Dynamic windowed codebook search algorithm in vector quantization

We present an efficient codebook search algorithm in a vector quantization (VQ)-based system that searches only through a window of consecutive codewords on the preordered codebook, rather than all codewords in the codebook, and achieves full-search-equivalent performance. The ordering technique used to rearrange the positions of codewords in the codebook utilizes the scattering orientation of codewords in the k-dimensional space or the compactness property of signal energy on the transform domain. The procedure for determining the search window on the ordered codebook relies on the geometric relations among input vector and codewords to eliminate those codewords that are certain not to be the closest codeword to the input vector. Finally, the closest codeword to an input vector is selected from the determined search window by an improved partial distortion search algorithm. In comparison with other existing fast algorithms, the proposed algorithm requires the least number of multiplications and the least total number of distortion measurements.