1、INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECT0 R OF ITU 5.52 (07/96) SERIES J: TRANSMISSION OF SOUND-PROGRAMME AND TELEVISION SIGNALS Dig i tal transmission of sou nd- p rog ram me signals Digital transmission of hig h-quality sound-programme signals using one, t
2、wo or three 64 kbitls channels per mono signal (and up to six per stereo signal) ITU-T Recommendation J .52 (Previously “CCITT Recommendation”) ITU-T J-SERIES RECOMMENDATIONS TRANSMISSION OF SOUND-PROGRAMME AND TELEVISION SIGNALS I General Recommendations J.1-J.9 General Recommendations concerning s
3、ound-programme transmissions Performance characteristics of sound-programme circuits Characteristics of equipment and lines used for setting up sound-programme circuits J.10-J.19 J.20-J.29 J.30-J.39 Characteristics of equipment for coding analogue sound-programme signais J.40-J.49 Characteristics of
4、 circuits for television transmissions Systems for television transmission over metallic lines and interconnection with radio- J.60-J.69 5.70-5.79 relay links Digital transmission of television signals Specific Recommendations for television transmission 5.80-5.89 J.90-J.99 Transmission of signals w
5、ith multiplexing of video, sound and data, and signals of new systems J.100-J.109 Interactive services J.110-5.119 For further details, please refer to ITU-T List of Recommendations. FOREWORD The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunica
6、tion Union (ITU). The ITU-T is responsible for studying technical, operating 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, e
7、stablishes 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 WTSC Resolution No. 1 (Helsinki, March 1-12,1993). IT-T Recommendation J.52 wa
8、s revised by ITU-T Study Group 9 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 1 lth of July 1996. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agenc
9、y. 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. Recommendation 5.52 (07/96) 1 STD-ITU-T RECMN J-52-ENGL Lb m 48b259L O
10、b2Li02L 537 CONTENTS Page O Scope 1 . 1 General features 1 2 Network interface formats 2 3 Synchronization and fiame alignment 4 . 4 Error control 12 5 Transmission of data 21 Annex A - Digital transmission of medium-quality sound-programme signals using a 64 kbith channel (or a part thereof) . 24 A
11、ppendix I - Performance of the forward error correction . 27 11 Recommendation 5.52 (07/96) STD-ITU-T RECMN J*CiZ-ENGL 1776 E 4Bb257L Ub24022 Y73 D SUMMARY The system described in this Recommendation makes possible the transmission of sound signals, coded by new methods recommended by ITU-R Study Gr
12、oup 10 and standardized by ISO/IEC 11 172-3, on 1 to 6 B-channels of the N-ISDN or on permanent connections with a 2048 kbits (or 1544 kbifs) frame. In the case of transmission via the N-ISDN, Recommendation H.221 is used to aggregrate up to six B-channels while maintaining the bit sequence integrit
13、y. The revised text contains clarifications that reflect experience gained in implementing the current version of this Recommendation, and a new chapter on transmission of program-associated data in the ancillary data field of the IS0 frame. INTRODUCTION The IS0 and IEC have approved the internation
14、al standard 11 172-3 for the reduction of the bit rate of high-quality digital sound-programme signals. With this system, it is possible to transmit high-quality mono sound-programme signals with bit rates in the range of 64 to 192 kbifs. Stereo signals are encoded in single bit streams with bit rat
15、es in the range 128 to 384 kbits. If sound signals coded by ISOIEC 11172-3 have to be transmitted in telecommunication networks, the properties of the networks are to be taken into account. The ITU-T has approved some Recommendations which describe the structure and function of 64 kbits channels for
16、 audiovisual applications (Recommendation H.200 contains a list of such Recommendations). The N-ISDN allows the assembly of single channels with the bit rate of 64 kbitk. If the bit rate is greater than 64 kbifs (two times, three times etc.), measures are necessary to maintain the bit sequence. The
17、equipment described in the following enables the transmission of source-coded sound signals on channels of N-ISDN or on connections with a 2048 kbits (or 1544 kbits) frame. . Recommendation 5.52 (07/96) 111 STD-ITU-T RECMN J.52-ENGL 199b 48b2591 Ob24053 047 5 . - * - -.un-.-*- Recommendation 5.52 So
18、und b b 1SO11172-3 encoder b Ancillary DIGITAL TRANSMISSION OF HIGH-QUALITY SOUND-PROGRAMME SIGNALS USING ONE, TWO OR THREE 64 kbit/s CHANNELS PER MONO SIGNAL (AND UP TO SIX PER STEREO SIGNAL) b Line interface Mux 4 (revised in 1996) O Scope The ITU-R Recommendation BS.1115 recommends, based on exte
