9. An apparatus for signal processing, comprising: a circuit configured to obtain a plurality of signals related to a plurality of subjects; at least one processor configured to: extract one or more generic features of the subjects based on the signals; train, 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; remove the generic features from the plurality of signals to obtain one or more updated patterns for each subject; obtain a set of discriminative features for each subject based on the updated patterns; add, 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; and a memory coupled with the at least one processor.
9. An apparatus for signal processing, comprising: a circuit configured to obtain a plurality of signals related to a plurality of subjects; at least one processor configured to: extract one or more generic features of the subjects based on the signals; train, 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; remove the generic features from the plurality of signals to obtain one or more updated patterns for each subject; obtain a set of discriminative features for each subject based on the updated patterns; add, 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; and a memory coupled with the at least one processor. 10. The apparatus of claim 9 , wherein the at least one processor is further configured to: determine, from a plurality of dictionaries, a dictionary best suited for recognizing the plurality of subjects, wherein the plurality of dictionaries comprises the first dictionary and the one or more second dictionaries; and recognize the subject based one the determined dictionary.