Network Working Group Q. Wu
Internet-Draft Huawei
Intended status: Standards Track G. Zorn
Expires: May 1, 2012 Network Zen
R. Schott
Deutsche Telekom Laboratories
K. Lee
China Telecom
October 29, 2011
RTCP XR Blocks for multimedia quality metric reporting
draft-wu-xrblock-rtcp-xr-quality-monitoring-04
Abstract
This document defines an RTCP XR Report Block and associated SDP
parameters that allow the reporting of multimedia quality metrics for
use in a range of RTP applications.
Status of this Memo
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This Internet-Draft will expire on May 1, 2012.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 3
3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Synthetical Multimedia Quality Metrics Block . . . . . . . . . 4
4.1. Metric Block Structure . . . . . . . . . . . . . . . . . . 5
4.2. Definition of Fields in Multimedia Quality Metrics
Block . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . . 9
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 9
A.1. draft-wu-xrblock-rtcp-xr-quality-monitoring-03 . . . . . . 9
A.2. draft-wu-xrblock-rtcp-xr-quality-monitoring-04 . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
This draft defines a new block type to augment those defined in
[RFC3611], for use in a range of RTP applications.
The new block type provides information on multimedia quality using
one of several standard metrics.
The metrics belong to the class of application level metrics defined
in [MONARCH] (work in progress).
2. Terminology
2.1. Standards Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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. Applicability
The Multimedia Quality Metrics Report Block can be used in any real-
time AV application.
The factors that affect real-time AV application quality can be split
into two categories. The first category consists of transport-
dependent factors such as packet loss, delay and jitter (which also
translates into losses in the playback buffer). The factors in the
second category are application-specific factors that affect real
time application (e.g., video) quality and are sensitivity to network
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errors. These factors can be but not limited to video codec and loss
recovery technique, coding bit rate, packetization scheme, and
content characteristics.
Compared with application-specific factors, the transport-dependent
factors sometimes are not sufficient to measure real time data
quality, since the ability to analyze the real time data in the
application layer provides quantifiable measurements for subscriber
Quality of Experience (QoE) that may not be captured in the
transmission layers or from the RTP layer down. In a typical
scenario, monitoring of the transmission layers can produce
statistics suggesting that quality is not an issue, such as the fact
that network jitter is not excessive. However, problems may occur in
the service layers leading to poor subscriber QoE. Therefore
monitoring using only network-level measurements may be insufficient
when application layer content quality is required.
In order to provide accurate measures of real time application
quality when transporting real time contents across a network, the
synthentical multimedia quality Metrics is highly required which can
be conveyed in the RTCP XR packets[RFC3611] and may have the
following three benefits:
o Tuning the content encoder algorithm to satisfy real time data
quality requirements
o Determining which system techniques to use in a given situation
and when to switch from one technique to another as system
parameters change
o Verifying the continued correct operation of an existing system
4. Synthetical Multimedia Quality Metrics Block
This block reports the multimedia application performance or quality
beyond the information carried in the standard RTCP packet format.
Information is recorded about multimedia application QoE metric which
provides a measure that is indicative of the user's view of a
service. Multimedia application QoE metric is commonly expressed as
a MOS ("Mean Opinion Score"), MOS is on a scale from 1 to 5, in which
5 represents excellent and 1 represents unacceptable. MOS scores are
usually obtained using subjective testing or using objective
algorithm. However Subjective testing to estimate the multimedia
quality may be not suitable for measuring the multimedia quality
since the results may vary from test to test. Therefore using
objective algorithm to calculate MOS scores is recommended. ITU-T
recommendations define the methodologies for assessment of the
performance of multimedia stream
[G.107][P.564][G.1082][P.NAMS][P.NBAMS] and provides a method to
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evaluate QoE estimation algorithms and objective model for video and
audio. Hence this document recommends vendors and implementers to
use these International Telecommunication Union (ITU)-specified
methodologies to measure parameters when possible.
