PAMI-AD: An Activity Detector Exploiting Part-attention and Motion Information in Surveillance Videos

Activity detection in surveillance videos is a challenging task caused by small objects, complex activity categories, its untrimmed nature, etc. In this work, we propose an effective activity detection system for person-only and vehicle-only activities in untrimmed surveillance videos, named PAMI-AD. It consists of four modules, i.e., multi-object tracking, background modeling, activity classifier and post-processing. In particular, we propose a novel part-attention mechanism for person-only activities and a simple but strong motion information encoding method for vehicle-only activities. Our proposed system achieves the best results on the VIRAT dataset. Furthermore, our team won the 1st place in the TRECVID 2021 ActEV challenge.