Research On Crucial Technology Of H.263-MPEG-4-H.264 Video Transcoding System

Recently, the mergence of fixed network and 3G network (FMC) has become the evolutive trend of communication domain. IP Multimedia Sub-system (IMS) that is based on SIP protocol, support the access of mobile and fixed network. IMS will play a crucial role in P2P IP multimedia business and network mergence.Video transcoder in this paper is an embedded multi-channel video transcoder resolution based on MSC8122DSP. The transcoder will be used in IMS media gate-way. Besides providing the multi-channel transform of H.264-H.263-MPEG-4 standard format in real time, the transcoder can transform picture resolution, frame rate, and bit rate according to the requirement of clients. The transcoder can work robustly in error-prone environment by efficient error detection and concealment of wireless and wire channel error.Firstly, this paper introduced video transcoding technology and related video coding standards comprehensively. And then, this paper discussed the implementation of video trancoder in detail, containing transcoding functionality, software architecture, temporal transcoding algorithm, network transmission, error tolerant algorithms and optimization.The three major innovations lie inâ‘ presenting a novel motion vector composition algorithm, which can realize the motion vector composition for all of H.263,MPEG-4 and H.264. The algorithm has been applied in the transcoder successfully.â‘¡presenting a set of resolutions that are suitable be implemented on DSP platform for RTP packet processing, error detection and concealment, which greatly enhance the real time performance, robustness and error tolerance of video transcoder..â‘¢presenting a fast mode decision algorithm for H.264 intra coding, which can speed up both reference software of H.264 and transcoder distinctly.â‘£the result that the transcoder can transcode the bitstream totally in real time. For input bitstream with CIF resolution, the speed of transcoding between H.263 and MPEG-4 can achieve 308 frames per second, while the speed of transcoding from H.263/MPEG-4 to H.264 is up to 168 frames per second.