The Design And Development Of Video Conference Terminal Software System

With the rapid development of Internet and the advancement of multimedia communications technology, multipoint video conferencing has been realized over IP network(Internet, Intranet, LAN).So network based video conferencing system which provides voice,video and interactive collabration is becoming a hotspot of the research field.H323 protocol provides the architecture of multimedia conferencing over packet-switched networks and defines function components of terminal and equipments that support multimedia communications over packet-switched networks, communication procedure and protocols to support audio,video and data communication. In this paper, based on researching and analyzing of standards and modules included in H323,we develop the H323 video conference terminal software system. The terminal software system includes human-computer interaction subsystem, main-control subsystem, protocol stack subsystem, video-process subsystem and audio-process subsystem, my main tasks is about developing the human-computer interaction subsystem, the main-control subsystem and protocol stack subsystem.The paper firstly introduces the basic concepts of video conferencing system(including video conference standard),at the same time, makes contrast analysis on the H323 protocol and SIP protocal. The ending of the chapter reviews the main work. The second chapter introduces the video conference architecture including terminal,gateway,gatekeeper,MCU and the stack of H323 protocol. As a complex set of protocols, the chapter gave a complete and systemic analyze on H323,including its main three parts: and RAS protocol,H225and H245.The third chapter introduces the interface using Swing, including the design of the interface architecture (class design)and the technology of the multithread. It is easier to operate the video conferencing system with the interface. The forth chapter introduces the development of MC subsystem. Aiming at simplifying the design of video conference based on H323,and contributing to the management and maintenance of the MC subsystem, modulized design based on functions was adapted, the MC subsystem'framework was fulfilled and the traditional modulized processing method was improved. At the same time, the interfaces of modules were implemented more easily and the division of labor was clearer .The test results indicate that the MC subsystem works in a steady condition and with a good maintainability. Finally the paper simply introduces VP/AP subsystem and the analysis of the stack module based on the RADVision's H323 Protocal Stack including the compare of terminal capability set,master-slave determination,the opening and closing logical channels and so on.Meanwhile, the paper illustrates simply the PST(the gramma tree).At last ,in order to test the functions of the video conferencing system, the system compares with some vendor products. The test results indicate the system can not only implement the basic call ,but also the higher quality audio-video communications. At the end, some remaining problems with the current work are discussed and the future research directions are summarized.