Fast Encoding Algorithm for H.265/HEVC Based on Tempo-spatial Correlation

The newest H.265/HEVC video coding standard adopts the quadtree-structured coding unit (CU) to match various texture characteristics of image. Therefore, H.265/HEVC can achieve significantly better coding efficiency than all existing video coding standards such as H.264/AVC. However, the computational complexity of the H.265/HEVC encoder increases dramatically due to its recursive quadtree representation to find the best coding tree unit (CTU) partition. To speed up the encoding procedure, a fast CU depth range decision method is proposed to reduce the depth search range in this paper. Based on the depth information correlation between tempo-spatial adjacent CTUs and the current CTU, some depths can be adaptively excluded from the depth search process in advance. The best depth of current CTU is determined by an intersection between temporal predicted depth ranges by 9 Gaussian weighting from encoded blocks and spatial predicted depth ranges by 4 best weighting from encoded blocks, separately. Experimental results show that the proposed scheme can achieve time improving ratio (TIR) about 42%~82% when compared to the default encoding scheme in HM 8.1 with insignificant loss of image quality. On the other hand, when compared with the other fast algorithm in [8], the proposed algorithm can further achieve an average TIR about 12%~ 8%.