US Patent 11368703 Image decoder and decoding method

An image decoder splits a block of a picture into a plurality of sub blocks in a first direction using a first partition mode; and decodes the plurality of sub blocks, wherein, when the block is sized N pixels by 2N pixels and the first direction is along the 2N pixels, N being an integer, the first partition mode includes splitting the block into the plurality of sub blocks including at least one sub block sized N/4 pixels by 2N pixels, and excludes splitting the block into two sub blocks sized N/2 pixels by 2N pixels.