Abstract: The video coding standards H.264 have adopted Simplified UMHexagonS Algorithm as an Improved and Simplified Fast Motion Estimation Method for integer PELs motion estimation. In this paper, based on the study of the principles of Simplified UMHexagonS algorithm, some improved ways are proposed, such as using a new way instead of selecting only one predictor in the init selection step used by other Predictive Motion Estimation that in the init predictor selection step, all of the predictors are used for the next step as different center points of different predictive areas. Furthermore ,we use different search patterns for different motion type and so on. Simulation results show that with similar or even better rate-distortion performance, the proposed method decreases about 10~40% of search points and reduces motion estimation time by about 6% to 20% on average when compared with those of Simplified UMHexagonS Algorithm.

Key words: H.264, fast motion estimation, Simplified UMHS algorithm, search in the different predictive areas

摘要： 视频编码标准H.264近期采纳“简化UMHexagonS算法”（Simplified UMHexagonS Algorithm）作为快速运动估计算法的可选项之一，其运算量可比H.264先前采纳的UMHexagonS算法节约46％~57％，且具有极相似的率失真性能。本文对“简化UMHexagonS算法”进行了介绍，对其特点及造成其优越性能的原因进行了初步分析，并提出了改进方案：总体流程部分改用“基于预测中心的分区细搜索”方案、搜索方案部分改用对不同运动类型采用不同搜索模板、初始搜索点预测部分对16×16块增加了时间预测，等等。仿真实验结果表明，改进方案可减少“简化UMHexagonS算法”约10%~40%的搜索点数和6%~20%的搜索时间，而率失真性能也略优于“简化UMHexagonS算法”，尤其对中、大运动序列，搜索性能有较明显的提升。

关键词: H.264, 快速运动估计, 简化UMHexagonS算法, 分区搜索