1. A method comprising: receiving an image stream; determining when a specialized classifier can be used to classify a subset of multiple aspects of content of the image stream, the specialized classifier exploiting class skew of the subset of the multiple aspects, the determining including identifying when the subset of the multiple aspects dominates the image stream; accessing the specialized classifier to classify the subset of the multiple aspects; using the specialized classifier rather than a general classifier to classify the subset of the multiple aspects in subsequent images of the image stream; determining when usage of the specialized classifier is to cease; and changing to using the general classifier, rather than the specialized classifier, to classify the subset of the multiple aspects in images of the image stream subsequent to the determination that usage of the specialized classifier is to cease.