Encoder, decoder, encoding method, and decoding method

A decoder which decodes a video, comprising:

• circuitry;
• and
• memory coupled to the circuitry, wherein
• the circuitry, in operation,
• parses a first parameter from a bitstream, the first parameter indicating, as a prediction mode, one of (i) a multiple prediction mode in which a prediction image is generated by overlapping an inter prediction image of a current block and an intra prediction image of the current block and (ii) one of a plurality of prediction modes including a non-rectangular mode in which a prediction image is generated for each non-rectangular partition in the current block;
• and
• decodes the current block according to the prediction mode, wherein
• decoding the current block using the multiple prediction mode and decoding the current block using the non-rectangular mode are mutually exclusive, and
• the first parameter is a flag.

A non-transitory computer readable medium storing a bitstream, the bitstream including information according to which a decoder performs a prediction mode, the information including a first parameter indicating, as a prediction mode, one of (i) a multiple prediction mode in which a prediction image is generated by overlapping an inter prediction image of a current block and an intra prediction image of the current block and (ii) one of a plurality of prediction modes including a non-rectangular mode in which a prediction image is generated for each non-rectangular partition in the current block, wherein,

• in the prediction mode:
• the current block is decoded according to the prediction mode, wherein
• decoding the current block using the multiple prediction mode and decoding the current block using the non-rectangular mode are mutually exclusive, and
• the first parameter is a flag.