Enhanced Decoder-Side Secondary Transform Derivation for Video Coding Beyond AVS3
Xin Liu, Yuhuai Zhang, Jiaqi Zhang, Yi Su, Weijia Jiang, Siwei Ma · 2025
The Decoder-side Secondary Transform Derivation (DSTD) method has been adopted by the exploration software of the fourth generation Audio Video coding Standard (AVS4), Exploration Video Model (EVM). Although DSTD can significantly improve the coding performance, it increases the encoding complexity simultaneously. To reduce the encoding complexity of DSTD, three enhanced DSTD methods are proposed in this paper, which consists of Deleting Mode Optimization (DMO), Intra Mode Dependent Optimization (IMDO) and Interleaved Intra Mode Dependent Optimization (IIMDO). The process of DMO is similar to that of the original DSTD method, but all the contents related to diagonal flipping have been removed. IMDO divides intra prediction modes into three areas based on the angle of the intra prediction mode, as shown in Fig. 1. Each area will correspondingly reduce a secondary transform type. IIMDO divides intra prediction modes into four areas, as shown in Fig. 2. The experimental results demonstrate that the proposed methods can effectively reduce the encoding complexity with negligible coding performance loss. The first enhanced method, Deleting Mode Optimization, has been adopted by EVM.