Adaptive motion search range adjustment algorithm for HEVC inter coding

The next generation international standard High Efficiency Video Coding (HEVC) can achieve higher compression performance than all previous video coding standards. In the inter mode decision process of HEVC, motion estimation (ME) adopts a fixed search range and using all the possible treeblock sizes and prediction modes to find the one with the least rate distortion (RD) cost using Lagrange multiplier. This technique achieves the highest possible coding efficiency, but it brings extremely high computational complexity which limits HEVC from practical applications. In this paper, an adaptive motion search range adjustment algorithm based on spatially and temporally correlations is proposed to reduce 3D-HEVC computational complexity. Since the optimal motion vectors (MVs) prediction is highly content-dependent, it is not efficient to use all MVs in a fixed search range. We can adjust MVs search range and skip some specific search ranges rarely used in the spatially and temporally neighboring treeblocks. Experimental results show that the proposed algorithm can reduce 48% computational complexity while maintaining almost the same rate-distortion (RD) performance in comparison with the original HEVC encoder.