ITU-R BR 1376-1998 Compression Families to be Used in Networked Television Production《用于网络电视产品的压缩族》.pdf

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1、Rec. ITU-R BR.1376 1RECOMMENDATION ITU-R BR.1376*COMPRESSION FAMILIES TO BE USED IN NETWORKEDTELEVISION PRODUCTION(Question ITU-R 238/11)(1998)Rec. ITU-R BR.1376The ITU Radiocommunication Assembly,consideringa) that Recommendation ITU-R BR.1356 User requirements for application of compression in tel

2、evisionproduction already exists;b) that maintaining video signals in compressed form as far as possible throughout the production andpost-production process offers the potential of increased operating efficiency;c) that the use of several, incompatible compression families within a production plant

3、 will counter-balance theexpected gains in productivity and programme throughput;d) that market forces prevent the adoption of a single compression family1);e) that the appropriate selection of a limited number of compatible compression schemes, will be of overridingimportance if efficient exploitat

4、ion of the potential offered by networked operating environments is to be achieved in thefuture;f) that the gamut of different quality requirements and economical constraints ranging from acquisition,production, post-production to contribution will require the allocation of different family members

5、for differentapplications;g) that the proponents of the compression families listed below have agreed to submit the specification of thecompressed data stream and for mapping audio, video and data into different transport mechanisms for standardization,recommends1 that for core applications in produ

6、ction and post-production for Standard Definition Television, one of the twocompression families which are currently advocated on the market as candidates for future networked televisionproduction should be used: DV-based 25 Mbit/s with a sampling structure of 4:2:0, DV-based 25 Mbit/s with a sampli

7、ng structure of4:1:1 and a DV-based 50 Mbit/s with a sampling structure of 4:2:2, using fixed bit rates and intra-framecoding techniques exclusively2); MPEG-2 4:2:2PML using different GOP structures and data rates up to 50 Mbit/s;2 that for mainstream television production applications requiring a h

8、igher margin of quality overhead forpost-production, the member within one compression family based on intra-frame encoding at a data rate close to50 Mbit/s should be chosen._*This Recommendation should be brought to the attention of the International Electrotechnical Commission.1)A compression fami

9、ly is defined by its ease of intra-family bit-stream transcoding and the availability of an “agile decoder“ inintegrated form.2)The DV chip-set has been developed for consumer applications which provides a broad application base with resultant scaled costin industrial production. The chip-set can be

10、 configured for either processing a 4:1:1 sampling raster (525-countries) or a4:2:0 sampling raster (625-countries). This chip-set is used within Camcorders for domestic and industrial use, designed bydifferent manufacturers but increasingly used in professional ENG and studio applications. The 4:2:

11、0 sampling raster requiresadditional vertical pre-filtering of the colour-difference channels to avoid aliasing.2 Rec. ITU-R BR.1376Appended to this are the following appendices, which provide background information on the Recommendation:Appendix 1: Compression issues, which outline the precondition

12、s which have to be met to adopt a compressionfamily for television production operations.Appendix 2: EBU Statement D 79 Open standards for interfaces for compressed television signals, which is apolicy statement by a large user group to insure an open platform for the development of hardware conform

13、ing to thestandard.Appendix 3: EBU Statement D 80 Compression in television programme production, which recognizes the needfor compression schemes at a higher data rate to meet more demanding post-production requirements.Appendix 4: EBU Statement D 82 M-JPEG in future networked television production

14、, which acknowledges thatthere is a large installed hardware based on M-JPEG. Most equipment employs mutually incompatible M-JPEG versions,however, with little likelihood of reconciliation of the different parameters implemented, thus preventing rather thanendorsing interoperability for future netwo

15、rked operations.APPENDIX 1Compression Issues*IntroductionThis appendix is an excerpt of the findings of the EBU/SMPTE Task Force concerning the criteria relevant for theadoption of a compression family for television production and post-production operations.CompressionSince the release of the last

