Research On The Method Of Implementation And Optimization Of H.264 Video Encoder Based On DM642

The purpose of video compression is to make the video take up less space of memory as possible in the same video quality. H.264, which can meet the requirement of real-time video communication, not only has excellent compression performance, but also good network compatibility. However, the perfect coding efficient and superior performance of H.264 are obtained by a huge amount of computation and complex coder structure, which is difficult to achieve on the general processors. Among the large number of embedded processors, TMS320DM642 of TI has a special signal processing instructions and good parallel processing capabilities, which is one of the ideal platforms to achieve the H.264 video encoder.The paper firstly introduces the structure and features of H.264 video encoder, and analyzes the key techniques in H.264, including predictive coding, DCT transformation, quantization and entropy coding technique. Then, it describes the hardware sources of DM642 platform, and focuses on the two-level Cache storage structure and the principle of EDMA, and builds the development environment of x264 encoder. After the source code of x264 and the three estimation search algorithms were analyzed, the paper migrates the x264 encoder to the DM642 platform successfully in the end, by cutting the source code of x264, allocating the storage space, and writing the .cmd file.Finally, the paper studies the optimization method of x264 encoder based on DM642, and the code-level optimization is the important aspect of study. Hybrid programming of C language and DSP assembly language is adopted in this paper. Because the speed of x264 encoder is still not ideal after several key techniques were applicated in C program, such as the data packing, inline function and software water flow, the paper analyzes and rewrites those functions which are computationally expensive and called frequently using linear assembly language. In addition, EDMA is taken full advantage to translate data for the purpose of improve the efficiency of the implementation of the program. And the experimental results show that the speed of x264 encoder optimized up to 15 fps ~ 25 fps, and increased several times faster than the encoder without optimization, but the video images have higher qulity.