A novel two-stream structure for video anomaly detection in smart city management

Video anomaly detection is the problem of detecting unusual events in videos. The challenges of this task lie mainly in the following aspects: first, unusual events tend to make up only a very small portion of a video, which means a large amount of useless information needs to be culled. It further aggravates the test of algorithm performance and the computing ability of devices. Second, anomaly detection techniques are always used in the surveillance system, which contains massive video data. The analysis of such large video data is difficult. Last, the feature extraction ability of the algorithm appears a high performance since unusual video streams may lie close to normal video. Benefiting from the development of deep learning-based in computer vision fields, the accuracy and the efficiency of video anomaly detection has been improved a lot during recent years. In this paper, we present a newly developed two-stream deep learning model, which uses a 3D convolutional neural network (C3D) structure as the feature extraction part, to handle this task. Both the sequence of frames and the optical flow are required as the input of the model. Then, features of these two streams will be extracted from C3D and traditional convolutional neural network (CNN). Finally, a fusion layer will be used to fuse both results of streams and generate a final detection. Our experimental results on UCF-Crime video dataset outperform other benchmark results such as traditional deep CNN and long short-term memory (LSTM) in terms of area under curve (AUC). As the result, our proposed method achieves the AUC of 85.18%, which is 3% higher than the second highest method.