An Interframe Coding System for Video Teleconferencing Signal Transmission at a 1.5 Mbit/s Rate

This paper describes the interframe coding system (TRIDEC 1.5) used for NTSC color television signal transmission at a 1.5 Mbit/s rate. TRIDEC 1.5 is developed with the intention of making video teleconferencing service more economical. The system utilizes the following highly efficient coding techniques: 1) interframe combinational difference coding 2) temporal subsample coding 3) noise reduction 4) demand refreshing to protect against channel errors, which makes periodic forced refreshing unnecessary. In addition, new coding parameter control methods have been devised to prevent buffer memory overflow. The subjective evaluation test results make it clear that the encoded picture quality is good enough for teleconferencing use.