The Study Of Low-bit Rate Image Coder Based On DSP

With the development of high-speed information way and multimedia technology, remote communication of image has been applied in more and more field. And the remote image civilian based on PSTN is a model application. Because of the limitation of bandwidth, signal must be transmitted in low speed. Designing a low-speed coder is the ultimate aim in the paper. There are several methods in which image is compressed, such as: i Implemented by software; ii Special image compression chip; iii Implemented by embedded CPU; iv Implemented by programmable DSP chip. In these methods, the efficiency of the first one is too low, because when the software written by advanced language based on PC is translated and edited, the redundant instruction is too much; the second and the third one is too expensive and the algorithm is single. Programmable DSP is introduced to implement image compression in this paper and the excellence is also presented. How to design image coder and which chip should be choosed are the main text in this paper. Not only appropriate hardware system but also right compression algorithm is important to implement low-bit rate image coder. JPEG, H.261, H.263 and MPEG are international image coding standard, H.263 and MPEG-4 are two low-bit rate video coding schemes. But a JPEG based video coding scheme with MPEG-4 is adopted and discussed particularly in this paper. How to implement the algorithm by programmable DSP chip is also presented in this paper.