A Fast Decision Algorithm for High Efficiency Video Coding

Fast mode decision algorithms in video intra coding are very useful and necessary for implementing practical real-time performance of the encoder. It can reduce the computational complexity by excluding impossible modes from candidate set. Anyway, most of these algorithms may give rise to the remarkable quality degradation, especially for the all intra coding scenario. In order to improve the encoding speed while avoiding the quality loss, this paper presents a new algorithm for fast CU size decision and mode decision in HEVC intra coding. First, the size of the coding unit is pre-determined according to judging the coding unit whether has the sub-block whose depth is 3 and analyzing the depth of the adjacent CU. Then a judgment by block-DCT coefficients is made on the texture direction of image block, determining candidate mode set based on the calculated direction and the best prediction mode of the adjacent block, which can reduce the number of candidate mode, thereby reducing the amount of computation to save coding time. The experimental results show that the algorithm provides about 34.6% reduction of intra coding time compared with the latest HM13.0 with negligible loss of PSNR and a little increase of bite-rate.