Efficient search algorithm for block motion estimation

Many suboptimal motion vector search algorithms have been proposed because the full search algorithm, which is an optimal method, requires huge computational cost. Most of these algorithms find motion vectors simply from the center of the search window. In this paper, we propose an efficient motion vector search algorithm which, in order to predict the initial search point, exploits the global motion information obtained from the previous three frames and the local motion information regarding the motion vectors of the neighboring blocks of the current block. Our proposed algorithm searches for a motion vector from this initial search point, instead of from the center of the search window, using either the diamond search algorithm [J. Y. Tham, S. Ranganath, M. Ranganath, and A. A. Kassim, "A novel unrestricted center-biased diamond search algorithm for block motion estimation," IEEE Trans. Circuits Syst. Video Technol. 8(4), 369-377 (1998) and S. Zhu and K. Ma, "A new diamond search algorithm for fast block matching motion estimation," in ICICS'97, pp. 9-12, Singapore (Sept. 1997)] or the unrestricted small diamond search algorithm which performs its search always with a smaller diamond search pattern. Experimental results show that our proposed algorithm is faster than other suboptimal block matching algorithms while it maintains lower average block distortion.