Optimum quantization step size for integer lossless transform coefficients

摘要

The DCT and wavelet coefficients have real values which are continuously distributed. Therefore the entropy of the quantized transform coefficients is also varied continuously, when the quantization step size is continuously changing. On the other hand, the integer lossless DCT and wavelet coefficients have integral values. Therefore the entropy of the quantized transform coefficients is not varied continuously for the quantization step size. Thus we must carefully determine the quantization step size for the integer lossless DCT and wavelet coefficients to make lossy compression efficiency high. In this paper, we will illustrate that we can not make use of the optimum step size of the lossy version as it is and propose the optimum quantization step size for the integer lossless transforms.