1、 Rec. ITU-R BS.707-5 1 RECOMMENDATION ITU-R BS.707-5*,*Transmission of multisound in terrestrial television systems PAL B, B1 D1, G, H and I, and SECAM D, K, K1 and L (1990-1994-1995-1998-2005) Scope This Recommendation provides systems specifications for television multisound. The ITU Radiocommunic
2、ation Assembly, considering a) the increasing requirement worldwide for suitable means of broadcasting stereophonic and/or multichannel sound and/or data from terrestrial television transmitters; b) the technical developments in this area and in particular the relative merits of various possible ana
3、logue and digital methods, as described in Report ITU-R BS.795; c) the improvements in television sound quality achieved with recent developments of equipment used for the transmission and reception of the two sound-carrier FM system; d) the improvements in television sound quality achieved with the
4、 NICAM-728 system using digital coding; e) Recommendation ITU-R BO.651 concerning “Digital PCM coding for the emission of high-quality sound signals in satellite broadcasting (15 kHz nominal bandwidth)”; f) Recommendation ITU-R BO.650 concerning the adoption of MAC/packet systems for satellite broad
5、casting in channels defined by the World Administrative Radio Conference for the Planning of the Broadcasting-Satellite Service (Geneva, 1977) (WARC BS-77) and the desirability of a close measure of commonality between digital systems for satellite and terrestrial broadcasting; g) the advantage of l
6、ow-cost analogue circuitry for multisound television receivers for the two sound-carrier FM system; h) the development of digital audio circuitry for other applications in the home; j) the ruggedness of the two sound-carrier FM system in difficult reception areas especially under multipath reception
7、 conditions and its excellent compatibility with existing receivers, transmitters, networks and services, including the case of 7 MHz channel spacing; k) the need to use a digital sound system in television that satisfies simultaneously and with a generous margin, the contradictory constraints of: r
8、uggedness in difficult reception areas, including the requirement for failure of sound after vision, and *This Recommendation should be brought to the attention of the International Electrotechnical Commission (IEC). *Radiocommunication Study Group 6 made editorial amendments to this Recommendation
9、in 2002 in accordance with Resolution ITU-R 44. 2 Rec. ITU-R BS.707-5 compatibility between the new and existing services, including the case of 7 MHz channel spacing; l) the fact that the two sound-carrier FM system was introduced to the ex-CCIR in 1974, became operational in 1981, and is now in ex
10、tensive use in the Federal Republic of Germany and in various other countries; m) the fact that the NICAM-728 system was introduced to the ex-CCIR in 1987, became operational in 1988, is now in extensive use in Finland, Sweden, Denmark, Norway, New Zealand and the United Kingdom and is planned for i
11、ntroduction in various other countries; n) the urgency of establishing unified standards in order to provide for the introduction of stereophonic and/or multichannel sound for the television broadcast services, recommends 1 that if analogue multisound is introduced in terrestrial television emission
12、s in countries using PAL television systems B, B1, G and H, the two sound-carrier FM system, as defined in Annex 1 should be used; 2 that if digital multisound is introduced in terrestrial television emissions in countries using PAL television systems B, B1, D1, G, H and I, and SECAM television syst
13、ems D, K, K1 and L, the system specified in Annex 2 should be used. NOTE 1 Studies are continuing to define multisound system parameters to be recommended for other television systems. NOTE 2 The transmission systems described can, in some cases, be used for data services. Where applicable, referenc
14、e to these data services will be found in the Annexes containing the system specifications. NOTE 3 Interference caused by multisound emission to other television systems is dealt with in Report ITU-R BT.1214. Annex 1 System specifications for the two sound-carrier FM system TABLE 1 Emission characte
15、ristics of the two sound-carrier FM system (Television systems B, B1, G and H) Characteristics Sound carrier 1 Sound carrier 2 RF-sound carriers Frequency referred to vision carrier (MHz) 5.5(1)5.5 0.2421875(1)Power referred to peak vision (dB) 13 20 Modulation MF MF Frequency deviation (kHz) 50 50
