ITU-R BT 1207-1-1997 Data Access Methods for Digital Terrestrial Television Broadcasting《数字地面电视广播的数据接入方法》.pdf
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1、Rec. ITU-R BT.1207-1 1RECOMMENDATION ITU-R BT.1207-1DATA ACCESS METHODS FOR DIGITAL TERRESTRIALTELEVISION BROADCASTING(Question ITU-R 121/11)(1995-1997)Rec. ITU-R BT.1207-1The ITU Radiocommunication Assembly,consideringa) that many kinds of service signals, from high-speed video signals to low-speed
2、 data signals may be multi-plexed within a channel;b) that multiple programme services may be multiplexed within a channel;c) that special care should be taken in choosing methods to access particular signals;d) that in many cases, particularly in the case of data services, receivers may not be requ
3、ired to deal with all themultiplexed signals carried by the channel,recommends1 that digital terrestrial television broadcasting (DTTB) systems should use the data access methods as specifiedin the International Organization for Standardization/International Electrotechnical Commission Standard 1381
4、8-1(ISO/IEC Standard 13818-1). The outline of the specifications is shown in Annex 1.ANNEX 11 IntroductionIn DTTB, many kinds of television programmes, sound programmes, and data broadcasting programmes are broadcastover one channel. The indirect identification by the Program Specific Information (P
5、SI) of ISO/IEC Standard 13818-1should be used as the data access method which enables viewers/listeners to easily access the desired program.Furthermore, the ISO/IEC Standard 13818-1 specifications allow the system to extend the receivers functions forviewers/listeners, using private sections or pri
6、vate descriptors.2 Basic data access flow in the receiverA program is received based on the following four tables of PSI in ISO/IEC Standard 13818-1 specifications: Program Map Table (PMT), which transmits the relationship among the elementary streams which constitute theprogram, its attribute infor
7、mation, and the Packet Identifier (PID) of the packet in which the program is sent. Network Information Table (NIT), which transmits the information about the transmission channel in which theprogram is sent. Program Association Table (PAT), which indicates the PIDs in which PMT or NIT is transmitte
8、d. Conditional Access Table (CAT).When the desired program is designated, the elementary streams which construct each program are received according tosuch a flow diagram as shown in Fig. 1 using these tables.2 Rec. ITU-R BT.1207-11207-01. . . . . . . . . . . . . . . . . . . . . . . . .FIGURE 1An ex
9、ample of data access flow in the receiverTransport streamReceivePID = 0Program AssociationTable (PAT)PR # = 0 PID = NPR # = X PID = PXProgram # = XSelectReceivePID = NNetworkInformationTable (NIT)ReceivePID = 1ConditionalAccessTable (CAT)ReceivePID = PXProgram MapTable (PMT)ReceivePID = PCReceivePID
10、 = PVReceivePID = PAProgramclock(PCR)Video PESpacketAudio PESpacketTimingregenerationVideodecodingAudiodecodingVideodisplayAudiodisplayPES : packetized elementary bit streamPCR: program clock referencePR # = X video PID = PVaudio PID = PAclock PID = PCFIGURE 1/BT.1207.D01 = 3 CMRec. ITU-R BT.1207-1
11、33 Outline of the PSI of the Moving Pictures Expert Group (MPEG) specifications andthe extensions for broadcasting applicationsFunctions of each field in the PSI of the ISO/IEC Standard 13818-1 specifications and the extensions and newdefinitions of descriptors for broadcasting applications are as f
12、ollows. NIT indicates the service, transport ID, channelfrequency, etc., in general, but it is not specified in ISO/IEC Standard 13818-1. Specifications for NIT standards andmore extensions for broadcasting applications are defined and recommended in Recommendation ITU-R BT.1300.3.1 Program Associat
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