Lookahead Search-Based Low-Complexity Multi-Type Tree Pruning Method for Versatile Video Coding (VVC) Intra Coding

摘要

The latest versatile video coding (VVC) introduces somenovel techniques such as quadtree with nested multi-type tree (QTMT),multiple transform selection (MTS) and multiple reference line (MRL).These tools improve compression efficiency compared with the previousstandard H.265/HEVC, but they suffer from very high computational complexity.One of the most time-consuming parts of VVC intra coding isthe coding tree unit (CTU) structure decision. In this paper, we propose alow-complexity multi-type tree (MT) pruning method for VVC intra coding.This method consists of lookahead search and MT pruning. The lookaheadsearch process is performed to derive the approximate rate-distortion (RD)cost of each MT node at depth 2 or 3. Subsequently, the improbable MTnodes are pruned by different strategies under different cost errors. Thesestrategies are designed according to the priority of the node. Experimentalresults show that the overall proposed algorithm can achieve 47.15 timesaving with only 0.93 Bj?ntegaard delta bit rate (BDBR) increase overnatural scene sequences, and 45.39 time saving with 1.55 BDBR increaseover screen content sequences, compared with the VVC referencesoftware VTM 10.0. Such results demonstrate that our method achieves agood trade-off between computational complexity and compression qualitycompared to recent methods.