16、Audio-bandwidth (Hz) 40 to 15 000 40 to 15 000 Pre-emphasis (s) 50 50 AF-signals Monophonic Monophonic 1 Monophonic 1 Stereophonic (A + B)/2 B Double sound Monophonic 1 Monophonic 2 Rec. ITU-R BS.707-5 3 TABLE 1 (end) Characteristics Sound carrier 1 Sound carrier 2 Identification signals(2)Subcarrie
17、r frequency (kHz) 54.6875(3)(3.5 line frequency) Modulation AM Modulation depth (%) 50(4)Modulation frequency:(3)(Hz) Monophonic 0 Stereophonic 117.5 (line frequency/133) Double sound 274.1 (line frequency/57) Frequency deviation of the second sound carrier by the subcarrier (kHz) 2.5 Audio-frequenc
18、y companding(5)Not yet defined (1)The frequency difference between both sound carriers is 15.5 line frequency = 242.1875 kHz. Phase-locking of both sound carriers with the line frequency gives improvements, but is not absolutely necessary. (2)Additional identification signals of the three sound mode
19、s may also be transmitted in the digital data line in the vertical blanking interval. (3)The subcarrier and identification frequencies are phase-locked with the line frequency. (4)The residual 50% AM modulation depth is reserved for future identification of audio-frequency companding. (5)The use of
20、a compatible audio companding system would improve the audio signal-to-noise ratio. Annex 2 Summary of the system specification for digital multisound with terrestrial television systems B, B1, G, H, I and L 1 Introduction The following is a summary of the specification of the systems for transmissi
21、on of digital multi-sound with terrestrial television systems B, B1, D1, D, G, H, I, K, K1 and L. 2 Frame format Frame length: 728 bits Frame transmission rate: 1 frame/ms 2.1 Frame structure Frame alignment word: 8 bits Control information: 5 bits Additional data: 11 bits Sound/data coding block: 7
22、04 bits _ Total: 728 bits 4 Rec. ITU-R BS.707-5 The 720 bits which follow the frame alignment word form a structure identical with that of the first-level protected, companded sound-signal blocks in the systems of the MAC/packet family, so that decoding of the sound signals may be performed by the s
23、ame type of decoder which is used in the above MAC systems. The first 16 bits of the block, which have not yet been allocated in the systems of the MAC/packet family, are used to signal control information (see 3.2) and as additional data bits (see 3.3). Frame structures for data services use the sa
24、me Frame Alignment Word (FAW), flag bit and additional data, with control bits as described in 3.2.2, but the audio samples are replaced by other data. 2.2 Bit interleaving Interleaving is applied to the sound/data coding block in order to minimize the effect of multiple-bit errors. The bits of each
25、 frame are transmitted in the following order: FAW 5 control bits C0 C411 additional data bits AD0 AD10704 bits of interleaved sound data 16 bits 44844766,7,81,2,3,4,5, 4484476,139,10,11,12 44444484444447624,21,22,23,7,18,19,2014,15,16,1 44 bits4 11 bitcompanded samples728156,112,68.688.116,72,28687
26、.115,71,27686.114,70,26685.157,113,69,2544444844444762.3 Energy dispersal scrambling After bit interleaving, the transmitted bit stream is scrambled for spectrum-shaping purposes by modulo-two addition of a Pseudo-Random Binary Sequence (PRBS). The framing code is not scrambled. The PRBS generator i
27、s reinitialized after the frame alignment word of each frame such that the first bit of the sequence is added to the bit that immediately follows the frame alignment word. The generator polynomial of the PRBS is x9+ x4+ 1 and the initialization word is 111111111. 3 Coding of information 3.1 Frame al
28、ignment word The frame alignment word is 01001110, the left-most bit being transmitted first. 3.2 Control information The control information is conveyed by a frame bit C0, three application control bits, C1, C2 and C3, and a reserve sound switching flag, C4. Rec. ITU-R BS.707-5 5 3.2.1 Frame flag b
29、it The frame flag bit, C0, is set to “1” for 8 successive frames and to “0” for the next eight frames; thus it defines a 16-frame sequence. This frame sequence is used to synchronize changes in the type of information being carried in the channel. C0= 1 Frames 1 8 C0= 0 Frames 9 16 3.2.2 Application
