Exemplary video processing methods and apparatuses for encoding or decoding a current block by bi-directional prediction. Multiple weight sets are utilized for blending List 0 and List 1 predictors, and the selection among multiple weight sets may be implicitly determined based on video information. Each weight set is composed of multiple candidate weights, and one candidate weight is selected for the current block. A weight pair associated with the selected weight for the current block is used for weighted averaging List 0 and List 1 predictors of the current block to generate a final inter predictor. The video processing methods and apparatuses encode or decode the current block according to the final inter predictor of the current block.