An Optimally Scalable and Cost-Effective Algorithm for 1/8-Pixel Motion Estimation for HEVC

In the state-of-the-art H.265/HEVC video coding standard, the highest resolution of motion vectors is 1/4-pixel. However, the 1/8-pixel motion vector performs better in some specific scenes but brings more time cost. In this paper, we propose an optimally scalable and cost-effective algorithm for fractional-pixel motion estimation with 1/8-pixel motion vector resolution, which fits well to varying and constrained computing resources. In proposed method, each of the search points is assigned with a cost-effective priority, which determines the order in a refinement search. Also, we demonstrate a new search pattern, which makes it more likely to check the optimal motion vector earlier. Extensive experiments indicate that our method is capable of maximizing the R-D gains of each search point. As a side product, our approach can also serve as a fast algorithm. It can enhance time performance greatly with nearly no loss in R-D gains. Even compared with full fractional pixels search with 1/4-pixel resolution, the proposed method shows averagely 9.8% improvement in terms of time performance, with almost 1.3% increase in coding efficiency.