PredGAN - a deep multi-scale video prediction framework for detecting anomalies in videos

In this paper we propose a multi-scale video prediction framework with adversarial training for detecting anomalies in videos. Anomalous events are those which do not conform to normal behavior. Supervised learning framework cannot account for all the unusual activities since a universal definition of anomaly cannot be adopted. To tackle this problem, we propose an unsupervised approach to learn the internal representation of videos and use this learning to accurately predict the future-frames of the videos. We train our network adversarially on videos consisting of only normal activities. When our network encounters unusual or irregular activities the generated frames consists of fuzzy regions where the irregular activities are present. These fuzzy regions consequently lower the peak signal to noise ratio (PSNR) of the generated frames. The PSNR values are normalized to have values between 0 and 1 and is used as a regularity score to tag a frame as anomalous or not-anomalous. We provide quantitative and qualitative evaluation of the proposed framework and also introduce Earth Mover's Distance as a new evaluation metric to assess the quality of the images generated. We demonstrate our framework on UCSD Pedestrian dataset and show that we achieve comparable results.