draft-ietf-xrblock-rtcp-xr-loss-conceal-06.txt   draft-ietf-xrblock-rtcp-xr-loss-conceal-07.txt 
Audio/Video Transport Working Group A. Clark Audio/Video Transport Working Group A. Clark
Internet-Draft Telchemy Internet-Draft Telchemy
Intended status: Standards Track G. Zorn, Ed. Intended status: Standards Track G. Zorn, Ed.
Expires: December 20, 2013 Network Zen Expires: January 9, 2014 Network Zen
C. Bi C. Bi
STTRI STTRI
Q. Wu, Ed. Q. Wu, Ed.
Huawei Huawei
June 18, 2013 July 8, 2013
RTCP XR Report Block for Concealment metrics Reporting on Audio RTCP XR Report Block for Concealment metrics Reporting on Audio
Applications Applications
draft-ietf-xrblock-rtcp-xr-loss-conceal-06.txt draft-ietf-xrblock-rtcp-xr-loss-conceal-07.txt
Abstract Abstract
This document defines two RTCP XR Report Blocks that allows the This document defines two RTCP XR Report Blocks that allows the
reporting of concealment metrics for audio applications of RTP. reporting of concealment metrics for audio applications of RTP.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 20, 2013. This Internet-Draft will expire on January 9, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Loss Concealment and Concealment Seconds Metrics 1.1. Loss Concealment and Concealment Seconds Metrics
Reporting Block . . . . . . . . . . . . . . . . . . . . . 3 Reporting Block . . . . . . . . . . . . . . . . . . . . . 3
1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 4 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 4
1.3. Performance Metrics Framework . . . . . . . . . . . . . . 4 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 4
1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 5 2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 5
2.2. Notations . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Loss Concealment Block . . . . . . . . . . . . . . . . . . . . 6 3. Loss Concealment Block . . . . . . . . . . . . . . . . . . . . 6
3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 6 3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 6
3.2. Definition of Fields in Loss Concealment Metrics Block . . 6 3.2. Definition of Fields in Loss Concealment Metrics Block . . 6
4. Concealment Seconds Block . . . . . . . . . . . . . . . . . . 10 4. Concealment Seconds Block . . . . . . . . . . . . . . . . . . 11
4.1. Report Block Structure . . . . . . . . . . . . . . . . . . 10 4.1. Report Block Structure . . . . . . . . . . . . . . . . . . 11
4.2. Definition of Fields in Concealed Seconds Metrics Block . 11 4.2. Definition of Fields in Concealed Seconds Metrics Block . 12
5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 15 5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 16
5.1. SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . 15 5.1. SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . 16
5.2. Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . 15 5.2. Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . 16
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
6.1. New RTCP XR Block Type values . . . . . . . . . . . . . . 16 6.1. New RTCP XR Block Type values . . . . . . . . . . . . . . 17
6.2. New RTCP XR SDP Parameters . . . . . . . . . . . . . . . . 16 6.2. New RTCP XR SDP Parameters . . . . . . . . . . . . . . . . 17
6.3. Contact information for registrations . . . . . . . . . . 16 6.3. Contact information for registrations . . . . . . . . . . 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 17 7. Security Considerations . . . . . . . . . . . . . . . . . . . 18
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 18 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 19
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
10.1. Normative References . . . . . . . . . . . . . . . . . . . 20 10.1. Normative References . . . . . . . . . . . . . . . . . . . 21
10.2. Informative References . . . . . . . . . . . . . . . . . . 20 10.2. Informative References . . . . . . . . . . . . . . . . . . 21
Appendix A. Metrics represented using RFC6390 Template . . . . . 21 Appendix A. Metrics represented using RFC6390 Template . . . . . 22
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 28 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 29
B.1. draft-ietf-xrblock-rtcp-xr-loss-conceal-06 . . . . . . . . 28 B.1. draft-ietf-xrblock-rtcp-xr-loss-conceal-07 . . . . . . . . 29
B.2. draft-ietf-xrblock-rtcp-xr-loss-conceal-05 . . . . . . . . 28 B.2. draft-ietf-xrblock-rtcp-xr-loss-conceal-06 . . . . . . . . 29
B.3. draft-ietf-xrblock-rtcp-xr-loss-conceal-04 . . . . . . . . 28 B.3. draft-ietf-xrblock-rtcp-xr-loss-conceal-05 . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29 B.4. draft-ietf-xrblock-rtcp-xr-loss-conceal-04 . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30
1. Introduction 1. Introduction
1.1. Loss Concealment and Concealment Seconds Metrics Reporting Block 1.1. Loss Concealment and Concealment Seconds Metrics Reporting Block
At any instant, the audio output at a receiver may be classified as At any instant, the audio output at a receiver may be classified as
either 'normal' or 'concealed'. 'Normal' refers to playout of audio either 'normal' or 'concealed'. 'Normal' refers to playout of audio
payload received from the remote end, and also includes locally payload received from the remote end, and also includes locally
generated signals such as announcements, tones and comfort noise. generated signals such as announcements, tones and comfort noise.