16、Special Rapporteur Report, the subgroup on Compression of the EBU-SMPTE Task Forcehas entertained in-depth discussions on the compression schemes available today and in the foreseeable future and on thebalances obtained in terms of: ultimate technical programme quality versus data rate; editing gran

17、ularity versus complexity of networked editing control; and interoperability of compression schemes using different encoding parameters.The subgroup is aware that the integration of new digital video data formats based on compression into existing digitalproduction environments is already occurring

18、at a rapid pace, creating a remarkable impact on storage media cost andpost-production functionality. Though the widely used Digital Betacam recording format is an obvious example for thesuccessful use of compression in digital television production and post-production operations, the manufacturer a

19、dvisedthe Group that Digital Betacam will continue to support digital interfacing at the SDI baseband level only. Interfacing inthe native compressed form is not recommended.Compression based on M-JPEG as the key enabling factor for opening Hard Disk technology for broadcast non-linearediting (NLE)

20、applications is yet another._*Except from the Document 10-11 R/11, February 1998 2nd Report of the Rapporteur Group on file formats, interfaces andnetwork protocols to be used in digital television recording for programme production.Rec. ITU-R BR.1376 3The routing of programme data in compressed for

21、m through local area as well as national and international Telcocircuits is expected to become the predominant form of distributed programme production in the future.Although compression can be applied to all data elements relevant to programme production video, audio andmetadata this Report focuses

22、 exclusively on the implications when applying compression to the video signal. It iscurrent thinking that digital audio in production and post-production should remain uncompressed although it cannot betotally excluded that external contributions may require handling of audio in compressed form as

23、well. In this case, theconsiderations described in this Report will also apply. It is further understood, that compression applied to metadatawould have to be totally lossless and reversible.Interfacing between equipment using identical or different compression formats is currently effected through

24、the SerialDigital Interface format in baseband exclusively. On this condition, the existence of different and incompatiblecompression formats within manufacturers implementations reflects on achievable picture quality and storage efficiencyexclusively.This situation is expected to slowly evolve into

25、 a state where programme data composed of compressed video, audio andrelated metadata will be processed and routed in its native form directly, employing methods and protocols borrowedfrom the IT community and adapted to meet the quality of service requirements of professional television production.

26、Although techniques for minimizing quality loss in production and post-production operations by direct manipulation ofthe compressed bit stream or by using special helper data are the subject of research, the subgroup has stated that themajority of broadcast production and post-production operations

27、 still cannot be performed by direct manipulation of thecompressed data stream, even within a single compression scheme. The consequent cascading of decoding and re-encoding processes within the production chain and the quality losses incurred therefore require the adoption ofcompression schemes and

28、 bit rates which support the quality requirements of the ultimate output product.Improved operating efficiency by multi-user access to identical programme segments as well as reduced data transfertimes for dubbing and transfer to and from different storage and processing platforms are further benefi

29、ts of thatapproach. Though recording formats used in production and for programme exchange will continue to be subject toconstant change due to the ever decreasing cycles of storage media development, the significance of guaranteeing futureproof replay of digital compressed television signals from a

30、 particular recording support will gradually be replacedhowever by the need for standardized protocols for data transfer across different and changing recording platforms. Thecompression scheme chosen for that purpose will then no longer be a kernel feature of a particular implementation butwill bea

31、r the potential of becoming the core element of a total television production chain, including a hierarchy of tape-and disk-based storage devices offered by different manufacturers alliances. Integrating compression and networktechnology into broadcast operations is therefore expected to increase bo

32、th operating flexibility and universal access totelevision archives.The EBU has acknowledged different quality levels within the confines of professional television production andpost-production. Further adaptations may be required to overcome bottlenecks created by particular constraints, e.g.bandw

33、idth, tariffs and media cost.The subgroup has defined the membership within a compression family by its ease of intra-family bit-streamtranscoding and the availability of an agile decoder in integrated form.The coexistence of different compression families in their native form within both local and

