An optimally complexity scalable multi-mode decision algorithm for HEVC

Quad-tree based Coding Unit structure in HEVC provides more motion compensation sizes to improve rate-distortion performance at the cost of greatly increased computational complexity. Different from other researches on fast algorithms, we develop an optimally complexity scalable multi-mode decision algorithm (OCSMD) for HEVC. There are two major contributions in this paper. The first one is a novel feature proposed to describe the relationship between MV field and CU depth. The second is that we build a cost-performance priority predicting model in frame level based on the feature with negligible overhead as well as no conflict with the standard. Our method may allocate computational resources to the MD of all the CUs in frame level under arbitrary complexity constraints, while obtaining nearly optimal coding performance. The experimental result shows that our algorithm can adjust complexity under varying computing capacity while achieving near-optimal R-D performance.