Video coding method and apparatus using transform based fraquency domain adaptive loop filter

PURPOSE: A method for coding and decoding an image using an adaptive loop filter on a frequency domain with conversion, and a device thereof are provided to perform filtering by using a conversion coefficient on a conversion domain, thereby reducing complexity of the device. CONSTITUTION: An image coding device determines a loop filter coefficient calculation area by using pixels of a restoration frame(202). The image coding device calculates a loop filter coefficient corresponding to determination of a loop filter coefficient calculation area determiner(204) by using a conversion coefficient of the restoration frame and a converted original frame(201). The image coding device determines a loop filtering flag by using the loop filter coefficient. The image coding device determines a loop filter size corresponding to a conversion size. The image coding device filters the restoration frame by using the loop filter coefficient. The image coding device predicts and codes a scaled loop filter coefficient. [Reference numerals] (201) Original frame; (202) Restoration frame; (203) Converter; (204) Loop filter coefficient calculation area determiner; (205) Loop filter coefficient calculator; (206) Loop filter flag determiner; (207) Loop filter size determiner; (208) Filtered restoration frame generator; (209) Loop filter coefficient scale and prediction coder