I need to read a video stream from a camera mounted about 10 feet in the air, and pointed at a steep downward toward a sidewalk. I simply need to detect if ANY person-sized object has moved into the camera's view, and remained there for a few seconds.
I know this is fairly trivial if I have a controlled environment and a relatively static background. I can remove the background, then run a contour detector. However, if it's an outdoor camera, I'll need to be constantly grabbing new background shots, waiting until the sidewalk is empty before grabbing, which seems far from foolproof.
I've experimented with HOG:
HOGDescriptor hog;
hog.setSVMDetector(HOGDescriptor::getDefaultPeopleDetector());
This seems to give some false positives, and may be more complex than I need (I don't care if an object is a person or not, I just care if it's present and big).
What approach would you all take for simply detecting whether there's a big thing on a sidewalk or not, across a wide range of weather and light conditions?