The Design And Implementation Of Embedded Video Conference System Based SIP

The R&D of digital video conference based on IP is a world focus. The architecture of video conference system can be classified as concentrated system and distributed one. The system based on H.323 protocol basically belongs to the concentrated architecture. This kind of systematic function is relatively strong, and benefits the centralized management. However, it needs extra hardware to support, such as expensive MCU, which limits its more wide application. To improve the centralized conference system, this paper puts forward a distributed systematic model of conference based on IP network. Combined with the application of SIP protocol and multicast protocol, this kind of conference system establishes a kind of new-style digital video conference infrastructure with many characteristics.This paper firstly reviews the history of video conference and introduces related standards, frameworks and key technologies, secondly analyses SIP conference model and demonstrates the rationality and advantage of distributed conference models by comparing it with H.323 centralized architecture. Then the paper put forward the detailed design of the network topology and terminal software and hardware structure. In this part, the design integrates codec, network transmission, and the collection and play of local audio&video by embedded technologies, and thus makes the terminal device secure, reliable and easy-using. To implement the design, MPC860 is used as hardware platform, and embedded Linux as software platform. The whole module comprises DSP for codec, SIP for signal, and RTP/RTCP for transmission. Finally, QoS, audio & video synchronization and media security are researched further.The innovation of this paper lies in combining the advantages of SIP and multicasting, putting forward a design pattern of video conference system based on conference terminals. The whole system can be built by some terminals without extra MCU. The video conference system also has some shortages such as its lack of managing functions and limit on user numbers, so the further R&D is required.