关键词: 块运动估计, H.264, UMHexagonS算法, 多八边形搜索算法

Abstract: With the high accuracy and low computational requirement，the UMHexagonS algorithm has been accepted for the possible implementation of the block motion estimation process in the H.264 video coding standard.In this paper，a new algorithm is proposed，which improves on the UMHexagonS algorithm in three aspects.Firstly，a new prediction vector is added into initial predictor for avoiding being trapped in a local minimum.Secondly，the 5×5 full-search is replaced by an litter octagon search and possibly two small diamond searches to reduce the computational requirement.Thirdly，the multi-octagon-grid search has taken the place of multi-hexagon-grid search to both reduce the computational complexity and better catch the direction of the optimal vector.Simulation results demonstrate that the proposed algorithm can reduce five to ten percent of the computational complexity of the UMHexagonS algorithm without loss of its accuracy.

Key words: block motion estimation, H.264, UMHexagonS algorithm, multi-octagon-grid search algorithm