Decision tree accelerated CTU partition algorithm for intra prediction in versatile video coding

Versatile video coding (VVC) achieves enormous improvement over the advanced high efficiency video coding (HEVC) standard due to the adoption of the quadtree with nested multi-type tree (QTMT) partition structure and other coding tools. However, the computational complexity increases dramatically as well. To tackle this problem, we propose a decision tree accelerated coding tree units (CTU) partition algorithm for intra prediction in VVC. Firstly, specially designated image features are extracted to characterize the coding unit (CU) complexity. Then, the trained decision tree is employed to predict the partition results. Finally, based on our newly designed intra prediction framework, the partition process is early terminated or redundant partition modes are screened out. The experimental results show that the proposed algorithm could achieve around 52% encoding time reduction for various test video sequences on average with only 1.75% Bjontegaard delta bit rate increase compared with the reference test model VTM9.0 of VVC.

Fast ISP coding mode optimization algorithm based on CU texture complexity for VVC

In lately published video coding standard Versatile Video Coding (VVC/ H.266), the intra sub-partitions (ISP) coding mode is proposed. It is efficient for frames with rich texture, but less efficient for frames that are very flat or constant. In this paper, by comparing and analyzing the rate distortion cost (RD-cost) of coding unit (CU) with different texture features for using and not using ISP(No-ISP) coding mode, it is observed that CUs with simple texture can skip ISP coding mode. Based on this observation, a fast ISP coding mode optimization algorithm based on CU texture complexity is proposed, which aims to determine whether a CU needs to use ISP coding mode in advance by calculating CU texture complexity, so as to reduce the computation complexity of ISP. The experimental results show that under All Intra (AI) configuration, the coding time can be reduced by 7%, while the BD rate only increase by 0.09%.

Research on Vortex Electromagnetic Wave Based on Coding Metasurface

The characteristics of vortex electromagnetic wave generated by coding metasurface were studied, and the transmission-type metasurface of vortex wave was designed based on coding unit. It was found that the coding metasurface could replace the quasi-continuous phase to reduce the difficulty of the unit design. But when the orbital angular momentum increased gradually the spacing of two main lobes increased, the side lobes increased, and the vortex waves of other orbital angular momentum reduced. Based on this limitation, this paper optimizes the arrangement of units by genetic algorithm in order to maximize the performance of vortex electromagnetic wave in the limited metasurface size, so that the vortex electromagnetic wave energy is concentrated in the main lobes, thereby enhancing the purity of the orbital angular momentum mode and reducing the electromagnetic wave carrying the orbital angular momentum with other modes, and reduce the main lobes spacing is conducive to propagation. Finally, the feasibility of the method is verified by simulation measurement.