<title>Improved search-order coding algorithm for lossless compression of VQ indexes</title>

Abstract

In a fixed-rate vector quantization system, an image is divided into smaller blocks, and each block is usually independently encoded by an index of the same length that points to the closest codevector in the codebook. Recently, an algorithm, called search-order coding, has been proposed to further reduce the bit rate by encoding the indexes but without introducing any extra encoding distortion. In this paper, we present an improved algorithm that extends the idea of the search-order coding algorithm by encoding the indexes pair by pair (instead of one by one). With this extension, four types of search results are considered. The simulation results indicate that our algorithm is able to achieve the bit rate up to 5.74% lower than the search-order coding algorithm.