Fast intra prediction method by adaptive number of candidate modes for RDO in HEVC

In this letter, we propose an efficient method to reduce the number of candidate modes adaptively by adjusting the threshold for Hadamard cost (HC). The threshold is determined using the weight based on the standard deviation of gray level of pixels in prediction unit. The proposed method performs the RDO process using the reduced number of candidate modes having smaller HC than the threshold. Simulation results show that the proposed method gives about 16% complexity reduction with just 0.08% BD-rate increase compared with the original HEVC test model. The proposed method gives significant improvement of BD-PSNR and BD-rate with similar complexity reduction compared with the previous state-of-the-art method.