Research Of QoS In Video Conference System Based On H.323 Protocol

With the development of network and multimedia technology, video conference system has changed from the H.320 system based on ISDN to the H.323 system based on IP. The current IP network does not offer any guarantees of quality of service (QoS) for real-time multimedia streaming. But transmission of real-time multimedia streaming typically require higher characteristic on network bandwidth, transmission delay and data loss, so it is necessary to control IP network with QoS technique to ensure the quality of service.First, the framework and components of H.323 system, the function of the main components are presented. H.323 protocol used in the system is analyzed. Considering the strict requirements of QoS in real-time multimedia system, the main QoS techniques used in H.323 system are investigated. A speed control algorithm based on sender terminal is designed. Test results show that the algorithm may momentarily adjust the output speed of encoder according to current usable bandwidth of IP network.Based on the above investigation, we perform a design of video conference terminal system on IP network, which mainly includes the whole plan of the hardware and software, the design of media subsystem, as well as the layered design of QoS control module. Finally, the terminal system has been debugged by Tornado, an integrated developed environment of embedded real-time operating system VxWorks. The speed control algorithm has been tested and an ideal result has been obtained. By the research work of this paper, the whole plan of video conference terminal system and design of QoS control module are realized. It is worth reference for the design of other real-time multimedia system.