The invention relates to an information signal processor suitable for use in conversion of, for example, an SD signal. Pixel data sets are extracted selectively from the SD signal. Class CL is then obtained using the pixel data sets. A coefficient production circuit produces coefficient data sets Wi for each class based on coefficient seed data sets for each class and values of picture quality adjusting parameters, h and v obtained by user operation. A tap selection circuit selectively extracts the data sets xi of the tap corresponding to the objective position in the HD signal from the SD signal and then, a calculation circuit produces the pixel data sets of the objective position in the HD signal according to an estimation equation using the data sets xi and the coefficient data sets Wi.