Masked Multi-Prediction for Multi-Aspect Anomaly Detection

Abstract

In this paper, we address the anomaly detection problem in the context of heterogeneous normal observations and propose an approach that accounts for this heterogeneity. Although prediction-based methods are common to learn normality, the vast majority of previous work predicts a single outcome, which is generally not sufficient to account for the multiplicity of possible normal observations. To address this issue, we introduce a new masked multi-prediction (MMP) approach that produces multiple likely normal outcomes, and show both theoretically and experimentally that it improves normality learning and leads to a better anomaly detection performance. In addition, we observed that normality can be characterized from multiple aspects, depending on the types of anomalies to be detected. Therefore, we propose an adaptation (MMP-AMS) of our approach to cover multiple aspects of normality such as appearance, motion, semantics and location. Since we model each aspect separately, our approach has the advantage of being interpretable and modular, as we can select only a subset of normality aspects. The experiments conducted on several benchmarks show the effectiveness of the proposed approach.