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; and using the specialized classifier rather than a general classifier to classify the subset of the multiple aspects in subsequent images of the image stream.