Feature Integration and Group Transformers for Action Proposal Generation

The task of temporal action proposal generation (TAPG) aims to provide high-quality video segments, i.e., proposals that potentially contain action events. The performance of tackling the TAPG task heavily depends on two key issues, feature representation and scoring mechanism. To simultaneously take account of both aspects, we introduce an attention-based model, termed as FITS, to address the issues for retrieving high-quality proposals. We first propose a novel Feature-Integration (FI) module to seamlessly fuse two-stream features concerning their interaction to yield a robust video segment representation. We then design a group of Transformer-driven Scorers (TS) to gain the temporal contextual supports over the representations for estimating the starting or ending boundary of an action event. Unlike most previous work to estimate action boundaries without considering the long-range temporal neighborhood, the proposed action-boundary co-estimation mechanism in TS leverages the bi-directional contextual supports for such boundary estimation, which shows the advantage of removing several false-positive boundary predictions. We conduct experiments on two challenging datasets, ActivityNet-1.3 and THUMOS-14. The experimental results demonstrate that the proposed FITS model consistently outperforms state-of-the-art TAPG methods.