IEC 62503:2008
(Main)Multimedia quality - Method of assessment of synchronization of audio and video
Multimedia quality - Method of assessment of synchronization of audio and video
IEC 62503:2008 provides a subjective (or perceptible) and statistical method of assessment of overall, or end-to-end, difference of delays between real world and reproduced scenes in terms of video and accompanying audio recoded in a medium.
Qualité pour les systèmes multimédia - Méthode d'évaluation de la synchronisation de l'audio et de la vidéo
L'IEC 62503:2008 fournit une méthode subjective (ou perceptible) et statistique d'évaluation de la différence globale, ou de bout en bout, des retards entre le monde réel et les scènes reproduites en termes de vidéo et d'audio d'accompagnement enregistrés sur un support. La présente version bilingue (2014-04) correspond à la version anglaise monolingue publiée en 2008-09.
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IEC 62503
Edition 1.0 2008-09
INTERNATIONAL
STANDARD
Multimedia quality – Method of assessment of synchronization of audio and
video
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
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IEC 62503
Edition 1.0 2008-09
INTERNATIONAL
STANDARD
Multimedia quality – Method of assessment of synchronization of audio and
video
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
M
ICS 33.160.01 ISBN 2-8318-9986-9
– 2 – 62503 © IEC:2008(E)
CONTENTS
FOREWORD.3
INTRODUCTION.5
1 Scope.6
2 Normative reference .6
3 Terms and definitions .6
4 Overview of methods of assessment.7
5 Subjective assessment of lip sync .7
5.1 Items to be assessed .7
5.2 Preparation of test video clips and test video sequence.8
5.2.1 Selection of content of a test video clip.8
5.2.2 Creation of a test video sequence.8
5.3 Procedures and condition for assessment of lip sync at the section 3-3’ .9
5.4 Reporting of the result of assessment.9
6 Data processing .10
6.1 Items to be assessed .10
6.2 Method of assessment.10
6.3 Reporting of the result of estimation .11
Bibliography.12
Figure 1 – Overview.7
Figure 2 – Preparation of test video clips with time shifted audio .8
Figure 3 – An example of subjective assessment of lip sync .10
Figure 4 – Normalized response for grading impairment caused by lip sync mismatch .11
Table 1 – Five-grade impairment scale and explanation of subjective opinion score.9
62503 © IEC:2008(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MULTIMEDIA QUALITY –
METHOD OF ASSESSMENT OF
SYNCHRONIZATION OF AUDIO AND VIDEO
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62503 has been prepared by technical area 11: Quality for audio,
video and multimedia systems, of IEC technical committee 100: Audio, video and multimedia
systems and equipment.
The text of this standard is based on the following documents:
CDV Report on voting
100/1277/CDV 100/1358/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
– 4 – 62503 © IEC:2008(E)
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
62503 © IEC:2008(E) – 5 –
INTRODUCTION
Contemporary multimedia systems are realized by digital technology. Depending on what
digital processing is being applied, time delays differ among medium channels for
reproduction as perceptible stimulus for a human audience. An example is video delay against
audio, which is identified by such terms as lip sync or AV-sync. Video delay against audio will
be inevitable for large sized displays, because necessary time for rendering and visualization
will be proportional to the number of picture elements.
There should also be additional factors to be considered. They include synchronization
problem during medium gathering, production, post-production, processing in various aspects
to combine these multiple media and to be sent out or recorded as “multimedia”.
There is a need for international standards to provide the following three related
methodologies:
a) an objective method of measurement for difference of delays between reproduced audio
and video (lip sync) by multimedia systems and equipment,
b) a subjective (or perceptible) and statistical method of assessment of overall difference of
delays between a real world and a reproduced scene and sound,
c) a method of estimation of implied difference of delays inherent in multimedia received,
recorded or under reproduction.
This International Standard addresses the item b) using typical multimedia content such as
bust shots of news casters because of easiness in defining synchronization of audio and
video. Since a range of perceptibly allowable miss-synchronization and sensitivity of human
audience for lead and delayed audio against accompanied video depends on human
sensation and the conditions for assessment, a clearly defined method of assessment of such
characteristics should be standardised.
This International Standard is intended to supplement Recommendation ITU-R BT.1359-1,
[1] , as well as partly answer the request of ITU-R to IEC that has been stated in
Recommendation ITU-R BT.1377 [2].
Technical contents are based on a study in Faculty of Engineering, Chiba University in Japan,
conducted in April 2006.
___________
Numbers in square brackets refer to the Bibliography.
