Local Abnormality Detection in Video Using Subspace Learning

On-line abnormality detection in video without the use ofobject detection and tracking is a desirable task in surveillance.We address this problem for the case when labeledinformation about normal events is limited and informationabout abnormal events is not available. We formulatethis problem as a one-class classification, where multiplelocal novelty classifiers (detectors) are used to first learnnormal actions based on motion information and then todetect abnormal instances. Each detector is associated toa small region of interest and is trained over labeled samplesprojected on an appropriate subspace. We discover thissubspace by using both labeled and unlabeled segments.We investigate the use of subspace learning and comparetwo methodologies based on linear (Principal ComponentsAnalysis) and on non-linear subspace learning (LocalityPreserving Projections), respectively. Experimental resultson a real underground station dataset shows that the linearapproach is better suited for cases where the subspacelearning is restricted to the labeled samples, whereas thenon-linear approach is preferable in the presence of additionalunlabeled data.