: See section 3.2, Playout Interrupt Count 850 definition [RFCXXXX]. 852 * Measurement Point(s) with Potential Measurement Domain: See 853 section 1.1, 3rd paragraph [RFCXXXX]. 855 * Measurement Timing: See section 3, 1st paragraph [RFCXXXX] for 856 measurement timing and section 3.2 [RFCXXXX] for Interval 857 Metric flag. 859 * Use and applications: See section 1.4 [RFCXXXX]. 861 * Reporting model: See RFC3611. 863 f. Unimpaired Seconds Metric 865 * Metric Name: Unimpaired Seconds 867 * Metric Description: A count of the number of unimpaired 868 Seconds that have occurred. 870 * Method of Measurement or Calculation: See section 4. 2, 871 Unimpaired Seconds definition [RFCXXXX]. 873 * Units of Measurement: See section 4.2, Unimpaired Seconds 874 definition [RFCXXXX]. 876 * Measurement Point(s) with Potential Measurement Domain: See 877 section 1.1, 5th paragraph [RFCXXXX]. 879 * Measurement Timing: See section 4, 1st paragraph [RFCXXXX] for 880 measurement timing and section 4.2 paragraph [RFCXXXX] for 881 Interval Metric flag. 883 * Use and applications: See section 1.4 [RFCXXXX]. 885 * Reporting model: See RFC3611. 887 g. Concealed Seconds Metric 889 * Metric Name: Concealed Seconds 891 * Metric Description: A count of the number of Concealed Seconds 892 that have occurred. 894 * Method of Measurement or Calculation: See section 4. 2, 895 Concealed Seconds definition [RFCXXXX]. 897 * Units of Measurement: See section 4.2, Concealed Seconds 898 definition [RFCXXXX]. 900 * Measurement Point(s) with Potential Measurement Domain: See 901 section 1.1, 5th paragraph [RFCXXXX]. 903 * Measurement Timing: See section 4, 1st paragraph [RFCXXXX] for 904 measurement timing and section 4.2 [RFCXXXX] for Interval 905 Metric flag. 907 * Use and applications: See section 1.4 [RFCXXXX]. 909 * Reporting model: See RFC3611. 911 h. Severely Concealed Seconds Metric 913 * Metric Name: Severely Concealed Seconds 915 * Metric Description: A count of the number of Severely 916 Concealed Seconds that have occurred. 918 * Method of Measurement or Calculation: See section 4. 2, 919 Severely Concealed Seconds definition [RFCXXXX]. 921 * Units of Measurement: See section 4.2, Severely Concealed 922 Seconds definition [RFCXXXX]. 924 * Measurement Point(s) with Potential Measurement Domain: See 925 section 1.1, 5th paragraph [RFCXXXX]. 927 * Measurement Timing: See section 4, 1st paragraph [RFCXXXX] for 928 measurement timing and section 4.2 [RFCXXXX] for Interval 929 Metric flag. 931 * Use and applications: See section 1.4 [RFCXXXX]. 933 * Reporting model: See RFC3611. 935 i. SCS Threshold Metric 937 * Metric Name: SCS Threshold 939 * Metric Description: The amount of time corresponding to lost 940 or discarded frames that must occur within a one second period 941 in order for the second to be classified as a Severely 942 Concealed Second. 944 * Method of Measurement or Calculation: See section 4. 2, SCS 945 Threshold definition [RFCXXXX]. 947 * Units of Measurement: See section 4.2, SCS Threshold 948 definition [RFCXXXX]. 950 * Measurement Point(s) with Potential Measurement Domain: See 951 section 1.1, 5th paragraph [RFCXXXX]. 953 * Measurement Timing: See section 4, 1st paragraph [RFCXXXX] for 954 measurement timing and section 4.2 [RFCXXXX] for Interval 955 Metric flag. 957 * Use and applications: See section 1.4 [RFCXXXX]. 959 * Reporting model: See RFC3611. 961 Appendix B. Change Log 963 Note to the RFC-Editor: please remove this section prior to 964 publication as an RFC. 966 B.1. draft-ietf-xrblock-rtcp-xr-loss-conceal-07 968 The following are the major changes to previous version : 970 o Change units for threshold and units used for reporting in loss 971 concealment block and concealment seconds block. 973 o Change 16bit "Mean Playout Interrupt Size" into 32bits. 975 B.2. draft-ietf-xrblock-rtcp-xr-loss-conceal-06 977 The following are the major changes to previous version : 979 o Comments in the WGLC are addressed in this version. 981 B.3. draft-ietf-xrblock-rtcp-xr-loss-conceal-05 983 The following are the major changes to previous version : 985 o Add text to clarify the definition of enhanced method. 987 o Add appendix to apply RFC6390 template to the metrics. 989 B.4. draft-ietf-xrblock-rtcp-xr-loss-conceal-04 991 The following are the major changes to previous version : 993 o Merge Concealment Seconds draft into this draft (i.e.,Loss 994 Concealment draft). 996 o Updated references. 998 Authors' Addresses 1000 Alan Clark 1001 Telchemy Incorporated 1002 2905 Premiere Parkway, Suite 280 1003 Duluth, GA 30097 1004 USA 1006 Email: alan.d.clark@telchemy.com 1008 Glen Zorn (editor) 1009 Network Zen 1010 77/440 Soi Phoomjit, Rama IV Road 1011 Phra Khanong, Khlong Toie 1012 Bangkok 10110 1013 Thailand 1015 Phone: +66 (0) 87 502 4274 1016 Email: gwz@net-zen.net 1018 Claire Bi 1019 Shanghai Research Institure of China Telecom Corporation Limited 1020 No.1835,South Pudong Road 1021 Shanghai 200122 1022 China 1024 Email: bijy@sttri.com.cn 1026 Qin Wu (editor) 1027 Huawei 1028 101 Software Avenue, Yuhua District 1029 Nanjing, Jiangsu 210012 1030 China 1032 Email: sunseawq@huawei.com