CAN CSA-ISO IEC 13818-9-2001 Information Technology - Generic Coding of Moving Pictures and Associated Audio Information - Part 9 Extension for Real Time Interface for Systems Deco.pdf

1、National Standard of CanadaCAN/CSA-ISO/IEC 13818-9-01(ISO/IEC 13818-9:1996)International Standard ISO/IEC 13818-9:1996 (first edition, 1996-12-15), has been adopted withoutmodification as CSA Standard CAN/CSA-ISO/IEC 13818-9-01, which has been approved as a NationalStandard of Canada by the Standard

2、s Council of Canada.ISBN 1-55324-370-6 February 2001Reference numberISO/IEC 13818-9:1996(E)The Canadian Standards Association, which The Standards Council of Canada is theoperates under the name CSA International coordinating body of the National Standards system, (CSA), under whose auspices this Na

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16、tario, M9W 1R3CanadaAlthough the intended primary application of this Standard is stated in its Scope, it is importantto note that it remains the responsibility of the users to judge its suitability for their particular purpose.Registered trade-mark of Canadian Standards AssociationInformation techn

17、ology Generic coding of moving pictures and associatedCAN/CSA-ISO/IEC 13818-9-01 audio information Part 9: Extension for real time interface for systems decodersFebruary 2001 CSA/1CAN/CSA-ISO/IEC 13818-9-01Information technology Genericcoding of moving pictures andassociated audio information Part 9

18、: Extension for real timeinterface for systems decodersCSA PrefaceStandards development within the Information Technology sector is harmonized with internationalstandards development. Through the CSA Technical Committee on Information Technology (TCIT),Canadians serve as the Canadian Advisory Commit

19、tee (CAC) on ISO/IEC Joint Technical Committee 1 onInformation Technology (ISO/IEC JTC1) for the Standards Council of Canada (SCC), the ISO memberbody for Canada and sponsor of the Canadian National Committee of the IEC. Also, as a member of theInternational Telecommunication Union (ITU), Canada par

20、ticipates in the International Telegraph andTelephone Consultative Committee (ITU-T).This International Standard was reviewed by the CSA TCIT under the jurisdiction of the StrategicSteering Committee on Information Technology and deemed acceptable for use in Canada. (A committeemembership list is av

21、ailable on request from the CSA Project Manager.) From time to time, ISO/IEC maypublish addenda, corrigenda, etc. The CSA TCIT will review these documents for approval and publication. For a listing, refer to the CSA Information Products catalogue or CSA Info Update or contact a CSA Salesrepresentat

22、ive. This Standard has been formally approved, without modification, by these Committeesand has been approved as a National Standard of Canada by the Standards Council of Canada.February 2001 CSA International 2001All rights reserved. No part of this publication may be reproduced in any form whatsoe

23、ver without the prior permission ofthe publisher. ISO/IEC material is reprinted with permission. Inquiries regarding this National Standard of Canada shouldbe addressed to CSA International, 178 Rexdale Boulevard, Toronto, Ontario, M9W 1R3.INTERNATIONAL STANDARD ISO/IEC 13818-9 First edition 1996-I

24、2-l 5 Information technology - Generic coding of moving pictures and associated audio information - Part 9: Extension for real time interface for systems decoders Technologies de I information - Codage g l real-time constraints are imposed on the values of PCR in relation to their arrival time in th

25、e RTD; l the buffer sizes defined in the T-STD are different in the RTD; and there is an extra requirement on the Transport Buffer occupancy (see the end of 2.4). 2.2 Clock Frequency Requirements The requirements on the system clock with respect to frequency and frequency slew given in ISO/IEC 138 1

26、8.1,2.4.2.1 are also mandatory for the Real-Time Interface. 2.3 PCR Accuracy Requirements This subclause defines a single constraint on the relationship between the arrival time of all the bytes containing the last bit of a program - clock reference base field for a single program of a Transport Str

27、eam, - - and the value carried in the corresponding program clock references. Specifically, l let system clock counter(t) be a counter that counts cycles of a system clock that satisfies the frequencyrequirGments specified in 2.2 above, where t represents time; l let i” be the index of a byte contai

28、ning the last bit of a program clock reference base field; l let t(i”) be the time at which byte i” arrives in the RTD; and - - - l let PCR(i”) be the value of the program clock reference associated with byte i”; then there shall exist such a system clock ISO/IEC 138 18-l Annex J) that satisfy - cou

29、nter(t), a sequence of times e(F), and a constant tjitter (see PCR(i”) = system clock - - counter(t(i”) + e(i”)%(300 x 233), and - tjitter/2 5 e(i” 5 tjitter/:!. 2.4 Buffer Requirements The buffers in the RTD have the same names as those in the T-STD, but are denoted with a “ r” suffix. - Their size

30、s are: TBS_r, = TBS, + (tjitter x Rx,) + 188 bytes TBS rsys = TBS, + ( tjitter x Rxn) + 188 bytes sb sL r = sb size + ( tjitter x sb leak - - - - rate) + 188 bytes - It should be noted that the use of the smoothing buffer (see ISO/IEC 138 18-1, 2.630) is opthA for this part of ISO/IEC 13818, as it i