Concealment refers to playout of locally-generated signals used to Concealment refers to playout of locally-generated signals used to
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The second block type provides metrics for concealment seconds, which The second block type provides metrics for concealment seconds, which
are measured at the receiving end of the RTP stream. Specifically, are measured at the receiving end of the RTP stream. Specifically,
the first metric (Unimpaired Seconds) reports the number of whole the first metric (Unimpaired Seconds) reports the number of whole
seconds occupied only with normal playout of data which the receiver seconds occupied only with normal playout of data which the receiver
obtained from the sender's stream. The second metric (Concealed obtained from the sender's stream. The second metric (Concealed
Seconds) reports the number of whole seconds during which the Seconds) reports the number of whole seconds during which the
receiver played out any locally-generated media data. A third metric receiver played out any locally-generated media data. A third metric
(Severely Concealed Seconds) reports the number of whole seconds (Severely Concealed Seconds) reports the number of whole seconds
during which the receiver played out locally-generated data for more during which the receiver played out locally-generated data for more
than SCS Threshold (ms). than SCS Threshold.
These metrics belongs to the class of transport-related terminal These metrics belongs to the class of transport-related terminal
metrics defined in [RFC6792]. metrics defined in [RFC6792].
1.2. RTCP and RTCP XR Reports 1.2. RTCP and RTCP XR Reports
The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] The use of RTCP for reporting is defined in [RFC3550]. [RFC3611]
defined an extensible structure for reporting using an RTCP Extended defined an extensible structure for reporting using an RTCP Extended
Report (XR). This draft defines a new Extended Report block that Report (XR). This draft defines a new Extended Report block that
MUST be used as defined in [RFC3550] and [RFC3611]. MUST be used as defined in [RFC3550] and [RFC3611].
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quality. quality.
2. Terminology 2. Terminology
2.1. Standards Language 2.1. Standards Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119]. document are to be interpreted as described in RFC2119 [RFC2119].
2.2. Notations
This report block makes use of binary fractions. The terminology
used is
Numeric formats S X:Y
where S indicates a two's complement signed representation, X
the number of bits prior to the decimal place and Y the number
of bits after the decimal place.
Hence 8:8 represents an unsigned number in the range 0.0 to
255.996 with a granularity of 0.0039. S7:8 would represent the
range -127.996 to +127.996. 0:16 represents a proper binary
fraction with range
0.0 to 1 - 1/65536 = 0.9999847
though note that use of flag values at the top of the numeric
range slightly reduces this upper limit. For example, if the
16- bit values 0xfffe and 0xffff are used as flags for "over-
range" and "unavailable" conditions, a 0:16 quantity has range
0.0 to 1 - 3/65536 = 0.9999542
3. Loss Concealment Block 3. Loss Concealment Block
The metrics block described here are intended to be used as described The metrics block described here are intended to be used as described
in this section, in conjunction with information from the Measurement in this section, in conjunction with information from the Measurement
Information block [RFC6776]. Instances of this Metrics Block refer Information block [RFC6776]. Instances of this Metrics Block refer
by Synchronization source (SSRC) to the separate auxiliary by Synchronization source (SSRC) to the separate auxiliary
Measurement Information block [RFC6776] which describes measurement Measurement Information block [RFC6776] which describes measurement
periods in use (see [RFC6776] section 4.2). This Metrics Block periods in use (see [RFC6776] section 4.2). This Metrics Block
relies on the measurement period in the Measurement Information block relies on the measurement period in the Measurement Information block
indicating the span of the report and SHOULD be sent in the same indicating the span of the report and SHOULD be sent in the same
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| BT=NLC | I |plc| rsv. | block length=5 | | BT=NLC | I |plc| rsv. | block length=5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of Source | | SSRC of Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| On-time Playout Duration | | On-time Playout Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Loss Concealment Duration | | Loss Concealment Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Buffer Adjustment Concealment Duration | | Buffer Adjustment Concealment Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Playout Interrupt Count | Mean Playout Interrupt Size | | Playout Interrupt Count | Reserved. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mean Playout Interrupt Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Report Block Structure Figure 1: Report Block Structure
3.2. Definition of Fields in Loss Concealment Metrics Block 3.2. Definition of Fields in Loss Concealment Metrics Block
Block type (BT): 8 bits Block type (BT): 8 bits
A Loss Concealment Metrics Report Block is identified by the A Loss Concealment Metrics Report Block is identified by the
constant NLC. constant NLC.
