Image encoder, image decoder, image encoding method, and image decoding method
An image encoder is provided including circuitry and a memory coupled to the circuitry. The circuitry, in operation, responds to a size of a block satisfying a size condition by generating a prediction image using a prediction mode selected from a plurality of prediction modes. The plurality of prediction modes include a first prediction mode in which a prediction process uses a motion vector and a reference block in a same picture as the block. The circuitry encodes the block using the prediction image.
1. An image encoding method comprising:
encoding a block, the encoding including:
in response to a size of the block satisfying a size condition, generating a prediction image using a prediction mode selected from a plurality of prediction modes including a first prediction mode, the first prediction mode including a prediction process using a motion vector and a reference block in a same picture as the block;
in response to the size of the block not satisfying the size condition, generating the prediction image using a prediction mode selected from the plurality of prediction modes excluding the first prediction mode; and
encoding the block using the prediction image.
2. An image decoding method comprising:
decoding a block, the decoding including:
in response to a size of the block satisfying a size condition, generating a prediction image using a prediction mode selected from a plurality of prediction modes including a first prediction mode, the first prediction mode including a prediction process using a motion vector and a reference block in a same picture as the block;
in response to the size of the block not satisfying the size condition, generating the prediction image using a prediction mode selected from the plurality of prediction modes excluding the first prediction mode; and
decoding the block using the prediction image.
3. A non-transitory computer readable medium storing a bitstream, the bitstream comprising an encoded signal and syntax information according to which a decoder performs:
in response to a size of a block satisfying a size condition, generating a prediction image using a prediction mode selected from a plurality of prediction modes including a first prediction mode, the first prediction mode including a prediction process using a motion vector and a reference block in a same picture as the block;
in response to the size of the block not satisfying the size condition, generating the prediction image using a prediction mode selected from the plurality of prediction modes excluding the first prediction mode; and
decoding the block using the prediction image.