An image decoder comprising: circuitry; a memory coupled to the circuitry; wherein the circuitry, in operation, performs a partition syntax operation including: parsing one or more parameters from a bitstream, wherein the one or more parameters include a partition parameter indicative of splitting of an image block into a plurality of partitions including a first partition having a non-rectangular shape and a second partition; splitting the image block into the plurality of partitions based on the partition parameter; and decoding the first partition and the second partition, characterized in that the partition parameter has a single index value indicative of all of (i) a split direction applied in the splitting of the image block into the plurality of partitions, (ii) a first motion vector for the first partition, and (iii) a second motion vector for the second partition, wherein the first partition and the second partition have a triangular shape, the first motion vector is selected from a first motion vector candidate prediction list, and the second motion vector is selected from a second motion vector candidate prediction list. circuitry; a memory coupled to the circuitry; wherein the circuitry, in operation, performs a partition syntax operation including: parsing one or more parameters from a bitstream, wherein the one or more parameters include a partition parameter indicative of splitting of an image block into a plurality of partitions including a first partition having a non-rectangular shape and a second partition; splitting the image block into the plurality of partitions based on the partition parameter; and decoding the first partition and the second partition, characterized in that the partition parameter has a single index value indicative of all of (i) a split direction applied in the splitting of the image block into the plurality of partitions, (ii) a first motion vector for the first partition, and (iii) a second motion vector for the second partition, wherein the first partition and the second partition have a triangular shape, the first motion vector is selected from a first motion vector candidate prediction list, and the second motion vector is selected from a second motion vector candidate prediction list. parsing one or more parameters from a bitstream, wherein the one or more parameters include a partition parameter indicative of splitting of an image block into a plurality of partitions including a first partition having a non-rectangular shape and a second partition; splitting the image block into the plurality of partitions based on the partition parameter; and decoding the first partition and the second partition, characterized in that the partition parameter has a single index value indicative of all of (i) a split direction applied in the splitting of the image block into the plurality of partitions, (ii) a first motion vector for the first partition, and (iii) a second motion vector for the second partition, wherein the first partition and the second partition have a triangular shape, the first motion vector is selected from a first motion vector candidate prediction list, and the second motion vector is selected from a second motion vector candidate prediction list. <EOS>