2 IMPROVED CODEBOOK SEARCH METHODS OF VECTOR QUANTIZATION BASED ON ORTHOGONAL CHECKING AND FIXED RANGE SEARCH

We present two improved methods for the codebook search in this articl e. We call them the improved eigenvector method (IEVM) and the improve d triangle inequality elimination (ITIE), respectively. IEVM is a full -search (FS) equivalent method, but ITIE is not In these two methods w e propose some techniques, such as the orthogonal checking and the fix ed range search, to speed up their performance. According to our exper imental results, IEVM is an efficient method. It is faster than FS, TI E, and EVM. Its execution time and number of operations per pixel were 4.86% and 4. 76% of those in FS, respectively As for ITIE, it is alwa ys faster than IEVM even ii we limit ifs peak signal-to-noise ratio de gradation to be no greater than 3% of the image quality of FS. Under t his limitation, the execution time and the number of operations per pi xel of ITIE were only 3.08% and 3.05% of those in FS, respectively. (C ) 1998 SPIE and IS&T. [S1017-9909(98)00802-2].