A Multi-Media Teleconference Terminal Controlling Quantity Of Flow In Packet Transmission.

This paper describes a new teleconference terminal constructed on the X.25 protocol for high speed packet switching over 1.5Mb/s subscriber lines. To develop a high performance teleconferencing system, the terminal incorporates three transmission techniques: variable bit rate coding and packet priority assignment of video signals, combining left and right audio channels and assignment of audio packet priority, and under severe traffic congestion the dropping of video data packets if there are no low priority audio packets that can be dropped. If a sending terminal detects traffic congestion severe enough to prevent transmission of all packets, the least signifi-cant audio packets are dropped until audio signal rate falls to 32kb/s. Next, video data packets are dropped if the traffic congestion is very severe. Sound localization, important in conferences, is maintained even under heavy traffic congestion. The influence of packet loss on picture and audio quality is described and decoded pictures suffering various packet losses are investigated. With this newly developed teleconferencing terminal, consistent and high quality multi-media services can be assured.