1. A method of coding video data, the method comprising: obtaining a motion vector for predicting a video block with a non-4:2:0 chroma format; determining a video block size for the video block; modifying the motion vector to generate a modified motion vector for obtaining samples of at least one reference picture with which to predict the video block if the video block size meets a size criterion; and generating a prediction block for the video block using the samples of the at least one reference picture and the modified motion vector.