A fast and efficient coding unit size decision algorithm based on temporal and spatial correlation

The latest video coding standard high efficiency video coding (HEVC) adopts the recursive quad-tree structured coding unit (CU) significantly outperforms previous standards in terms of coding efficiency. In the motion estimation (ME) process of HEVC, all the possible CU size (depth level) and prediction modes are both employed to select 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, a fast CU size decision algorithm based on temporal and spatial correlation is proposed to reduce HEVC computational complexity. The basic idea of the algorithm is to utilize video temporal and spatial property of coding information in previous coded frames to predict the current treeblock prediction mode and early skip unnecessary CU size (depth level). Experimental results demonstrate that the proposed algorithm can significantly reduce computational complexity of HEVC encoding while maintaining almost the same rate-distortion (RD) performance.