H. 264 To The AVS And Mpeg-2 To H. 264 Study On Video Transcoding

With the high demanding for coding efficiency and video quality,the newest video coding standard H.264/AVS is developed collaboratively by the ITU-T and ISO/IEC.AVS video coding standard is developed by the Audio Video Coding Standard Working Group of China(AVS working group in short),which was approved by the Chinese Science and Technology Department of Ministry of Information Industry. The mandate of the AVS working group is to establish the China's national standards for compression,manipulation and digital right management in digital audio and video multimedia equipment and systems.So at least,the AVS standard will be used widely in China in several years;there is an instance need to transcode H.264 to AVS.As the video coding standard MPEG-2 has been established for long time,there are many studies about the video transcoding from MPEG-2 to H.264,including the fast transcding in pixel domain and transform domain.So in this dissertation,only focus on the chroma transcoding in transform domain and transcoding while down-sampling at the same time for MPEG-2 to H.264 transcoder,the formula of reconstructing for chroma is given,and the algorithm of transcoding while down-sampling at the same time is proposed.In this dissertation,the video coding standards H.264/AVC,AVS and MPEG-2 are firstly introduced.Secondly,we discuss the main difference between them,and develop the algorithms used for H.264 to AVS transcoding in pixel and transform domain,include the coefficients transforming algorithm,motion vectors reconstructing and mode decision.Using the concept parallel disposing,we implement the H.264 to AVS transcoder to quicken the transcoding rate.For Intra trancoding of H.264 to AVS,a fast prediction mode decision is proposed,with the testing of different sequences,the algorithm can save about 56%computations;a fast fractional pel motion estimation algorithm is also proposed,the simulation results show that the proposed algorithm successfully optimizes the fractional-pixel motion search on both half and quarter-pixel accuracy,and improves the processing speed 63%for fast movement sequence with low PSNR penalty.The algorithm of chroma from MPEG-2 to H.264 in transform domain, and the method of down-sampling and transcoding at the same time for MPEG-2 to H.264 transcoder are also studied in this dissertation.For H.264 video coding standard, we propose a fast fractional pel motion estimation algorithm based on statistics.