We present a new active learning approach to incorporate
human feedback for on-line unusual event detection. In contrast to most
existing unsupervised methods that perform passive mining for unusual
events, our approach automatically requests supervision for critical points
to resolve ambiguities of interest, leading to more robust and accurate
detection on subtle unusual events. The active learning strategy is formulated
as a stream-based solution, i.e. it makes decision on-the-fly on
whether to query for labels. It adaptively combines multiple active learning
criteria to achieve (i) quick discovery of unknown event classes and (ii)
refinement of classification boundary. Experimental results on busy public
space videos show that with minimal human supervision, our approach
outperforms existing supervised and unsupervised learning strategies in
identifying unusual events. In addition, better performance is achieved
by using adaptive multi-criteria approach compared to exis...