Content Adaptive Weighted Prediction for Video Coding Beyond AV1.

In AV1, the compound prediction supports three methods for averaging two prediction blocks. The weighting factors for two prediction blocks can be based on either the wedge mask, the difference between prediction samples, or predefined weighting factors. However, for single prediction, only one predefined weighting factor is used, which is suboptimal when there are illumination changes between reference frames and the current frame. To address this limitation, this paper proposes a content adaptive weighted prediction method. This approach aims to enhance the prediction accuracy for single prediction. It involves the use of multiple predefined weighting factor look-up tables, and the selection among these different look-up tables are implicitly determined based on coded information of the current block, and the index of scaling factor in the look-up table is signaled in bitstream and parsed at the decoder side. Experimental results show that the proposed method can achieve an average 0.31% and 0.24% coding gain in terms of BD-rate with random access and low delay configurations, respectively.