19、nsive tests carried out by ITU-R Study Group 10 for different applications of the transmission in a broadcast chain (contribution, distribution, emission, commentary), the bit rate reduction system according to ISOAEC 11172-3. The encoding layers and bit rates (per mono channel) recommended by ITU-R
20、 SG 10 depend on the application and are in the range of 120 - 180 kbits using Layer II, except for commentq where 60 kbit/s using Layer III may be used. For details, see ITU-R BS.1115. For transmission of high-quality sound programmes and associated data it is desirable to use standardized 64 kbit/
21、s channels or multiples thereof. This Recommendation defines formatter and reformatter for the transport of the bit rate reduced audio signals according to ISOAEC 11 172-3 and associated data on these standardized 64 kbWs channels. The bit stream to be transmitted on 64 kbit/s channels could be prot
22、ected optionally by means of error-correction measures. The ITU-R has not (before the end of 1995) made any recommendation for the use of the ISOAEC 13818-3 lower samplingpequencies. If and only if the extension to lower samplingfrequencies is to be implemented, the provisions in Annex A shall apply
23、. The implementation of the lower samplingfrequency modes is in no way mandatory as they inherently limit the bandwidth, and would therefore not permit the high-quality criteria to be met. 1 General features 1.1 Purpose of the equipment The purpose of the equipment is to process a bit rate reduced h
24、igh-quality sound-programme signal for transmission on standardized 64 kbit/s channels. For this purpose, it is appropriate that the source encoder and the multiplexer form a unit with an output to the line interface (see Figure 1). Control FIGURE 1/5.52 Connection between encoder, multiplexer and L
25、ine interface Transmission neiwork T0902350-941d01 Recommendation 5.52 (07/96) 1 - STDBITU-T RECMN J.52-ENGL 2b m 98L25L Ob2902Li 2Yb m Header 1.2 Incoming signals (PCM level) The source encoder provides a bit stream according to IS0 Standard 11 172-3 (Layer I, Layer II or Layer III). Layer I is not
26、 recommended for broadcast applications, the block structure of Layers II and III with the block length 24 ms (in case of 48 kHz sampling frequency) is shown in Figure 2. Ancillary data CRC Bit (optionai) ailocation SI c L - a) Block structure of the Layer II bit stream I Mono 136 bits else 256 kits
27、 32 bits 16 bits Length coded in side-info -. b) Block structure of Layer Ill bit stream TO9031 80-95/d02 FIGURE 2fJ.52 If possible, this bit stream has to be transmitted unchanged. In most cases, this is impossible for the following reasons: - - additional framing bits are necessary for the transmi
28、ssion on the ISDN B-channels; if it is necessary to include error control in order to correct the bit errors, another coding hierarchy level has to be used. Table 1 gives all frame lengths defined in IS0 11 172-3. If the padding bit in the header is set, the frame contains an additional slot (1 byte
29、 for Layers II and III, 4 bytes for Layer I). The bit rate is encoded with 4 bits (bit rate index). The coding of the bit rate is different for the three layers (see IS0 11 172-3). Layer I and sampling frequency 44.1 kHz are not recommended for broadcast applications. 2 Network interface formats The
30、re is a distinction between dial-up connections (ISDN) and permanent connections. This distinction consists of the different routing of several B-channels constituting a virtual sound channel of more than 64 kbit/s, which requires a delay difference compensation in case of dial-up connections. Two t
31、ransmission formats are required: transmission of one mono/stereo signal using one to six 64 kbit/s channels or a single Ho channel in a switched ISDN network; transmission of one or more mono/stereo signais using, for example, Ho or Hl channels for permanent connections.) - - 1 For transmission of
32、one mono/stereo signal at a bit rate of 1 to 6 x 64 kbits on permanent connections, the X.21 leased circuit option can be used. In this case, H.221 framing is optional. 2 Recommendation 5.52 (07/96) STD*ITU-T RECMN J-52-ENGL L97b m 4Ab259L Ob24025 LA2 m Sampling Frequency (Hz) Layer TABLE VJ.52 7 32
33、 O00 44 100 48 O00 I II III I II III I II III 32 O00 40 O00 I Bitrate(bit/s) I I I I I I 1- I Ir1 48 144 144 32 104 104 32 96 96 120 - - 180 - - 130 - - 416000 448 O00 t 384 O00 I 576 I 1728 I - I 416 I 1253 I - I 384 I 1152 I - I I I I I I I I I 624 - - 452 - - 416 - - 672 - - 484 - - 448 - - I NOT
34、E - A dash “-“ in the table means that the combination of sampling frequency, bit rate and layer is not specified in ISO/IEC 1 1 172-3. 2.1 According to Recommendation 1.412 the following possibilities exist: Dial-up connections (switched ISDN network) a) B-channel interface structures i) ii) basic