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I=10: Interval Duration - the reported value applies to the I=10: Interval Duration - the reported value applies to the
most recent measurement interval duration between successive most recent measurement interval duration between successive
metrics reports. metrics reports.
I=11: Cumulative Duration - the reported value applies to the I=11: Cumulative Duration - the reported value applies to the
accumulation period characteristic of cumulative measurements. accumulation period characteristic of cumulative measurements.
I=01: Sampled Value - the reported value is a sampled I=01: Sampled Value - the reported value is a sampled
instantaneous value. instantaneous value.
In this document, Loss Concealment Metrics can only be measured
over definite intervals, and cannot be sampled. Also, the value
I=00 is reserved for future use. Senders MUST NOT use the values
I=00 or I=01. If a block is received with I=00 or I=01, the
receiver MUST discard the block.
Packet Loss Concealment Method (plc): 2 bits Packet Loss Concealment Method (plc): 2 bits
This field is used to identify the packet loss concealment method This field is used to identify the packet loss concealment method
in use at the receiver, according to the following code: in use at the receiver, according to the following code:
bits 014-015 bits 014-015
0 = silence insertion 0 = silence insertion
1 = simple replay, no attenuation 1 = simple replay, no attenuation
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block length: 16 bits block length: 16 bits
The length of this report block in 32-bit words, minus one. For The length of this report block in 32-bit words, minus one. For
the Loss Concealment Block, the block length is equal to 5. the Loss Concealment Block, the block length is equal to 5.
SSRC of source: 32 bits SSRC of source: 32 bits
As defined in Section 4.1 of [RFC3611]. As defined in Section 4.1 of [RFC3611].
On-time Playout Duration (ms): 32 bits On-time Playout Duration: 32 bits
'On-time' playout is the uninterrupted, in-sequence playout of 'On-time' playout is the uninterrupted, in-sequence playout of
valid decoded audio information originating from the remote valid decoded audio information originating from the remote
endpoint. This includes comfort noise during periods of remote endpoint. This includes comfort noise during periods of remote
talker silence, if VAD [VAD] is used, and locally generated or talker silence, if VAD [VAD] is used, and locally generated or
regenerated tones and announcements. regenerated tones and announcements.
An equivalent definition is that on-time playout is playout of any An equivalent definition is that on-time playout is playout of any
signal other than those used for concealment. signal other than those used for concealment.
On-time playout duration MUST include both speech and silence On-time playout duration is expressed in units of 1/65536 seconds
intervals, whether VAD is used or not. This duration is reported and MUST include both speech and silence intervals, whether VAD is
in millisecond units. used or not.
If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE
MUST be reported to indicate an over-range measurement. If the MUST be reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFFFFFF MUST be reported. measurement is unavailable, the value 0xFFFFFFFF MUST be reported.
Loss Concealment Duration (ms): 32 bits Loss Concealment Duration: 32 bits
The duration, in milliseconds, of audio playout corresponding to The duration, expressed in units of 1/65536 seconds, of audio
Loss-type concealment. playout corresponding to Loss-type concealment.
Loss-type concealment is reactive insertion or deletion of samples Loss-type concealment is reactive insertion or deletion of samples
in the audio playout stream due to effective frame loss at the in the audio playout stream due to effective frame loss at the
audio decoder. "Effective frame loss" is the event in which a audio decoder. "Effective frame loss" is the event in which a
frame of coded audio is simply not present at the audio decoder frame of coded audio is simply not present at the audio decoder
when required. In this case, substitute audio samples are when required. In this case, substitute audio samples are
generally formed, at the decoder or elsewhere, to reduce audible generally formed, at the decoder or elsewhere, to reduce audible
impairment. impairment.
