Fast intra coding algorithm for HEVC based on depth range prediction and mode reduction

The latest High Efficiency Video Coding (HEVC) standard only requires 50% bitrate of the H.264/AVC at the same video quality. Due to introduction of more advanced coding tools and techniques, its computational complexity rises rapidly. In this paper, we propose a novel fast Intra coding algorithm. Firstly, a novel feature is proposed to measure the complexity of video content based on the analysis of mode information obtained from a previous frame. Then, a model is built based on the relationship between this feature and Coding Tree Unit (CTU) depth range. According to the model, the unnecessary operations of Coding Unit (CU) split are skipped. Secondly, the correlation between CU distribution structure and mode selection is established. For the prediction of unlikely CU, the last few intra modes in candidate list are eliminated before rate-distortion optimization process. Experimental results demonstrate that the proposed algorithm reduces the encoding time by 43.2% with just 0.47% BD-rate increase compared with HEVC test model. Compared with other state-of-art algorithms, the proposed algorithm achieves better trade-off between complexity reduction and RD performance.