About MPEG

About MPEG
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The Moving Picture Coding Experts Group (MPEG) was established in January 1988 with the mandate to develop standards for coded representation of moving pictures, audio and their combination. It operates in the framework of the Joint ISO/IEC Technical Committee (JTC 1) on Information Technology and is formally WG11 of SC29.

Starting from its first meeting in May 1988 when 25 experts participated, MPEG has grown to an unusually large committee. Usually some 350 experts from some 200 companies and organisations from about 20 countries take part in MPEG meetings. As a rule, MPEG meets three times a year (in March, July and November) but meets more frequently when the workload so demands. In 1998 it will hold 5 meetings, all lasting 5 days.

A large part of the MPEG membership is made of individuals operating in research and academia. Even though the MPEG environment looks rather informal, it has to be borne in mind standards can be of high strategic relevance. It should be no surprise that operation of ISO standards committees is carefully regulated by "Directives" issued by ISO/IEC and "Procedures for the Technical Work" issued by JTC1.

Unlike other standards committees where the development work is done outside and the role of the committee is simply managing the formal process of standards approval, the actual development takes place in MPEG, where the different technical submissions are reviewed by the committee and work is assigned to members for the next meeting. This allows MPEG to attract the best expertise in its fields and to produce the technically most advanced standards.

As a result of this working method MPEG manages some 500 documents at each meeting. About 300 are input documents from members and about 200 are output documents produced by the committee.

These documents are restricted to MPEG memebers. From time to time, however, MPEG decides to post publicly some of its output documents. These are typically calls for proposals, general descriptions of standards, approved or under development, the text of standards under ballot etc. As a rule standards in final form are not posted here. They can be purchased from sales@iso.ch.

The ISO standards produced by MPEG are indicated by 5 digits (the ISO number for MPEG-1 is 11172 and for MPEG-2 is 13818). Published standards are the last stage of a long process that starts with the proposal of new work within a committee. These proposals of work (NP = New Proposal) are approved at Subcommittee and then at the Technical Committee level (SC29 and JTC1 respectively, in the case of MPEG).

When the scope of new work has been sufficiently clarified, MPEG usually makes open requests for proposals. MPEG has issued tens of Calls for proposals, the early ones being

  • MPEG-1 Audio and Video (July 1989)
  • MPEG-2 Audio and Video (July 1991)
  • MPEG-4 Audio and Video (July 1995)
  • Synthetic/Natural Hybrid Coding (March 1996)
  • and others.

Stay tuned to this MPEG Hot news page for further information Calls.

Depending on the nature of the standard documents of different nature may be produced. For Audio and Video coding standards the first document that is produced is called a Verification Model (VM). In MPEG-1 and MPEG-2 this was called Simulation and Test Model, respectively. The VM describes, in some sort of programming language, the operation of the encoder and the decoder. The VM is used to carry out simulations to optimise the performance of the coding scheme. When MPEG has reached sufficient confidence in the stability of the standard under development, a Working Draft (WD) is produced. This is already in the form of a standard but is kept internal to MPEG for revision. At the planned time the WD has become sufficiently solid and becomes Committee Draft (CD). It is then sent to National Bodies (NB) for ballot. If the number of positive votes is above the quorum, the CD becomes Final Committee Draft (FCD) and is again submitted to NBs for the second ballot after a thorough review that may take into account the comments issued by NBs. If the number of positive votes is above the quorum the FCD becomes Final Draft International Standard (FDIS). ISO will then hold a yes/no ballot with National Bodies where no technical changes are allowed. The document then becomes International Standard (IS).

A WD usually undergoes several revisions before moving to CD stage. A key role is played by "Core experiments" where different technical options are studies by at least two different partners. Each revision involves a large number of experts who draw the committee's attention to possible errors contained in the document. Moreover, depending on the nature of comments that usually accompany National Body votes, important changes may have to be made on documents when they progress from CD to DIS and from DIS to IS. The net result is that standard produced by MPEG are of very high quality. No single error was discovered in MPEG-1 and small errors, better described as items of text of dubious interpretation, were found in MPEG-2 Video and MPEG-2 Audio. Corrections are produced using the "Corrigendum" process. In MPEG-2 Systems, Video and Audio it was found useful to introduce some new features that built upon the standards as originally released. This was done using the "Amendment" process defined by ISO. For MPEG-2 Audio it has been found useful to produce a new revision of the standard.

A large part of the technical work is done at MPEG meetings, usually lasting one full week. Several hundreds contributions are submitted by members by electronic means to the MPEG FTP site. Delegates are then able to come to meetings without having to spend precious time to study other delegates' contributions at the meeting. The meeting is structured in Plenaries (4 hours on Monday morning, 2 hours on Wednesday morning and all the afternoon of Friday) and in subgroup meetings.

About 150 documents are produced at every meeting that capture the agreements reached. Particular importance assume

  • "Resolutions" which document the outline of each agreement and make reference to the documents produced, and
  • "Ad-hoc groups", groups of delegates working on some specified area of work, usually until the following meeting. Ad-hoc groups work by e-mail and in some exceptional cases they are authorised to hold physical meetings.

Output documents, too, are stored on the MPEG FTP site. Access to input and output documents, however, is restricted to MPEG members

Attendance at MPEG meetings requires accreditation by a National Standards Body or standards committee in liaison. Experts attending MPEG not representing a committee in liaison must be members of a National Delegation. Heads of Delegation are appointed by the corresponding National Bodies and meet during the week to address matters of general interest to the group.

To know whom to contact in your country click here. Please be aware that national standards bodies have competence in manifold areas. You should make sure that you seek membership of the right committee (formally ISO/IEC JTC 1/SC 29/ WG 11 (MPEG).