Motion estimation is the most important and time consuming part of H.264 video coding standard,it takes about 60%～80%of encoding time.Study on high performance,fast motion estimation in video compression technology now is an important research topic.Based on the H.264 video coding standard,select x264 as the test code,the paper has analyzed the x264 four kinds of movement estimate algorithm,through joins the asymmetrical small diamond search,reduces the search points,the partial algorithms optimize,has made the improvement to asymmetrical cruciform multi-level hexagon grid point search algorithm （UMHexagonS）,enhances the movement estimate algorithm efficiency,proposes the asymmetrical cruciform multi-level octagon grid point search algorithm（x264_ME_UMO）.Testing with a variety of video sequences proves that,remained of the original coding performance and image quality and the encoding speed average increase of about 17%,to better meet the needs of practical application.
