基于上下文的自适应二阶二进制算术编码算法

H．264是国际上最新的视频编解码标准，是未来几年内视频编码技术研究的主要方向。基于上下文的二进制算术编码算法（CABAC）是H．264中一种能适应信号统计特性的变化，容易达到渐进性能的高效率的熵编码算法。提出了基于CAB-AC的二阶二进制算术编码算法（2-CABAC），把待编码比特流binstring转换成theta string，通过对theta string进行编码提高对bin string的压缩比。给出了2-CABAC的原理、设计方法和程序流程。测试结果表明，与CABAC相比较，2-CABAC明显提高了压缩比。最后，对转换函数Phi的设计进行了讨论。

Context-based adaptive 2-level binary arithmetic coding algorithm

H.264 is the newest video coding recommendation in the world, which is the focus of video coding technology in the futureyears. Context-based adaptive 2-level binary arithmetic coding (2-CABAC) algorithm, which is based on CABAC, is presented. Thealgorithm converts bin string into theta string and improves the performance by coding the theta string. The principle, designing methodand program flowchart are introduced. The experimental result shows that the compression ratio of 2-CABAC, compared to CABAC,is obviously improved. At last, the design of the converting function Phi is discussed.