– 6 – 62503 © IEC:2008(E)
MULTIMEDIA QUALITY –
METHOD OF ASSESSMENT OF
SYNCHRONIZATION OF AUDIO AND VIDEO
1 Scope
This International Standard provides a subjective (or perceptible) and statistical method of
assessment of overall, or end-to-end, difference of delays between real world and reproduced
scenes in terms of video and accompanying audio recoded in a medium.
This International Standard does not specify limiting values for those results obtained by the
application of the provisions in this standard. It excludes applications to professional
broadcast systems.
2 Normative reference
The following referenced document is indispensable for the application of this document. For
dated references, only the edition cited applies. For undated references, the latest edition of
the referenced document (including any amendments) applies.
ITU-R BT.500-11:2002, Methodology for the subjective assessment of the quality of television
pictures
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
lip sync
video delay against accompanying audio
3.2
outlier
subjective opinion score outside ms± , where m is a sample mean of the original scores of a
set of subjects for the same video delay and s is a standard deviation of the scores
3.3
subject
ordinary untrained human audience of audio and video reproduction; random sample of
individual members of general public
3.4
test video clip
short duration of video frames with accompanying audio to be used as original
3.5
test video sequence
random series of test video clips where the audio channels are shifted in time compared to
the original
62503 © IEC:2008(E) – 7 –
4 Overview of methods of assessment
Figure 1 depicts overview of possible objective methods of measurement and subjective
method of assessment to acquire necessary parameters corresponding to lip sync.
0 1
2 3
A Decompression and A'
Encoding and
reproduction
compression
Listen
V V'
Decompression and
Encoding and
reproduction
compression
Speak and act
Watch
0' 1' 2' 3'
Δt = 0 Δt Δt Δt
0 1 2 3
IEC 1487/08
Figure 1 – Overview
The leftmost in Figure 1 is a real world and the rightmost in Figure 1 is a reproduced world.
Lip sync at the section 0-0’, i.e. scene delay in reference to accompanying sound, is normally
zero; in other words null video delay against accompanying audio is expected; Δ=t 0 . Where
Δ≠t 0 is foreseen, it shall also be taken into account.
Lip sync at the section 1-1’ is supposed to be introduced b
...
IEC 62503 ®
Edition 1.0 2008-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Multimedia quality – Method of assessment of synchronization of audio and
video
Qualité pour les systèmes multimédia – Méthode d'évaluation de la
synchronisation de l'audio et de la vidéo
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
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About the IEC
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International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
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IEC 62503 ®
Edition 1.0 2008-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Multimedia quality – Method of assessment of synchronization of audio and
video
Qualité pour les systèmes multimédia – Méthode d'évaluation de la
synchronisation de l'audio et de la vidéo
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX M
ICS 33.160.01 ISBN 978-2-8322-1359-9
– 2 – IEC 62503:2008 © IEC 2008
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative reference . 6
3 Terms and definitions . 6
4 Overview of methods of assessment . 7
5 Subjective assessment of lip sync . 7
5.1 Items to be assessed . 7
5.2 Preparation of test video clips and test video sequence . 8
5.2.1 Selection of content of a test video clip . 8
5.2.2 Creation of a test video sequence. 8
5.3 Procedures and condition for assessment of lip sync at the section 3-3’ . 9
5.4 Reporting of the result of assessment. 9
6 Data processing . 10
6.1 Items to be assessed . 10
6.2 Method of assessment. 10
6.3 Reporting of the result of estimation . 11
Bibliography . 12
Figure 1 – Overview . 7
Figure 2 – Preparation of test video clips with time shifted audio . 8
Figure 3 – An example of subjective assessment of lip sync . 10
Figure 4 – Normalized response for grading impairment caused by lip sync mismatch . 11
Table 1 – Five-grade impairment scale and explanation of subjective opinion score. 9
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MULTIMEDIA QUALITY –
METHOD OF ASSESSMENT OF
SYNCHRONIZATION OF AUDIO AND VIDEO
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62503 has been prepared by technical area 11: Quality for audio,
video and multimedia systems, of IEC technical committee 100: Audio, video and multimedia
systems and equipment.
This bilingual version (2014-04) corresponds to the monolingual English version, published in
2008-09.
The text of this standard is based on the following documents:
CDV Report on voting
100/1277/CDV 100/1358/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
The French version of this standard has not been voted upon.
– 4 – IEC 62503:2008 © IEC 2008
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
INTRODUCTION
Contemporary multimedia systems are realized by digital technology. Depending on what
digital processing is being applied, time delays differ among medium channels for
reproduction as perceptible stimulus for a human audience. An example is video delay against
audio, which is identified by such terms as lip sync or AV-sync. Video delay against audio will
be inevitable for large sized displays, because necessary time for rendering and visualization
will be proportional to the number of picture elements.
T
...
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