Research And Implementation Of Low Bit Rate Video Coding Based On DSP

Technology of video coding for low bit rate communication has been a focus of attention in the domain of video processing. ITU-T Recommendation H.263 which can be used for compressing the moving Picture component of audio-visual services at low bit rate less than 64kbs is adopted in my article. The basic coding algorithm of the video source is a hybrid of encoder based on ITU-T Recommendation H.261 .In addition to the core H.263 algorithm, four negotiable coding options are used to improve the performance of coder and decoder. Although there are many methods that implement video coding, the method based on DSP chip has remarkable advantage besides pure software method since video coding is essentially a digital signal processing.The project is based on design of network video server and has implemented H.263 recommendation on a video processing platform based on DSP. TFs EVM642 image&video processing platform is used as the system hardware foundation. Coming with a core processor-DM642, It provides A/D and D/A transforming chips for video processing, FPGA logic control chip and other on board devices. Using of the platform magnificently reduces hardware design work. The system software design is based on DSP/BIOS kernel and Reference Framework blueprint. The former provides multiple threads operation with synchronization and a preemptive real-time kernel. The latter constructs application software foundation with many channels and algorithms. With help of these two tools, the software design has became much easier.According to structure features of DSP, multiple methods including compiler parameters setting, intrinsics, PING-PONG algorithm and word or double-word data accessing are used to optimize video coding process. And higher code performance has been archived. Besides, further optimization has been attempted for H.263 core algorithm modules: DCT, IDCT and motion estimation module. The optimization uses early detection method of all zero coefficients technology and diamond search algorithm respectively.For consideration of reducing design difficulty, project didn't use H.264 recommendation as video coding standard. However as the newest video coding standard of the ITU-T Video Coding Experts Group (VCEG) and the ISO/IEC Moving Picture Experts Group (MPEG), H.264 recommendation has a bright future. So the next goal of our research work is to implement H.264 recommendation after we have well implemented H.263 recommendation.