The Research And Design Of IP Multicast Desktop Video Conference Based On SIP

With the rapid development of multimedia and network communication technology, the research and application of video conference system have become a hot topic. At pre-sent, most of video conference systems are based on H.323 protocol, which is mature but is complicated in implementation, costs much and difficult to extend, so it brings inadequate flexibility in application. On the other side, SIP protocol, proposed by IETF, has received broad application in multimedia communication for its concision, flexibility, easy exten-sion and implementation. Building multimedia conference system using SIP not only can realize the function of H.323 conveniently, but also cost low. SIP conferencing framework is still on a draft period and hasn't become a formal standard; therefore the research and implementation on SIP conferencing framework have certain theoretics and practice sig-nificance.At present most of video conference systems need to depend on expensive hardware device. On the basis of SIP, IP Multicast technique and RTP protocol, this paper has de-veloped a system to implement multipoint control of conference and transmission of media stream, and has realized IP Multicast desktop video conference system based on SIP. The paper's research and work include the following:First discuss the related protocol standards and techniques of video conference, including SIP protocol, SDP protocol, RTP protocol and IP multicast technique. Analyze the processing of SIP message on the basis of introducing SIP protocol, and also analyze the specific meaning of field and message format of SDP and RTP, and discuss the feasibility of IP multicast technique in video conference ap-plication.Research and analyze the present SIP conference model of IETF, by the research and comparison of the conference model, we choose centralized signaling,distributed media conference model, and design the system structure of SIP video conference system based on this model, and partition detailed function module, and have a detailed description to the elementary conference function of confer-ence system.Design SIP signaling processing module of video conference system, and imple-ment the module functions using JAIN SIP technique on the basis of NIST SIP open source protocol stack.Design the audio/video transmission module of video conference system, and re-alize the capture, encoding, transmission and reception and playing back of au-dio/video in conference terminals using JMF technique, and process the sychro-nization between audio and video.Test and analyze the running results of system modules.