draft-ietf-avt-rtcp-xr-concsec-00.txt   draft-ietf-avt-rtcp-xr-concsec-01.txt 
Audio/Video Transport Working G. Hunt Audio/Video Transport Working G. Hunt
Group BT Group BT
Internet-Draft A. Clark Internet-Draft A. Clark
Intended status: Standards Track Telchemy Intended status: Standards Track Telchemy
Expires: April 28, 2009 October 25, 2008 Expires: August 29, 2009 February 25, 2009
RTCP XR Report Block for Concealed Seconds metric Reporting RTCP XR Report Block for Concealed Seconds metric Reporting
draft-ietf-avt-rtcp-xr-concsec-00.txt draft-ietf-avt-rtcp-xr-concsec-01.txt
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Abstract Abstract
This document defines an RTCP XR Report Block that allows the This document defines an RTCP XR Report Block that allows the
reporting of Concealed Seconds metrics primarily for audio reporting of Concealed Seconds metrics primarily for audio
applications of RTP. applications of RTP.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Concealed Seconds Block . . . . . . . . . . . . . . . . . 3 1.1. Concealed Seconds Block . . . . . . . . . . . . . . . . . 3
1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3
1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3
1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4
2. Concealed Seconds Metrics Block . . . . . . . . . . . . . . . 5 2. Concealed Seconds Metrics Block . . . . . . . . . . . . . . . 5
2.1. Report Block Structure . . . . . . . . . . . . . . . . . . 5 2.1. Report Block Structure . . . . . . . . . . . . . . . . . . 5
2.2. Definition of Fields in Concealed Seconds Metrics Block . 5 2.2. Definition of Fields in Concealed Seconds Metrics Block . 5
3. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 9 3. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 10
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 4.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 11
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.3. Contact information for registrations . . . . . . . . . . 11
7.1. Normative References . . . . . . . . . . . . . . . . . . . 13 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7.2. Informative References . . . . . . . . . . . . . . . . . . 13 6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 7. Changes from previous version . . . . . . . . . . . . . . . . 14
Intellectual Property and Copyright Statements . . . . . . . . . . 15 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.1. Normative References . . . . . . . . . . . . . . . . . . . 15
8.2. Informative References . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
1.1. Concealed Seconds Block 1.1. Concealed Seconds Block
This draft defines a new block type to augment those defined in This draft defines a new block type to augment those defined in
[RFC3611], for use primarily in audio applications of RTP. [RFC3611], for use primarily in audio applications of RTP.
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
mask the impact of network impairments or to reduce the audibility of mask the impact of network impairments such as lost packets or to
jitter buffer adaptations. reduce the audibility of jitter buffer adaptations.
The new block type provides metrics for concealment. Specifically, The new block type provides metrics for concealment. 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 (ms).
skipping to change at page 4, line 8 skipping to change at page 4, line 8
The Performance Metrics Framework [PMOLFRAME] provides guidance on The Performance Metrics Framework [PMOLFRAME] provides guidance on
the definition and specification of performance metrics. Metrics the definition and specification of performance metrics. Metrics
described in this draft either reference external definitions or described in this draft either reference external definitions or
define metrics generally in accordance with the guidelines in define metrics generally in accordance with the guidelines in
[PMOLFRAME]. [PMOLFRAME].
1.4. Applicability 1.4. Applicability
This metric is primarily applicable to audio applications of RTP. This metric is primarily applicable to audio applications of RTP.
EDITOR'S NOTE: are there metrics for concealment of transport errors The reason for this restriction is that, for many video codecs,
for video? packet data may contain occasional complete reference pictures, and
otherwise consists of data specifying picture changes relative to a
complete reference picture. Loss of an RTP video media packet could
degrade the user experience for a variable amount of time between the
time of loss and the next complete reference picture. In contrast,
in the audio case the degradation almost always persists for a
predictable period of time from the loss of the packet, which might
be simply the duration of the audio data encoded in the lost packet.
However if a useful Concealed Seconds metric can be defined for an
RTP video application, either in general or for a specific type of
video codec, the Concealed Seconds and Severely Concealed Seconds
metrics and the metric block type defined here MAY be used.
2. Concealed Seconds Metrics Block 2. Concealed Seconds Metrics Block
This sub-block provides a description of potentially audible This sub-block provides a description of potentially audible
impairments due to lost and discarded packets at the endpoint, impairments due to lost and discarded packets at the endpoint,
expressed on a time basis analogous to a traditional PSTN T1/E1 expressed on a time basis analogous to a traditional PSTN T1/E1
errored seconds metric. errored seconds metric.
