A computing system receives a video bitstream comprising a current picture that includes a first block. The system determines that the first block is encoded using a first reference block and a second reference block. The system identifies a high-level syntax (HLS) flag in the video bitstream that indicates a weighting scheme for using the first and second reference blocks. The system reconstructs the first block using a first set of weighting factors for reference values from the first reference and second reference blocks when the HLS flag has a first value. The system reconstructs the first block using a second set of weighting factors for the reference values from the first and second reference blocks when (i) the HLS flag has a second value and (ii) at least one of the first and second reference blocks is at least partially outside of a corresponding reference boundary.