关键词: H.264, 运动估计, 非对称十字型多层次六边形格点搜索算法（UMHexagonS）, 阈值判断, 搜索模板

Abstract: H.264 adopts Unsymmetrical cross Multi Hexagon grid Search（UMHexagonS） algorithm for motion estimation.This paper proposes a new fast adaptive motion estimation algorithm based on UMHexagonS algorithm.The idea of a new adaptive factor is introduced in initial search point prediction step for early termination.Different search patterns are adopted for different search patterns so that the search precision is in accordance with search rate.Experimental results show that the improved strategies can reduce 7%~43% of motion estimation time while keeping the bit rate and PSNR almost unchanged.

Key words: H.264, motion estimation, Unsymmetrical cross Multi Hexagon grid Search（UMHexagonS）, threshold judgement, search pattern