Wondering about using vpi backgrond subtractor with contour finding

Hello all,
I am looking to take a 4K video, run VPI background subtractor on it, mark contours on resulted foreground and have some kind of image recognition pointed to contours as ROI.
My question is, since I have not been able to find the x, y values for the background subtractor algorithm neither have I seen a parameter in either of the algorithms listed in background subtractor page, how can I gain access to those values? is it even out for the public?
If not, which way do you suggest, since I do not wish to add unnecessary computing to it.
Thank you dearly.