31、s in ISO/IEC 13818-l. 2 0 lSO/IEC ISO/IEC 13818-9: 1996(E) The multiplex buffer (for video) and the decoder buffer (for audio and systems data) in the RTD have the sizes: MBS-r, = MBS, + (2x tjitter x Rx,), BS_rn = BS, + (2 x tjitter x Rx& and BS rsys - = BS, + (2 x tjitter x Rx,), respectively. Not

32、e that in all these equations, Rxn, which is identical in definition to the same variable in the T-STD, is expressed in bytes/second for convenience. Given the RTD buffers as defined above, and a system clock that fulfils the above requirements, the RTD imposes that all the buffer constraints impose

33、d by the T-STD in ISO/IEC 138 18-l be complied with. In addition, the buffer state of the buffer TB_r, in the RTD at the arrival of the first byte of any Transport Stream packet shall be no more than the size of that buffer minus 188 bytes. 2.5 Real-Time Interface for Low Jitter Applications This su

34、bclause specifies the Real-Time Interface for Low Jitter Applications (RTI-LJ). For a bitstream and its byte delivery schedule to comply with the RTI-LJ, they must obey all of the compliance tests in clause 3 below with tjitter equal to 50 microseconds. For a decoder to comply with the RTI-LJ, the d

35、ecoder shall be capable of operating correctly when fed by any such bitstream and byte delivery schedule. 2.6 Other Applications Applications other than those described in 2.5 may use this part of ISO/IEC 138 18 to specify interoperability constraints on bitstream delivery and bitstream decoders. In

36、 such usage, compliance with this part of ISO/IEC 13 8 18 shall be stated relative to a specified value for tjitter. For example, a decoder may be called “RTI-compliant for tjitter equals x”. 3 Compliance Testing for RTI 3.11 Objectives The objectives of a testing procedure for this part of ISO/IEC

37、138 18 are the following: 1. Test for compliance with the system clock frequency accuracy specification, 2. Test for compliance with the system clock slew rate specification, 3. Test for compliance with the PCR jitter specification in this part (tjitter), and 4. Test for compliance with the buffer r

38、equirements in this part. For some Transport Streams, e.g. very short streams or streams with frequent PCR discontinuities, it may be impossible to verify all of these requirements. In streams with many closely spaced PCR discontinuities it is not possible to distinguish between system clock inaccur

39、acy and jitter. Streams need to have a minimum duration of continuous PCRs for accurate determination of system clock frequency error. The duration of continuous PCRs must be sufficient so that the random component of arrival time inaccuracy due to jitter is much smaller than the steadily increasing

40、 arrival time inaccuracy caused by system clock frequency error. ISO/IEC 13818=9:1996(E) 0 ISO/IEC 3.2 Testing System Clock Frequency Accuracy, System Clock Slew Rate, and PCR Jitter The compliance test is carried out for one program at a time. The procedure uses a plot of PCR values (which represen

41、t the system clock time at which the data was transmitted) against PCR arrival times, as illustrated in Figure 2. The arrival times are plotted on the X axis and represent accurate time at the receiver. The PCR values are plotted on the Y axis. Time PCR Value (converted to time) PCR Arrival Time Dec

42、oder Time Figure 2 - Plot of PCR values versus Arrival Time If the PCR values are converted to system clock time values, this plot has the following properties: l If there is no system clock frequency error and no jitter, the plot will be a straight line with unity slope. 0 If there is jitter in the

43、 arrival times, the average slope will remain unity but the points will be scattered to the left and right of the best fit unity slope line. The jitter of each arriving value is the horizontal distance between the average line and the plotted point. 0 If there is frequency error in the system clock,

44、 the slope of the plotted points is no longer unity. The frequency error can be determined from the slope of the line (the first derivative). 0 If the system clock frequency is changing (slewing), then the plot will no longer be a straight line. The rate of change of the system clock frequency (amou

45、nt of slew) can be determined from the rate of change of the slope (the second derivative). In general, there will be system clock frequency error and slew as well as jitter. As noted above, separating these three to the desired level of accuracy may not always be possible, depending on the amount o

46、f arrival time jitter and how often PCR discontinuities occur. The basic procedure is described for one program called P: 1. For each byte that carries the last bit of a PCR field for P, the arrival time of that byte and the value of the corresponding PCR itself are noted. These values are called t(

47、i) and PCR(i), respectively. PCR(i) can be converted to a system clock time value. (In what follows, rollover of the PCR register is ignored.) 2. When all PCR values in the segment of stream to be tested have been noted, their values are plotted against their arrival times 0 lSO/IEC ISO/IEC 13818=9:

48、1996(E) The stream is compliant if a curve can be drawn such that everywhere its slope is compliant with the system clock frequency accuracy requirement, its second derivative everywhere does not exceed the maximum system clock frequency slew rate, and its horizontal distance to any of the points (t

49、(il pCR( i is not greater than tjitter/2 in any case. A stream is compliant whenever such a graph can be found, and a stream is not proven non-compliant until it can be proven that no such graph exists. This can be proven in some cases by for example taking a suspect point (t(i), PCR(i) and drawing a region which includes all other permissible points in the bitstream. If another point falls outside that region, the stream is non-compliant. A stream shall be assumed to be compliant unless it can be proven to be non-compliant. 3.3 Approximate Tests for System Clock F