Devices, systems and methods for sub-block based prediction are described. In a representative aspect, a method for video encoding includes partitioning, based on a first rule, a luma component of a block of video data into a first set of sub-blocks. The method also includes partitioning, based on a second rule, a first chroma component of the block of video data into a second set of sub-blocks. The first and the second set of sub-blocks include different numbers of sub-blocks. The method also includes performing a subsequent motion prediction based on the first and the second set of sub-blocks.