Research On H.264 Video Coding Standard And H.264 Software Codec Development And Optimization

As the newest generation of video coding standard, H.264 inherits merits from contemporary video coding standards as well as brings up many new ideas to achieve a better compression performance. But the performance improvement is at the expense of computational complexity increment. H.264 main profile decoder requires 3 times computing capability than MPEG4 simple profile, and an increase of more than one order of magnitude of the computational complexity is reported at encoder end.In this paper, our work is mainly focused on H.264 software codec optimization, which includes optimization on algorithm level and optimization on program level. On algorithm level we propose a novel fast inter prediction mode decision algorithm and a CAVLC lookup table search method for speeding up the codec and a background-frame based motion search and motion compensation algorithm for performance improvement in surveillance application. (1) Although prediction modes selection and R-D optimization process can brings up significant performance gain in H.264, during this process, all prediction modes need to be tested thus increase the computational load on encoder. In this paper, a novel fast inter prediction mode decision algorithm for H.264 is presented. A down sampled small image of original image is pre-encoded to get best inter prediction modes in the small image. Then the modes obtained from the pre-encoding process are mapped to a candidate modes subset used for original image encoding process. Our algorithm can reduce the prediction modes to a small subset thus can speed up the encoder.(2) A CAVLC lookup table search method is presented in this paper for H.264 decoder. By convert 2-D tables to a binary tree format, the speed for table lookup can be improved. (3) In surveillance application, video sequences usually have many regions containing static background. Based on this observation, we proposed a background-frame based motion search and motion compensation algorithm. By generating background-frame and detecting moving objects, the motion compensation for background parts and moving objects parts can be done in background-frame and typical reference frame separately. The errors during motion compensation process can be reduced and performance can be improved.On program level, we refine the program structures and use MMX/SSE instructions to rewrite the 4x4 transformation part and sub-pixel interpolation part to improve speed.We also use C++ to rewrite a baseline profile codec and provide the VFW interface to interact with some popular multimedia software such as VirtualDub and MS Media Player. When compared with the reference software under baseline profile, our encoder and decoder achieve speed improvement of more than 10 times and 3 times respectively. Our codec can encode CIF size video sequences on P4 2.6G PC at a speed of 15f/s and can decode CIF size video sequences on P3 800 PC in real time.