1、Multimedia quality Method of assessment ofsynchronization of audioand videoBS EN 62503:2008raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI British StandardsNational forewordThis British Standard is the UK implementation of EN 62503:2008. It is ide
2、ntical to IEC 62503:2008.The UK participation in its preparation was entrusted to Technical CommitteeEPL/100, Audio, video and multimedia systems and equipment.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to includ
3、e all the necessary provisions of acontract. Users are responsible for its correct application. BSI 2009ISBN 978 0 580 60095 1ICS 33.160.01BRITISH STANDARDBS EN 62503:2008Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the aut
4、hority of the StandardsPolicy and Strategy Committee on 31 March 2009 Amendments issued since publicationAmd. No. Date Text affectedEUROPEAN STANDARD EN 62503 NORME EUROPENNE EUROPISCHE NORM October 2008 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation E
5、lectrotechnique Europisches Komitee fr 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 ICS 33.160.01 English version Multimedia
6、 quality - Method of assessment of synchronization of audio and video (IEC 62503:2008) Qualit des dispositifs multimdia - Mthode dvaluation de la synchronisation des flux audio et vido (CEI 62503:2008) Multimedia-Qualitt - Verfahren zur Beurteilung der Synchronisation von Ton und Bild (IEC 62503:200
7、8) 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 bibliographic
8、al 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 C
9、ENELEC 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, Hungar
10、y, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. BS EN 62503:2008EN 62503:2008 - 2 - Foreword The text of document 100/1277/CDV, future edition 1 of IEC 62503,
11、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
12、 the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2009-07-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2011-10-01 Annex ZA has been added by CENELEC. _ Endorsement notice The t
13、ext of the International Standard IEC 62503:2008 was approved by CENELEC as a European Standard without any modification. _ BS EN 62503:2008- 3 - EN 62503:2008 Annex ZA (normative) Normative references to international publications with their corresponding European publications The following referen
14、ced 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 mod
15、ifications, indicated by (mod), the relevant EN/HD applies. Publication Year Title EN/HD Year ITU-R Recommendation BT.500-11 2002 Methodology for the subjective assessment of the quality of television pictures - - BS EN 62503:2008 2 62503 IEC:2008(E) CONTENTS FOREWORD.3 INTRODUCTION.5 1 Scope.6 2 No
16、rmative 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 clip8 5.2.2 Creation of a test video sequenc
17、e8 5.3 Procedures and condition for assessment of lip sync at the section 3-3 9 5.4 Reporting of the result of assessment9 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 Bibliography12 Figure 1 Overview7 Figure 2 Preparation
18、 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 BS EN 62503:200862503 IEC:
19、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
20、 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,
21、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-go
22、vernmental 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 IE
23、C 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 acce
24、pted 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 internatio
25、nal 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 la
26、tter. 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
27、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 ar
28、ising 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 i
29、s 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 mul
30、timedia 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 repor
31、t on voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. BS EN 62503:2008 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
32、 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. BS EN 62503:200862503 IEC:2008(
33、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 ident
34、ified 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 syn
35、chronization 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 m
36、ethod 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
37、 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
38、 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 Inte
39、rnational Standard is intended to supplement Recommendation ITU-R BT.1359-1, 11, 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 Apr
40、il 2006. _ 1Numbers in square brackets refer to the Bibliography. BS EN 62503:2008 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 over
41、all, 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 a
42、pplications 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 ame
43、ndments) 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 opi
44、nion 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 t
45、est 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 BS EN 62503:200862503 IEC:2008(E) 7 4 Overview of methods of assessment Figure
46、1 depicts overview of possible objective methods of measurement and subjective method of assessment to acquire necessary parameters corresponding to lip sync. A A V V Encoding andcompressionEncoding andcompressionDecompression andreproductionDecompression andreproduction0 1 2 3 0 1 2 3 t0= 0 Speak a
47、nd act Listen Watch t1t2t3IEC 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 accompanyi
48、ng audio is expected; 00t=. Where 00t is foreseen, it shall also be taken into account. Lip sync at the section 1-1 is supposed to be introduced by separate acquisition of physical phenomena by microphones and video cameras followed by yet further separate digital processing for audio and video data
49、. It will cause lip sync of t10. NOTE In case of MPEG-2 encoding, there is the scheme of synchronization using Decoding Time Stamp (DTS) as well as Presentation Time Stamp (PTS) embedded in the header of Packetized Elementary Stream (PES). See ISO/IEC 13818-1 11. Lip sync at the section 2-2 is supposed to be introduced by reproduction process for audio and video channels separately such as decompression, rendering and reproduction.
