Abstract
This paper proposes a method of improving performance for DCT-zonal coding of images by M-transform. In the zonal coding, efficiency is degraded due to large distortion caused by Max quantizer for DCT coefficients, because they have broad-tailed distributions. Moreover, quality of reconstructed images in deteriorated by block artifact. In the proposed method, by appling M-tranform to each sample sequence of the DCT coefficient over different blocks, the distributions of the DCT coefficients are restrictively tranformed to Gaussian. Consequently distortion can be reduced and mismatch of distributions between quantizer and input signal can be eliminated. Simultanously, the block artifact becomes inconspicuous because the quantization error is scrambled into almost random noise by inverse M-transform. Simulation results for many test images show those improvements were attained as good as expected above, in both adaptive and non-adaptive coding. Evaluation of computational complexity also shows the usefulness of this methed.
