INTERNATIONAL ORGANISATION FOR STANDARDISATION
ORGANISATION INTERNATIONALE DE NORMALISATION
CODING OF MOVING PICTURES AND ASSOCIATED AUDIO
ISO/IEC JTC1/SC29/WG11 N0822
11 November 1994
|Source:||Leonardo Chiariglione - Convenor|
|Status:||Approved at 29th meeting|
The 29th meeting of ISO/IEC JTC1/SC29/WG11 (MPEG) was held in Singapore this week, hosted by the National Computer Board and the National IT Standards Committee (Singapore).
The results achieved at this meeting include: the final approval of part 4 of ISO/IEC 11172-4 (MPEG-1 Conformance Testing) as International Standard (IS); the promotion of ISO/IEC 11172-5 (Software for MPEG-1 coding) to Draft International Standard (DIS) status; the final approval of ISO/IEC 13818-1 (MPEG-2 Systems), ISO/IEC 13818-2 (MPEG-2 Video) and ISO/IEC 13818-3 (MPEG-2 Audio) as IS; the production of the Working Draft of the DSM-CC (Digital Storage Media Command and Control) extension; and the issuing of a Call for Proposals for MPEG-4, the next item of work.
The approval of MPEG-2 for publication as an international standard constitutes an important milestone in international standardization that will make possible the establishment of interoperable digital audio-visual services and applications on a world-wide scale while making sure that international standardisation of digital audio-visual matters will not be overtaken by the progression of technology. The continuing work will ensure continued responsiveness to the needs of the digital audio-visual community.
This week saw the promotion of the Draft International Standard 13818-1, better known as "MPEG-2 Systems" to IS status. This part of the MPEG-2 standard provides for the multiplex and synchronisation of multiple audio, video, and data streams. MPEG-2 Systems will form the infrastructure for delivery of audio and video information in many industry sectors, including television distribution, visual telecommunications, and a host of computer and multimedia applications.
MPEG-2 Systems specifies two syntaxes, the Transport Stream and the Program Stream, each designed for different applications. Both syntaxes offer a wide range of functions and capabilities. In addition to multiplexing, a major feature is the accurate synchronisation of audio, video, and data for correct presentation at the decoder. The standard addresses the management of buffers at the decoder. Additional functions include random access, identification of information carried within the stream, procedures to support user access control, and error protection mechanisms.
Contribution to the development of the MPEG-2 Systems standard has come from many different industry groups, representing the wide range of interest in the standard. ITU-T Study Group 15 has also participated in the development of the standard and the ITU-T will adopt MPEG-2 Systems as ITU-T Recommendation H.222.0, as part of its Broadband-ISDN audio visual telecommunications terminal.
With new transmission technologies allowing high bandwidth connections, and switching technologies such as ATM, MPEG-2 Systems will form the basis of new audio and visual services applications for many years to come.
Digital Storage Command and Control
The Working Draft of the Digital Storage Media Command and Control (DSM-CC) extension was also completed this week. This standard will facilitate the interoperability of MPEG applications and equipment by providing a common command and control interface. An example application is the control of remote video servers from home based terminals. A Committee Draft (CD) of the DSM-CC Extension is scheduled for March 1995 and International Standard in November 1995.
A requirements document on a multimedia scripting language was also produced. The standard will be developed together with the Multimedia and Hypermedia Experts Group (MHEG), a parallel committee within JTC1/SC29. The language is an important element for the rapid introduction of stand-alone and networked interactive multimedia applications and services.
Real Time Interface
Part 9 of ISO/IEC 13818 is the Real Time Interface (RTI), an extension of the MPEG-2 Systems standard defining a common interface point to which terminal equipment manufacturers and network operators can design. RTI specifies a delivery model for the bytes of an MPEG-2 Systems stream at the input of a real decoder, while MPEG-2 Systems defines an idealised byte delivery schedule. Part 9 was promoted to Working Draft (WD) status at this week's Singapore meeting. It is expected to become an International Standard in November 1995.
The standard 13818-2, better known as "MPEG-2 Video" was promoted from DIS to IS status. The standard provides for the digital coding of video at various data rates from about 1.5 Mbit/s to in excess of 60 Mbit/s, enabling a common technology to be adopted for many applications ranging from home entertainment quality video up to HDTV. Subsets of the total video standard known as profiles have been defined to assist in interchange of coded video data between these various applications. Early adopters of this standard include pay-TV cable and satellite broadcasters as well as the emerging interactive ‘Video on Demand’ market, for which the ‘Main Profile’ is identified as the most suitable. Other profiles support layered coding techniques suitable for terrestrial broadcasting and IT environments.
MPEG-2 Video has been developed jointly with ITU-T SG 15 and will be adopted by that Standards Body as Recommendation H.262.
10 bit video and new profiles.
The need to extend the MPEG-2 tools and provide support of efficient bitrate reduction for high-quality video signals quantised with 10 bits, such as those used in the studio, has been recognised and a Call for Proposals has been issued in July 1994. The deadline for submissions is March 1995, but a number of companies have already stated their intention to make proposals.
