PDVQ图像编码系统的算法研究

PDVQ图像编码系统首先将码书进行方向性分类，把每类方向性码书中的码字按码字和值进行升序排列，并根据EBNNS算法将码书分块。编码时，先根据输入图像块的相关性进行PDVQ编码，然后分析输入图像块的方向性来选择相应的分类子码书，在该子码书中根据输入图像块的和值确定码字搜索范围，最后在确定的搜索范围内搜索最匹配码字。仿真结果表明，该系统集合了动态图像块划分（PDVQ）、基于方向性分类编码和等和值块扩展最近邻码字搜索（EBNNS）三种算法的优点，在保证重建图像质量前提下，缩短了编码时间，并提高了压缩比。

Research on image encoding system for PDVQ algorithm

First the PDVQ(Partition Dynamically VQ) image encoding system categorizes the codebook based on the directions of the codewords,in each category codebook all codewords are sorted in the ascending order of their sum,and then each category codebook is divided into blocks in average.During the encoding process,the encoding system analyzes the correlation of the input image block and its neighboring blocks using PDVQ algorithm,and judges the direction of input image block to choose corresponding category codebook.And a nearest codeword to the input image block can be found out in the search range which can be gotten based on the sum of the input image block using EBNNS(Equal-sum Block-extending Nearest Neighbor Search) algorithm.Experimental results demonstrate that this encoding system integrates the merits of PDVQ with EBNNS and category encoding algorithm based on direction,which can improve the compression rate and coding speed in contrast with the normal VQ,and will not affect the quality of the image reconstructed.