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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) == Unused Reference: 'RFC2119' is defined on line 370, but no explicit reference was found in the text ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) == Outdated reference: A later version (-12) exists of draft-ietf-pmol-metrics-framework-02 Summary: 2 errors (**), 0 flaws (~~), 4 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Audio/Video Transport Working G. Hunt 3 Group BT 4 Internet-Draft A. Clark 5 Intended status: Standards Track Telchemy 6 Expires: November 16, 2009 May 15, 2009 8 RTCP XR Report Block for Loss Concealment metric Reporting 9 draft-ietf-avt-rtcp-xr-loss-conceal-02.txt 11 Status of this Memo 13 This Internet-Draft is submitted to IETF in full conformance with the 14 provisions of BCP 78 and BCP 79. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on November 16, 2009. 34 Copyright Notice 36 Copyright (c) 2009 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents in effect on the date of 41 publication of this document (http://trustee.ietf.org/license-info). 42 Please review these documents carefully, as they describe your rights 43 and restrictions with respect to this document. 45 Abstract 47 This document defines an RTCP XR Report Block that allows the 48 reporting of Loss Concealment metrics primarily for audio 49 applications of RTP. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 1.1. Loss Concealment Report Block . . . . . . . . . . . . . . 3 55 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 56 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 4 57 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 58 2. Loss Concealment Block . . . . . . . . . . . . . . . . . . . . 5 59 2.1. Report Block Structure . . . . . . . . . . . . . . . . . . 5 60 2.2. Definition of Fields in Loss Concealment Report Block . . 5 61 3. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 9 62 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 63 4.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 10 64 4.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 10 65 4.3. Contact information for registrations . . . . . . . . . . 10 66 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 67 6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12 68 7. Changes from previous version . . . . . . . . . . . . . . . . 13 69 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 70 8.1. Normative References . . . . . . . . . . . . . . . . . . . 14 71 8.2. Informative References . . . . . . . . . . . . . . . . . . 14 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 74 1. Introduction 76 1.1. Loss Concealment Report Block 78 This draft defines a new block type to augment those defined in 79 [RFC3611], for use in a range of RTP applications. 81 At any instant, the audio output at a receiver may be classified as 82 either 'normal' or 'concealed'. 'Normal' refers to playout of audio 83 payload received from the remote end, and also includes locally 84 generated signals such as announcements, tones and comfort noise. 85 Concealment refers to playout of locally-generated signals used to 86 mask the impact of network impairments or to reduce the audibility of 87 jitter buffer adaptations. 89 The new block type provides metrics for actions taken by the receiver 90 to mitigate the effect of packet loss and packet discard. 91 Specifically, the first metric (On-Time Playout Duration) reports the 92 duration of normal playout of data which the receiver obtained from 93 the sender's stream. A second metric (Loss Concealment Duration) 94 reports the total time during which the receiver played out media 95 data which was manufactured locally, because the sender's data for 96 these periods was not available due to packet loss or discard. A 97 similar metric (Buffer Adjustment Concealment Duration) reports the 98 duration of playout of locally-manufactured data replacing data which 99 is unavailable due to adaptation of an adaptive de-jitter buffer. 100 Further metrics (Playout Interrupt Count and Mean Playout Interrupt 101 Size) report the number of times normal playout was interrupted, and 102 the mean duration of these interruptions. 104 Loss Concealment Duration and Buffer Adjustment Concealment Duration 105 are reported separately because buffer adjustment is typically 106 arranged to occur in silence periods so may have very little impact 107 on user experience, whilst loss concealment may occur at any time. 109 The metric belongs to the class of transport-related terminal metrics 110 defined in [MONARCH] (work in progress). 112 Instances of this Metrics Block refer by tag to the separate 113 auxiliary Measurement Identity block [MEASIDENT] which contains 114 information such as the SSRC of the measured stream, and RTP sequence 115 numbers and time intervals indicating the span of the report. 117 1.2. RTCP and RTCP XR Reports 119 The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] 120 defined an extensible structure for reporting using an RTCP Extended 121 Report (XR). This draft defines a new Extended Report block that 122 MUST be used as defined in [RFC3550] and [RFC3611]. 