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A fast skip and direction adaptive search algorithm for Sub-Pixel Motion Estimation on HEVC

Motion Estimation (ME) is one of the most time-consuming parts in video coding loop. It is important to develop fast Sub-Pixel ME (SPME) algorithm which brings higher prediction accuracy as well as higher computational complexity. In this paper, we propose a fast skip and direction adaptive search algorithm for SPME in order to balance the coding performance and complexity. Firstly, a fast skip algorithm is utilized to skip SPME directly in most stationary regions and an error-tolerant algorithm is introduced to avoid over-optimization. Next, a direction adaptive search algorithm with early-termination technique is applied to 1/2-pixel and 1/4-pixel motion search. Experimental results demonstrate the advantage of the proposed algorithm on HEVC reference software HM-16.0, which succeeds in reduction of the total encoding time averagely for up to 42.37% on surveillance videos and 26.60% on conference videos with a negligible coding efficiency loss.