4.1. Metric Block Structure
The report block contents are dependent upon a series of flag bits
carried in the first part of the header. Not all parameters need to
be reported in each block. Flags indicate which are and which are
not reported. The fields corresponding to unreported parameters MUST
be present, but are set to zero. The receiver MUST ignore any
Perceptual Quality Metrics Block with a non-zero value in any field
flagged as unreported.
The Synthetical Multimedia Quality Metrics Block has the following
format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BT=TBD |I| MC | Rsd.| block length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Rsv. | MOS Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.2. Definition of Fields in Multimedia Quality Metrics Block
Block type (BT): 8 bits
The Synthetical Multimedia Quality Metrics Block is identified by
the constant <SMQM>.
Interval Metric flag (I): 1 bit
This field is used to indicate whether the Basic Loss/Discard
metrics are Interval or Cumulative metrics, that is, whether the
reported values applies to the most recent measurement interval
duration between successive metrics reports (I=1) (the Interval
Duration) or to the accumulation period characteristic of
cumulative measurements (I=0) (the Cumulative Duration).
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MoS Type (MT): 4 bits
This field is used to indicate the MOS type to be reported. The
MOS type is defined as follows:
0000 MOS-LQ - Listening Quality MoS.
0001 MOS-CQ - Conversation Quality MoS.
0010 MOS-V - Video Quality MOS.
0011 MOS-AV - Audio-Video Quality MOS.
0100~1111 - Reserved for future definitions.
MoS-LQ measures the quality of audio for listening purposes only
while MoS-CQ measures the quality of audio for conversation
purpose only. MoS-V and MoS-AV measures the quality of video
application or Audio-Video application.Both MoS-LQ and MoS-CQ are
commonly used in VoIP applications. MOS-LQ uses either wideband
audio codec or narrowband audio codec, or both and does not take
into account any of bidirectional effects, such as delay and echo.
MOS-CQ uses narrowband codec and takes into account listening
quality in each direction, as well as the bidirectional effects.
If MoS type is MoS-LQ and MoS-CQ, the MoS value can be calculated
based on ITU-T G.107[G.107], ITU-T P.564 [P.564]or ETSI TS 101
329-5 [ETSI], if the Mos type is MoS-V or MoS-AV, the Mos value
can be calculated based on ITU-T P.NAMS [P.NAMS]or ITU-T P.NBAMS
[P.NBAMS]. If new MOS types are defined, they can be added by an
update to this document. If the receiver does not understand the
MOS type defined in this document it should discard this report.
Rsd.:3 bits
This field is reserved for future definition. In the absence of
such a definition, the bits in this field MUST be set to zero and
MUST be ignored by the receiver.
Block Length: 16 bits
The length of this report block in 32-bit words, minus one. For
the Packet Delay Variation Metrics block, the block length is
equal to 2.
SSRC of source: 32 bits
As defined in Section 4.1 of [RFC3611].
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Rsd.:16 bits
This field is reserved for future definition. In the absence of
such a definition, the bits in this field MUST be set to zero and
MUST be ignored by the receiver.
MOS Value: 16 bits
The estimated mean opinion score for multimedia application
quality is defined as including the effects of delay,loss,
discard,jitter and other effects that would affect multimedia
quality . It is expressed in numeric format 8:8 with the value in
the range 0.0 to 255.996. The valid the measured value ranges
from 0.0 to 50.0, corresponding to MoS x 10 as for MoS. If the
measured value is over ranged, the value 0xFFFE SHOULD be reported
to indicate an over-range measurement. If the measurement is
unavailable, the value 0xFFFF SHOULD be reported. Values other
than 0xFFFE,0xFFFF and the valid range defined above MUST NOT be
sent and MUST be ignored by the receiving system.
5. SDP Signaling
One new parameter is defined for the report block defined in this
document to be used with Session Description Protocol (SDP) [RFC4566]
using the Augmented Backus-Naur Form (ABNF) [RFC5234]. It has the
following syntax within the "rtcp-xr" attribute [RFC3611]:
rtcp-xr-attrib = "a=rtcp-xr:"
[xr-format *(SP xr-format)] CRLF
xr-format = multimedia-quality-metrics
multimedia-quality-metrics = "multimedia-quality-metrics"
Refer to Section 5.1 of RFC 3611 [RFC3611] for a detailed description
and the full syntax of the "rtcp-xr" attribute.
