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

摘要

Provided is an image encoding method that uses arithmetic encoding and that comprises the following: a first flag encoding step (S701) for arithmetically encoding a first flag (greater1_flag) indicating whether an absolute value of a processing-object coefficient included in the coefficient block of the processing object is greater than 1; and a second flag encoding step (S702) for arithmetically encoding a second flag (greater2_flag) indicating whether the absolute value of the processing-object coefficient is greater than 2. In the first flag encoding step and the second flag encoding step, it is determined whether there is a coefficient the absolute value of which exceeds a threshold in the coefficient block immediately prior to the coefficient block of the processing object (S711), and depending on the determination results, the context used in the arithmetic encoding of the first flag and the second flag is switched (S712).