Image coding method, image coding apparatus, image decoding method, image decoding apparatus, and image coding and decoding apparatus

An image decoding apparatus that decodes a current block included in a bitstream, the image decoding apparatus comprising:

• a processor;
• and
• a non-transitory memory,
• wherein the processor performs, using the non-transitory memory, processes including:
• deriving a first candidate having a first motion vector that has been used to decode a first block;
• deriving a second candidate having a second motion vector and a first reference picture index value that identifies a first reference picture corresponding to the second motion vector, the second motion vector being a first zero vector;
• deriving a third candidate having a third motion vector and a second reference picture index value that identifies a second reference picture corresponding to the third motion vector, the third motion vector being a second zero vector, the first reference picture index value being different from the second reference picture index value;
• decoding a coded index attached to the bitstream using a maximum number of a plurality of candidates including the first candidate, the second candidate, and the third candidate, the coded index indicating one candidate of the plurality of candidates;
• and
• selecting the candidate, based on the coded index, the candidate being used for decoding the current block, the selected candidate including a motion vector and a reference picture index value.