TS流分析标准24翻译版.docx

1、TS流分析标准24翻译版2.4 Transport Stream bitstream requirements2.4.1 Transport Stream coding structure and parametersThe ITU-T Rec. H.222.0 | ISO/IEC 13818-1 Transport Stream coding layer allows one or more programs to be combinedinto a single stream. Data from each elementary stream are multiplexed togethe

2、r with information that allowssynchronized presentation of the elementary streams within a program.TS编码层允许将一个或多个节目组合成一个流。每个ES的数据由同一个节目中ES的同步表示的信息来复合。A Transport Stream consists of one or more programs. Audio and video elementary streams consist of access units.一个TS是由一个或多个节目组成。音频和视频的ES是由访问单元(AU)组成。El

3、ementary Stream data is carried in PES packets. A PES packet consists of a PES packet header followed by packetdata. PES packets are inserted into Transport Stream packets. The first byte of each PES packet header is located at thefirst available payload location of a Transport Stream packet.PES包装载有

4、ES数据。PES包是由包头和包数据组成。PES包又插入到TS包中。每个PES包头的第一个字节装载于TS包的第一个有效负载位置。The PES packet header begins with a 32-bit start-code that also identifies the stream or stream type to which the packetdata belongs. The PES packet header may contain decoding and presentation time stamps (DTS and PTS). The PESpacket he

5、ader also contains other optional fields. The PES packet data field contains a variable number of contiguousbytes from one elementary stream.PES包头由一个32位长的起始码开始，它定义了包数据所属的流或流类型。PES包头还包含有解码和表示时间戳(DTS and PTS)。PES包头还有其它的可选域。PES包数据域包含有变长且连续的ES数据字节。 Transport Stream packets begin with a 4-byte prefix, wh

6、ich contains a 13-bit Packet ID (PID), defined in Table 2-2. ThePID identifies, via the Program Specific Information (PSI) tables, the contents of the data contained in the TransportStream packet. Transport Stream packets of one PID value carry data of one and only one elementary stream.TS包由4字节的前缀开始

7、，它包含一个13比特长的包ID(PID),定义见于Table2-2。PID的识别要通过PSI表(它被包含在TS包中)。一个PID的TS包有且只能有一个ES。The PSI tables are carried in the Transport Stream. There are four PSI tables: Program Association Table; 节目相关表 Program Map Table; 节目映射表 Conditional Access Table; 条件访问表 Network Information Table. 网络信息表These tables contain

8、the necessary and sufficient information to demultiplex and present programs. The Program MapTable, in Table 2-28, specifies, among other information, which PIDs, and therefore which elementary streams areassociated to form each program. This table also indicates the PID of the Transport Stream pack

9、ets which carry the PCRfor each program. The Conditional Access Table shall be present if scrambling is employed. The Network InformationTable is optional and its contents are not specified by this Recommendation | International Standard.这些表包含了必须而充分的信息来解复用和显示节目。Table 2-28对应的节目映射表指明了哪个PID(也就是哪个ES)对应的

10、是哪个节目。这个表也同样指明了TS包(它带有每个节目的PCR域)的PID。条件访问表用于scrambling时。网络信息表是可选的，它的说明不在本说明书。Transport Stream packets may be null packets. Null packets are intended for padding of Transport Streams. They may beinserted or deleted by re-multiplexing processes and, therefore, the delivery of the payload of null packe

11、ts to the decodercannot be assumed.TS包可以是空包。This Recommendation | International Standard does not specify the coded data which may be used as part of conditionalaccess systems. This Specification does, however, provide mechanisms for program service providers to transport andidentify this data for d

12、ecoder processing, and to reference correctly data which are specified by this Specification. Thistype of support is provided both through Transport Stream packet structures and in the conditional access table (refer toTable 2-27 of the PSI).条件访问表的说明不在本文档2.4.2 Transport Stream system target decoderT

13、he semantics of the Transport Stream specified in 2.4.3 and the constraints on these semantics specified in 2.7 requireexact definitions of byte arrival and decoding events and the times at which these occur. The definitions needed are setout in this Recommendation | International Standard using a h

14、ypothetical decoder known as the Transport Stream SystemTarget Decoder (T-STD). Informative Annex D contains further explanation of the T-STD.TS语义的说明在2.4.3节，对这些语义的限定在2.7节。The T-STD is a conceptual model used to define these terms precisely and to model the decoding process during theconstruction or

15、verification of Transport Streams. The T-STD is defined only for this purpose. There are three types ofdecoders in the T-STD: video, audio, and systems. Figure 2-1 illustrates an example. Neither the architecture of theT-STD nor the timing described precludes uninterrupted, synchronized play-back of

16、 Transport Streams from a variety ofdecoders with different architectures or timing schedules.Figure 2-1 Transport Stream system target decoder notationThe following notation is used to describe the Transport Stream system target decoder and is partially illustrated inFigure 2-1 above.i, i, i are in

