Three-sided side match finite-state vector quantization

Several low bit-rate still-image compression methods have been presented fo r the past two years, such as SPHIT, hybrid VQ, and the Wu-Chen method. In particular, the image "Lena" can be compressed using less than 0.15 bpp at 31.4 dB or higher. These methods exercise the analysis techniques (wavelet or subband) before distributing the bit rate to each piece of an image, thu s the dilemma between bit rate and distortion can he solved, In this paper, we propose a simple but comparable method that adopts the technique of sid e match VQ only. The side match vector quantization (SMVQ) is an effective VQ coding scheme at low bit-rate, The conventional side match (two-sided) V Q utilizes the codeword information of two neighboring blocks to predict th e state codebook of an input vector. In this paper, we propose a hierarchic al three-sided side match finite-state vector quantization (HTSMVQ) method that can: 1) make the state codebook size as small as possible-the size is reduced to one if the prediction can perform perfectly; 2) improve the pred iction quality for edge blocks; and 3) regularly refresh the codewords to a lleviate the error propagation of side match. In the simulation results, th e image "Lena" can be coded with PSNR 34.682 dB at 0.25 bpp, It is better t han SPIHT, EZW, FSSQ and hybrid VQ with 34.1, 33.17, 33.1, and 33.7 dB, res pectively. At a bit rate lower than 0.15 bpp, only the enhanced version of EZW performs better than our method, about 0.14 dB.