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 local clock. This local clock does NOT need to be
skipping to change at page 7, line 25 skipping to change at page 7, line 25
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 1000ms
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 (defined in Section 3.6) has occurred. Buffer concealment has occurred. Buffer adjustment-type concealment
adjustment-type concealment SHALL not cause Concealed Seconds to SHALL not cause Concealed Seconds to be incremented, with the
be incremented, with the following exception. An implementation following exception. An implementation MAY cause Concealed
MAY cause Concealed Seconds to be incremented for 'emergency' Seconds to be incremented for 'emergency' buffer adjustments made
buffer adjustments made during talkspurts. during talkspurts.
Loss-type concealment is reactive insertion or deletion of samples
in the audio playout stream due to effective frame loss at the
audio decoder. "Effective frame loss" is the event in which a
frame of coded audio is simply not present at the audio decoder
when required. In this case, substitute audio samples are
generally formed, at the decoder or elsewhere, to reduce audible
impairment.
Buffer Adjustment-type concealment is proactive or controlled
insertion or deletion of samples in the audio playout stream due
to jitter buffer adaptation, re-sizing or re-centering decisions
within the endpoint.
Because this insertion is controlled, rather than occurring
randomly in response to losses, it is typically less audible than
loss-type concealment. For example, jitter buffer adaptation
events may be constrained to occur during periods of talker
silence, in which case only silence duration is affected, or
sophisticated time-stretching methods for insertion/deletion
during favorable periods in active speech may be employed. For
these reasons, buffer adjustment-type concealment MAY be exempted
from inclusion in calculations of Concealed Seconds and Severely
Concealed Seconds.
However, an implementation SHOULD include buffer-type concealment
in counts of Concealed Seconds and Severely Concealed Seconds if
the event occurs at an 'inopportune' moment, with an emergency or
large, immediate adaptation during active speech, or for
unsophisticated adaptation during speech without regard for the
underlying signal, in which cases the assumption of low-audibility
cannot hold. In other words, jitter buffer adaptation events
which may be presumed to be audible SHOULD be included in
Concealed Seconds and Severely Concealed Seconds counts.
Concealment events which cannot be classified as Buffer
Adjustment- type MUST be classified as Loss-type.
For clarification, the count of Concealed Seconds MUST include the For clarification, the count of Concealed Seconds MUST include the
count of Severely Concealed Seconds. count of Severely Concealed Seconds.
If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE
SHOULD be reported to indicate an over-range measurement. If the SHOULD be reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFFFFFF SHOULD be measurement is unavailable, the value 0xFFFFFFFF SHOULD be
reported. The duration, in milliseconds, of audio playout reported.
corresponding to Loss-type concealment.
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 1000 ms 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.
skipping to change at page 9, line 27 skipping to change at page 10, line 27
this parameter is present, the RTP system receiving the SDP SHOULD this parameter is present, the RTP system receiving the SDP SHOULD
use this value for the current session. If the parameter is not use this value for the current session. If the parameter is not
present, the RTP system SHOULD use a locally configured value. present, the RTP system SHOULD use a locally configured value.
rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF
(defined in [RFC3611]) (defined in [RFC3611])
xr-format = xr-format / xr-conc-sec-block xr-format = xr-format / xr-conc-sec-block
xr-conc-sec-block = "xr-concsec" ["=" thresh] xr-conc-sec-block = "conc-sec" ["=" thresh]
thresh = 1*DIGIT ; threshold for SCS (ms) thresh = 1*DIGIT ; threshold for SCS (ms)
DIGIT = %x30-39 DIGIT = %x30-39
4. IANA Considerations 4. IANA Considerations
This document creates a new block type within the IANA "RTCP XR Block New block types for RTCP XR are subject to IANA registration. For
Type Registry" called the Concealed Seconds Metrics Block, and a new general guidelines on IANA considerations for RTCP XR, refer to
parameter xr-concsec within the "RTCP XR SDP Parameters Registry". [RFC3611].
4.1. New RTCP XR Block Type value
This document assigns the block type value NCS in the IANA "RTCP XR
Block Type Registry" to the "Concealed Seconds Metrics Block".
