6.1 History

The ITU is a part of the United Nations, and its purpose is to develop formal "Recommendations" to ensure worldwide communications are accomplished efficiently and effectively. In 1984, the first recommendations for a video teleconferencing codec (H.120 and H.130) were established. These recommendations were defined specifically for the European region (625 lines, 2.048-Mbps primary rate) and for interconnection between Europe and other regions. Since no recommendation existed for non-European regions, it lacked true international scope, and in 1984 the ITU established a Specialists Group on Coding for Visual Telephony to develop a truly international recommendation. The ITU established two objectives for the Specialists Group: to develop a recommendation for a video codec for teleconferencing application operating at the bit rates of N X 384 Kbps (N = 1 through 5), and to begin the standardization process for a video codec for teleconferencing and video telephone applications operating at bit rates of M X 64 Kbps (M-1, 2).

The Specialists Group, chaired by S. Okubo from Japan, met 17 times between 1984 through 1989. At the September meeting in 1988, it was determined that the compression algorithm chosen for N X 384 Kbps was sufficiently flexible that it could be extended, with good performance, down to 64 Kbps. At that time, the Specialists Group shifted their focus to develop a single recommendation to code at all bit rates from 64 Kbps to 2 Mbps, that is, to code at rates of p X 64 Kbps, where the key values...