I am referring to the the following paper : Non-contact, automated cardiac pulse measurements using video imaging and blind source separation
In the above article, the authors are able to extract cardiac pulse signal out from RGB components. I try to visualize the process as follow.
R' = R + cardiac pulse G' = G + cardiac pulse B' = B + cardiac pulse
R', G' and B' are the colour components observed by camera. R, G, B are the colour components for a person, by assuming that he doesn't have any cardiac pulse.
It seems that we will be having 4 sources (R, G, B, Cardiac pulse). We are now trying to obtain 1 of the 4 sources (Cardiac pulse) from 3 mixture signals (R', G', B'), by using ICA.
Does it make sense? Am I missing some techniques? Or, am I making a wrong assumption on the process?