面向VVC帧内编码的快速CU划分和角度模式决策

Fast CU partition and angle mode decision for VVC intra coding

多功能视频编码(versatile video coding,VVC)是最新的视频编码标准,与高效视频编码(high efficiency video coding,HEVC)相比进一步提高了压缩效率,但由于引入了包括二叉树和三叉树在内的多类树结构,同时帧内角度模式从35种增加到67种,导致编码复杂度剧增。为了降低计算复杂度,本文提出了一种基于快速编码单元(coding unit,CU)划分和角度模式决策的VVC帧内编码算法。首先根据自适应标准差阈值对CU纹理复杂度进行分类,初步缩减划分模式列表;然后采用Sobel梯度算子确定纹理方向,跳过非最优划分模式;最后根据统计结果筛选淘汰掉概率小于2%的角度模式。实验结果表明,与VTM-2.1相比,该算法能节省51.05%的编码时间,BDBR(Bjontegarrd delta bit rate)仅上升1.98%。

Versatile video coding(VVC)is the latest video coding standard.Compared with high efficiency video coding(HEVC),the compression efficiency is further improved.However,due to the introduction of binary trees and tri-trees quadtree with nested multi-type tree(QTMT)structure,and the intra-frame angle mode has also increased from 35 to 67,resulting in a sharp increase in coding complexity.In order to reduce the computational complexity,this paper proposes a VVC intra coding algorithm based on fast coding unit(CU)division and angle mode decision.First,classify the CU texture complexity according to the adaptive standard deviation threshold,and initially reduce the list of division modes;then use the Sobel gradient operator to determine the texture direction,remove the non-optimal direction division mode;finally eliminate the angles with lower probability according to the statistical results mode.Experimental results show that compared with VTM-2.1,this algorithm saves 51.05% of coding time,and Bjontegarrd delta bit rate(BDBR)only increases by 1.98%.