1. A signal processing device for processing an image signal, comprising: a signal processing unit for signal processing of input signals; wherein the structure of processing of said signal processing unit is changed based on operating signals supplied according to user operations, and wherein the signals processing unit comprises: a characteristics detecting unit for detecting characteristics from said input signals; a processing deciding unit for deciding prediction coefficients of contents of processing as to said input signals, based on characteristics detected by said characteristics detecting unit; a processing executing unit for executing processing to said input signals, following said prediction coefficients of contents of processing decided by said processing deciding unit, wherein the structure of processing of at least one of said characteristics detecting unit, said processing deciding unit, or said processing executing unit, is changed based on said operating signals so that an algorithm to determine said prediction coefficients of contents of processing is changed; and an output unit for outputting the processed image signal based on the signal processing by the signal processing unit, wherein the changing of the structure of processing is performed as a function of user input in response to a user evaluation of the outputting of the processed signal.