[jitter] Motion Tracking | Matrix Scanning

My project:

Using a camera placed on the top of a room, I want to use frame differencing to determine how many people are in the space. Depending on the amount of people in the space being tracked (or the amount of whitespace on black) I would like Jitter to light a different colored light through a MIDI Light Controller.

My issues:
Has anyone improved upon the frame differencing/threshold so that the camera is not as grainy? Is there anyway to smooth that out?

How do I ask Jitter to scan the matrix and look for what percentage of the pixels are white versus which are black in real time? (Assuming black is the background and white in a mobile entity) This is a way to tell my MIDI Light Controller that the room is, let's say, 75% full, light the red lamp.

Research:
I have completed most of the Jitter tutorials and downloaded the jit.cv library. 

I have also done an extensive search in the forums for "frame differencing", "motion tracking", and "optical flow". I have tested patches found in these posts. I have found a few that do frame differencing to my liking, but the smoothness of the background constant and the actual motion was very very grainy.

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I am very new to Jitter, about three days in, and need a little bit of help. Can anyone point me in the right direction to my issues? I'm primarily interested in the second issue since I have already found/played with/tweaked a quasi-working differencing imaging patch...but any info for getting rid of the graininess of the camera would also be a massive help.

Thanks and sorry for the novel,
~TSG