甚低带宽环境下的多媒体通信传输控制模型

介绍了基于H．324协议框架的可视电话基本原理．H．324协议是基于PSTN普通电话线路的多媒体可视通信协议．通过深入研究H．223数据复用协议和V．80同步传输协议，针对甚低带宽的PSTN线路特点，提出了一种有效的多媒体通信传输控制模型，改进了H．324可视电话的性能．

Control of Multimedia Communication Under Very Low Bit-rate Environment

The paper introduces the basic principle of video-telephone based on ITU-T recommendation H.324. Recommendation H.324 covers the technical requirements for two multimedia telephone terminals over a PSTN voice band network connection. In allusion to the characteristics of low bit-rate multimedia communication on PSTN, author researches the recommendation H.223 which is the multiplexing protocol for low bit rate multimedia communication, and constructs the multiplex entry and multiplex model of H.223. And based on the Recommendation V.80 which is in-band DCE control and synchronous data modes for asynchronous DTE, The model selects a synchronization access mode for the real PSTN telephone line. By combining the recommendation H.223 and the recommendation v.80, the author puts forward an effective model of the transmission control for multimedia communication under very low bit-rate line environment. This prototype improves on the performance of H.324 videophone greatly.