| With the mature of multiedia communication technology, it is possible to use various technical means and realize real-time audio and video communication in government agencies, institutions, military and medical fields. The multimedia communication system based on audio and video has become one of the hot topics in the study of network communication. Multimedia communication system is a communication system using communication networks to transmit multiple users’ continuous activity image, voice and data, and enable geographically dispersed users to communicate interactively through video, voice, text and so on in the network. The technology which has been widely applied at present is Microsoft DirectShow, it is already widely used in audio and video capture, video chat, video on demand, media player, and other fields.In this paper, the author first reviews the development, applications, existing problems of audio and video technology based on the domestic and international. Then, this paper expounds the DirectShow framework, introduces detailly the structure of the framework and the principle of COM programming, analyzes the principle of Filter in the DirectShow frame and the description of data flow in Filter, and analyzes the key points of DirectShow application development, summarizes the general development process of DirectShow application, these provide theoretical support for the system design and implementation. Secondly, the author puts forward the key technology of audio and video real-time transmission which is necessary to solve based on the current Internet transmission characteristics.These technologies include network transmission protocol and IP multicast technology. The author introduces multithreading technology and Winsock programming principle according to the design of the real-time transmission system. Again, the autor puts forward a idea to combine P2 P peer network technology in view of the problems include audio and video transmission systems need to consume large amounts of network bandwidth, center server load pressure is big, the maintenance work is complex. Then the author summes up three kinds of P2 P network transmission system, and compares them. At last, the author obtains the structure of audio and video real-time transmission system, changes the traditional network transmission structure, reduces the burden of the server, makes full use of network bandwidth and improves the network transmission environment.Finally, the page designed and implemented a communication system model based on voice video communications, text communications, file transfer, broadcast message, and other functions of a peer to peer network LAN under Visual Studio 2010 development environment. It descripes detailly the way of user communication connection, text information communication, file transfer and the implementation of control information using Winsock programming, using Directshow framework constructed Filter Graph which is the self-checking module needed. It designs the Filter for audio and video data sending and receiving in audio and video transmission module. It tests the function of the whole system, the test proved that the system had good network adaptability and could obtain better visual quality. |
