This invention controls the code generation quantity adaptively with respect to the pattern of images and changes in the images, etc., so as to alleviate degradation in image quality, and to effectively reduce the spatial redundancy in order to provide a margin in the code quantity and to improve the overall image quality. An adaptive filter has a coefficient table memory that holds N coefficient tables, filter coefficients F.sub.1, F.sub.2 . . . F.sub.N that provide different filtering characteristics, a filter coefficient selecting 46 for selecting one filter coefficient F.sub.k from filter coefficient tables and filter calculating unit performing prescribed calculations on the DCT coefficients using the selected filter coefficient F.sub.K.