Based On The Mpeg-4 Multimedia Network Teaching System

New challenges and opportunities are brought to humanity society in Information era. Traditional teaching mode centers on teacher, classroom and textbook will gradually be unfit for the need of Information era. With the rapid development of both computer and networks technology, networks teaching will be a certain trend. The thesis analyses some contemporary multimedia networks teaching system, and designs a multimedia networks teaching system based on MPEG-4, combined with the characteristic of networks teaching on campus.The aim of this thesis is to build a virtual networks classroom on campus network. By which, students and teachers in different places can join in the teaching activity at the same time. With the system, students can not only receive the contents of the teacher's screen, voice but also receive the video of the teacher's movement. Meanwhile, the system provides the function of electronic whiteboard for communication. The designed system includes functions of audio and video broadcast, screen image broadcast, interaction of electronic whiteboard, real-time courseware making, etc. The realization of the system relies on technologies of MPEG-4, streaming media, network, database, SMIL and takes Visual C++ of Microsoft as the development tool. Results of functional unit testing and practical system networking testing show that the system can fulfill the networks teaching requirement.The characteristic and key technologies of the system are as follows:(1) In realizing the live broadcast of audio and video, the problem of immense multimedia data and low networks bandwidth utilizationratio is solved by using MPEG-4 as format of audio and video data. Audio and video data are collected by video card CV500 which developed by Beijing Sum tone Company; meanwhile, the contradictory between the delay of networks transmitting and the quality of the image is well solved by setting a "bi-buffer area".(2) In realizing the live broadcast of the screen image, multimedia interlinkage and screen rolling control is accomplished by "screen-copying".(3) In realizing real-time courseware making, a graphical editing tool of SMIL is made by SMIL language, providing a simple text editing environment; the live broadcast of audio and video stream, image stream and text stream in client realizes by using SMIL and Realone player.