On Improving JPEG Entropy Coding by means of Sub-Stream Extraction

Abstract

SUMMARYWe introduce an entropy coding method to enhance the compression efficiency of JPEG. Because run-length coding and earlytermination work more effectively for longer zero sequences, we extract ones and negative ones from the coefficients and reduce the magnitude of all coefficients by one. The extracted coefficients are encoded with a designated entropy coding method. The proposed method can transmit images in two parts progressively, where the first contains JPEG-compatible image with a small amount of degradation and the second is used to add fine details. Our method improves the compression ratio by more than 5% without sacrificing the efficiency of JPEG.