1、ITU-T RECMN*J-SL 94 m 4862591 0595888 T59 m INTERNATIONAL TELECOMMUNICATION UN ION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU J.51 (ex CMTT.659) (08/94) TELEVISION AND SOUND TRANSMISSION GENERAL PRINCIPLES AND USER REQUIREMENTS FOR THE DIGITAL TRANSMISSION OF HIGH QUALITY SOUND PROGRAMMES
2、 ITU-T Recommendation J.51 (Formerly “Recommendation ITU-R CMT) ITU-T RECMN*J-SL 74 = 4862593 0595889 995 FOREWORD The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The ITU-T is responsible for studying technical, operating
3、and tariff questions and issuing Recommen- dations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their tur
4、n, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). ITU-T Recommendation J.51 was revised by ITU-T Study Group 9 (1993-1996) and was approved under the WTS
5、C Resolution No. 1 procedure on the 22nd of August 1994. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. O ITU 1995 All rights reserved. No part of this publication may be repr
6、oduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. ITU-T RECMN*J*5L 94 W 48b257L 0575870 607 H CONTENTS Annex A . Parameters to be used for the definition of future systems . A.l Sampling frequen
7、cy A.2 Dynamic range A.3 Transmission delay . A.4 Ancillary data A.5 Error control . A.6 ISDN compatibility . Annex B - Recommendations for digital transmission of high-quality sound programmes existing at the end of 1993 . Page 1 1 2 2 2 2 2 3 Recommendation J.51 (08/94) 1 ITU-T RECMNtJ-51 94 48b25
8、9L 0595893 543 = SUMMARY This Recommendation has been developed to help planners of circuits for digital sound-programme transmission. It refers to the coding form and the studio interface, and it lists different codecs recommended for use. Additionally, the Recommendation gives some guidance to des
9、igners of fture systems on the parameters of a general nature which will need to be specified. 11 Recommendation 5.51 (08/94) ITU-T RECMNUJ.51 94 = 4862591 0595892 48T 9 Recommendation J.51 GENERAL PRINCIPLES AND USER REQUIREMENTS FOR THE DIGITAL TRANSMISSION OF HIGH QUALITY SOUND PROGRAMMES (1986;
10、revised 1994) The ITU-T, considering (4 (b) procedure; (cl possible to the transmitted message content; (4 (e) (0 in the transmission circuit; (ia selection of an existing one for a specific application, that it is desirable to use common standards for the transmission of high-quality sound; that it
11、 is desirable to use as few code conversions as possible in the international digital sound exchange that to facilitate the exchange of signals, it is desirable to render the transmission interfaces as transparent as that the network interface bit rates should take into account the hierarchical leve
12、ls recommended by ITU-T; that it may be efficient to apply bit-rate reduction and error-protection methods to lower transmission costs; that quality and availability should not be restricted by the signal processing equipment or methods employed that there is a need to clearly identify users require
13、ments in the development of future systems and in the recommends (1) transmission; (2) to ITU-R Recommendation BS.647; (3) (4) quality applications (Annex B lists such Recommendations existing at the end of 1993). that a sound programme originating in digital form should preferably be maintained in
14、digital form for that the interface between the studio and the codec should, where possible, be in digital form and in accordance that parameters listed in Annex A should be used for guidance in the definition of future systems; that the selection of a transmission system should be made among those
15、recommended by ITU-R for high- Annex A Parameters to be used for the definition of future systems (This annex forms an integral part of this Recommendation) A.l Sampling frequency ITU-R Recommendation BS.646 specifies a sampling frequency of 48 kHz to be used in digital studios. Conversion of sampli
16、ng frequency leads to a reduction of signal-to-noise ratio and erodes the system bandwidth; it also introduces an additional delay. For contribution of sound-programme signals of digital studio quality it is recommended to maintain the 48 kHz sampling frequency. Formerly Recommendation IT-R CMT.659.
17、 Recommendation J.51 (08/94) 1 ITU-T RECMN*J*SL 94 m 4862591 0595893 3Lb m For distribution or contribution, if it is not likely that post-production will take place, it may be acceptable to use a 32 kHz sampling frequency for transmission. A.2 Dynamic range As a minimum, the contribution system mus
18、t proi le a dynamic range equivalent to 16 lits per sample ant if possit .e should be extendible to 18 bits per sample or more. The present trend seems to be in favour of a higher dynamic range, to reduce operational problems. A.3 Transmission delay The user requirements are known to be very short.
19、For example, for monitoring off-air signals with headphones, only 5 to 10 ms may be acceptable. Since the actual delay will be the sum of the coding transmission and decoding delays, it may be difficult to meet this expectation. In that case, the only solution may be to adopt new procedures in the p
20、lanning and operation of broadcast systems to allow for higher delays. A.4 Ancillary data The transmission system should provide capacity for programme associated data. The minimum capacity seems to be in the order of 2 kbih per programme. The maximum is defined by ITU-R Recommendation BS.647 (chann
21、el status and user data channels). AS Error control The system should provide error control taking into account the network constraints (e.g. random errors, burst errors, controlled slips, ATM cell losses, short interruptions, etc.). A.6 ISDN compatibility The transmission system should be compatibl
22、e with the user-network interfaces and transmission channels being specified by IT-T (e.g. HI, Ho and multiple B-channels). In general, the encoding process should be locked to the network clock to avoid the use of justification techniques. 2 Recommendation J.51 (OW94) - ITU-T RECflN+Jm5L 94 W 48625
23、91 0595894 252 Maximum resolution Sampling frequency (bits) Ocw Recommendation ITU-R Annex B Channel rate (kbitls) Recommendations for digital transmission of high-quality sound programmes existing at the end of 1993 CMT.724 (Note 1) CMT.7 18 (Note 2) CMT.660 (Note 3) (This annex forms an integral part of this Recommendation) 20 48 192011536 for a stereo channel 16 32 4801496 14 . 32 384 CMT.719 (Note 3) 14 32 320 Recommendation J.51 (08/94) 3
