3. The method of claim 1 , wherein each video is associated with a feature vector determined by a set of initial classifiers, and training the unified classifier based on the plurality of positive bags and plurality of negative bags comprises training the unified classifier based on the feature vectors associated with the videos in the plurality of positive bags and the plurality of negative bags.
3. The method of claim 1 , wherein each video is associated with a feature vector determined by a set of initial classifiers, and training the unified classifier based on the plurality of positive bags and plurality of negative bags comprises training the unified classifier based on the feature vectors associated with the videos in the plurality of positive bags and the plurality of negative bags. 5. The method of claim 3 , further comprising training the set of initial classifiers, the set of initial classifiers including a first initial classifier trained using a first initial training set comprising videos, and a second initial classifier trained using a second initial training set comprising non-video media.