In one example, a device for decoding video data includes a memory configured to store video data and a video decoder configured to determine that a motion prediction candidate for a current block of video data indicates that motion information is to be derived for sub-blocks of the current block, in response to the determination: partition the current block into the sub-blocks, for each of the sub-blocks, derive motion information using motion information for at least two neighboring blocks, and decode the sub-blocks using the respective derived motion information.