Encoder, decoder, encoding method, and decoding method

A decoder comprising:

• memory;
• and
• circuitry coupled to the memory, and configured to:
• select a first table from among tables, each of the tables associates indexes with respective correction values, each of the tables to be used to change a motion vector of a current block included in a picture;
• parse a parameter indicating a first index selected from among indexes included in the first table;
• identify a correction value associated with the first index;
• change the motion vector by the correction value in a predetermined direction;
• and
• decode the current block based on the changed motion vector,
• wherein a difference between two correction values among the correction values varies from table to table, the two correction values in each of the tables being associated with the same two indexes, and
• minimum correction values included in each of the tables are different from each other.

A method for transmitting a bitstream via a network, the method comprising:

• selecting a first table from among tables, each of the tables associates indexes with respective correction values, each of the tables to be used to change a motion vector of a current block included in a picture;
• writing a parameter into a bitstream, the parameter indicating a first index from among indexes in the first table;
• identifying a correction value associated with the first index;
• changing the motion vector by the correction value in a predetermined direction;
• encoding the current block based on the changed motion vector;
• and
• transmitting the bitstream via the network, the bitstream including the coded current block,
• wherein
• a difference between two correction values among the correction values varies from table to table, the two correction values in each of the tables being associated with the same two indexes, and
• minimum correction values included in each of the tables are different from each other.