STMP: Spatial Temporal Multi-level Proposal Network for Activity Detection

We propose a network for unconstrained scene activity detection called STMP to provide a deep learning method that can encode effective multi-level spatiotemporal information simultaneously and perform accurate temporal activity localization and recognition. Aiming at encoding meaningful spatial information to generate high-quality activity proposals in a fixed temporal scale, a spatial feature hierarchy is introduced in this approach. Meanwhile, to deal with various time scale activities, temporal feature hierarchy is proposed to represent activities of different temporal scales. The core component in STMP is STFH, which is a unified network implemented Spatial and Temporal Feature Hierarchy. On each level of STFH, an activity proposal detector is trained to detect activities in inherent temporal scale, which allows our STMP to make the full use of multi-level spatiotemporal information. Most importantly, STMP is a simple, fast and end-to-end trainable model due to its pure and unified framework. We evaluate STMP on two challenging activity detection datasets, and we achieve state-of-the-art results on THUMOS’14 (about 9.3% absolute improvement over the previous state-of-the-art approach R-C3D [1]) and obtains comparable results on ActivityNet1.3.