I'm trying to implement iOS heart rate monitor using front camera (for my bachelor thesis) and I did some work on it already, but I'm having problems because the system is not stable enough. I'm showing a frame where user should place his/her head during the measurement and app records the video and calculates average intensity of green color for each frame (in the selected rect, not the whole frame so I could get the informations just for face) and sometimes I got really good results (PPG) like this one where I can easily calculate HR from:
But sometimes it's really messy, just like this one:
I guess it's caused because user's do not keep hand (or head) steady enough during the measurement, but these differences are not that big, so is there any advices how to make app less sensitive on small hand movements during the measurement?
