Optimization Of Algorithm And Data Memory Organization For H.264 Encoder Based On DSP

H.264/AVC is the latest international video coding standard. It has achieved a significant improvement in coding efficiency compared to previous standards. Therefore, H.264 will be widely used in the near future. However, it is too complex to be applied in real-time applications. Aimed at accelerating the coding speed of H.264/AVC, several aspects about the encoder of H.264/AVC based on DSP are studied in this paper.The video coding technique and international standards is first introduced. And then the new coding features adopted by H.264/AVC are discussed in detail. After that, kinds of methods to implement and optimize the video codec are analyzed and it is summaried that both spacial complexity and time complexity should be considered while performing the optimization of video codec on DSP.Secondly, the schedule of the data buffering and transmission of H.264/AVC encoder on DSP platform are studied in order to reduce the storage requirement. A mechanism of data buffering based on macroblock is proposed, and then the corresponding data scheduling scheme is established using the two-dimension DMA. This method makes full use of the fast on-chip memory and reduces the time taken by data transmission task.Thirdly, in order to reduce the computational complexity, the most time-consuming module of mode selection in H.264/AVC is optimized. The process of mode selection speeds up by reducing the number of candidates reasonably. And then the multimedia instructions of DSP are used to optimize the calculation of SAD and sub-pel interpolation. After the optimization on both the algorithm level and the assembly level, the speed of the mode selection on DSP is increased obviously.At last, a new macroblock rate control algorithm is proposed based on a relatively simple R-Q model. And several adaptive methods of parameter regulation and the schedule of the skip-mode pre-decision are integrated into the proposed algorithm to reduce the coding time while maintaining the quality of the picture and the output bit rate.