At this meeting another range of applications which may take benefit from the MPEG technology has been identified regarding compression coding of non-chroma-subsampled ordinary video signals at bitrates up to 50 Mbit/s. While many of the committee members are confident that the MPEG coding tools can be successfully applied at these high bitrates, the very demanding performance required by the mentioned applications has prompted MPEG to establish an ad-hoc group with the mandate of providing technical evidence to be submitted at the 30th MPEG meeting in March 1995. The successful outcome of the work of the ad-hoc group will enable MPEG to make a decision on this important extension of its current work.
Video Quality Verification Test
MPEG has put considerable efforts into evaluating the quality obtained by the application of its standards to video information sources. This evaluation has been made on various MPEG-2 video profiles for TV and HDTV.
A first set of results, obtained as early as March through a set of test video sequences, proved that MPEG-2 Video at 9 Mbit/s coding provides near transparent quality while at 6 Mbit/s the quality equals or exceeds that of conventional TV systems. At lower bit rates, such as 4 Mbit/s high quality pictures will be obtained on most picture material.
Expert viewing tests were also carried out on the "Spatially Scalable Profile at H14", a profile for 1440 line HDTV. This profile defines layered coding techniques used to generate a base layer bitstream with an enhancement layer bitstream used to create a higher resolution image. The layered coding allows simultaneous reception of an HDTV signal by both HDTV and standard resolution TV receivers.
Initial results seem to indicate that the high layer satisfies the required quality for HDTV at 36 Mbit/s. The quality of the base layer, using 9 of the 36 Mbit/s, is high enough for normal TV broadcasting; it is however not sufficient for an HDTV ‘fall back solution’, which could occur in the case of bad reception conditions.
More tests are planned for testing MPEG-2’s "Main Profile" for HDTV use at bitrates of 18, 30 and 45 Mbit/s. Taking into account the intended use of these profiles, the tests will be carried out with video and movie material.
The multichannel MPEG-2 Audio coding system (IS13818-3) has been promoted to IS status during the Singapore meeting. This standard supports the extension of the MPEG-1 Audio compression standard (ISO/IEC 11172-3) to multichannel (up to 5 channels). It also supports the extensions of the MPEG-1 Audio compression standard to lower sampling frequencies and lower bitrates. These extensions have proven to outperform conventional speech codecs at the same rates.
Use of the MPEG-2 Audio standard will be further promoted through continuing work on improvements in quality, largely dependent on encoder optimisation, and the distribution of reference software and compressed multichannel audio sequences over the Internet.
MPEG is also working on the development of a multichannel audio coding standard that is not backward compatible to MPEG-1 Audio but still part of the MPEG-2 standard. A Call for Proposals was issued in July 1994 and twelve companies have already responded presenting an outline of their intended proposals. Detailed proposals will be presented at the next MPEG meeting (March ’95), but the collaboration among the proposers has already started in Singapore using a common reference model.
In its MPEG-4 phase of work MPEG will develop an audio-visual coding standard with new functionalities, such as support for manipulation of the content of audio-visual data, that will find application in diverse areas such as entertainment, distance learning, remote monitoring, and home shopping. Thus continuous improvement in performance of coding is necessary. To provide this capability, MPEG-4 will develop a flexible syntactic descriptive language, and a number of audio-visual coding tools. This approach will provide the ability for decoders to use a rich set of algorithms according to the content or applications.
Software implementations of MPEG standards
The full software implementation of the three parts of MPEG-1, contained in part 5 of MPEG-1, was promoted to Draft Technical Report status at this meeting. The software is an aid to implementors and novices providing an example encoder and decoder for Systems, Video, and Audio. This software has also a wide domain of applicability thanks to the ever increasing processing capability of computers that promise to make possible software implementation of the standard under certain conditions.
The same work is also being carried out for MPEG-2: a technical report for MPEG-2 Video, including reference software for coding and decoding, was approved for balloting as Proposed Draft Technical Report 13818-5.
The work on MPEG-1 conformance testing was closed at this meeting. This part of MPEG-1 guarantees the quality of MPEG-1 products, and helps to make sure that they conform to the standard.
The work on MPEG-2 Conformance is at an advanced stage of development: the conformance document was reviewed and approved as CD 13818-4 and submitted for balloting.
MPEG is the nickname of an ISO working group. As such it is assigned work items and produces standards. Therefore there is no such thing as an "MPEG-2 committee".
This is the full list of work items
|11172 (MPEG-1)||Coding of moving pictures and associate audio for digital storage media at up to about 1.5 Mbit/s||IS date|
|Part 4||Conformance testing||94/11|
|Part 5||Simulation software||95/03|
|13818 (MPEG-2)||Generic coding of moving pictures and associated audio|
|Part 4||Conformance testing||95/07|
|Part 5||Simulation software||95/07|
|Part 6||Digital storage media command and control||95/09|
|Part 7||Non-backwards compatible audio||97/03|
|Part 8||10 bit video||96/07|
|Part 9||Real-time interface||95/11|
|14496 (MPEG-4)||Very low bitrate audio-visual coding|