Hybrid Video Transcoding Architecture And Its Rate Control Algorithm

This thesis states out the two year's work of my graduate study. Mygraduate research topic is video Transcoding and its application. VideoTranscoding is to change one video stream with certain format, frame rate,spatial resolution and bit-rate into another video stream with new format, newframe rate, spatial resolution and new bit-rate in order to satisfy thetransmission requirement and terminal processing capability. It can be appliedinto video serer, video conference and video gateway in Home Network.My work focuses on two aspects: the first is the combined temporal-spatial resolution reduction Transcoding, the second is rate control algorithmin Transcoding.As to the combined temporal-spatial resolution reduction Transcoding,the research is devided into three sub-parts. The first part is motion-vectrore-estimation after frame-skipped and spatial resolution down-sampled, thesecond is to calculate the prediction residual in DCT domain, and the thirdpart is coding mode selection for macroblock. In addition to the research, theimplement of the Transcoding architecture is another issue. By comparing theperformance of the temporal-first architecture and the spatial-first architecture,the former is selected as the final Transcoding architecture.I implement the transcoder in pure software style. The softwaretransocder is based on Xvid codec which complies with MPEG4 standard.There are four modules in the transcoder: decoding module, motion-vectorcompostion module, temporal-spatial resolution downsampling module, andencoding module.The second part of my work is the rate control algorithm in videoTranscoding. I analyzed the buffer constraint in video transmission usingtranscoder and discussed how to calculate the bandwidth of transmissionchannel. In my research, I modify the existed frame-layer rate control andmacroblock-layer rate control algorithm in TMN8 and apply them into videoTranscoding.The thesis not only introduces the state of arts in video Transcoding, butalso proposes some more efficient algorithm and architecutes. The transcoderimplement is also described in detail, with experimental result. In the end ofthe thesis, the bottleback of video trascoding is pointed out and future worksare estimated.