Image coding using multiple scale leader lattice vector quantization
Adriana Vasilache, Ioan Tăbuş · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2003
This paper presents an image coding method, based on wavelet transform, where the distribution of the subband coefficients is assumed to be generalized Gaussian. The shape factor and the standard deviation are estimated in all subbands. A procedure of bit allocation distributes then the available bitrate to the retained coefficients. The multiple scale leader lattice vector quantization (MSLLVQ) has shown its superiority compared to other structured quantization schemes and now we propose its use for the quantization of the wavelet coefficients. The main contribution of the paper is the procedure for selecting the structure and the leaders for the MSLLVQ. An iterative construction of the MSLLVQ scheme is presented along with the derivation of the operational rate-distortion function. The bit allocation procedure is based on the exponential fitting of the operational rate-distortion curve. The results in terms of peak signal to noise ratio are compared to other image codecs from the literature, the advantage of such a coding structure being particularly important for the fixed rate encoding.