Fast Inter Mode Decision with Resolution Sampling For VVC 360-Degree Video Coding

Versatile Video Coding (VVC) achieves advanced coding performance for 360-degree video, while speeding up the related encoding is in great need, especially for inter-frame coding which takes the majority of the coding time. Targeted at fast inter mode decision, we design an algorithm including two-stage early mode skipping, region-dependent early precision skipping, and partial calculation for point skipping. The proposed algorithm takes the impact of resolution sampling operation on spherical rate distortion performance of equirectangular projection (ERP) format 360-degree video into account. Correspondingly, we propose a new scheme of region division and a new method for deformation coefficient calculation to better fit the resolution sampling in fast inter mode decision. Different from the existing schemes which generally artificially set the stretched regions and traverse the coefficients in threshold setting to obtain the optimal parameters, the overall solution is more interpretable and robust. Experimental results show that the proposed algorithm for inter mode decision speeds up VVenC by a multithread time saving of 10.55%/12.08% at a BD-BR loss of 1.54%/1.70% on average under two configurations.