Pseudo-anomaly generation for improving the unsupervised anomaly detection task.: Implementation of a generative neural network

Daasbjerg, Andreas Bach

4. term

Vision, Graphics and Interactive Systems, Master

2023

2023-06-01

91 pages

Anomaly detection can be seen as a one-class classification problem, due to the rare occurrence of anomalous frames. Introducing pseudo-anomalies to the training set can potentially improve the performance of the anomaly detection model. This project introduces a pipeline for improving the unsupervised anomaly detection task, by teaching a generator to generate pseudo-anomalies. The pseudo-anomalies are generated by increasing a loss component in the overall loss function of the generator. Two loss components were tested, kullback-leibler divergence and flow loss. The pseudo-anomalies are used to train a classifier to classify normal and abnormal frames. Upon evaluation of the model, an AUC score is calculated using a combination of the classification score and the psnr score. The pipeline achieved an AUC-score of 72.42\% evaluated on the CUHK Avenue dataset. While not achieving state-of-the-art results, the pipeline shows potential for improving the performance of anomaly detection tasks. Future work could include adding a second generator branch to generate normal frames. Another approach is to evaluate the performance of the pipeline on a different dataset, such as the ShanghaiTech dataset.

GAN ; neural network ; generative modelling ; Master Thesis

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