1、 Rec. ITU-R SNG.1561 1 RECOMMENDATION ITU-R SNG.1561 Digital transmission of high-definition television for satellite news gathering and outside broadcasting (Question ITU-R 226/4) (2002) The ITU Radiocommunication Assembly, considering a) that in point-to-point video transmission via satellite, qua
2、lity of service objectives are fixed on the basis of large sized transmitting and receiving station antennas; b) that the introduction of highly portable transmitting stations is essential particularly for news gathering operations and can provide a satisfactory technical solution; c) that the speci
3、al characteristics needed for portable and transportable stations and the reduced link availability characteristics of highly portable stations may necessitate acceptance of reduced transmission performance objectives; d) that it may be necessary to provide, on the same satellite bearer, the auxilia
4、ry signals required for the operation of portable and transportable transmitting stations but that these auxiliary signals should not have a perceptible effect on the transmission quality of the television signals; e) that throughout the world, where news events take place, standardized and uniform
5、technical and operating procedures should be established to ensure prompt activation of satellite news gathering (SNG) and outside broadcasting services; f) that to facilitate the international coverage of news, it is necessary to adopt uniform operating parameters for high-definition television (HD
6、TV) digital SNG, to ensure interoperability between equipment from different manufactures, noting a) that Recommendation ITU-R SNG.1007 provides uniform technical standards for SNG; b) that Recommendation ITU-R SNG.1421 gives common operating parameters to ensure interoperability for transmission of
7、 digital conventional television SNG, recommends 1 that when requiring international interoperability, the HDTV digital SNG equipment should comply with the uniform operating parameters described in Annex 1. 2 Rec. ITU-R SNG.1561 ANNEX 1 1 Scope The system is based on the following technical require
8、ments: The system should be applicable to all possible satellite transponders, including future planned ones. The source coding system should conform to the MPEG-2 systems1. The channel coding system should be as flexible as possible, with the highest possible efficiency for the intended application
9、. It should be selectable by the user according to the characteristics of the transmission channel. The user bit rate should meet the picture quality requirements which may be requested from other relevant ITU Study Groups. The information bit rate with outer coding should be defined, taking account
10、 of connectivity with existing international digital hierarchies as well as coding performance. The SNG system may include the auxiliary channels, such as communication channels. 2 Source encoding, service information and multiplexing 2.1 Video encoding Video encoding in accordance with MPEG-2 4:2:2
11、PHL is recommended. The use of MPEG-2 MPHL may also be considered. Video source and bit rate (horizontal and vertical resolution) do not affect interoperability. These parameters are not specified in this Recommendation as integrated receiver decoders (IRD) should handle these automatically. 2.2 Aud
12、io encoding Audio encoding to MPEG-1 Layers I and II, MPEG-2 Layers I and II, MPEG-2 AAC, or AC-3 should be used. Audio channel configuration, source and bit rate do not affect interoperability. These parameters are not specified in this Recommendation as IRD should handle these automatically. 2.3 D
13、ata encoding Subject for further study. _ 1MPEG-2 refers to ITU-T Recommendations H.222 and H.262, or ISO/IEC 13818. Rec. ITU-R SNG.1561 3 2.4 Program Specific Information (PSI) and Service Information (SI) 2.4.1 General PSI and SI should conform to all relevant requirements in accordance with appli
14、cable standards and guidelines. The following tables are mandatory for MPEG-2 digital video broadcasting using satellite (DVB-S) compliance: PAT: Program Association Table PMT: Program Map Table CAT: Conditional Access Table NIT: Network Information Table, actual delivery system SDT: Service Descrip
15、tion Table, (actual transport stream) TDT: Time and Date Table EIT: Event Information Table, present/following actual transport stream. Some of these service information tables or their contents may not be relevant to digital SNG service, but they are still required. This Recommendation does not spe
16、cify values or syntax of the service information tables but recommends that wherever possible default values should be used by the equipment to facilitate simple and rapid deployment of digital SNG. In digital SNG transmissions, editing of the SI tables in the field may be impossible due to operatio
17、nal problems. Therefore, only the following MPEG-2 defined SI tables PAT, PMT and SDT transport stream Service Description Table are mandatory. 2.4.2 First SDT descriptor See Recommendation ITU-R SNG.1421. 2.4.3 Second SDT descriptor See Recommendation ITU-R SNG.1421. 2.4.4 Guidelines 2.4.4.1 Guidel
18、ines for the usage of the SDT (transport stream Service Description Table) within digital SNG streams SDTs are repeated at least every 10 s. The station_identification_char field contains the following items, comma-separated and in the following order: usual station code; SNG headquarter; SNG provid
19、er. The usual station code is the code assigned to the station by the satellite operator with which the station is most frequently used. 4 Rec. ITU-R SNG.1561 The SNG headquarter (operating during the transmission period) is the control centre through which the station can uniquely be identified (by
20、 giving its usual station code) and quickly located. The SNG provider is the owner of the SNG station. IRDs should be flexible enough to handle at least the mandatory service information table, and intelligent enough to ignore optional service information that they have not been designed to utilize.
