Dark-DSAR: Lightweight one-step pipeline for action recognition in dark videos.

Dark video human action recognition has a wide range of applications in the real world. General action recognition methods focus on the actor or the action itself, ignoring the dark scene where the action happens, resulting in unsatisfied accuracy in recognition. For dark scenes, the existing two-step action recognition methods are stage complex due to introducing additional augmentation steps, and the one-step pipeline method is not lightweight enough. To address these issues, a one-step Transformer-based method named Dark Domain Shift for Action Recognition (Dark-DSAR) is proposed in this paper, which integrates the tasks of domain migration and classification into a single step and enhances the model's functional coherence with respect to these two tasks, making our Dark-DSAR has low computation but high accuracy. Specifically, the domain shift module (DSM) achieves domain adaption from dark to bright to reduce the number of parameters and the computational cost. Besides, we explore the matching relationship between the input video size and the model, which can further optimize the inference efficiency by removing the redundant information in videos through spatial resolution dropping. Extensive experiments have been conducted on the datasets of ARID1.5, HMDB51-Dark, and UAV-human-night. Results show that the proposed Dark-DSAR obtains the best Top-1 accuracy on ARID1.5 with 89.49%, which is 2.56% higher than the state-of-the-art method, 67.13% and 61.9% on HMDB51-Dark and UAV-human-night, respectively. In addition, ablation experiments reveal that the action classifiers can gain ≥1% in accuracy compared to the original model when equipped with our DSM.