1. A computer implemented method for training a system for detecting multi-class objects in an image or a video sequence, the method performed by the computer comprising the steps of: identifying an ensemble of weak binary classifiers that are common to a set of object classes, wherein each object class shares a common set of features with the other object classes, and wherein each feature of said common set of features is associated with a weak binary classifier in said ensemble of weak binary classifiers, for each object class, forming an individual strong classifier by adapting a separate set of weights for the ensemble of weak classifiers, wherein a same ensemble of weak binary classifiers is incorporated into each individual strong classifier by the separate set of weights for each object class, wherein said steps of identifying an ensemble of weak binary classifiers and, for each object class, forming an individual strong classifier are performed by a computer processor.