A Spatio-Temporal Identity Verification Method for Person-Action Instance Search in Movies

As one of the challenging problems in video search, Person-Action Instance Search (INS) aims to retrieve shots with specific person carrying out specific action from massive video shots. Existing methods mainly include two steps: First, two individual INS branches, i.e., person INS and action INS, are separately conducted to compute the initial person and action ranking scores; Second, both scores are directly fused to generate the final ranking list. However, direct aggregation of two individual INS scores cannot guarantee the identity consistency between person and action. For example, a shot with "Pat is standing" and "Ian is sitting on couch" may be erroneously understood as "Pat is sitting on couch" or "Ian is standing". To address the above identity inconsistency problem (IIP), we study a spatio-temporal identity verification method. Specifically, in the spatial dimension, we propose an identity consistency verification scheme to optimize the direct fusion score of person INS and action INS. The motivation originates from an observation that face detection results usually locate in the identity-consistent action bounding boxes. Moreover, in the temporal dimension, considering the complex filming condition, we propose an inter-frame detection extension operation to interpolate missing face/action detection results in successive video frames. The proposed method is evaluated on the large scale TRECVID INS dataset, and the experimental results show that our method can effectively mitigate the IIP and surpass the existing second places in both TRECVID 2019 and 2020 INS tasks.