35、interface structure: 2 B-channels + 1 D-channel(l6 kbits); primary rate B-channel interface structures: - - 1544 kbits primary rate: 23 B + 1 D (64 kbit/s); 2048 kbit/s primary rate: 30 B + 1 D (64 kbits). b) H-channel interface structures i) primary rate interface Ho-channel structures: - 1544 kbit
36、/s primary rate: 4 Ho; 3Ho + D. - 2048 kbit/s primary rate: 5 Ho + D. For the following parameters, appropriate means have to be provided: - - clock synchronization between source coder and network; time synchronization (delay difference compensation) between several B-channels. Recommendation 5.52
37、(07/96) 3 STDSITU-T RECMN J-52-ENGL L77b 48b257L Ob2Y02b 017 2.2 Permanent connections 2048 kbits or 1544 kbit/s signals are used. Framing is according to Recommendation G.704. The following parameters need consideration: - - - time slot allocation. clock synchronization between source coder and net
38、work; octet sequence integrity within the same frame; 3 Synchronization and frame alignment 3.1 Dial-up connections For all 64 kbit/s channels of the basic interface structure in dial-up connections, the framing according to Recommendation H.221, in conjunction with Recommendation H.242, should be u
39、sed. With the use of the H.221 framing there is a possibility to achieve both clock synchronization and time synchronization between up to six B-channels. This is permanently provided, also in case of a change of the routing during the transmission. Furthermore, the addition of H.221 framing to diai
40、-up connections (HO or 1 to 6 B-channels) provides a control channel harmonized with other N-ISDN audiovisual equipment. The procedure for initialization of the communication at the start of a call shall be according to Recommen- dationH.242, except that, if there is no requirement for intercommunic
41、ation with 3 kHz speech terminals, it is not necessary to transmit G.711 audio during the period until Sequence A is completed. The capabilaities to be transmitted during Sequence A include appropriate values from Table A.2kI.22 1, and a single command from that table introduces a mode switch to the
42、 required sound transmission mode. Particular attention is drawn to clause 13H.242 for the cases of transmission within a restricted network (multiple 56 kbits channels) and of intenvorking between unrestricted and restricted networks. Terminals on both types of network shall transmit within their c
43、apability sets the relevant values from attribute (1 10) of Table A.lM.221. 3.1.1 Basic interface structure To achieve the synchronization according to Recommendation H.221, an overhead consisting of a Frame Alignment Signal (FAS) and Bit Rate Allocation Signal (BAS) of 1.6 kbits is required per 64
44、kbit/s channel or in the first time slot of an Ho channel. For the transmission of bit rate reduced high-quality sound signals, Recommendation H.22 1 has been extended. 3.1.2 Realization of bit rates which are not explicitly listed in the bit rate table of the ISO/IEC 11172-3 Standard Figure 3 descr
45、ibes the different sections of the transmission system. The network provides data channels each with 64 kbits. If H.221 framing and an additional error protection is applied, the full channel capacity cannot be used by the IS0 1 1 172-3 encoder for audio data. The ISOiEC 11 172-3 bit stream is sub-d
46、ivided in audio frames corresponding to a sequence of 384 PCM audio samples for Layer I and 1152 PCM audio samples for Layers II and III. The audio frame length (see Table 1) is dependent on the bit rate index, the sampling frequency and the status of the padding bit, an information that is given in
47、 the audio frame header. The ISO/IEC 11 172-3 Standard allows for 14 different, explicitly listed bit rates, indicated by the so-called bit rate index value. An additional format, the “free format”, i.e. a user-defined audio frame length, can be chosen by using the bit rate index “0000”. Two methods
48、 may be used in order to realize those bit rates that are not explicitly listed in the bit rate tables of the ISO/IEC 11 172-3 Standard. These methods are: - - using the ancillary data field (recommended for Layers I and 11); dynamic bit rate switching (recommended for Layer III). The use of free fo
49、rmat is not recommended. 4 Recommendation 5.52 (07/96) 4 O c-4 2 a . i I- Recommendation 5.52 (07/96) 5 3.1.2.1 The last field in a ISOAEC 11 172-3 frame is the “ancillary data” field, which consists of all bits that are not used for audio. A minimum length of this field can be guaranteed by constraining the bit allocation in the encoder. The desired bit rate can be obtained by selecting a bit rate higher than the desired bit rate, taking into account the constraining of the ISOAEC Standard, and stripping off a number of bytes from eac
