Variable length coding method and variable length decoding method

A coding apparatus which performs arithmetic coding, on a block basis, on coefficients of a two-dimensional array of frequency components in a predetermined scanning order starting at a high frequency component toward a low frequency component, the coefficients being generated by frequency transformation performed on picture data of a block which has a predetermined size of pixels, the coding apparatus comprising:

• an arithmetic coding unit operable to perform arithmetic coding on each absolute value of a plurality of Level values, wherein each of the Level values indicates a value of a non-zero coefficient, the value of which is non-zero, on a block basis, according to a predetermined scanning order starting at a high frequency component toward a low frequency component by using a plurality of probability tables;
• and
• a table switching unit operable to switch a probability table to a new probability table based on a result of a comparison between an absolute value of a target Level value to be coded and a predetermined threshold value,
• wherein, in the table switching unit, the switching between a plurality of probability tables is performed in one direction such that each probability table, which has been used before said new probability table, is not used after switching to said new probability table.