Gated fusion network for SAO filter and inter frame prediction in Versatile Video Coding

In order to achieve higher coding efficiency, the Versatile Video Coding (VVC) standard includes several new components at the expense of an increase in decoder computational complexity. These technologies often create ringing and contouring effects on the reconstructed frames at a low bit rate and introduce blurring and distortion. To smooth those visual artifacts, the H.266/VVC framework supports four post-processing filter operations. The state-of-the-art CNN-based in-loop filters prefer to deploy multiple networks for various quantization parameters and frame resolutions, which increases training resources and subsequently becomes overhead at decoder frame reconstruction. This paper presents a single deep-learning-based model for sample adaptive off-set (SAO) non-linear filtering operation on the decoder side, uses feature correlation among adjacent frames, and substantiates the merits of intra–inter frame quality enhancement. We introduced a variable filter size dual multi-scale convolutional neural network (D-MSCNN) to attenuate the compression artifact and incorporated strided deconvolution to restore the high-frequency details on the distorted frame. Our model follows sequential training across all QP values and updates the model weights. Using data augmentation, weight fusion, and residual learning, we demonstrated that our model could be trained effectively by transferring the convolution prior feature indices to the decoder to produce a dense output map. The Objective measurements demonstrate that the proposed method outperforms the baseline VVC method in PSNR, MS-SSIM, and VMAF metrics and achieves an average of 5.16% bit rate saving on different test sequence categories.