[Note to RFC Editor: please replace NCS with the IANA provided RTCP
XR block type for this block.]
4.2. New RTCP XR SDP Parameter
This document also registers a new parameter "conc-sec" in the "RTCP
XR SDP Parameters Registry".
4.3. Contact information for registrations
The contact information for the registrations is:
Geoff Hunt (geoff.hunt@bt.com)
Orion 2 PP3, Adastral Park, Martlesham Heath, Ipswich IP5 3RE, United
Kingdom
5. Security Considerations 5. Security Considerations
It is believed that this proposed RTCP XR report block introduces no It is believed that this proposed RTCP XR report block introduces no
new security considerations beyond those described in [RFC3611]. new security considerations beyond those described in [RFC3611].
This block does not provide per-packet statistics so the risk to This block does not provide per-packet statistics so the risk to
confidentiality documented in Section 7, paragraph 3 of [RFC3611] confidentiality documented in Section 7, paragraph 3 of [RFC3611]
does not apply. does not apply.
6. Contributors 6. Contributors
The authors gratefully acknowledge the comments and contributions The authors gratefully acknowledge the comments and contributions
made by Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin made by Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin
Connor, Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert Connor, Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert
Higashi, Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith Higashi, Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith
Lantz, Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, Lantz, Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho,
Ravi Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada. Ravi Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada.
7. References 7. Changes from previous version
7.1. Normative References Intro: Added "such as lost packets" as example to clarify concealment
in Intro, and text in Section 2.2, to meet Roni Even's request for a
definition of concealment (post 5-Dec-2008)
Intro, Applicability: Removed editor's note about metrics for
concealment in video. Added text based on Roni Even's and Randall
Jessup's posts of 5-Dec-2008 and 19-Dec-2008, explaining difficulty
of applying Concealed Seconds to video but stating that metric MAY be
used for video if a useful Concealed Seconds metric may be defined.
Extended and clarified IANA considerations section.
Changed SDP tag for block to "conc-sec".
8. References
8.1. Normative References
[MEASIDENT] [MEASIDENT]
Hunt, G., "RTCP XR Measurement Identifier Block", Hunt, G., "RTCP XR Measurement Identifier Block",
ID draft-ietf-avt-rtcp-xr-measid-00, August 2008. ID draft-ietf-avt-rtcp-xr-measid-01, February 2009.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP 14, March 1997. Requirement Levels", RFC 2119, BCP 14, March 1997.
[RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time
Applications", RFC 3550, July 2003. Applications", RFC 3550, July 2003.
[RFC3611] Friedman, T., "RTP Control Protocol Extended Reports (RTCP [RFC3611] Friedman, T., "RTP Control Protocol Extended Reports (RTCP
XR)", RFC 3611, November 2003. XR)", RFC 3611, November 2003.
[RFC4566] Handley, M., "SDP: Session Description Protocol", [RFC4566] Handley, M., "SDP: Session Description Protocol",
RFC 4566, July 2006. RFC 4566, July 2006.
7.2. Informative References 8.2. Informative References
[MONARCH] Hunt, G., "Monitoring Architectures for RTP", [MONARCH] Hunt, G., "Monitoring Architectures for RTP",
ID draft-hunt-avt-monarch-01, August 2008. ID draft-hunt-avt-monarch-01, August 2008.
[PMOLFRAME] [PMOLFRAME]
Clark, A., "Framework for Performance Metric Development", Clark, A., "Framework for Performance Metric Development",
ID draft-ietf-pmol-metrics-framework-00, July 2008. ID draft-ietf-pmol-metrics-framework-00, July 2008.
Authors' Addresses Authors' Addresses
Geoff Hunt Geoff Hunt
BT BT
Orion 1 PP9 Orion 2 PP3
Adastral Park Adastral Park
Martlesham Heath Martlesham Heath
Ipswich, Suffolk IP4 2TH Ipswich, Suffolk IP5 3RE
United Kingdom United Kingdom
Phone: +44 1473 608325 Phone: +44 1473 651704
Email: geoff.hunt@bt.com Email: geoff.hunt@bt.com
Alan Clark Alan Clark
Telchemy Incorporated Telchemy Incorporated
2905 Premiere Parkway, Suite 280 2905 Premiere Parkway, Suite 280
Duluth, GA 30097 Duluth, GA 30097
USA USA
Email: alan.d.clark@telchemy.com Email: alan.d.clark@telchemy.com
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