1、INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU SERIES J: TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Specific Recommendations for television transmission J .92 (04/97) Recommended operating guidelines for point-to-point transm
2、ission of television programmes ITU-T Recommendation J.92 (Previously CCITT Recommendation) - STD*ITU-T RECMN J.72-ENGL 1997 = 48b257L Ub35205 Til ITU-T J-SERIES RECOMMENDATIONS TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS General Recommendations General Recommendations c
3、oncerning sound-programme transmissions Performance characteristics of sound-programme circuits Characteristics of equipment and lines used for setting up sound-programme circuits Characteristics of equipment for coding analogue sound-programme signals Digital transmission of sound-programme signals
4、 Characteristics of circuits for television transmissions Systems for television transmission over metallic lines and interconnection with radio-relay links Digital transmission of television signals J.l-J.9 J.10-J. 19 5.20-5.29 J.30-J.39 J.40-J.49 J.50-J.59 J.60-J.69 J.70-J.79 5.80-5.89 - Specific
5、Recommendations or television transmission Jio-J99 Transmission of signals with multiplexing of video, sound and data, and signals of new systems J.100-J.109 Interactive services J. 110-J. 119 Forfurther details, please refer to ITU-T List of Recommendations. FOREWORD The ITU-T (Telecommunication St
6、andardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommu
7、nication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTS
8、C Resolution No. I (Geneva, October 1996). ITU-T Recommendation J.92 was prepared by ITU-T Study Group 9 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 22nd of April 1997. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate
9、both a telecommunication administration and a recognized operating agency. O ITU 1997 All rights reserved. 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 the ITU
10、. Recommendation 5.92 (04/97) i CONTENTS i Scope 2 Acronyms 3 Operational guidelines 4 ITS and IDS Appendix I - Background to the Recommendation General considerations . Television transmission over mixed analogue-and-digital links ITS and IDS signals . I . 1 1.2 1.3 1.4 Interaction of signal format
11、s and compression schemes in the TV chain 11 Recommendation 5.92 (04197) Page 1 1 1 2 2 2 2 3 3 SUMMARY This Recommendation provides guidelines to operate point-to-point television transmission using bit-rate reduction techniques and to avoid uncontrolled cascading. Recommendation 5.92 (04197) . 111
12、 Recommendation 5.92 RECOMMENDED OPERATING GUIDELINES FOR POINT-TO-POINT TRANSMISSION OF TELEVISION PROGRAMMES (Geneva, 1997) 1 Scope This Recommendation describes a number of operating guidelines that are recommended for use in point-to-point transmission of television signais. They cover the opera
13、ting aspects listed below: television transmission over mixed analogue-and-digital or all-digitai link, impacts from coding processes; signal format transitions within a TV chain (e.g. composite signals, component signals, etc.); insertion points for ITS and IDS signals. 2 Acronyms This Recommendati
14、on uses the following acronyms: DCT Discrete Cosine Transform IDS Insertion Data Signals ITS Insertion Test Signals SNG Satellite News Gathering VTR Video Tape Recorder 3 Operational guidelines The following guidelines concerning contribution and primary distribution (point-to-point transmission) of
15、 TV programmes are based on current practical experience with cascading of bit-rate reduction systems. The effects of the cascading of bit-rate reduction systems and signal format transitions can reasonably be assured only if the whole chain of TV processing and transmission is considered at the ear
16、ly planning stage. Guidelines should be established for the use of bit-rate reduction on transmission links, preferably together with equipment for TV production, as required for the complete TV chain. TV chains leading to a dubious quality should be avoided as far as possible. In general, contribut
17、ion circuits require more quality head-room than distribution circuits, so coding schemes and bit- rates should be chosen accordingly. For example, once coding artifacts have been introduced, coding criticality is increased with an adverse effect on all downstream compression systems. Objective meth
18、ods for the measurement of picture quality in quasi real-time on TV chains with cascaded coding processes and signal format transitions is a subject for further study. o Programme providers and network operators should be made aware of the problems caused by uncontrolled cascading. Recommendation 5.
19、92 (04197) 1 4 ITS and IDS The implementation of ITS and IDS is optional, but when they are implemented, the following rules apply: An ITS and a blank line signal should be inserted to evaluate the performance of the analogue parts of the TV chain. It should be transmitted transparently through the
20、digital parts of the TV chain using a separate data channel. An IDS identifjing the video signal source should be inserted and transported through the digital parts of the TV chain using a separate data channel, normally the service data channel. This channel would not be scrambled, thereby permitti
21、ng monitoring of the IDS without the need for descrambling. The IDS should be reinserted as appropriate in the composite analogue video output signal of the decoder. 0 If IDS is absent at the input to the digital encoder, the encoder should automatically insert its own IDS instead. Moreover, to ensu
22、re that ITS and IDS go hand-in-hand, the encoder should insert new ITS if there is no IDS present at the encoder input. This includes blanking the blank line for noise measurement. Appendix I Background to-the Recommendation I. 1 General considerations Techniques used in television are changing rapi
23、dly in the digital domain affecting the whole signal chain from TV signal generation up to the reproduction of the pictures in the consumer?s television set. The rationale behind this change is to open new features in the field of TV production techniques but, at the same time, to reduce costs for p
24、rogramme production and signal transmission. Despite these rapid changes, it should be kept in mind that at least for a long transition period the introduction of digital techniques for generation, editing and distribution of TV programmes coexists with different signal formats including analogue on
25、es (e.g. formats used up to now for archiving) and with an increasing use of systems individually applying (different) bit-rate reduction algorithms to the picture signals. Signal format transitions as well as different bit-rate reduction processes will be involved in the programme production (e.g.
