Dense Video Captioning using Graph-based Sentence Summarization

--Recently, dense video captioning has made attractive progress in detecting and captioning all events in a long untrimmed video. Despite promising results were achieved, most existing methods do not sufficiently explore the scene evolution within an event temporal proposal for captioning, and therefore perform less satisfactorily when the scenes and objects change over a relatively long proposal. T o address this problem, we propose a graph-based partition-and-summarization (GPaS) framework for dense video captioning within two stages. For the "partition" stage, a whole event proposal is split into short video segments for captioning at a finer level. For the "summarization" stage, the generated sentences carrying rich description information for each segment are summarized into one sentence to describe the whole event. We particularly focus on the "summarization" stage, and propose a framework that effectively exploits the relationship between semantic words for summarization. We achieve this goal by treating semantic words as nodes in a graph and learning their interactions by coupling Graph Convolutional Network (GCN) and Long Short T erm Memory (LSTM), with the aid of visual cues. Two schemes of GCN-LSTM Interaction (GLI) modules are proposed for seamless integration of GCN and LSTM. The effectiveness of our approach is demonstrated via an extensive comparison with the state-of-the-arts methods on the two benchmarks ActivityNet Captions dataset and Y ouCook II dataset. ENSE video captioning, which aims at detecting all events and giving language descriptions in an untrimmed long video, is a very challenging problem in computer vision and has attracted a lot of research attentions recently. This task consists of two sub-tasks: 1) temporal proposal generation to localize the events and 2) video captioning to describe the events.