34、remote networkedproduction environments requires the implementation of hardware-based, agile decoders. Software-based agiledecoding is currently not considered to be a practical option. It is currently still undefined how an agile decoder willoutput the audio and metadata part of the bit stream.In m

35、any instances, such decoders must allow glitchless switching and can therefore realistically be implementedwithin one compression family only. The subgroup on Compression concluded, that within the foreseeable future,coexistence and inter-operation of different compression families within a networke

36、d television plant will pose anumber of operational problems and will therefore be the exception and not the rule.4 Rec. ITU-R BR.1376The appropriate selection of a single compression scheme or a limited number of compression schemes within onecompression family, together with the publicly available

37、 specifications of the relevant transport streams and interfaces will be of overriding importance if efficient exploitation of the potential offered by networked operating environments isto be achieved in the future.For core applications in production and post-production for Standard Definition Tele

38、vision, two different compressionfamilies are currently advocated on the market as candidates for future networked television production: DV-based 25 Mbit/s with a sampling structure of 4:2:0, DV-based 25 Mbit/s with a sampling structure of4:1:1 and a DV-based 50 Mbit/s with a sampling structure of

39、4:2:2, using fixed bit rates and intra-framecoding techniques exclusively. MPEG-2 4:2:2PML using different GOP structures and data rates up to 50 Mbit/s.(For specific applications, this could also include MPEG-2 MPML if decodable with a single agile decoder.)Very recently, M-JPEG compression has bee

40、n submitted to the Task Force as a further contender for use within certainareas of production and post-production, once all requirements have been fulfilled as outlined in the list of requirementsbelow. The Production Management Committee of the EBU has carefully evaluated the impact of a further,

41、incompatiblecompression family on system complexity of networked production. There was agreement that the EBU will not endorseM-JPEG as yet another compression family.The positioning of the above compression families within a future networked digital production scenario requires carefulanalysis and

42、differentiated weighting of the current and future potential influence of various technical constituents onthat scenario. This also has to take into account the possible coexistence of Standard Definition Television and HDTV,where the operation at very high data rates within a range of different pix

43、el rasters and frame rates will add yet an extralayer of complexity. There is agreement in the subgroup that the general rules outlined in this document alsoapply for HDTV.The subgroup has identified the following elements which all have a significant impact on the objectives describedabove: Format

44、stabilityAvailability of chip-sets.Format commitment by each manufacturer.Status of standardization. Picture quality ceiling, post-production potential, storage requirementsAs a first step, the EBU has divided the requirements for picture quality and post-production margin of networkedbroadcast appl

45、ications into the following categories: News and sports applications. Mainstream broadcasting applications requiring more post-processing overhead. InterfacesA stream interface for use within a television production plant has been standardized recently by SMPTE (305M). TheStandard defines a Serial D

46、ata Transport Interface for the flexible transport of packetized video, audio and metadataover coaxial cable interfaces for different bearers, applications and functionalities have already been standardized or willbe standardized in the near future, e.g. fibre-channel, ATM. The DV-based data stream

47、is pending specifications bySMPTE Data structure of audio, compressed video and subcode data for the 25 Mbit/s and the 50 Mbit/s structure at525/60 and 625/50 system.The mapping of the data stream on SDTI is described in a SMPTE draft Standard document Data stream for theexchange of DV-based audio,

48、data and compressed video over SDTI.Rec. ITU-R BR.1376 5The specification for 422PML MPEG-2 follows the MPEG rules. The mapping of 422PML MPEG-2 compliantdata as a transport stream (TS) or as an elementary stream (PES) is currently under investigation. The actual status of thediverse specifications

49、can be found in the section describing possible production scenarios based on DV and 422PML. Agile decodersAgile decoders for intra-family decoding (see NOTE) must be available in integrated form. They are expected to decodestreamed real-time packetized video only. Such decoders should comply with the following requirements:a) Decoding of different bit streams with identical decoding delay at the outputAgile decoderAgile decoderswitched during VBIBit stream 1Bit stream 2Bit stream 1Bit stream 2ORO