An optimized motion estimation algorithm based on UMHexagonS

UMHexagonS is one of the fast motion estimation algorithm adopted by H.264/AVC. It saves about 90% computational work compared with the Full Search Algorithm, and still keeps a good rate-distortion quality. In this paper, the characteristics of UMHexagonS were firstly analyzed, and three aspects of improvements, which include zero-motion block pre-determination after starting point prediction; improvement on 5*5 spiral search; optimized multi-grid hexagon search, were also proposed. Experimental results show that the proposed algorithm can save motion estimation time effectively and improve the real-time performance of the H.264/AVC encoder without much PSNR degradation and bit-rate increasing.