Balancing cardiac privacy with quality in video recordings

Remote photoplethysmography (rPPG) is a technique that extracts physiological signals, such as heart rate, from facial videos using standard Red-Green-Blue cameras. While rPPG offers valuable health insights, it also exposes individuals to potential misuse, as sensitive information can be inferred without consent.

This paper introduces a reversible video modification framework for removing, encrypting, transmitting, and restoring rPPG signals in facial videos, using frame-wise sinusoidal modulation applied to specific rPPG-rich facial regions, with a focus on maintaining perceptual quality and concealing the true heart rate. Our approach is contrasted with prior methods using seven rPPG techniques on the LGI-PPGI dataset, encompassing various activities. Evaluation metrics include PSNR, SSIM, correlation, dynamic time warping, and a composite score reflecting both signal suppression and visual fidelity.

Here we show that our method achieves an overall score above 0.75 across all rPPG methods, approximately 50% higher than previous approaches. It also demonstrates high visual fidelity (PSNR ≈ 68, SSIM ≈ 0.97) and effectively conceals physiological information, inducing an average heart rate estimation error 22 bpm higher than prior methods.

This study presents the first end-to-end reversible framework for secure, privacy-preserving video transmission of facial recordings. The approach is lightweight, effective across diverse activities, and holds promise for real-time applications such as video conferencing and telehealth.