Multi-point Desktop Video Frequency Convention System Design And Realization

Video conferencing is a kind of multimedia communication systems. It uses a variety of electrical transmission media to distribute moving images, voice, text, pictures and other information to a set of computer users, allowing them to communicate and exchange information. Video conferencing system can be classified as tow types: point-to-point systems and group video conferencing systems. This thesis only studies the second type of video conferencing systems. The designing and realization techniques are discussed.The proposed system based on the Windows platform and Direetshow is developed by means of VC++ in the framework of the program in conjunction with WindowsMedia video conferencing technology. We have studied some related key techniques. According to the features of TCP, UDP and the RTP protocols, we schoice the suitable transmission protocols for different parts of the network to ensure smooth transmission of media data and real-time response. By using a very specific image segmentation technique which can seperate the body of a conference participant from the background, we only need to transmit part of the vedio data so as to save network bandwidth. Combining audio of ADPCM and MPEG4 video and using compression technology and IP Multicast, we optimize the network transmission. Synthesis of data flow and the so called push-technique, which can easily push streaming media to users, make our video conferencing more real-time. To achieve real-time information exchange between the various types of communication objects, we develop a stack-based news class, the cMsgstatinn class. Based on this class, other types of business logics are inherited from it. So, this type of messages can be received in real time by other objects. Lastly, the standards of COM programming is employed, so the software can be more easily expanded and updated in the future.