Variable-length encoding method, variable-length decoding method, storage medium, variable-length encoding device, variable-length decoding device, and bit stream

A variable-length encoding method that encodes unit data composed of a plurality of sub-data while switching variable-length code tables, said method comprising:

• setting a variable-length code table to initial values;
• encoding information that indicates the initialized variable-length code tables;
• selecting a variable-length code table to be used in encoding sub-data;
• performing encoding of the sub-data with reference to the selected variable-length code table;
• and
• placing encoded information indicating the initialized variable-length code table at a position before the encoded unit data,
• wherein the variable-length code table is selected based on a value of the encoded sub-data, and the variable-length code table to be used in said encoding of the sub-data is a variable-length code table selected based on a value of the sub-data to be encoded.

A readable storage medium that stores a program for executing variable-length encoding on a computer, wherein the variable-length encoding is a variable-length encoding method that encodes unit data while switching variable-length code tables, said method comprising:

• setting a variable-length code table to initial values;
• encoding information that indicates the initialized variable-length code table;
• selecting a variable-length code table to be used in encoding the sub-data;
• performing encoding of the sub-data with reference to the selected variable-length code table;
• and
• placing encoded information indicating the initialized variable-length code table at a position before the encoded unit data,
• wherein the variable-length code table is selected based on a value of the encoded sub-data, and the variable-length code table to be used in said encoding of the sub-data is selected based on a value of the immediately prior encoded sub-data.