Action Progression Networks for Temporal Action Detection in Videos

This study introduces an innovative Temporal Action Detection (TAD) model that is distinguished by its lightweight structure and capability for end-to-end training, delivering competitive performance. Traditional TAD approaches often rely on pre-trained models for feature extraction, compromising on end-to-end training for efficiency, yet encounter challenges due to misalignment with tasks and data shifts. Our method addresses these challenges by processing untrimmed videos on a snippet basis, facilitating a snippet-level TAD model that is trained end-to-end. Central to our approach is a novel frame-level label, termed ‘‘action progressions,’’ designed to encode temporal localization information. The prediction of action progressions not only enables our snippet-level model to incorporate temporal information effectively but also introduces a granular temporal encoding for the evolution of actions, enhancing the precision of detection. Beyond a streamlined pipeline, our model introduces several novel capabilities: 1) It directly learns from raw videos, unlike prevalent TAD methods that depend on frozen, pre-trained feature extraction models; 2) It is flexible for training with trimmed and untrimmed videos; 3) It is the first TAD model to avoid the detection of incomplete actions; and 4) It can accurately detect long-lasting actions or those with clear evolutionary patterns. Utilizing these advantages, our model achieves commendable performance on benchmark datasets, securing averaged mean Average Precision (mAP) scores of 54.8%, 30.5%, and 78.7% on THUMOS14, ActivityNet-1.3, and DFMAD, respectively.