124 1.3. Performance Metrics Framework 126 The Performance Metrics Framework [PMOLFRAME] provides guidance on 127 the definition and specification of performance metrics. Metrics 128 described in this draft either reference external definitions or 129 define metrics generally in accordance with the guidelines in 130 [PMOLFRAME]. 132 1.4. Applicability 134 This metric is primarily applicable to audio applications of RTP. 135 EDITOR'S NOTE: are there metrics for concealment of transport errors 136 for video? 138 2. Loss Concealment Block 140 2.1. Report Block Structure 142 Loss Concealment metrics block 143 0 1 2 3 144 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 7 145 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 146 | BT=NLC |I| tag |plc|rsv| block length=4 | 147 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 148 | On-time Playout Duration | 149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 150 | Loss Concealment Duration | 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 152 | Buffer Adjustment Concealment Duration | 153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 154 | Playout Interrupt Count | Mean Playout Interrupt Size | 155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 157 Figure 1: Report Block Structure 159 2.2. Definition of Fields in Loss Concealment Report Block 161 block type (BT): 8 bits 163 A Loss Concealment Metrics Report Block is identified by the 164 constant NLC. 166 [Note to RFC Editor: please replace NLC with the IANA provided RTCP 167 XR block type for this block.] 169 Interval Metric flag (I): 1 bit 171 This field is used to indicate whether the Loss Concealment metric 172 block is an Interval or a Cumulative report, that is, whether the 173 reported values apply to the most recent measurement interval 174 duration between successive metrics reports (I=1) (the Interval 175 Duration) or to the accumulation period characteristic of 176 cumulative measurements (I=0) (the Cumulative Duration). 177 Numerical values for both these intervals are provided in the 178 Measurement Identifier block referenced by the tag field below. 180 Measurement Identifier association (tag): 3 bits 182 This field is used to identify the Measurement Identifier block 183 [MEASIDENT] which describes this measurement. The relevant 184 Measurement Identifier block has the same tag value as the Loss 185 Concealment Metrics block. Note that there may be more than one 186 Measurement Identifier block per RTCP packet. 188 Packet Loss Concealment Method (plc): 2 bits 190 This field is used to identify the packet loss concealment method 191 in use at the receiver, according to the following code: 193 bits 014-015 194 0 = silence insertion 195 1 = simple replay, no attenuation 196 2 = simple replay, with attenuation 197 3 = enhanced 199 Reserved (rsv): 2 bits 201 These bits are reserved. They SHOULD be set to zero by senders 202 and MUST be ignored by receivers. 204 block length: 16 bits 206 The length of this report block in 32-bit words, minus one. For 207 the Loss Concealment Metrics block, the block length is equal to 208 4. 210 On-time Playout Duration (ms): 32 bits 212 'On-time' playout is the uninterrupted, in-sequence playout of 213 valid decoded audio information originating from the remote 214 endpoint. This includes comfort noise during periods of remote 215 talker silence, if VAD is used, and locally generated or 216 regenerated tones and announcements. 218 An equivalent definition is that on-time playout is playout of any 219 signal other than those used for concealment. 221 On-time playout duration MUST include both speech and silence 222 intervals, whether VAD is used or not. This duration is reported 223 in millisecond units. 225 If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE 226 SHOULD be reported to indicate an over-range measurement. If the 227 measurement is unavailable, the value 0xFFFFFFFF SHOULD be 228 reported. 230 Loss Concealment Duration (ms): 32 bits 231 The duration, in milliseconds, of audio playout corresponding to 232 Loss-type concealment. 234 Loss-type concealment is reactive insertion or deletion of samples 235 in the audio playout stream due to effective frame loss at the 236 audio decoder. "Effective frame loss" is the event in which a 237 frame of coded audio is simply not present at the audio decoder 238 when required. In this case, substitute audio samples are 239 generally formed, at the decoder or elsewhere, to reduce audible 240 impairment. 242 If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE 243 SHOULD be reported to indicate an over-range measurement. If the 244 measurement is unavailable, the value 0xFFFFFFFF SHOULD be 245 reported. 247 Buffer Adjustment Concealment Duration (ms): 32 bits 249 The duration, in milliseconds, of audio playout corresponding to 250 Buffer Adjustment-type concealment, if known. 252 If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE 253 SHOULD be reported to indicate an over-range measurement. If the 254 measurement is unavailable, the value 0xFFFFFFFF SHOULD be 255 reported. 