17、dices to bytes in the Transport Stream. The first byte has index 0.j is an index to access units in the elementary streams.k, k, k are indices to presentation units in the elementary streams.n is an index to the elementary streams.p is an index to Transport Stream packets in the Transport Stream.t(i

18、) indicates the time in seconds at which the i-th byte of the Transport Stream enters the system target decoder. The value t(0) is an arbitrary constant.PCR(i) is the time encoded in the PCR field measured in units of the period of the 27 MHz system clockwhere i is the byte index of the final byte o

19、f the program_clock_reference_base field.An(j) is the j-th access unit in elementary stream n. An(j) is indexed in decoding order.tdn(j) is the decoding time, measured in seconds, in the system target decoder of the j-th access unit inelementary stream n.Pn(k) is the k-th presentation unit in elemen

20、tary stream n. Pn(k) results from decoding An(j). Pn(k) isindexed in presentation order.tpn(k) is the presentation time, measured in seconds, in the system target decoder of the k-th presentationunit in elementary stream n.t is time measured in seconds.Fn(t) is the fullness, measured in bytes, of th

21、e system target decoder input buffer for elementary stream nat time t.Bn is the main buffer for elementary stream n. It is present only for audio elementary streams.BSn is the size of buffer, Bn, measured in bytes.Bsys is the main buffer in the system target decoder for system information for the pr

22、ogram that is in theprocess of being decoded.BSsys is the size of Bsys, measured in bytes.MBn is the multiplexing buffer, for elementary stream n. It is present only for video elementary streams.MBSn is the size of MBn, measured in bytes.EBn is the elementary stream buffer for elementary stream n. I

23、t is present only for video elementarystreams.EBSn is the size of the elementary stream buffer EBn, measured in bytes.TBsys is the transport buffer for system information for the program that is in the process of being decoded.TBSsys is the size of TBsys, measured in bytes.TBn is the transport buffe

24、r for elementary stream n.TBSn is the size of TBn, measured in bytes.Dsys is the decoder for system information in Program Stream n.Dn is the decoder for elementary stream n.On is the re-order buffer for video elementary stream n.Rsys is the rate at which data are removed from Bsys.Rxn is the rate a

25、t which data are removed from TBn.Rbxn is the rate at which PES packet payload data are removed from MBn when the leak method is used.Defined only for video elementary streams.Rbxn(j) is the rate at which PES packet payload data are removed from MBn when the vbv_delay method isused. Defined only for

26、 video elementary streams.Rxsys The rate at which data are removed from TBsys.Res The video elementary stream rate coded in a sequence header.2.4.2.1 System clock frequencyTiming information referenced in the T-STD is carried by several data fields defined in this Specification. Refer to2.4.3.4 and

27、2.4.3.6. In PCR fields this information is coded as the sampled value of a programs system clock. The PCRfields are carried in the adaptation field of the Transport Stream packets with a PID value equal to the PCR_PID definedin the TS_program_map_section of the program being decoded.T-STD的时钟信息参考定义在2

28、.4.3.4，2.4.3.6节的多个数据域中，在PCR域中，时钟信息编码成节目的系统时钟的样本值。而PCR域定义在TS包的PID等于PCR_PID的adaptation域中Practical decoders may reconstruct this clock from these values and their respective arrival times. The following areminimum constraints which apply to the programs system clock frequency as represented by the valu

29、es of the PCRfields when they are received by a decoder.实际的解码器可能会这些值和期望到达时间来重建时钟。重建节目的系统时钟频率定义如下。The value of the system clock frequency is measured in Hz and shall meet the following constraints:NOTE Sources of coded data should follow a tighter tolerance in order to facilitate compliant operation

30、of consumer recordersand playback equipment.A programs system_clock_frequency may be more accurate than required. Such improved accuracy may be transmittedto the decoder via the System clock descriptor described in 2.6.20.节目的system_clock_frequency可以比上面描述的精度更高。这个更高精度可以通过系统时钟描述子(见于2.6.20节)传输给解码器。Bit r

31、ates defined in this Specification are measured in terms of system_clock_frequency. For example, a bit rate of27 000 000 bits per second in the T-STD would indicate that one byte of data is transferred every eight (8) cycles of thesystem clock.本说明书中的比特率以system_clock_frequency为单位。例如，在T-STD中27Mb/s指的是传

32、输一个字节数据需要8个系统时钟。The notation system_clock_frequency is used in several places in this Specification to refer to the frequency of a clockmeeting these requirements. For notational convenience, equations in which PCR, PTS, or DTS appear, lead to values oftime which are accurate to some integral multiple of (300 233/system_clock_frequency) seconds. This is due to theencoding of PCR timing information as 33 bits of 1