Advanced transform coding methods for next-generation video coding beyond AV1

This paper presents cutting-edge design and application techniques for secondary transforms in the context of the next generation of video coding standardization beyond AV1 by the Alliance for Open Media (AOM). It thoroughly discusses methods for applying flexible secondary transform sets and kernels to both intra and inter coded blocks. The proposed methods enable the encoder to optimize transform sets for each intra prediction residual block and extend the use of secondary transforms for inter prediction residuals. Experimental results using the reference software show that the proposed approach enhances overall coding efficiency, measured in weighted YUV PSNR BD-Rates, by 3.40% for All Intra (AI), 1.70% for Random Access (RA), and 1.10% for Low Delay (LD) configurations according to AOM CTC (Common Test Condition) version 7.