SIST EN 62503:2008

Multimedia quality - Method of assessment of synchronization of audio and video (IEC 62503:2008)

IEC 62503:2008(E) 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.

Multimedia-Qualität - Verfahren zur Beurteilung der Synchronisation von Ton und Bild (IEC 62503:2008)

Qualité des dispositifs multimedia - Méthode d'évaluation de la synchronisation des flux audio et video (CEI 62503:2008)

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.

Večpredstavnostna kakovost - Metoda ocenjevanja sinhronizacije pri avdiu in videu (IEC 62503:2008)

General Information

• Status: Published
• Publication Date: 21-Oct-2008
• ICS: 33.160.60 - Multimedia systems and teleconferencing equipment
• Technical Committee: AVM - Audio, video and multimedia systems and equipment
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 22-Oct-2008
• Due Date: 27-Dec-2008
• Completion Date: 22-Oct-2008
• Ref Project: EN 62503:2008 - Multimedia quality - Method of assessment of synchronization of audio and video

Overview

SIST EN 62503:2008 (IEC 62503:2008) defines standardized methods for the assessment of synchronization (lip sync or AV-sync) between audio and video in multimedia systems. Specifically, it provides subjective (perceptible) and statistical approaches to determine the end-to-end sync difference between real-world events and their reproduced scenes via audio and video media. This standard is widely applicable to multimedia systems and equipment, except for professional broadcast systems.

Ensuring proper synchronization of audio and video is critical for high-quality user experiences in multimedia applications, including teleconferencing and home entertainment. Audio-video sync errors, commonly perceived as lip sync issues, can distract viewers, reduce content quality, and impact service perception.

Key Topics

• Assessment Methods: The standard describes subjective (user-based) and statistical techniques for measuring audio-video synchronization.
• Human Subject Approach: Focuses on gathering input from a minimum group of 15 untrained subjects to rate perceived synchronization using a standardized five-grade impairment scale.
• Test Material Preparation: Details selection and manipulation of audiovisual test clips, especially using speech content to accentuate perceptible lip sync errors.
• Controlled Testing Conditions: Specifies playback environment settings including viewing distance, lighting, and audio reproduction to ensure repeatable, valid results.
• Reporting and Data Processing: Outlines requirements for objective reporting, including mean opinion scores and measurement of time-shifted audio against video.

Applications

SIST EN 62503:2008 is valuable for manufacturers, content providers, and service operators seeking to evaluate and enhance multimedia quality. Major application areas include:

• Consumer Electronics Testing: Used in development and quality assurance to verify synchronization in TVs, set-top boxes, streaming devices, and home theater systems.
• Teleconferencing Systems: Ensures that real-time communication platforms deliver audio and video in sync, boosting intelligibility and reducing user frustration.
• Digital Media Production: Helps identify and correct audio or video processing delays introduced during editing, format conversion, or compression.
• End-to-End System Validation: Provides guidelines to test and document the overall latency between live events or source footage and their final presentation to users.

By systematically identifying and quantifying synchronization differences, organizations can enhance end-user satisfaction, minimize perceptible errors, and support compliance with international multimedia quality standards.

Related Standards

SIST EN 62503:2008 references and complements several other international standards essential for multimedia systems:

• ITU-R BT.500: Methodology for subjective assessment of the quality of television pictures.
• ITU-R BT.1359: Guidance on relative timing of sound and vision for broadcasting.
• ITU-R BT.1377: Labelling of video and audio apparatus throughput delays.
• ISO/IEC 13818-1: Systems layer standard for audiovisual coding, relevant to synchronization metadata.
• IEC/TS 62312-2: Guidelines for audio and video synchronization methods.

Following these standards together ensures robust, repeatable, and internationally recognized assessment of multimedia quality, particularly with respect to audio and video synchronization.

---

Keywords: multimedia quality, audio-video synchronization, lip sync assessment, IEC 62503:2008, SIST EN 62503:2008, subjective testing, AV sync, multimedia systems, teleconferencing equipment, end-to-end delay, multimedia standards.

Standards Content (Sample)

SLOVENSKI STANDARD
01-december-2008
9HþSUHGVWDYQRVWQDNDNRYRVW0HWRGDRFHQMHYDQMDVLQKURQL]DFLMHSULDYGLXLQ
YLGHX,(&
Multimedia quality - Method of assessment of synchronization of audio and video (IEC
62503:2008)
Multimedia-Qualität - Verfahren zur Beurteilung der Synchronisation von Ton und Bild
(IEC 62503:2008)
Qualité des dispositifs multimedia - Méthode d'évaluation de la synchronisation des flux
audio et video (CEI 62503:2008)
Ta slovenski standard je istoveten z: EN 62503:2008
ICS:
33.160.60 9HþSUHGVWDYQLPXOWLPHGLMVNL Multimedia systems and
VLVWHPLLQRSUHPD]D teleconferencing equipment
WHOHNRQIHUHQFH
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 62503
NORME EUROPÉENNE
October 2008
EUROPÄISCHE NORM
ICS 33.160.01
English version
Multimedia quality -
Method of assessment of synchronization
of audio and video
(IEC 62503:2008)
Qualité des dispositifs multimédia -  Multimedia-Qualität -
Méthode d'évaluation Verfahren zur Beurteilung
de la synchronisation der Synchronisation
des flux audio et vidéo von Ton und Bild
(CEI 62503:2008) (IEC 62503:2008)

This European Standard was approved by CENELEC on 2008-10-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62503:2008 E
Foreword
The text of document 100/1277/CDV, future edition 1 of IEC 62503, prepared by Technical area 11,
Quality for audio, video and multimedia systems, of IEC TC 100, Audio, video and multimedia systems
and equipment, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 62503 on 2008-10-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
(dop) 2009-07-01
national standard or by endorsement
– latest date by which the national standards conflicting
(dow) 2011-10-01
with the EN have to be withdrawn
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 62503:2008 was approved by CENELEC as a European
Standard without any modification.
__________
- 3 - EN 62503:2008
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following referenced documents are 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.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year

ITU-R 2002 Methodology for the subjective assessment - -
Recommendation of the quality of television pictures
BT.500-11
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.
...