Research Of The Transprotation Of Network Video Signal Based On VxWorks

In recent years, with the rapid development of Internet, video codes and Embedded Operating System, the field of real-time transportation of video signal is becoming more and more widely. The real-time transportation of MPEG-4 video is very essential in the network transportation system. It is of very importance to the robust of the whole system. Video and Audio transportation system has delay and loss requirements and been instability, which cannot be adequately supported by the current network. So it is an important topic to research a transportation system suite for the transportation of MPEG-4.The thesis first introduces the network transportation, RTP protocol and MPEG-4 standard which are widely applied, describes real-time Transport Protocol and RTP Control Protocol deeply, then the thesis chooses appropriate transport scheme based on the features of transportation network, and designs the transport network.The system adopted the real-time Operate System VxWorks for the sake of the stability of the system. We have written the PCI driver for the integration of the cards for collecting audio and video. The driver could make the cards worked normally and the driver we wrote could provide the frame for writing PCI driver based on Vx Works.For the RTP packed strategy, the thesis analyses the packed algorithm that regards VOP as the unit, and gives an improvement. For reducing the packet numbers in maximum and giving attention to the real-time character of monitor system, the thesis adopts the strategy that one packet loads several VOPs. For reducing the packets-lost influence to the decode quality on receiver, the thesis put forward the interleaving packed strategy. Then the thesis depicts the packed algorithm and designs the payload type. The experiments indicate that the improved packed algorithm has been reduced the quantity of the RTP payload. In order to assure the quantity of the real-time receiver, while the play system receives the RTP packets from the sender, the system uses Random Early Detection method to control network congestion. Receive uses two buffers to insure the synchronization of the video and audio. According the experiment, it is shown that the system got the well result through the improvement.