SAC-BL: A hypothesis testing framework for unsupervised visual anomaly detection and location.

Reconstruction-based methods achieve promising performance for visual anomaly detection (AD), relying on the underlying assumption that the anomalies cannot be accurately reconstructed. However, this assumption does not always hold, especially when suffering weak anomalous (a.k.a. normal-like) examples. More significantly, the existing methods primarily devote to obtaining the strong discriminative score functions, but neglecting the systematic investigation of the decision rule based on the proposed score function. Unlike previous work, this paper solves the AD issue starting from the decision rule within the statistical framework, providing a new insight for AD community. Specifically, we frame the AD task as a multiple hypothesis testing problem, Then, we propose a novel betting-like (BL) procedure with an embedding of strong anomaly constraint network (SACNet), called SAC-BL, to address this testing problem. In SAC-BL, BL procedure serves as the decision rule and SACNet is trained to capture the critical discriminative information from weak anomalies. Theoretically, our SAC-BL can control false discovery rate (FDR) at the prescribed level. Finally, we conduct extensive experiments to verify the superiority of SAC-BL over previous method.