The flexible partitioning structure such as quad-tree plus binary-tree (QTBT) plays important roles in the next generation video coding standard. This paper investigates new coding unit (CU) partitioning methods to further improve the compression efficiency. In particular, we propose the extended quad-tree partitioning and asymmetric ternary-tree partitioning to further develop the principle behind the existing partitioning structure. First, a central extended quad-tree (CENTRAL-EQT) partitioning is introduced, which extends the traditional QT partitioning with central pattern and generates four elaborately designed sub-CUs with different sizes. Second, we propose a parallel extended quad-tree (PARALLEL-EQT) partitioning that allows the CU to split along a single direction, leading to four identical size sub-blocks. Third, we present an asymmetric ternary-tree (ATT) method, which splits the CU asymmetrically into three sub-blocks. The proposed new partitioning methods allow the interleaving with binary-tree partitioning for enhanced adaptability, and they can be jointly enabled to capture different characteristics of the local content. Simulation results on the JEM7-QTBT-Only platform show that averagely 4.92%, 4.81% and 5.08% BD-Rate savings are achieved for the luma component by the proposed methods under random access (RA), low-delay P (LDP) and low-delay B (LDB) configurations, respectively, with around 725% encoding time increase and negligible decoding time increase. Furthermore, experimental results also reveal that the proposed partitioning schemes are effective when cooperating with the upcoming Versatile Video Coding standard.
Bibliographical noteThis work was supported in part by the Hong Kong ITF UICP under Grant 9440203, in part by the Hong Kong RGC Early Career Scheme under Grant 9048122 (CityU 21211018), and in part by the City University of Hong Kong Applied Research under Grant 9667192.
- asymmetric ternary-tree partitioning
- CU partitioning
- quad-tree partitioning
- video coding