We propose a weakly supervised temporal action localization algorithm on
untrimmed videos using convolutional neural networks. Our algorithm learns from
video-level class labels and predicts temporal intervals of human actions with
no requirement of temporal localization annotations. We design our network to
identify a sparse subset of key segments associated with target actions in a
video using an attention module and fuse the key segments through adaptive
temporal pooling. Our loss function is comprised of two terms that minimize the
video-level action classification error and enforce the sparsity of the segment
selection. At inference time, we extract and score temporal proposals using
temporal class activations and class-agnostic attentions to estimate the time
intervals that correspond to target actions. The proposed algorithm attains
state-of-the-art results on the THUMOS14 dataset and outstanding performance on
ActivityNet1.3 even with its weak supervision.

该篇论文提出了一种利用卷积神经网络进行弱监督时间动作定位的算法，其通过学习视频级别的类标签来预测人类动作的时间区间，利用注意力模块鉴别与目标动作有关的重要片段，并通过自适应时间池化融合这些关键片段，同时在损失函数中考虑视频级别的动作分类误差和这些关键片段的稀疏性，利用类别激活和类别无关的注意力在推断时提取和评分时间建议，以估计与目标动作对应的时间区间，在 THUMOS14 数据集上取得了最先进的结果，并具有卓越的 ActivityNet1.3 性能。