If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE
MUST be reported to indicate an over-range measurement. If the MUST be reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFFFFFF MUST be reported. measurement is unavailable, the value 0xFFFFFFFF MUST be reported.
Buffer Adjustment Concealment Duration (ms): 32 bits Buffer Adjustment Concealment Duration: 32 bits
The duration, in milliseconds, of audio playout corresponding to The duration, expressed in units of 1/65536 seconds, of audio
Buffer Adjustment-type concealment, if known. playout corresponding to Buffer Adjustment-type concealment, if
known.
If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE
MUST be reported to indicate an over-range measurement. If the MUST be reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFFFFFF MUST be reported. measurement is unavailable, the value 0xFFFFFFFF MUST be reported.
Buffer Adjustment-type concealment is proactive or controlled Buffer Adjustment-type concealment is proactive or controlled
insertion or deletion of samples in the audio playout stream due insertion or deletion of samples in the audio playout stream due
to jitter buffer adaptation, re-sizing or re-centering decisions to jitter buffer adaptation, re-sizing or re-centering decisions
within the endpoint. within the endpoint.
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Playout Interrupt Count: 16 bits Playout Interrupt Count: 16 bits
The number of interruptions to normal playout which occurred The number of interruptions to normal playout which occurred
during the reporting period. during the reporting period.
If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be
reported to indicate an over-range measurement. If the reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFF MUST be reported. measurement is unavailable, the value 0xFFFF MUST be reported.
Mean Playout Interrupt Size (ms): 16 bits Reserved (resv): 16 bits
The mean duration, in ms, of interruptions to normal playout which These bits are reserved. They MUST be set to zero by senders and
occurred during the reporting period. ignored by receivers (See [RFC6709] section 4.2).
Mean Playout Interrupt Size: 32 bits
The mean duration, expressed in units of 1/65536 seconds, of
interruptions to normal playout which occurred during the
reporting period.
If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be
reported to indicate an over-range measurement. If the reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFF MUST be reported. measurement is unavailable, the value 0xFFFF MUST be reported.
4. Concealment Seconds Block 4. Concealment Seconds Block
This sub-block described here is intended to be used as described in This sub-block described here is intended to be used as described in
this section, in conjunction with information from the Measurement this section, in conjunction with information from the Measurement
Information block [RFC6776] and provides a description of potentially Information block [RFC6776] and provides a description of potentially
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by Synchronization source (SSRC) to the separate auxiliary by Synchronization source (SSRC) to the separate auxiliary
Measurement Information block [RFC6776] which describes measurement Measurement Information block [RFC6776] which describes measurement
periods in use (see [RFC6776] section 4.2). This Metrics Block periods in use (see [RFC6776] section 4.2). This Metrics Block
relies on the measurement period in the Measurement Information block relies on the measurement period in the Measurement Information block
indicating the span of the report and SHOULD be sent in the same indicating the span of the report and SHOULD be sent in the same
compound RTCP packet as the measurement information block. If the compound RTCP packet as the measurement information block. If the
measurement period is not received in the same compound RTCP packet measurement period is not received in the same compound RTCP packet
as this Metrics Block, this metrics block MUST be discarded. as this Metrics Block, this metrics block MUST be discarded.
The following metrics are based on successive one second intervals as The following metrics are based on successive one second intervals as
declared by a local clock. This local clock does NOT need to be declared by a RTP clock. This RTP clock does NOT need to be
synchronized to any external time reference. The starting time of synchronized to any external time reference. The starting time of
this clock is unspecified. Note that this implies that the same loss this clock is unspecified. Note that this implies that the same loss
pattern could result in slightly different count values, depending on pattern could result in slightly different count values, depending on
where the losses occur relative to the particular one-second where the losses occur relative to the particular one-second
demarcation points. For example, two loss events occurring 50ms demarcation points. For example, two loss events occurring 50ms
apart could result in either one concealed second or two, depending apart could result in either one concealed second or two, depending
on the particular 1000 ms boundaries used. on the particular one second boundaries used.
The seconds in this sub-block are not necessarily calendar seconds. The seconds in this sub-block are not necessarily calendar seconds.
At the tail end of a session, periods of time of less than 1000ms At the tail end of a session, periods of time of less than one second
shall be incorporated into these counts if they exceed 500ms and shall be incorporated into these counts if they exceed 500ms and
shall be disregarded if they are less than 500ms. shall be disregarded if they are less than 500ms.
