Graph-based motion prediction for abnormal action detection

Abnormal action detection is the most noteworthy part of anomaly detection, which tries to identify unusual human behaviors in videos. Previous methods typically utilize future frame prediction to detect frames deviating from the normal scenario. While this strategy enjoys success in the accuracy of anomaly detection, critical information such as the cause and location of the abnormality is unable to be acquired. This paper proposes human motion prediction for abnormal action detection. We employ sequence of human poses to represent human motion, and detect irregular behavior by comparing the predicted pose with the actual pose detected in the frame. Hence the proposed method is able to explain why the action is regarded as irregularity and locate where the anomaly happens. Moreover, pose sequence is robust to noise, complex background and small targets in videos. Since posture information is non-Euclidean data, graph convolutional network is adopted for future pose prediction, which not only leads to greater expressive power but also stronger generalization capability. Experiments are conducted both on the widely used anomaly detection dataset ShanghaiTech and our newly proposed dataset NJUST-Anomaly, which mainly contains irregular behaviors happened in the campus. Our dataset expands the existing datasets by giving more abnormal actions attracting public attention in social security, which happen in more complex scenes and dynamic backgrounds. Experimental results on both datasets demonstrate the superiority of our method over the-state-of-the-art methods. The source code and NJUST-Anomaly dataset will be made public at https://github.com/datangzhengqing/MP-GCN.