关键词: 图像压缩, JPEG2000, 率控制, 优化截断的嵌入式分块编码, 最速下降法

Abstract: A fast rate control algorithm based on Steepest-Descent (SD) was proposed for JPEG2000. The essence of this algorithm is an iterative selection process. In each iteration step, the code passes with maximal ratio of decrease in distortion to increase in bit rate were chosen and reserved as a part of the final compression codestream. Considering the high time complexity of the sorting process in each iteration step, the maxheap structure was introduced into this algorithm to reduce the time complexity. By encoding the candidate passes in the course of rate control, this algorithm not only eliminates the encoding redundancy existing in JPEG2000, but also decreases the time spent on the rate allocation procedure. The experimental results show that this method significantly reduces the time complexity of the processes of rate allocation and encoding and improves the coding effciency compared with JPEG2000.

Key words: image compression, JPEG2000, rate control, Embedded Block Coding with Optimal Truncation (EBCOT), steepest-descent