4.1. Report Block Structure 4.1. Report Block Structure
Concealed Seconds Metrics Block Concealed Seconds Metrics Block
0 1 2 3 0 1 2 3
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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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I=10: Interval Duration - the reported value applies to the I=10: Interval Duration - the reported value applies to the
most recent measurement interval duration between successive most recent measurement interval duration between successive
metrics reports. metrics reports.
I=11: Cumulative Duration - the reported value applies to the I=11: Cumulative Duration - the reported value applies to the
accumulation period characteristic of cumulative measurements. accumulation period characteristic of cumulative measurements.
I=01: Sampled Value - the reported value is a sampled I=01: Sampled Value - the reported value is a sampled
instantaneous value. instantaneous value.
In this document, Concealment Seconds Metrics can only be measured
over definite intervals, and cannot be sampled. Also, the value
I=00 is reserved for future use. Senders MUST NOT use the values
I=00 or I=01. If a block is received with I=00 or I=01, the
receiver MUST discard the block.
Packet Loss Concealment Method (plc): 2 bits Packet Loss Concealment Method (plc): 2 bits
This field is used to identify the packet loss concealment method This field is used to identify the packet loss concealment method
in use at the receiver, according to the following code: in use at the receiver, according to the following code:
bits 014-015 bits 014-015
0 = silence insertion 0 = silence insertion
1 = simple replay, no attenuation 1 = simple replay, no attenuation
2 = simple replay, with attenuation 2 = simple replay, with attenuation
3 = enhancement 3 = enhancement
Other values reserved Other values reserved
Note that the enhancement method (plc =3) for packet loss Note that the enhancement method (plc =3) for packet loss
concealment offers an improved audio quality and or a better concealment offers an improved audio quality and or a better
robustness against packet losses [G.711] and is equivalent to robustness against packet losses [G.711] and is equivalent to
enhanced in section 4.7.1 of [RFC3611], enhanced in section 4.7.1 of [RFC3611],
Reserved (resv): 4 bits Reserved (resv): 4 bits
These bits are reserved. They MUST be set to zero by senders and These bits are reserved. They MUST be set to zero by senders and
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the Concealment Seconds Block, the block length is equal to 4. the Concealment Seconds Block, the block length is equal to 4.
SSRC of source: 32 bits SSRC of source: 32 bits
As defined in Section 4.1 of [RFC3611]. As defined in Section 4.1 of [RFC3611].
Unimpaired Seconds: 32 bits Unimpaired Seconds: 32 bits
A count of the number of unimpaired Seconds that have occurred. A count of the number of unimpaired Seconds that have occurred.
An unimpaired Second is defined as a continuous period of 1000ms An unimpaired Second is defined as a continuous period of one
during which no frame loss or discard due to late arrival has second during which no frame loss or discard due to late arrival
occurred. Every second in a session must be classified as either has occurred. Every second in a session must be classified as
OK or Concealed. either OK or Concealed.
Normal playout of comfort noise or other silence concealment Normal playout of comfort noise or other silence concealment
signal during periods of talker silence, if VAD is used, shall be signal during periods of talker silence, if VAD is used, shall be
counted as unimpaired seconds. counted as unimpaired seconds.
If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE
MUST be reported to indicate an over-range measurement. If the MUST be reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFFFFFF MUST be reported. measurement is unavailable, the value 0xFFFFFFFF MUST be reported.
Concealed Seconds: 32 bits Concealed Seconds: 32 bits
A count of the number of Concealed Seconds that have occurred. A count of the number of Concealed Seconds that have occurred.
A Concealed Second is defined as a continuous period of 1000ms A Concealed Second is defined as a continuous period of one second
during which any frame loss or discard due to late arrival has during which any frame loss or discard due to late arrival has
occurred. occurred.
Equivalently, a concealed second is one in which some Loss-type Equivalently, a concealed second is one in which some Loss-type
concealment has occurred. Buffer adjustment-type concealment concealment has occurred. Buffer adjustment-type concealment
SHALL not cause Concealed Seconds to be incremented, with the SHALL not cause Concealed Seconds to be incremented, with the
following exception. An implementation MAY cause Concealed following exception. An implementation MAY cause Concealed
Seconds to be incremented for 'emergency' buffer adjustments made Seconds to be incremented for 'emergency' buffer adjustments made
during talkspurts. during talkspurts.
skipping to change at page 14, line 20 skipping to change at page 15, line 25
If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE
MUST be reported to indicate an over-range measurement. If the MUST be reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFFFFFF MUST be reported. measurement is unavailable, the value 0xFFFFFFFF MUST be reported.
