The Construction And Research Of Interactive Multimedia Real-time Teaching System

With the rapid progress of Internet technology and multimedia compressioncoding, multimedia communication systems based on Internet have become more andmore important. In this paper, our research focused on some key themes on interactivemultimedia real-time teaching in order to construct an available prototype system.The network topology of our teaching system is based on c/s mode including foursegments: server, client for teacher, client for student and record and playback ofteaching. By the way, the record and playback part also can be used as an independentsystem for lessons of famous tutor , remote teaching and so on.As to gathering multimedia information ,we discussed the following questions:the structure of VFW , the principle and standards of audio and video encoding , and ageneral process of gathering multimedia information .In record and playback of teaching part, we created a new multimedia file formatMSF(Multi Streams Format) to record three streams(video for teacher , video forscreen and audio for teacher) into one file. At the same time, we compiled appropriateplayer to play the MSF file. Compared with the traditional method, it has thecharacteristics of simple control, lower cost, better expansibility and so on. For thedifferent demand, we captured the screen in two different methods. The one is basedon time;the other is based on event. By the way, after analysing several familiarsynchronization models , we presented a new multimedia synchronization modelwhich is based on OCPN(Object Composition Petri Net) and has a link with referencepoint-based model to synchronize the multimedia streams.The transmission and synchronization of multimedia streams is the key problemsin real-time multimedia system. We researched into the transmission protocols, delaymodles and synchronization methods in transmission of multimedia streams andcalculated the buffer size of client for student in static state. In addition, we broughtforward a new method, which changes the playing rate in case of alteration in buffer,to realize the multimedia synchronization.