Despite the recent advances in video classification, progress in spatio-temporal action recognition has lagged behind. A major contributing factor has been the prohibitive cost of annotating videos frame-by-frame. In this paper, we present a spatio-temporal action recognition model that is trained with only video-level labels, which are significantly easier to annotate. Our method leverages per-frame person detectors which have been trained on large image datasets within a Multiple Instance Learning framework. We show how we can apply our method in cases where the standard Multiple Instance Learning assumption, that each bag contains at least one instance with the specified label, is invalid using a novel probabilistic variant of MIL where we estimate the uncertainty of each prediction. Furthermore, we report the first weakly-supervised results on the AVA dataset and state-of-the-art results among weakly-supervised methods on UCF101-24.

本文提出了一种基于视频级别标签进行训练的视频动作识别模型，该模型利用大型图像数据集中训练的逐帧人物检测器，在多实例学习框架内实现。此外，我们使用新的概率多实例学习方法来估计每个预测的不确定性，并在AVA数据集上取得了第一个弱监督结果，在UCF101-24上获得了弱监督方法的最新成果。

从未剪辑的视频中识别不确定动作