The Study For H.264 Intra Mode Selection Algorithm And Encoder's Optimization On DSP

H.264/AVC video coding standard is designed to give a new technicial solution to a broad rang of applications, such as low-bit-rate conversational services and entertainment quality broadcast, interactive video-on-demand service etc. So this standard obtains much attention from academic and industrial fields. Compared with prior standards, H.264 has achieved great efficiency in compression of video, but the high-complexity of H.264 has always been a factor of restriction of application mostly, so to study the implement and optimization of H.264 based on DSP is significant.In this paper, the key technologies of H.264 are introduced first, such as intra/inter prediction, integer transform and quantization, entropy coding. We give a detailed analysis about the innovation and the research actuality mentioned above, sequentially the future about H.264.Secondly, the paper gives a detailed analysis about two arithmetics of fast intra prediction, the one is named as a sub-pixel rapid mode-decision algorithm, which uses a sub-pixel point instead of a block-pixel point. Every step in the mode-decision only to calculation a sub-pixel point to reduce the complexity of calculation; The other is based on the direction of the edge of the histogram rapid mode-decision algorithm, and counts the brink direction of the macroblock, determining the direction of forecasting models, in order to obtain the best or the second-best intra-prediction mode. Considering the cost function and the number of prediction models, the paper proposes a fast intra prediction algorithm. The results show that the new algorithm can reduce the coding time by 50% while the rate and PSNR change little.Lastly, the paper gives an introduction of structure of TMS320DM642 chips.Several key techniques concerning the porting of H.264 encoder from PC to DSP, such as the memory assignment, the modification of access mode and variable definition, inline assembly and application of pipeline, linear assembly, DMA based on two-level hierarchy cache, are adopted in the optimization procedures. The H.264 encoder on DSP is optimized to 8.35 frames per second encoding perfomace for CIF resolution video, compared to 1.45 frames per second before optimization.