 was merged into MPEG-2. Ironically, it has emerged as a popular music file format. Because that is the only common application for MPEG-3, we will not discuss it further in this text. MPEG defines only the operations that a decoder must perform to interpret a compressed bit stream. It does not address what constitutes a valid bit stream (although it is implicit in the decoding process). Encoding is left up to the individual manufacturers. This allows a proprietary advantage to be obtained in spite of the fact that MPEG is a publicly available international specification. The MPEG committee meets four times a year. During its meetings, it reviews the work that has been accomplished during the quarter and plans its next steps. ensure that harmonized solutions to the widest range of applications are achieved the committee works jointly with the ITU-T Study Group 15 and its successor, Study Group 16. MPEG also collaborates with representatives from other organizations including the ITU-R, the SMPTE, and the ATSC. Work Group 11 began meeting in 1988. Its original goal was to define a format for compressing audiovisual sequences for CD-ROM storage and playback. As it turned out, its work engendered a great deal of international interest. Technical experts from all over the world (more than 200 participants by 1992) collaborated on the development of a syntax for MPEG-1. To represent an object using compact and coded data, it is necessary to develop a language that is capable of dealing with abstraction. The ISO refers to a unique language (the specific bit codes used to represent objects-and their meaning) as syntax. For example, a few tokens can represent a large block of data. Syntax is also used to decode a complex string of bits and to map those bits from their compact representation back into their original form (or a semblance thereof). In video coding, syntax exploits common characteristics (block-oriented motion, spatial and temporal redundancy, color-to-brightness ratios, etc.). By the end of 1990, the MPEG-1