257 Buffer Adjustment-type concealment is proactive or controlled 258 insertion or deletion of samples in the audio playout stream due 259 to jitter buffer adaptation, re-sizing or re-centering decisions 260 within the endpoint. 262 Because this insertion is controlled, rather than occurring 263 randomly in response to losses, it is typically less audible than 264 loss-type concealment. For example, jitter buffer adaptation 265 events may be constrained to occur during periods of talker 266 silence, in which case only silence duration is affected, or 267 sophisticated time-stretching methods for insertion/deletion 268 during favorable periods in active speech may be employed. 270 Concealment events which cannot be classified as Buffer 271 Adjustment- type MUST be classified as Loss-type. 273 Playout Interrupt Count: 16 bits 275 The number of interruptions to normal playout which occurred 276 during the reporting period. 278 If the measured value exceeds 0xFFFD, the value 0xFFFE SHOULD be 279 reported to indicate an over-range measurement. If the 280 measurement is unavailable, the value 0xFFFF SHOULD be reported. 282 Mean Playout Interrupt Size (ms): 16 bits 284 The mean duration, in ms, of interruptions to normal playout which 285 occurred during the reporting period. 287 If the measured value exceeds 0xFFFD, the value 0xFFFE SHOULD be 288 reported to indicate an over-range measurement. If the 289 measurement is unavailable, the value 0xFFFF SHOULD be reported. 291 3. SDP Signaling 293 [RFC3611] defines the use of SDP (Session Description Protocol) 294 [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used 295 without prior signaling. 297 This section augments the SDP [RFC4566] attribute "rtcp-xr" defined 298 in [RFC3611] by providing an additional value of "xr-format" to 299 signal the use of the report block defined in this document. 301 rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF 303 (defined in [RFC3611]) 305 xr-format =/ xr-conceal-block 307 xr-conceal-block = "loss-conceal" 309 4. IANA Considerations 311 New block types for RTCP XR are subject to IANA registration. For 312 general guidelines on IANA considerations for RTCP XR, refer to 313 [RFC3611]. 315 4.1. New RTCP XR Block Type value 317 This document assigns the block type value NLC in the IANA "RTCP XR 318 Block Type Registry" to the "Loss Concealment Metrics Block". 320 [Note to RFC Editor: please replace NLC with the IANA provided RTCP 321 XR block type for this block.] 323 4.2. New RTCP XR SDP Parameter 325 This document also registers a new parameter "loss-conceal" in the 326 "RTCP XR SDP Parameters Registry". 328 4.3. Contact information for registrations 330 The contact information for the registrations is: 332 Geoff Hunt (geoff.hunt@bt.com) 334 Orion 2 PP3, Adastral Park, Martlesham Heath, Ipswich IP5 3RE, United 335 Kingdom 337 5. Security Considerations 339 It is believed that this proposed RTCP XR report block introduces no 340 new security considerations beyond those described in [RFC3611]. 341 This block does not provide per-packet statistics so the risk to 342 confidentiality documented in Section 7, paragraph 3 of [RFC3611] 343 does not apply. 345 6. Contributors 347 The authors gratefully acknowledge the comments and contributions 348 made by Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin 349 Connor, Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert 350 Higashi, Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith 351 Lantz, Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, 352 Ravi Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada. 354 7. Changes from previous version 356 Changed BNF for SDP following Christian Groves' and Tom Taylor's 357 comments (4th and 5th May 2009), now aligned with RFC 5234 section 358 3.3 "Incremental Alternatives". 360 Updated references 362 8. References 364 8.1. Normative References 366 [MEASIDENT] 367 Hunt, G., "RTCP XR Measurement Identifier Block", 368 ID draft-ietf-avt-rtcp-xr-meas-identity-02, May 2009. 370 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 371 Requirement Levels", RFC 2119, BCP 14, March 1997. 373 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 374 Applications", RFC 3550, July 2003. 376 [RFC3611] Friedman, T., "RTP Control Protocol Extended Reports (RTCP 377 XR)", RFC 3611, November 2003. 379 [RFC4566] Handley, M., "SDP: Session Description Protocol", 380 RFC 4566, July 2006. 382 8.2. Informative References 384 [MONARCH] Hunt, G., "Monitoring Architectures for RTP", 385 ID draft-hunt-avt-monarch-01, August 2008. 387 [PMOLFRAME] 388 Clark, A., "Framework for Performance Metric Development", 389 ID draft-ietf-pmol-metrics-framework-02, March 2009. 391 Authors' Addresses 393 Geoff Hunt 394 BT 395 Orion 2 PP3 396 Adastral Park 397 Martlesham Heath 398 Ipswich, Suffolk IP5 3RE 399 United Kingdom 401 Phone: +44 1473 651704 402 Email: geoff.hunt@bt.com 404 Alan Clark 405 Telchemy Incorporated 406 2905 Premiere Parkway, Suite 280 407 Duluth, GA 30097 408 USA 410 Email: alan.d.clark@telchemy.com