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partofthestars / Spatial-Subspace-Rotation

(Paper) A Novel Algorithm for Remote Photoplethysmography: Spatial Subspace Rotation
GNU General Public License v3.0
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Camera Specification Issue #2

Open leptonleo opened 5 years ago

leptonleo commented 5 years ago

Dear Prof. Pilz, I am working on rPPG project as well. Besides the uncompressed image data that you mentioned, Is the frame rate important? I saw you were using frame rate =25. What if I use frame rate = 13? Thanks in advance.

partofthestars commented 5 years ago

hi, the threshold for the frame rate is given by the Nyquist frequency (see Nyquist–Shannon sampling theorem). given an approx. maximal human heart rate of 180 bpm (e.q. 3 Hz) we would need at least 6 Hz (e.q. 6 frames per second) sampling rate. one major problem that occurs when working with cameras is to asceratin that all samples (e.q. images) are taken equally spaced in time (e.q. uniform sampling) since these image sensors are not designed as DSP (digital signal processing) devices. at least, the image capture process should be placed into a seperate thread implemented non-blocking. best, christian

leptonleo commented 5 years ago

Thanks for your prompt reply! One more issue now. I don't understand why the frame rate shown in the video properties is 15 fps. But when I extract the frame using the Matlab code is 1214 frames for 60 seconds, which gives around 1214/60 = 20 fps. Shall I set my frame rate to 15 fps or 20 fps in the Matlab code??