VARIABLE LENGTH ENCODING METHOD AND VARIABLE LENGTH DECODING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a variable length encoding method for enhancing the encoding efficiency in image encoding and to provide a variable length decoding method.

SOLUTION: The encoding method includes the steps of: scanning coefficient values in a block in a prescribed scanning sequence from high frequency to low frequency components by an RL column generating unit 201, a re-arranging unit 202, and a thresholding unit 203; and arithmetic-encoding absolute values of the coefficient values scanned in the coefficient scanning step above by an arithmetic encoding unit 205 and a table storage unit 204 by selecting and using probability tables 1 to 4, wherein the probability table in use is switched unidirectionally when there exists the absolute value whose value exceeds a prescribed threshold value among the absolute values of the coefficients subjected to the arithmetic encoding.

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