21、 Digital SNG IRDs shall be able to decode and interpret the SDT and the descriptors specified. 2.4.4.2 Guidelines to achieve compatibility with consumer IRDs If compatibility with consumer IRDs is required, the SDT shall contain three descriptors: The first descriptor is a transport stream descripto
22、r 0x67 containing the ASCII string DVB. The presence of this descriptor implies that all SI tables shall be present according to the DVB-SI specification. The second descriptor is the transport stream descriptor 0x67 containing the ASCII string CONA. The presence of this descriptor indicates that th
23、e transmission is of contribution nature. For digital SNG transmissions, the third descriptor is the digital SNG descriptor 0x68. 2.5 Multiplexing The system input stream is organized in fixed length packets, following the MPEG-2 transport multiplexer MUX (see ITU-T Recommendation H.222). The total
24、packet length of the MPEG-2 transport multiplex packet is 188 bytes. 3 Transmission system The system is defined as the functional block of equipment performing the adaptation of the baseband TV signal, from the output of the MPEG-2 transport multiplexer (see ITU-T Recommendation H.222), to the sate
25、llite channel characteristics. The system transmission frame is synchronous with the MPEG-2 multiplex transport packets (see ITU-T Recommendation H.222). The system uses 8-phase shift keying (8-PSK) modulation, and optionally quadrature (QPSK) or 16-quadrature amplitude modulation (16-QAM) modulatio
26、ns, and the concatenation of convolutional and Reed-Solomon (RS) codes. For 8-PSK and 16-QAM, pragmatic trellis coding applies, optimizing the error protection of the convolutional code defined in Recommendation ITU-R BO.1211. The convolutional code is able to be configured flexibly, allowing the op
27、timization of the system performance for a given satellite transponder bandwidth. All the transmission systems are according to Recommendation ITU-R SNG.1421 (see Fig. 1). Rec. ITU-R SNG.1561 5 1561-0113nRS (204,188)2FIGURE 1Functional block diagram of the systemInnercoderBasebandshapingBitmappingin
28、toconstellationModulatorMultiplexingadaptationandenergydispersalAccording to Rec. ITU-R SNG.1421* = 0.25 for 8-PSK and 16-QAM (optional).InterleaverI = 12OutercoderAccording to Rec. ITU-R BO.1211Satellite channel adapterMPEG-2 source codingand multiplexingAudiocoderDatacoderVideocoderTransportmultip
29、lexerProgrammemultiplexerTo the RFsatellitechannelQPSK (optional)8-PSK16-QAM (optional)Convolutionaltype = 0.35*Servicecomponents Services6 Rec. ITU-R SNG.1561 The following processes are applied to the data stream (see Fig. 1): transport multiplex adaptation and randomization for energy dispersal (
30、according to Recommendation ITU-R BO.1211); outer coding (i.e. RS) (according to Recommendation ITU-R BO.1211); convolutional interleaving (according to Recommendation ITU-R BO.1211); inner coding: punctured convolutional coding (according to Recommendation ITU-R BO.1211); pragmatic trellis coding a
31、ssociated with 8-PSK and 16-QAM (optional); bit mapping into constellations: 8-PSK; QPSK (optional); 16-QAM (optional); squared-root raised-cosine baseband shaping: roll-off factor = 0.35 according to Recommendation ITU-R BO.1211 for QPSK, 8-PSK and 16-QAM; additional optional roll-off factor = 0.25
32、 (for the modulations 8-PSK and 16-QAM); quadrature modulation (according to Recommendation ITU-R BO.1211). If the received signal is above C/N and C/I threshold, the forward error correction technique adopted in the system is designed to provide a quasi-error-free (QEF) quality target. The QEF mean
33、s less than one uncorrected error-event per transmission hour, corresponding to bit error ratio = 1 1010to 1 1011at the input of the MPEG-2 demultiplexer. 3.1 Adaptation to satellite transponder characteristics The symbol rate is matched to given transponder characteristics, and, in the case of mult
34、iple carriers per frequency division multiplexing (FDM) transponder, to the adopted frequency plan. Examples of possible use of the system are given in Appendix 1. 3.2 Interfacing See Recommendation ITU-R SNG.1421. 3.3 Channel coding See Recommendation ITU-R SNG.1421. 3.4 Baseband shaping and quadra
35、ture modulation See Recommendation ITU-R SNG.1421 taking into account that 8-PSK is the recommended modulation scheme. 3.5 Error performance See Recommendation ITU-R SNG.1421 taking into account that 8-PSK is the recommended modulation scheme. Rec. ITU-R SNG.1561 7 3.6 Transmission set-ups for emerg
