Dual-Path TokenLearner for Remote Photoplethysmography-Based Physiological Measurement With Facial Videos

Remote photoplethysmography (rPPG)-based physiological measurement is an emerging yet crucial vision task, whose challenge lies in exploring accurate rPPG prediction from facial videos accompanied by noises of illumination variations, facial occlusions, head movements, etc., in a noncontact manner. Existing mainstream convolutional neural network (CNN)-based models make efforts to detect physiological signals by capturing subtle color changes in facial regions of interest (ROI) caused by heartbeats. However, such models are constrained by the limited local spatial or temporal receptive fields in the neural units. Unlike them, a native transformer-based framework called dual-path TokenLearner (dual-TL) is proposed in this article, which utilizes the concept of learnable tokens to integrate both spatial and temporal informative contexts from the global perspective of the video. Specifically, the proposed dual-TL uses a spatial TokenLearner (S-TL) to explore associations in different facial ROIs, which promises the rPPG prediction far away from noisy ROI disturbances. Complementarily, a temporal TokenLearner (T-TL) is designed to infer the quasi-periodic pattern of heartbeats, which eliminates temporal disturbances such as head movements. The two TokenLearners, S-TL and T-TL, are executed in a dual-path mode. This enables the model to reduce noise disturbances for final rPPG signal prediction. Extensive experiments on four physiological measurement benchmark datasets are conducted. The dual-TL achieves state-of-the-art performances in both intra and cross-dataset testings, demonstrating its immense potential as a basic backbone for rPPG measurement.