Multi-octagon-grid search algorithm for fast motion estimation

The UMHexagonS algorithm has been accepted for the block motion estimation process in the H.264 video coding standard due to its high accuracy and low computational requirement. In this paper, a new algorithm is proposed, which improves on the UMHexagonS algorithm in three aspects. Firstly, a new prediction vector is added for avoiding being trapped in a local minimum. Secondly, the 5×5 full-search is replaced with an octagon search and possibly two small diamond searches to reduce the computational requirement. Thirdly, the multi-hexagon-grid search is changed to a multi-octagon-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.