Abstract: An algorithm of combining SPIHT and arithmetic coding algorithm for image compression is presented and both theory deduction and simulation result prove the correctness and feasibility of the algorithm.According to the characteristic of context-based adaptive binary arithmetic coding and entropy，SPIHT is modified to cooperate with the optimized piecewise arithmetic coding.This algorithm improves the compression ratio without any additional time consumption compared to traditional method.

Key words: piecewise Context-based Adaptive Binary Arithmetic Coding（CABAC）, modified SPIHT, combined encode

摘要： 为提高图像压缩效率，提出了分段自适应二进制算术编码CABAC与SPIHT算法相结合的混合编码算法，并从理论和仿真实验两个方面证明了该算法的有效性。根据SPIHT算法产生码流概率的特点及二进制熵编码的特性将SPIHT算法产生的二进制码流分为符号和数据两段，并按照SPIHT编码阈值对数据码流再次分段，采用优化的CABAC对各二进制码流段分别编码，在不增加计算量的情况下能够得到更好的图像压缩效果。

关键词: 分段自适应二进制算术编码, 改进的SPIHT, 混合编码