We address the problem of text-based activity retrieval in video. Given a
sentence describing an activity, our task is to retrieve matching clips from an
untrimmed video. To capture the inherent structures present in both text and
video, we introduce a multilevel model that integrates vision and language
features earlier and more tightly than prior work. First, we inject text
features early on when generating clip proposals, to help eliminate unlikely
clips and thus speed up processing and boost performance. Second, to learn a
fine-grained similarity metric for retrieval, we use visual features to
modulate the processing of query sentences at the word level in a recurrent
neural network. A multi-task loss is also employed by adding query
re-generation as an auxiliary task. Our approach significantly outperforms
prior work on two challenging benchmarks: Charades-STA and ActivityNet
Captions.

本文提出了一种多层级的模型，早期并更紧密地集成了视觉和语言特性，用于解决从未剪辑的视频中基于文本的活动检索问题，其中包括注入文本特性以加速处理和提高性能，以及利用视觉特征在循环神经网络中模拟查询句子的单词级处理以学习细粒度的相似性度量，同时采用多任务损失函数。该方法在 Charades-STA 和 ActivityNet Captions 两个具有挑战性的基准测试中表现出较高效果。