| Real-time video transmission is a typical application service of3G network.Compared with other network service, the amount of video data is large, so it requiresdata compressed before transmission. H.264is now widely used in digital videocompression. Although real-time video transmission based on H.264compressed is wellsupported by3G networks in theory, due to the instability of network bandwidth andjitter of3G network, therefore，how to dynamically adjust the control strategies ofH.264rate which can promise the quality of video services under unstable3G networkis an important technical issue.The purpose of the thesis is that ensure the quality of video transmission throughthe advance prediction of network congestion and discard policy of frame, which areprovided by sending end. Some of the following tasks are carried out:①in the real-time video communication process, the parameters of networkbandwidth which can be perceived by sending end is analyzed. A model of rate controlis proposed. According to the buffer size of sending end and predicted networkbandwidth and trends, some measure of rate control is taken by the model.②On the basis of the mode proposed above, the optimization strategy of differentstages of processing in the model stages of processing is proposed. First, for theproblem of processing overhead of mobile device caused by switch of bit rate, a newconvert method of bit rate is proposed. Through setting and monitoring of somethreshold of related parameters, buffer is managed; According to the importance offrame encoded by H.264, a discard policy of discarding Non-key frames in different3Gnetwork environment.③In VCEG-N80offline environment, preliminary experiments is carried out onplatform of JM. In order to test the effectiveness of the method of forecasting networkbandwidth. In order to verify the validity of the proposed model, Comparison of thevalue of PSNR between our proposed model and traditional model, which measurespacket loss rate, is carried out. |
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