Digital television transmission using bandwidth compression techniques

It has been shown that interframe coding techniques provide an effective means to reduce the transmission bit rate of video signals without sacrificing picture quality. The channel capacity of various coding schemes over existing digital transmission links is listed. For digital satellite, for example, even a single television (TV) channel cannot be transmitted by conventional PCM, whereas one or two channels of TV can be transmitted by employing efficient coding techniques. However, much greater advantage is obtained by use of interframe coding. Three network quality TV signals can becarried through a transponder. For teleconferencing applications, a single satellite transponder can managuep to 20 simultaneous conference signals on a TDMA basis, if one uses a 3M bit/s interframe coder. Our satellite experiment has demonstrated excellent performance for network digital TV application. The TRIDEC teleconferencing system has been commercially used by NTT in Japan since 1979 and the NETEC-6/3 interframe encoder is being seriously considered for application in North American teleconferencing applications.