6. IANA Considerations
New report block types for RTCP XR are subject to IANA registration.
For general guidelines on IANA allocations for RTCP XR, refer to
Section 6.2 of [RFC3611].
This document assigns one new block type value in the RTCP XR Block
Type Registry:
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Name: SMQM
Long Name: Synthetical Multimedia Quality Metric
Value <SMQM>
Reference: Section 4
This document also registers one new SDP [RFC4566] parameter for the
"rtcp-xr" attribute in the RTCP XR SDP Parameters Registry:
* "multimedia-quality-metrics"
The contact information for the registrations is:
Qin Wu
sunseawq@huawei.com
101 Software Avenue, Yuhua District
Nanjing, JiangSu 210012 China
7. Security Considerations
The new RTCP XR report blocks proposed in this document introduces no
new security considerations beyond those described in [RFC3611].
8. Acknowledgements
The authors would like to thank Alan Clark, Bill Ver Steeg, David R
Oran, Ali Begen,Colin Perkins, Roni Even,Youqing Yang, Wenxiao Yu and
Yinliang Hu for their valuable comments and suggestions on this
document.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
Protocol Extended Reports (RTCP XR)", RFC 3611,
November 2003.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
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Specifications: ABNF", STD 68, RFC 5234, January 2008.
9.2. Informative References
[ETSI] ETSI, "Quality of Service (QoS) measurement
methodologies", ETSI TS 101 329-5 V1.1.1, November 2000.
[G.107] ITU-T, "The E Model, a computational model for use in
transmission planning", ITU-T Recommendation G.107,
April 2009.
[G.1082] ITU-T, "Measurement-based methods for improving the
robustness of IPTV performance", ITU-T
Recommendation G.1082, April 2009.
[MONARCH] Wu, Q., "Monitoring Architectures for RTP",
ID draft-ietf-avtcore-monarch-00, April 2011.
[P.564] ITU-T, "Conformance testing for narrowband Voice over IP
transmission quality assessment models", ITU-T
Recommendation P.564, July 2006.
[P.NAMS] ITU-T, "Non-intrusive parametric model for the Assessment
of performance of Multimedia Streaming", ITU-T
Recommendation P.NAMS, November 2009.
[P.NBAMS] ITU-T, "non-intrusive bit-stream model for assessment of
performance of multimedia streaming", ITU-T
Recommendation P.NBAMS, November 2009.
Appendix A. Change Log
A.1. draft-wu-xrblock-rtcp-xr-quality-monitoring-03
The following are the major changes compared to previous version 02:
o Remove the tag field.
o Define MOS Value field as 32 bits integer value field.
o Clear unused references.
o Add text to MOS type field for clarification.
o Other Editorial changes.
A.2. draft-wu-xrblock-rtcp-xr-quality-monitoring-04
The following are the major changes compared to previous version 03:
o Add Numeric format definition and express the MoS-Value in Numeric
format.
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o Change 32bits MoS Value into 16bits MoS Value.
o Add some text to MoS Type definition to clarify the algorithm
calculation.
o Separate MoS-A into MoS-LQ and MoS-CQ and add some text to clarify
the difference between them.
o Add one more reference for MoS-LQ and MoS-CQ value calculation.
o Other Editorial changes.
Authors' Addresses
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: sunseawq@huawei.com
Glen Zorn
Network Zen
77/440 Soi Phoomjit, Rama IV Road
Phra Khanong, Khlong Toie
Bangkok 10110
Thailand
Phone: +66 (0) 87 502 4274
Email: gwz@net-zen.net
Roland Schott
Deutsche Telekom Laboratories
Deutsche-Telekom-Allee 7
Darmstadt 64295
Germany
Email: Roland.Schott@telekom.de
Kai Lee
China Telecom
China Telecom Beijing Research Institute
Email: leekai@ctbri.com.cn
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