| With the continuous increase of railway train speed, train operation safety is directly related to quality of the operations that schedule performs on duty. Now, the establishment of remote video surveillance system, which content is the operation of schedule on duty, is an important measure guarantees safety of railway traffic. But on the other hand, the best-effort service based on IP isn't suitable for the transmission of video information. The video information transmission always pauses because of congestion. The playback effect of video information is always affected by fluctuation of network states. QOS is difficult to be guaranteed.Coming from the demand for improving the quality of video transmission in multimedia applications, a video transmission control method based on RTP/RTCP is discussed. Through a comparative analysis of the current streaming media transmission protocol, the lack of UDP and TCP in real-time multimedia data transmission is pointed out in this thesis. Then on the base of analysis of the reasons that RTP is suitable for real-time video data transmission and predigest design of the standard RTP/RTCP protocol, an adaptive transmission control algorithm based on rate control in multimedia data transmission is realized.In packaging of video data over RTP, the algorithm based on maximal MTU of link layer is proposed. And for stagnation of video that is caused by the loss of I frame in transmission, a fault-tolerant processing algorithm based on I frame integrity of the receivers is summarized in this thesis.The Research focus of the paper is the adaptive transmission control algorithm based on rate control of the senders, which can reduce the network congestion, and improve the QOS of video. It is realized by estimating the congestion level of the network according to packet loss rate over RTP, and smoothing the output of the senders.Finally, the adaptive transmission control algorithm is effectively verified through simulation test in this thesis. |
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