A Comparative Study of rPPG-Based Pulse Rate Tracking Algorithms for Fitness Activities

Recent studies have shown that subtle changes in human face color due to heartbeats can be captured by regular RGB digital video cameras. It is possible, though challenging, to track one's pulse rate when a video contains significant subject's body motions in a fitness setting. The robustness gain in the recently proposed systems is often achieved by adding or changing certain modules in the system's pipeline. Most existing works, however, only evaluate the performance of the pulse rate estimation at the system level of particular pipeline configurations, whereas the contribution from each module remains unclear. To gain a better understanding of the performance at the module level and facilitate future research in explainable learning and artificial intelligence (AI) in physiological monitoring, this paper conducts an in-depth comparative study at the module level for video-based pulse rate tracking algorithms; a special focus is placed on challenging fitness scenarios involving significant movement. The representative efforts over the past decade in the field are reviewed, upon which a reconfigurable rPPG framework/pipeline is constructed comprising of major processing modules. For performance attribution, different candidates for each module are evaluated while having the rest of modules fixed. The performance evaluation is based on a signal quality metric and four pulse-rate estimation metrics and uses the simultaneously recorded ECG-based heart rate measurement as a reference. Experimental results using a challenging fitness dataset reveals the synergy between pulse color mapping and adaptive motion filtering in obtaining accurate pulse rate estimates. The results also suggest the importance of robust frequency tracking for accurate PR estimation in low signal-to-noise ratio fitness scenarios.