Low-Complexity CTU Partition Structure Decision and Fast Intra Mode Decision for Versatile Video Coding
Low-Complexity CTU Partition Structure Decision and Fast Intra Mode Decision for Versatile Video Coding
复制标题
适用于多功能视频编码的低复杂度 CTU 分区结构决策和快速帧内模式决策
DOI：
10.1109/tcsvt.2019.2904198
复制
发表时间：
2020-06-01
影响因子：
8.4
通讯作者：
Jiang, Gangyi
中科院分区：
文献类型：
--
作者：
Yang, Hao;Shen, Liquan;Jiang, Gangyi
基于嵌套多类型树（QTMT）划分结构的四叉树是对高级高效视频编码（HEVC）标准中四叉树（QT）结构的有效改进。除了递归QT分区结构外，每个叶节点都采用递归多类型树分区，生成的块大小更加灵活。此外，内部预测模式从35种扩展到67种，以满足不同的纹理模式。这些新技术实现了很高的编码效率，但也导致了很高的计算复杂度。为了解决这一问题，本文提出了一种由低复杂度编码树单元（CTU）结构决策和快速模式内决策组成的快速内编码算法。本文算法的贡献主要体现在：1)首先探索了新的分组大小和编码模式分布特征，提出了合理的快速编码方案；2)开发了一种新的QTMT快速分区决策框架，该框架采用一种新的级联决策结构，既可以在QT上又可以在多类型树上进行分区决策；3)引入了基于梯度下降搜索的快速模内决策，并对最佳初始搜索点和搜索步长进行了研究。仿真结果表明，与VVC参考软件（VTM）相比，该算法的复杂度降低了70%，在BDBR提高1.93%的情况下，平均节省了63%的编码时间。这样的结果表明，与最先进的方法相比，我们的方法在计算复杂度和压缩质量方面具有优越的性能。
Quadtree with nested multi-type tree (QTMT) partition structure is an efficient improvement in versatile video coding (VVC) over the quadtree (QT) structure in the advanced high-efficiency video coding (HEVC) standard. With the exception of the recursive QT partition structure, recursive multi-type tree partition is applied to each leaf node, which generates more flexible block sizes. Besides, intra prediction modes are extended from 35 to 67 so as to satisfy various texture patterns. These newly developed techniques achieve high coding efficiency but also result in very high computational complexity. To tackle this problem, we propose a fast intra-coding algorithm consisting of low-complexity coding tree units (CTU) structure decision and fast intra mode decision in this paper. The contributions of the proposed algorithm lie in the following aspects: 1) the new block size and coding mode distribution features are first explored for a reasonable fast coding scheme; 2) a novel fast QTMT partition decision framework is developed, which can determine the partition decision on both QT and multi-type tree with a novel cascade decision structure; and 3) fast intra mode decision with gradient descent search is introduced, while the best initial search point and search step are also investigated in this paper. The simulation results show that the complexity reduction of the proposed algorithm is up to 70% compared to VVC reference software (VTM), and averagely 63% encoding time saving is achieved with 1.93% BDBR increasing. Such results demonstrate that our method yields a superior performance in terms of computational complexity and compression quality compared to the state-of-the-art methods.