Hello.
I am building a application where it need to check for faces, and work on it if they are after a point on the screen. Up to there it works, but processing the face at every frame, what reduces FPS from 20 to 2 in some seconds. So, how does I can know if a detected face was already there? And if it was processed before (check if it already crossed the desired point). I tried using arrays to store the previous position of the faces, but didn't worked well, since it was index based, what completely ends up everything if there are more than 1 face. To try predict if the face being detected is the same as before, I tried a position prediction algorithm, that didn't worked well with multiple faces. It worked picking all previous positions of what the applications think is the same face, takes the average of the values and pick the nearest face, into a range, of the predicted point. Just by reading I think you could notice that if the predicted face moves to the other way, and there is someone at the place the algorithm predicted, it thinks that it is the same face.