Three-sided side match finite state vector quantization

Several effective low bit rate still image compression methods have been presented in these two years, such as SPHIT [9], Hybrid VQ [7], Wu and Chen method [10]. These methods exercise the analysis techniques (wavelet or subband) before distributing the bit rate to each piece of image, thus the tradeoff between bit rate and distortion can be resolved. In this paper, we try to propose a simple but comparable method that adopts the technique of side match VQ only. Side match vector quantization (SMVQ) is an efficient VQ coding scheme for low bit rate coding. Conventional side match (two-sided) utilizes the codeword information of two neighboring blocks to predict the state codebook of an input vector. In this paper, we propose a hierarchical three-sided side match finitestate vector quantization (HTSMVQ) method that can (1) make the state codebook size as small as possible, it can be reduced to 1 if the prediction is performed perfectly; (2) improve the prediction quality for edge blocks; (3) regularly refresh the codewords to alleviate the error propagation of side match. In the simulation results, the image "Lena" can be coded with PSNR 34.682 dB at 0.25 bpp. It is better than SPIHT, EZW, FSSQ and hybrid VQ with 34.1, 33.17, 33.1 and 33.7 dB, respectively. At the bit rate lower than 0.15 bpp, only the enhanced versions of EZW perform better than our method about 0.14 dB.