A method of processing, by a computer, an input signal including obtaining input signal samples that represents a physical quantity. The method includes transforming the samples from an original domain into a plurality of coefficients in a transform domain, using an over-complete transform, such that the plurality of coefficients is sufficient to redundantly reconstruct the input signal samples. The method also includes modifying the coefficients independently of each other by applying a correction function, obtaining a set of corrected coefficients. The method also includes transforming the set of corrected coefficients back to the original domain. In the method, the correction function is determined by using a set of training pairs, each training pair including an uncorrected signal and a corrected signal, and by reducing a specified aggregate measure of error between the uncorrected signal and the corrected signal in the original domain across the training pairs.