Based On Network Learning Platform For Streaming Video And Audio

E-learning platform, a full-scale supporting software system of web teaching, combines the real-time video, the real-time audio and the teaching tools. These characteristics make the information shared and communicated between teachers and students can be carried out by internet, which results in teaching and answering in-distance. It is the key technology and bottle-neck of the development of E-learning platform where video/audio media is controlled by software.A design idea of E-learning platform in view of the studying theory of constructivism is proposed in this paper to help the students learning knowledge. In the proposed scheme, the students are the center of E-learning environment. According to the function, the system of the video/audio media processing is divided into 4 modules, e.g. Capture/playback, compression/ decompression, network transmission and media synchronization.Based on the structure of DirectX, VC++ program is used to control the USB interface, the video card and audio card, which has improved the speed and quality for capture and playback greatly. Based on the principium and the characters of the Mpeg-4 standard, the scheme of XviD codec and Mp3 audio codec is proposed, which has improved the compression efficiency, redundancy and reliability. Based on the RTP/RTCP and WinSocket technology, the IP multicast that is proposed to realize the real-time video/audio transmission can support 16 display windows, reduce the network resources and acquire satisfying quality of transmission. On account of the synchronous control of the video/audio media, a mathematical model of time stamp synchronous control is proposed to analyze the mechanism of the cache synchronous control, which make the synchronous error between video and audio less than 10% and remarkable reduce the delay and jitter.The video/audio processing modules have finished and combined with the date module and management module. The teachers and students think that the E-learning platform combines clear menu, coherent voice and simple handle after using. The specialists think that the platform is consistent with thecustom of the teachers and the students, has the classroom atmosphere, and is an efficiency tool for learning and answering in-distance.In this paper, the research content belong to the project of "+2l" digital teaching environment and is financially supported by the project of electrician and electron technology multimedia network course of Northwestern Polytechnical University.