Improved MPEG-4 visual texture coding using perceptual dithering for transparent image coding

Abstract

MPEG-4 VTC provides coding efficiency using the zerotree entropy coding (ZTC) to remove the statistical redundancy among the coefficients within each wavelet tree. To improve the coding efficiency of ZTC, we propose an MPEG-4 compliant perceptual dithering coding (PDC) approach. In the ZTC technique, there is a parent-children relationship within each wavelet tree while the redundancy among the sibling nodes of different spatial orientations at the same frequency level is not exploited, The PDC approach perturbs the magnitudes of the sibling nodes for each wavelet tree according to the statistical distribution of AC coefficients within the subband at the same frequency level to achieve more energy compaction, The level of perturbation of each wavelet coefficient is constrained by the noise tolerance levels according to the perception model. For the same visual quality, we found that the PDC approach achieves bit savings over MPEG-4 VTC by 11similar to30%.