Data converting apparatus, method thereof, and recording medium

A picture reducing circuit 1 reduces a supplied original picture. A higher picture memory 2 stores an input higher picture. A predictive tap extracting circuit 3 extracts predictive taps from the higher picture stored in the higher picture memory 2 and outputs the extracted predictive taps to a mapping circuit 4, predictive coefficient generating circuit 5, and pixel value updating circuit 8. The mapping circuit 4 calculates a linear combination of predictive taps and predictive coefficients and obtains a predictive picture. The predictive picture is output to an error calculating circuit 6. The error calculating circuit 6 calculates an error (S/N ratio) between pixel value of the predictive picture and that of the original picture. A comparing and determining circuit 7 controls a non-linear processing circuit 9 corresponding to the difference of the errors. The non-linear processing circuit 9 adds or subtracts a predetermined value to/from the pixel value of each pixel of the updated higher picture corresponding to the variation amount of pixel value updated by the pixel value updating circuit 8.