30、 control bits The application control bits define the application of the 704-bit sound/data coding block, as shown below. When a change to a new application is required, these control bits change to define the new application on frame 1 of the last 16-frame sequence of the current application. The 7
31、04-bit sound/ data blocks change to the new application on frame 1 of the following 16-frame sequence. Application control information C1C2C3(1)Contents of 704-bit sound/data block 0 0 0 Stereo signal comprising alternate A-channel and B-channel samples 0 1 0 Two independent mono sound signals trans
32、mitted in alternate frames (designated M1 and M2) 1 0 0 One mono signal and one 352 kbit/s transparent data channel transmitted in alternate frames 1 1 0 One 704 kbit/s transparent data channel (1)C3= 1 provides for signalling additional sound or data coding options which have not yet been specified
33、. When C3= 1, decoders not equipped for such additional options should provide no sound output. 3.2.3 Reserve sound switching flag C4= 0 The analogue sound signal is not carrying the same programme as the digital signal. C4= 1 The analogue sound signal is carrying the same programme as the digital s
34、tereo signal (or mono signal in M1 frames). 3.3 Additional data Eleven additional data bits AD0 to AD10 indicated in 2.2 are reserved for future applications yet to be defined. 6 Rec. ITU-R BS.707-5 3.4 Sound/data block Sampling frequency: 32 kHz Initial resolution: 14 bit/sample Companding characte
35、ristics: near-instantaneous, with compression to 10 bit/ sample in 32-sample (1 ms) blocks Coding for compressed samples: 2s complement Pre-emphasis: ITU-T Recommendation J.17 Audio overload level: Systems B, B1, D1, G, H: +12 dBu0 at 2.0 kHz System I: +14.8 dBu0 at 2.0 kHz System L: +12 dBu0 at 2.0
36、 kHz Error protection: 1 parity bit/sample Scale factor transmission: signalled in parity Stereo sound signal transmission: odd-numbered samples of each block convey A-channel (left); even-numbered samples convey B-channel (right) Mono sound signal transmission: mono signal M1 in odd-numbered frames
37、; mono signal M2 in even-numbered frames. If only one mono signal is transmitted it will be M1 Bit transmission order: the bits of each sample are transmitted least significant bit first with parity following the m.s.b. The control information is not used. However other information could be transmit
38、ted by the same means, i.e. two information bits modifying samples 55, 56, 57, 58, 59 and 60, 61, 62, 63, 64 respectively. Receivers should be designed to take advantage of this facility. 4 Modulation parameters 4.1 Analogue signals Systems B, B1, D1, G, and H System I Systems D, K, K1, L 4.1.1 Visi
39、on component As given in Rec. ITU-R BT.470 As given in Rec. ITU-R BT.470 As given in Recommen-dation ITU-R BT.470 except for the following parameters: the nominal width of the main sideband is reduced to approximately 5.1 MHz. With the L standard, the video levels in the radiated signal are reduced
40、in order to leave a minimum of 5% level residual radiated carrier Rec. ITU-R BS.707-5 7 4.1.2 Analogue sound component As given in Recommendation ITU-R BT.470 except for sound carrier power as given below 4.1.3 Power ratio between the peak vision carrier and the analogue sound carrier Approx. 20:1 A
41、pprox. 10:1 Approx. 10:1 and 40:1 4.2 Digital signal Systems B, B1, D1, D, G, H, K, K1 and L System I 4.2.1 Type of modulation Differentially encoded Quadrature Phase Shift Keying (DQPSK) 4.2.2 Bit rate 728 kbit/s 10 part/million 4.2.3 Carrier frequency 5.85 MHz (unrelated to bit-rate) above the vis
42、ion carrier frequency 6.552 MHz above the vision carrier frequency. (In some countries the relative carrier frequency and bit rate may be locked to each other.) 4.2.4 Signal level The power ratio between the peak vision carrier and the modulated digital signal is approximately 100:1 for systems B, B
43、1, G, H and I and 500:1 for systems D, K, K1 and L. 4.2.5 Spectrum Impulses at the symbol rate of 364 kHz are filtered by a lowpass filter with the following amplitude-frequency response before quadrature modulation. The filter has constant group delay. Systems B, B1, D1, D, G, H, K and L System I ms 3641ms 36414.0 1for 01for 2cos)( 21for 0212t1for 212cos21for 1)(s=+=ssssssssssttktftfftfHtkftkfktkfkttkffHUse of the same filter on reception gives 40% cosine roll-off overall Use of the same filter on reception gives 100% cosine roll-off overall
