JPEG encoded data are entropy-decoded to quantized DCT coefficients which are sent to a prediction tap extraction circuit (41) and to a class tap extraction circuit (42). The prediction tap extraction circuit (41) and the class tap extraction circuit (42) extract what is needed from the quantized DCT coefficients to form prediction taps and class taps. A classification circuit (43) effects classification based on the class taps. A coefficient table storage unit (44) sends tap coefficients corresponding to the classes resulting from the classification to a sum of products circuit (45), which sum of products circuit (45) then effects linear predictive calculations, using the tap coefficients and the class taps, to generate decoded picture data.