The Research Of Key Technique In Video System For SIP

In recently years, along with the build and improvement of network environment by transportation merchant, and application and spread of some techniques such as ISDN,DDN,VPN,xDSL,ATM,IP, the application range of video system becomes more and more abroad. So either communication trade or IT,attaches importance to the research of video transportation area.Video system is a tool which can be used to realize real time communication in audio/video between differnet humans. Its main function is to transport user's voice,video and other data to another user. SIP(Session Initiation Protocol), a new gerneration session control protocol which is constituted by IETF, has many advantages such as simple,open,agility,expandable and so on. It is the key technique of NGN(Next Generation Network) soft switch hierarchy.Compared with H.323,SIP has advantages in agility,expandable,and compatibleness with IP networks and so on.Thereby, the problem that applies SIP to the viedo system has practicality and significance.The main work in this thesis is a research of key technique which is related to the part of media in the video system.In the article,we introduce the conception of video communication system and the current research of it. We analyze the architecture of video system and some kinds of network transmission forms(unicast,multicast,P2P) which are used in video system,and compare the characteristic and applications of them. We also analyze SIP , the support protocol of video system, we analyze some audio/video coder/decoder standards,and compare 3 video coders/decoders(H.263,H.264,MPEG-4) in performance according to the result of their performance test.In the article,we design media part of a distributed video conference syestm based on SIP. we choose techniques used in the system according to their performance. We design the interfaces between SIP signaling and media, including normal operation interfaces and abnormal operation interfaces.accomplish the control on media part by signaling part, and transport messages from media part to signaling part. In chapter 5,we describe the realization of some modules(video collection and RTP transmission).In video collection module,we analyze the flow of video collection based on VFW and purpose of some functions.In RTP transmisson module, after video collection,we capsulize the H.263 stream in RTP, and transport RTP stream inoder to keep the QoS of the media stream. This part we use the open code (JRTPLIB).