Research On The Key Technologies For Fast H.264 Transcoding

This thesis is based on H.264/AVC standard, mainly focusing on efficienthomogeneous bit-rate transcoding for H.264 and heterogeneous transcoding fromH.263 to H.264.First, for homogenous H.264 bit-rate transcoding, the direct mode selectionalgorithm is proposed based on the analysis of the RDO algorithm and the cascadedarchitecture. From the macroblock mode statistics and residual calculation of originalbitstream as well as the reference frame, the optimal macroblock mode can be decidedby using the estimated distortion. The experimental results show that the proposedtranscoding method provides acceptable performance, decreasing less than 0.5 dB andsaving 90% encoding time, compared with the cascaded transcoding.Second, for H.263 to H.264 transcoding, the bit rate reduction, 2:1 ratio resolutionreduction, frame rate reduction and combined transcoding are respectively focused on.The fast decision of inter-frame macroblock is presented on the basis of reusing H.263macroblock information such as mode, motion vectors, CBP and COD. For theresolution and frame rate reduction, different methods for motion vector reconstructionand refinement are also proposed. Finally, the overall framework of transcoding fromH.263 to H.264 is presented. The experimental results show that compared with thecascaded architecture the proposed algorithm can promote the speed of transcoding by25%~45%, as well as reduce PSNR less than 0.8 dB.