A method and apparatus for determining a region-based weighted prediction with improved global brightness detection. The method includes applying a global brightness change detection methods by computing the weighted prediction parameters, determining if the brightness change is different amount of change for the different regions, if the change is not different, calculate motion estimation and setting Refidx to 1 and setting Refidx is set to 0 when there is change, determining the best motion vector, motion vector cost and the best reference input, and determining a region-based weighted prediction with improved global brightness detection based on the motion vector data.