The Design And Implementation Of Video Transcoding Transmission System

With the rapid progress of multimedia communication technology, video codec, video transmission and video surveillance technologies have got a rapid development on live transcoding transmission and playing of oneline videos. Meanwhile, as the establishment of safety society, the real-time monitoring at anytime and anywhere becomes a key point issue at present. Due to the differences in devices and multimedia applications, people may have various requirements such as conversion of format, resolution, bit rate, and frame rate. A video transcoding system can be used to deal with the situation. With the support of codec theory and the Web Service, this paper tries to develop a video transcoding transmission system based on Windows platform.Firstly, the thesis analyzes the structure of FFMPEG source code library, and designs the transcoding module by using codec module and interface functions provided by FFMPEG. Due to the fact that the FFMPEG fails to support the encoding of the H.264 and AVS(Audio Video Coding Standard), we realize the extension of the H.264 and AVS external encoding module in FFMPEG. Meanwhile, in order to resolve the nonsupport problem of packing and unpacking for AVS in FFMPEG, we implement the above two modules based on RTP(Real-time Transport Protocol) protocol, and extend FFMPEG through the establishment of a data structure and interface functions. Then we design the general transcoding interface functions in order to provide facilitate for the establishment of Web Service. Through the test of the above modules, experimental results show that the transcoding module can support the mutual conversion of format, bit rate, frame rate and resolution among the four video types, that is H.264, H.263, MPEG-4 and AVS.Finally, based on the above general transcoding interface functions, this paper creates the business modules of video source end and transcoding end by using the Web Service. Then, with the help of g SOAP tool, we deploy the services of the source and transcoding end, design the client control program and realize the message transmission by the socket programming of TCP(Transmission Control Protocol). At the same time we create a client user interface by using the python language and complete the design of the system based on Windows platform. The detailed introduction of each module are also presented in this paper.This client software provides a simple, friendly and easy-to-use interface. After the actual testing, we can conclude that, under control of client device, the source end can play and transmit the native stream files or surveillance videos, while the transcoding end executes the receiving, transcoding and transmitting process, and the client end plays videos in real time. Client could start or stop the video at any time. It shows that the system can support the transcoding and fluent display of the high definition videos at 25 fps in the error-free environment. Time delay is less than 1s when dealing with the resolution of 720 P or less, and within 1.5s of 720 P and 1080 P, while the whole system runs stably.