36、ency situations At least one set of operating parameters should be defined for preset or default mode of operation. 4 Two-way communication channels Subject for further study. APPENDIX 1 TO ANNEX 1 Examples of possible use of the system In single carrier per transponder configurations, the transmiss
37、ion symbol rate, Rscan be matched to given transponder bandwidth (BW) (at 3 dB), to achieve the maximum transmission capacity compatible with the acceptable signal degradation due to transponder bandwidth limitations. To take into account possible thermal and ageing instabilities, reference can be m
38、ade to the frequency response mask of the transponder. In the multi-carrier FDM configuration, Rscan be matched to the frequency slot, BS, allocated to the service by the frequency plan, to optimize the transmission capacity while keeping the mutual interference between adjacent carriers at an accep
39、table level. Table 1 gives examples of the maximum useful bit-rate capacity Ruachievable by the system versus the allocated bandwidths BW or BS. The figures for very low and very high bit rates may be irrelevant for specific applications. In these examples the adopted BW/Rsor BS/Rsratios are = 1 + =
40、 1.35, where is the roll-off factor of the modulator. This choice allows to obtain a negligible Eb/N0degradation due to transponder bandwidth limitations, and also to adjacent channel interference on a linear channel. Higher bit rates can be achieved with the narrow roll-off factor = 0.25 (optional
41、for 8-PSK and 16-QAM) and BW/Rsor BS/Rsequal to = 1 + = 1.25. Table 2 considers possible examples of use of the system in the single carrier per transponder configuration. Different modulation and inner code rates are given with the relevant bit rates. According to typical practical applications, a
42、BW/Rsratio equal to 1.31 is considered, offering a slightly better spectrum efficiency than the examples of Table 1 for the same modulation/coding schemes. The considered transponder bandwidth of 36 MHz is wide enough to allow high-quality 4:2:2PHL single channel per carrier (SCPC) transmissions, as
43、 well as MPHL and 4:2:2PHL multiple channels per carrier (MCPC) transmissions. Table 3 gives useful transmission set-up examples conformed for the use of BW/Rsratio equal to 1.207. 8 Rec. ITU-R SNG.1561 TABLE 1 Examples of maximum bit rates versus transponder BW or BS, for BW/Rsor BS/Rs= = 1.35 (app
44、licable for HDTV) TABLE 2 Examples of system configurations by satellite: single carrier per transponder Quasi-constant envelope modulations, such as QPSK and 8-PSK, are power efficient in single carrier per transponder configuration, since they can operate on transponders driven near saturation. Co
45、nversely, 16-QAM is not power efficient since it can only operate on quasi-linear transponders (i.e. with large output-back-off (OBO). The use of the narrow roll-off = 0.25 with 8-PSK can produce a larger non-linear degradation by satellite. Ru (Mbit/s)(2)QPSK 8-PSK 16-QAM BW or BS (MHz) Rs = BW/1.3
46、5 (MBd)(1)Rate 1/2 Rate 2/3 Rate 3/4 Rate 5/6 Rate 7/8 Rate 2/3 Rate 5/6 Rate 8/9(3)Rate 3/4 Rate 7/8 72 53.333 49.1503 65.5338 73.7255 81.9172 86.0131 98.3007 122.876 131.068 147.451 172.026 54 40.000 36.8627 49.1503 55.2941 61.4379 64.5098 73.7255 92.1568 98.3007 110.588 129.020 46 34.074 31.4016
47、41.8688 47.1024 52.3360 54.9528 62.8032 78.5040 83.7376 94.2047 109.906 41 30.370 27.9884 37.3178 41.9826 46.6473 48.9797 55.9768 69.971 74.6357 83.9651 97.9593 36 26.666 24.5752 32.7669 36.8627 40.9586 43.0065 49.1503 61.4379 65.5338 73.725 86.0131 33 24.444 22.5272 30.0363 33.7908 37.5454 39.4227
48、45.0545 56.3181 60.0726 67.5817 78.8453 30 22.222 20.4793 27.3057 30.7190 34.1322 35.8388 40.9586 51.1983 54.6115 61.4379 71.6776 27 20.000 18.4314 24.5752 27.6471 30.7190 32.2549 36.8627 46.0784 49.1503 55.2941 64.5098 18 13.333 16.3834 18.4314 20.4793 21.5030 24.5752 30.7190 32.7669 36.8627 43.006
49、5 15 11.111 17.0661 17.9194 24.5752 25.5991 27.3057 30.7190 35.8388 12 8.888 16.3834 20.4793 21.8446 24.5752 28.6710 9 6.666 16.3834 18.4314 21.5033 (1)BW/Rsor BS/Rsratios different from 1 + may be adopted for different service requirements. The adoption of BS/Rsfigures significantly lower than 1 + (e.g. BS/Rs= 1.207 associated with = 0.35), to improve the spectrum exploitation, should be carefully studied on a case-by-case basis, since sev
