A Fast Transform Algorithm for VVC Intra Coding

The new generation of video coding standard Versatile Video Coding (VVC) has adopted a series of new transform coding techniques. Multiple Transform Selection (MTS) is one of the new tools, which introduces DST7 and DCT8 as new transform kernels in addition to the conventional DCT2. Although the new transform kernels provide considerable coding gain, the coding complexity has also been greatly increased because we need to perform Rate Distortion Optimization (RDO) process for several times to determine the best kernels. According to the analysis, DCT2, DST7 and DCT8 are suitable for flat, gradually increasing and gradually decreasing residual distribution respectively, which we make use of to propose a novel fast algorithm to select the most possible transform kernels to reduce the RDO times of MTS. The proposed algorithm is implemented on VVC test model, and the experimental results show that it can achieve 25% time reduction with only 0.19% Bjøntegaard-Delta rate (BD-rate) increase.