Research On Key Implementation Technologies For Distributed Multimedia Distance Learning System

Distributed multimedia distance learning system is becoming more and more widely used in the field of distance education because of low cost and the characteristic that enable students to learn at any times and places. Then how to transport multimedia data streams involving video and audio of a classroom instructor via Internet quickly and effectively and manage the live synchronization presentation of different media at remote client are key issues to implement the distance learning system.Firstly, a solution of real-time multimedia transmission for the distance learning system is proposed in this thesis based on the analysis of transport and control protocols on streaming media to support the effectively multimedia transmission over a packet switched network. It combines RTSP with RSVP to set up and manage multimedia sessions that are carried by RTP. RSVP can reserve Internet resource and RTCP control packets can be used to determine the network congestion state and modify transmission rate dynamically in the solution to guarantee quality of session.Secondly, a synchronization mechanism was proposed which can adjust evaluations based on the network delay to implement the live synchronization presentation of the remote client-side. The proposed method can estimate the network delay by using control information such as timestamp and sequence number provided by RTP and adjust evaluations simultaneously to guarantee the required service for synchronized presentation in the multimedia distance learning system. An analysis of emulation results indicates the feasibility and validity of the method.