Severely Concealed Seconds: 16 bits Severely Concealed Seconds: 16 bits
A count of the number of Severely Concealed Seconds. A count of the number of Severely Concealed Seconds.
A Severely Concealed Second is defined as a non-overlapping period A Severely Concealed Second is defined as a non-overlapping period
of 1000 ms during which the cumulative amount of time that has of one second during which the cumulative amount of time that has
been subject to frame loss or discard due to late arrival, exceeds been subject to frame loss or discard due to late arrival, exceeds
the SCS Threshold. the SCS Threshold.
If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be
reported to indicate an over-range measurement. If the reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFF MUST be reported. measurement is unavailable, the value 0xFFFF MUST be reported.
Reserved: 8 bits Reserved: 8 bits
These bits are reserved. They MUST be set to zero by senders and These bits are reserved. They MUST be set to zero by senders and
ignored by receivers (See [RFC6709] section 4.2). ignored by receivers (See [RFC6709] section 4.2).
SCS Threshold: 8 bits SCS Threshold: 8 bits
The SCS Threshold defines the amount of time corresponding to lost The SCS Threshold is defined as the percentage of packets
or discarded frames that must occur within a one second period in corresponding to lost or discarded frames that must occur within a
order for the second to be classified as a Severely Concealed one second period in order for the second to be classified as a
Second. This is expressed in milliseconds and hence can represent Severely Concealed Second. This is expressed in numeric format
a range of 0.1 to 25.5 percent loss or discard. 0:8 and hence can represent a range of 0.1 to 25.5 percent loss or
discard.
A default threshold of 50ms (5% effective frame loss per second) A default threshold of 5% effective frame loss (50ms effective
is suggested. frame loss ) per second is suggested.
5. SDP Signaling 5. SDP Signaling
[RFC3611] defines the use of SDP (Session Description Protocol) [RFC3611] defines the use of SDP (Session Description Protocol)
[RFC4566] for signaling the use of XR blocks. XR blocks MAY be used [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used
without prior signaling. without prior signaling.
5.1. SDP rtcp-xr-attrib Attribute Extension 5.1. SDP rtcp-xr-attrib Attribute Extension
This section augments the SDP attribute "rtcp-xr" [RFC3611] by This section augments the SDP attribute "rtcp-xr" [RFC3611] by
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* Use and applications: See section 1.4 [RFCXXXX]. * Use and applications: See section 1.4 [RFCXXXX].
* Reporting model: See RFC3611. * Reporting model: See RFC3611.
Appendix B. Change Log Appendix B. Change Log
Note to the RFC-Editor: please remove this section prior to Note to the RFC-Editor: please remove this section prior to
publication as an RFC. publication as an RFC.
B.1. draft-ietf-xrblock-rtcp-xr-loss-conceal-06 B.1. draft-ietf-xrblock-rtcp-xr-loss-conceal-07
The following are the major changes to previous version :
o Change units for threshold and units used for reporting in loss
concealment block and concealment seconds block.
o Change 16bit "Mean Playout Interrupt Size" into 32bits.
B.2. draft-ietf-xrblock-rtcp-xr-loss-conceal-06
The following are the major changes to previous version : The following are the major changes to previous version :
o Comments in the WGLC are addressed in this version. o Comments in the WGLC are addressed in this version.
B.2. draft-ietf-xrblock-rtcp-xr-loss-conceal-05 B.3. draft-ietf-xrblock-rtcp-xr-loss-conceal-05
The following are the major changes to previous version : The following are the major changes to previous version :
o Add text to clarify the definition of enhanced method. o Add text to clarify the definition of enhanced method.
o Add appendix to apply RFC6390 template to the metrics. o Add appendix to apply RFC6390 template to the metrics.
B.3. draft-ietf-xrblock-rtcp-xr-loss-conceal-04 B.4. draft-ietf-xrblock-rtcp-xr-loss-conceal-04
The following are the major changes to previous version : The following are the major changes to previous version :
o Merge Concealment Seconds draft into this draft (i.e.,Loss o Merge Concealment Seconds draft into this draft (i.e.,Loss
Concealment draft). Concealment draft).
o Updated references. o Updated references.
Authors' Addresses Authors' Addresses
 End of changes. 32 change blocks. 
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