1、 STD-ITU-T RECMN J-100-ENGL 1770 LIBb2591 Ob30183 TTL1 INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECT0 R OF ITU J.100 (ex CMTT.717) (06/90) TELEVISION AND SOUND TRANSMISSION TOLERANCES FOR TRANSMISSION TIME DIFFERENCES BETWEEN THE VISION AND SOUND COMPONENTS OF A
2、TELEVISION SIGNAL ITU-T Recommendation J.1 O0 (Formerly Recommendation ITU-R CMTT.717) FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The ITU-T is responsible for studying technical, operating and tariff question
3、s and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommenda
4、tions on these topics. ITU-T Recommendation J. 100 (formerly Recommendation ITU-R CMTT.717) was elaborated by the former ITU-R Study Group CMTT. See Note 1 below. NOTES 1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 F
5、ebruary 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector (ITU-R). Conforming to a joint decision by the World Telecommunication Sta
6、ndardization Conference (Helsinki, March 1993) and the Radiocommunication Assembly (Geneva, November 1993), the ITU-R Study Group CMTT was transferred to ITU-T as Study Group 9, except for the satellite news gathering (SNG) study area which was transferred to ITU-R Study Group 4. 2 telecommunication
7、 administration and a recognized operating agency. In this Recommendation, the expression ?Administration? is used for conciseness to indicate both a O ITU 1990 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, inclu
8、ding photocopying and microfilm,?%thout permission in writing from the ITU. Recommendation 5.100) TOLERANCES FOR TRANSMISSION TIME DIFFERENCES BETWEEN THE VISION AND SOUND COMPONENTS OF A TELEVISION SIGNAL (1990) The CCIR, CONSIDERING that a perceptible time difference between the sound and vision c
9、omponents of a television signal impairs the that Report 1081 gives figures for time differences between sound and vision components that are “detectable” that the effect is less critical when the sound is delayed with respect to the picture; that transmission links are not the only elements in the
10、broadcast chain that may cause a time difference that the time difference between sound and vision components introduced by a transmission link is not a) viewers enjoyment of the programme; 4 and “subjectively annoying”; 4 4 between sound and vision components; e) necessarily related to the length o
11、f the link, UNANIMOUSLY RECOMMENDS that for any connection used for the international exchange of television signals the time difference between the sound and vision components should not exceed 20 ms if the sound is advanced with respect to the picture or 40 ms if the sound is delayed with respect to the picture. Note -The application of these values to circuits is a subject for further study. Formerly Recommendation ITU-R CMTT.7 17. Recommendation 5.100 (06190) 1 -
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