1. A method of generating motion vectors in a video processing device, the method comprising: determining a motion distance between a block motion vector and a sub-block motion vector, wherein the block motion vector corresponds to a video block that includes a sub-block corresponding to the sub-block motion vector; comparing the motion distance to a first threshold; selecting one of the block motion vector and the sub-block motion vector as a spatially-estimated motion vector for the sub-block based on neighboring motion vectors when the motion distance is greater than the first threshold; comparing the motion distance to a second threshold when the motion distance is not greater than the first threshold; selecting the block motion vector as the spatially-estimated motion vector for the sub-block when the motion distance is greater than the second threshold; and selecting the sub-block motion vector as the spatially-estimated motion vector for the sub-block when the motion distance is not greater than the second threshold.