A modified Rough Mode Decision process for fast High Efficiency Video Coding (HEVC) intra prediction

High Efficiency Video Coding (HEVC/H.265), the latest standard in video compression, aims at half the bit rate while maintaining the same quality compared to its predecessor, AVC/H.264. However, the increase in number of modes (35) for intra prediction in HEVC has significantly impacted on the encoder complexity. In this paper, a reduced number of candidate modes is therefore proposed to improve the encoding time. The most probable modes (MPMs) are inserted in the candidate list based on their computed Rough Mode Decision (RMD) cost rather than appending them to the list. In addition, the number of modes selected for the 4×4 and 8×8 PUs are based on the analysis of the graph obtained by plotting the cost of each mode against the mode number. Using this approach, the number of candidate modes in the RDO process is further reduced. Experimental results show that the average time savings of the proposed method is 38.0% along with an acceptable loss in quality (0.059dB) and a negligible increase in bit rate (0.30%) compared to HM 10.