Research And Optimization On Multi-role Video Transcoding System

IP Multimedia Subsystem (IMS) is a widely recognized platform for multimedia service and for internet adaptation. Such system can offer the operators flexibility in providing services and the end users convenience in switching between different networks and applications.The Multi-role Video Transcoding System presented in this paper is a versatile Freescale MSC8122DSP based video transcoder resolution, with support for H.263, MPEG-4 and H.264 standards. It can perform bit-rate transcoding, frame-rate transcoding and resolution downscaling at the request of users and at high channel density. The system is about to be used in IMS media gateway.Firstly, this paper makes an overview of recent proposed video transcoding technology. Secondly, this paper presents the architecture of video transcoding system and its key modules. Thirdly, an improved Macroblock mode-mapping algorithm is proposed. And lastly, details about the optimization are discussed.The three major innovations are as follows.①Presents an improved mode-mapping algorithm based on FDVS, which can effectively improve the temporal transcoding quality. The algorithm has been integrated into the transcoder successfully.②Proposes a novel fast sub-pixel motion estimation algorithm. This algorithm can speed up encoding dramatically without severe video quality degradation.③The transcoder can perform at high channel density in real time. For CIF bitstream, the MSC8122DSP can transcode 404 frames for H.263 to H.263 and 173 frames for H.264 to H.264 at 400MHz frequency.