Frequency content oriented modification of quantization matrix in DCT-based compression

Abstract

In order to improve the compression rate for comparable values of error metrics, we propose a method to modify the standard quantization matrix used in JPEG, according to image frequency content. Unlike the method which allows varying levels of image compression and quality, by scaling all the elements in the quantization matrix by the same factor, we propose a way to modify differently the quantization step for low and high frequencies, respectively.