VVC Intra Coding Complexity Optimization Based on Early Skipping of the Secondary Transform

The new generation video coding standard, H.266/-VVC, brings performance gains while significantly increasing coding complexity. Most of the complexity optimization methods for intra coding focus on reducing the number of prediction modes entering the rate-distortion optimization, but there are few concerning the newly introduced secondary transform. This letter extends the scope of existing studies and provides valuable insights for intra coding complexity optimization based on early skipping of the secondary transform. Specifically, considering the distribution of residuals assessed by coefficients after the primary transform, we propose to skip the secondary transform when the residual variation is relatively flat or the distortion caused by zeroing high-frequency coefficients is significant. Based on this analysis, we establish two skip conditions through statistical analysis and enable efficient decision-making by skipping the unnecessary secondary transform. Experimental results demonstrate the effectiveness of our algorithm, achieving 3.84% and 10.29% reductions in encoding time with only 0.39% and 1.03% increases in Bjontegaard delta bit-rate compared to Fraunhofer Versatile Video Encoder (VVenC)'s medium preset, under random-access (RA) and all-intra (AI) configurations respectively.