JPEG 정지 영상의 교류 계수 분리를 통한 압축 효율 향상 연구

In this paper, we propose a novel entropy coding method to enhance compression ratio of the JPEG standard. Based on the observation that JPEG entropy coding performs better for the data with longer sequences of consecutive zeros and lower coefficients in their magnitudes, we extract low values from the AC coefficients of a JPEG block to replace then with zeros. The resulting blocks are entropy-encoded with JPEG standard method, while the extracted sequence of the low coefficients are compressed with a method designated to those values. This allows us to transmit the JPEG compatible part and the remaining part separately to provide semi-progressive transmission, where the standard JPEG decoder can produce an image with little degradation using the former part, and a custom decoder can also add fine details using the later. The compression ratio of the proposed method for the standard image is better than the standard JPEG up to 5% while not sacrificing the high computation efficiency of JPEG.