Encoder, decoder, encoding method, and decoding method

A decoder, comprising:

• processing circuitry;
• and
• memory connected to the processing circuitry,
• wherein, using the memory, the processing circuitry:
• parses, from a bitstream, one or more parameters indicating a first region within a first picture;
• generates the first picture, the first picture including a plurality of regions, the plurality of regions including the first region and a second region different from the first region;
• and
• performs an inter prediction process on the first picture, and
• the inter prediction process includes a padding process in which first values of first pixels in the first region are replaced with second values of second pixels, the second pixels being provided in the second region of the first picture.