1. A method for signal processing, comprising: obtaining a plurality of signals related to a plurality of subjects; extracting, using at least one processor, one or more generic features of the subjects based on the signals; training, based on the one or more generic features, a first dictionary used to recognize the subjects, wherein the first dictionary is applied in an initial level of reconstruction of the signals; removing, using the at least one processor, the generic features from the plurality of signals to obtain one or more updated patterns for each subject; obtaining a set of discriminative features for each subject based on the updated patterns; and adding, based on the set of discriminative features, one or more second dictionaries used to recognize the subjects, wherein the one or more second dictionaries are applied at a level of reconstruction of the signals subsequent to the initial level.