MPEG-4 Video Compression Coding And Its Implementation Based On DSP

Responding to multimedia technology rapidly developing and application domain promptly enlarging, many multimedia compression and coding standards progress and are perfected continuously. Among them, MPEG-4 plays an important role in the multimedia field. Due to its object-based idea, it has the virtue of high compression ratio, scalability, inter-activity with users and so on. MPEG-4 is in vigorous development, which indicates the tendency of multimedia data compression and coding technique. Thus, it is a significant work to track and understand the development tendency of MPEG-4 in time, and to grasp its core technology, and to innovate and develop in certain essential domain with practical applications. Because of the very complex algorithms of MPEG-4 video compression and large sum of computing, software method can't satisfy real-time requirement. Accordingly these systems mostly work by using hardware method. In hardware implementing methods, video processing chip for special purpose is powerful but is not flexible, and its application is limited. However, general high-performance Digital Signal Processing (DSP) is applied widely due to flexible software design and powerful adaptive capability. In market of chips for general DSP, TI company's TMS320C6201 DSPs which have strong processing capability, flexible external interfaces and completed development tools are adapted by the systems. This project conducts the key research on the core of MPEG-4 standard –the compression and coding of video signal, on the basis of comprehensively understanding of the fundaments of MPEG-4 standard. According to the characteristic of video image, the goal of this study is to implement the real-time compression and coding and low bit rate transmission of the original video source. Therefore, the most important target is compression and coding speed and the compression ratio as well as the subjective image quality. Based on this, this project firstly extensively studies, optimizes and ameliorates the key algorithm in coding -DCT (Discrete Cosine Transformation) and the movement estimation algorithm, so as to implement fast coding and the high compression ratio. DCT is optimized in view of the hardware resources condition, and the execution time of this algorithm is reduced; meanwhile the improvement algorithm based on the diamond search algorithm is proposed. The test result proves that the improved algorithm reduces the search points so that the search speed is accelerated and increases the search precision. Then the video compression of MPEG-4 is implemented through C language in the Visual C++ environment. The result of test sequence proves that the software has achieved high compression of MPEG-4 video image and satisfactory subjective image compression quality. Finally, the coding program was ported to DSP, and a great deal of optimization was applied to the coding program considering the resources of TMS320C6201 DSP hardware, so as to achieve real-time encoding. Hardware emulation on a C6201 DSP EVM board was applied to the algorithm; the result indicates that more than 25 frames of CIF (352×288) images can be processed per second. Thus, the MPEG-4 encoder provided in this article has guaranteed the real-time video compression.