Fast QTMT Partition Decision Algorithm in VVC Intra Coding based on Variance and Gradient Quadtree with nested multitype tree (QTMT) partition structure in Versatile Video Coding (VVC) contributes to superior encoding performance compared to the basic quadtree (QT) structure in High Efficiency Video Coding (HEVC). However, the improvement of performance leads to an unavoidable increase of computational complexity. To achieve a balance between coding efficiency and compression quality, we propose a fast intra partition algorithm based on variance and gradient to solve the rectangular partition problem in VVC. First, further splitting of smooth areas is terminated. Then, QT partition is chosen depending on the gradient features extracted by Sobel operator. Finally, one partition from five possible QTMT partitions is directly chosen by computing the variance of variance of subCUs. The theoretical basis of our method is that a homogeneous area tends to be predicted with a larger coding unit (CU), and subparts of a split CU are prone to have different textures from each other. To our knowledge, this is the first attempt to apply traditional method to accelerating the rectangular partition problem in VVC intra prediction. Experimental results show that the proposed method can save averagely 53.17% encoding time with only 1.62% BDBR increase and 0.09dB BDPSNR loss compared to anchor VTM4.0.

Fast Intra size decision and mode decision algorithm for HEVC intra coding The latest High Efficiency Video Coding (HEVC) standard could achieve much higher coding efficiency than the current mainstream video coding standards (H.264AVC). Compared with H.264AVC, H.265 saves 50% cost than H.264AVC at the same quality. But compression ratio gets improved with at least 24 times increase in computational complexity. HEVC provides a quadtree based coding unit (CU) block partitioning structure. The predication mode of CU has been extended from 8 to 35. To alleviate the encoder computational complexity, we proposed an algorithm based on complexity of CU and cart decision tree to determine whether the current CU should be divided into quadtree. In the mode decision process, we reduce the number of candidate modes involved in the rough mode decision(RMD) and the rate distortion optimization (RDO) process. The experiment results demonstrate that the proposed algorithm could significantly reduce compression time with little loss.