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Visual Pulse Monitoring: Measuring Heart Rate of Faces in Ambient Lighting I had this idea last year while building an atmega pulse monitor with infrared LEDs and photoresistors. I was taking an information theory course and thought it was a perfect opportunity to try out some real world signal processing. I found that research into "photoplethysmography" is well-established if not industry-ready. N.B. This was a course project; this implementation is not robust, and not particularly suited for any purpose. The most closely related work is: "Non-contact, automated cardiac pulse measurements using video imaging and blind source separation" Ming-Zher Poh, Daniel J. McDuff, Rosalind W. Picard. OSA (2010). This project will begin by replicating their method and then (I hope) extend or simplify it. Input: 1.video of a person's forehead 2.video of a person's face without movement 3.video a moving face 4.video of several faces / a face in different illumination conditions 5.realtime video from a webcam Pipeline: 0.capture webcam video in 24-bit color at 640x480 resolution and 15 fps; one minute duration; indoor illumination and sunlight illumination 1.detect faces or segment skin * detect faces w/ OpenCV implementation of viola-jones on captured video frames * take top 60% and middle 60% of each detected face as region of interest 2.process the RGB color channels as three sources (+ infrared, perhaps) and extract independent components * process RGB channels over 30 s moving window w/ 96.7% overlap (by increments of 1 s) * normalize channels to have zero mean and unit variance * whiten channels through eigendecomposition or singular-value decomposition. decorrelating channels and scaling to unit covariance simplifies the optimization by restricting the necessary transformations to rotations * find independent components through RADICAL by minimizing the total estimated entropy of the channels 3.Fast-Fourier Transform independent components to identify frequency powers 4.Take the most powerful peak in the operational range of healthy human pulses: 45-240 BPM or [.75, 4] Hz Output: 1.Calculuated rate over a time window 2.Mark each pulse detected? 3.Face/skin detection visualizations? Validation: 1.Off-the-shelf pulse oximeter with heart rate monitoring 2.Good old-fashioned counting
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Measure heart rate from standard video recording (UMass CS 691A final project)
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