1. A method for coding video data, the method comprising: generating a prediction block for a coding unit (CU) of a frame of the video data, the prediction block including a transition zone at a boundary between samples of the prediction block associated with a first prediction unit (PU) of the CU and samples of the prediction block associated with a second PU of the CU; making, by the computing device, a determination based on a size of the first PU whether to perform a first smoothing operation; and after the computing device makes the determination to perform the first smoothing operation, performing the first smoothing operation to smooth samples of the prediction block that are within the transition zone.