做视频监控或异常检测的团队，不用逐帧标注就能定位异常区域，直接省下大量标注成本，值得关注。
该论文提出一种弱监督方法，仅利用视频级标签（正常/异常）训练网络，无需帧级或像素级标注。通过多实例排序损失（MIL）将异常和正常视频片段分别视为正包和负包，提取特征并训练分类器，从而为时空区域生成异常分数。方法同时检测时间（片段级）和空间（帧内局部区域）异常，在UCF Crime2Local数据集上验证了有效性。这解决了视频异常标注成本高的问题，为实际监控场景提供了更实用的方案。
Weakly-Supervised Spatiotemporal Anomaly Detection
In this paper, we explore a weakly supervised method for anomaly detection. Since annotating videos is time-consuming, we only look at weak video-level labels during training. This means that given a video, we know that it is either normal or contains an anomaly, but no further annotations are used to train the network. Features are extracted from video clips that are either normal or anomalous. These features are used to determine anomaly scores for spatiotemporal regions of the clips based on a classifier and the implementation of a multiple instance ranking loss (MIL). We represent both anomalous and normal video clips as positive and negative bags, respectively, to apply MIL. Furthermore, since anomalies are usually localized to a part of a frame rather than the whole frame, we chose to explore temporal as well as spatial anomaly detection. We show our results on the UCF Crime2Local Dataset, which contains spatiotemporal annotations for a portion of the UCF Crime Dataset.