Research QoS Technology Solution For IP Network-based Video Conference System

With the development of Internet and multimedia, There are more and more applications based on IP network, which results in the more and more serious occupation of network resource.The current IP network fluctuate seriously and the bandwidth is not stable; And also because the characteristic of IP network is"best effort", all these can make serious effect on delay,jitter , packet loss rate and synchronous picture and sound of video conference system base on IP network, and therefore the quality of visual and audio frequency can not be ensured. In order to solve this problem, QoS (Quality of service )based on IP network video conference system become a focus of research。The QoS technology of video conferencing system based on IP network include the technology in two parts.The first part is the IP network QoS technology. As IP network is the transmission medium of video conferencing system, IP network QoS can decide the quality of video conferencing, and the effect can be very stable and reliable. At present this technology is divided into several types, and it can only be implemented on IP network. However, it has the shortcomings of difficult implementation, high cost, inflexible and some limitation. The second part is the terminal QoS technology of video conferencing system. This technology is supported by the key technology and the relative protocol of the video conference system, and the terminal QoS technology of the video conference system can enable the bandwidth of the visual and audio frequency transmitted through the terminal of the video conference system dynamically match the changing of the IP network bandwidth, so that it can realize the purpose to control the visual and audio frequency effect of the video conferencing. The outstanding advantages of this technology is the convenient and flexible implementation, and not limited by time and place. This thesis made a detailed introduction to the QoS technology of the video conference system in these two parts respectively, and at last put forward the technologic index plan to use the terminal QoS technology of video conference system, adopt the soft ware design and realize controlling video conference QoS. The overall design idea of this plan is based on the control for packet loss rate and delay, the main characteristics are to comprehensively consider delay, jitter and packet loss rate, this plan makes the three indexes reach a dynamic adjustment effect; This plan firstly ensures the continuous sound and no distortion, the major technology used is self adaptive code rate control .The design of this plan mainly uses RTP and RTCP protocol control, under the precondition that the maximum delay can be controlled within 400ms, so that the packet loss rate and jitter can be controlled in a reasonable scope, and finally realize the synchronous picture and sound; After verification of each technologic index, the average delay from terminal to terminal in WAN can not be over 230ms, and the average jitter is controlled in 40ms, so that basically the picture is clear and the sound is continuous and without distortion.