Motion estimation using an efficient four-step search method

The method consists of initial-point determination and low-complexity four-step search. For each block, we determine an initial point from the stationary point and motion point with the same displacement of its neighboring block according to their block-matching performances. Based on this initial point, low-complexity four-step search with half-way stop technique is performed to achieve the motion vector. The total number of searching points is varied from 13 to 20. Simulation results show that our method yields a very competitive performance in terms of computational complexity and picture quality as compared to the three-step search, new three-step search, and four-step search methods