Abstract

Appearance features are good at discriminating activities in a fixed view, but behave poorly when aspect is changed. We describe a method to build features that are highly stable under change of aspect. It is not necessary to have multiple views to extract our features. Our features make it possible to learn a discriminative model of activity in one view, and spot that activity in another view, for which one might poses no labeled examples at all. Our construction uses labeled examples to build activity models, and unlabeled, but corresponding, examples to build an implicit model of how appearance changes with aspect. We demonstrate our method with challenging sequences of real human motion, where discriminative methods built on appearance alone fail badly.