The Research Of Video Conference System Based On IP Network

IP technology has developped for many years, so far, it is undoubting that it will become the core technology of next generation network. At present, internet has already become the main multi-media communication network. And as the first stage of future broadband multi-media communication network, the application system that has multi-media communication function and based on IP protocol will also become the main developing trend, especially the multi-media video conference system which is paid close attention to at home and abroad.In video communication, terminals using IP address and port to establish data transmission chunnel. In order to establish data connection, terminals need to listen to the callings of others at any moment, but a firewall is usually configured to hold back the packet that was not invited. Also there is the problem of address translation, an user under a NAT uses private IP address, but the router on internet only transmits data to facilities which have public IP address. For these reasons, it is difficult for multimedia communication to through firewall and NAT.Presently, there are mainly hardware and software two ways to implement video conference system. Hardware has its superiority on system stability and transmission quality, but its costly. As a result, the system realized by software is becoming a research hotspot during the enhancement of broad-band and improving of compression technique of image and voice.This paper researched the video conference system based on IP network, and used visual c++ platform to realize several key techniques of multipoint to multipoint software video conference system. 1st chapter is the summary of entire video conference system, analyzes relative protocol standards put forward by international, compares the development and application of this protocols, introduces the main research contents and problems of this paper. The 2nd chapter introduces relevant technologys of video conference, including analysis of network communication protocols, researchment of multicast technology and its application in video conference. And compares some compressing standards of video and audio data, also the choosing of the compressing method in this paper. The 3rd chapter is the realization of every modules, puts forward the whole frame of the system, and realizes network programming using Winsock class provided in visual c++ and a part of code is given. Also in this chapter introduces multi-thread technology, and collection, compressing and playing of video and audio data. In 4th chapter, several methods of firewall and NAT traversal are discussed, and brings forward a simple plan. The 5th chapter is the conclusion of this research, and gives out the result of the system.