16. A computing device comprising: one or more processors; and a computer-readable storage device having stored thereon multiple instructions that, responsive to execution by the one or more processors, cause the one or more processors to perform acts comprising: obtaining an image stream; determining when a specialized classifier can be used to classify a particular subset of multiple aspects of content of the image stream, the specialized classifier exploiting class skew of the particular subset of the multiple aspects, the determining including identifying when the particular subset of the multiple aspects dominates the image stream; accessing the specialized classifier to classify the particular subset of the multiple aspects; and using the specialized classifier rather than a general classifier to classify the particular subset of the multiple aspects in subsequent images of the image stream.
16. A computing device comprising: one or more processors; and a computer-readable storage device having stored thereon multiple instructions that, responsive to execution by the one or more processors, cause the one or more processors to perform acts comprising: obtaining an image stream; determining when a specialized classifier can be used to classify a particular subset of multiple aspects of content of the image stream, the specialized classifier exploiting class skew of the particular subset of the multiple aspects, the determining including identifying when the particular subset of the multiple aspects dominates the image stream; accessing the specialized classifier to classify the particular subset of the multiple aspects; and using the specialized classifier rather than a general classifier to classify the particular subset of the multiple aspects in subsequent images of the image stream. 20. The computing device as recited in claim 16 , the acts further comprising: 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 particular subset of the multiple aspects in images of the image stream subsequent to the determination that usage of the specialized classifier is to cease.