Based On The Hardware Of The Dsp Mpeg-4 Image Coding Algorithm Optimization And Coding System

With the development of multimedia techniques, video encoding system became more and more important in surveillance system. At present, it is very common to construct such a system by special video encoding chips, which suffers from high cost, low performance and poor scalability. So it is meaningful to begin research on real-time MPEG-4 encoding system based on DSP.This paper presented the hardware design and MPEG-4 algorithm optimization of an encoding system based on TMS320DM642, software implementation of OSD and channel multiplexer were also discussed.MPEG-4 algorithm transplantation and optimization are the main tasks of DSP programmers. The author did a comprehensive research on the open source MPEG-4 algorithm and transplanted it into DSP. To make full use of its structural advantage, ram of DSP chip are reallocated and configured in code transplanting process. Furthermore, to improve real-time performance, lots of efforts have been made in many ways. One of them is to cut down effectively the cost of exchanging data between SDRAM and DSP caches. Another way is to create parallel codes as much as possible, which can be achieved by C and linear assembly optimization. Finally, I frame encoding time reaches to 20ms/frame, P frame and B frame encoding time are reduced from 400ms/frame to 22ms/frame and from 800ms/frame to 22ms/frame respectively.Channel multiplexer and OSD are both implemented in application layer. QDMA is adopted to overcome the difficulty of image zooming of channel multiplexer. Not only it is the fastest, but it can zoom in from QCIF to CIF resolution without noticeable quality deterioration. In our implementation, we add OSD the function of changing character color with background, which makes sure that all characters can be displayed on any background.