26、SNG using digital contribution links from remote sites, recording of the TV signals on digital VTRs, storing the signals on ?tapeless? production servers), in the transmission of TV programmes for broadcast via satellites or terrestrial transmitter networks, for cable distribution and for the econom
27、ic delivery of programmes to individuals in the evolving area of video or information on demand. Many combinations of signal format transitions and bit-rate reduction processes may be found in the future for contribution, post- processing, and distribution. If unexpected results are to be avoided, a
28、ccount should be taken of all effects caused by the cascading of signal formats and the impact from these processes on the use of point-to-point transmission schemes for the delivery and distribution of TV programmes. 1.2 Television transmission over mixed analogue-and-digital links In current pract
29、ice it may well happen that various television transmission links are cascaded, which may be analogue or compressed digital with various degrees of compression. Furthermore, these links may be part of the whole TV chain where post-processing including further signal compression and/or signal format
30、conversions could be applied. Such cascading of television and signal compression processes is generally degrading the received picture quality, but the amount of such degradation depends on circuit configuration, the processing of the TV signai for post-production as well as on the characteristics
31、of the picture material fed into the TV chain, since transmission systems as well as production processes can interact with undesirable results. 2 Recommendation 5.92 (04/97) For instance, when a received analogue signal, with a poor signal-to-noise ratio or with significant PAL artifacts or showing
32、 quantizing noise from a preceding compression step, is DCT encoded for further digital transmission or processing, noise or other artifacts may overload the encoder with adverse effects on the digital picture. 1.3 ITS and IDS signals ITS and IDS were introduced as a means of monitoring the performa
33、nce of composite analogue transmission chains and for identification of the video signal source respectively. ITS have no direct relevance to the monitoring of compressed component digital transmission systems, since they would be severely degraded by such systems if included in the compression proc
34、ess. However, it is of interest to transmit them transparently through such digital systems, using a separate data channel. This enables the analogue sections of mixed analogue/digial transmission chains to be monitored correctly, even when a digital section separates two analogue sections for examp
35、le. Note that the blank line, used for signalhoise measurement, should be included in this process. Advantage can be taken of the fact that the ITS do not need to be refreshed at frame rate, to reduce the bit rate required to transport them. 10-bits per sample should be used to ensure “high fidelity
36、“ transmission of the ITS. 1.4 Interaction of signal formats and compression schemes in the TV chain In the future, operating scenarios for programme production for news presentation and for the preparation of broadcasting sequences will inevitably include a variety of compression algorithms. These
37、will be used within complex and varying configurations of TV chains for signal transport, server-based editing and archiving, and server-based broadcasting. Various bit rates have to be handled within studio and operation environments as well as within wide area networks including B-ISDN. As a conse
38、quence, several signal formats and compression schemes may be cascaded. The degradation of picture quality (not surprisingly) is strongly dependent on the picture content, but furthermore degradation caused by single sections of the TV chain can accumulate. Picture sequences, which are relatively un
39、critical for a single section, may become critical by the addition of artifacts generated by cascaded compression systems. Pixel shifts involved between succeeding coding steps may lead to additional degradation of the picture quality and should be avoided. Even if there is awareness that the introd
40、uction of new digital techniques for production and transport of TV signals needs to be based on a compromise between enhanced functionality, lower costs and resulting picture quality; nevertheless, care must be taken that the uncontrolled cascading of different compression systems is avoided in ord
41、er to minimize visible degradation of the picture quality at the end of the TV chain. The isolated treatment of coding algorithms in separate sections of the whole chain may lead to serious problems with planning and implementation of new systems. In addition, impacts on the internal and external ne
42、twork operation and topology have to be studied and new solutions will be necessary in the near future. Recommendation 5.92 (04197) 3 STD-ITU-T RECMN J-92-ENGL 3997 48b259L Ob35212 181 Series A Series B Series C Series D Series E Series F Series G Series H Series I Series J Series K Series L Series
43、M Series N Series O Series P Series Q Series R Series S Series T Series U Series V Series X Series Z ITU-T RECOMMENDATIONS SERIES Organization of the work of the IT-T Means of expression: definitions, symbols, classification General telecommunication statistics General tariff principles Overall netw
44、ork operation, telephone service, service operation and human factors Non-telephone telecommunication services Transmission systems and media, digital systems and networks Audiovisual and multimedia systems Integrated services digital network Transmission of television, sound programme and other mul
45、timedia signals Protection against interference Construction, installation and protection of cables and other elements of outside plant Maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits Maintenance: international sound programme and televi
46、sion transmission circuits Specifications of measuring equipment Telephone transmission quality, telephone installations, local line networks Switching and signalling Telegraph transmission Telegraph services terminal equipment Terminals for telematic services Telegraph switching Data communication over the telephone network Data networks and open system communication Programming languages
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