Trying to distinguish between lighting changes and people

Add any particular hints or tricks you have found to help with your ZoneMinder experience.
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haus
Posts: 208
Joined: Thu Oct 11, 2007 5:10 am

Trying to distinguish between lighting changes and people

Post by haus »

I have a camera over the front door walkway with the goal of alerting when someone approaches the front door. It is working, but every morning and evening when the camera switches between day/night mode, I get an alarm. I had assumed that if I set a max alarmed area and an overload count to a couple of frames that would take care of things, but it was still happening. So I turned on analysis images and stats, and instead of the whole zone showing a change, here's the first alarm frame from this morning:

zm-snip.jpg
zm-snip.jpg (34.04 KiB) Viewed 5744 times

It's roughly the size a person might be, which has me a bit stymied in terms of trying to distinguish this from a person.

The stats on this frame are:
Pixel Diff: 35
Alarm Px: 32547 (31%)
Filter Px: 24043 (23%)
Blobs: 1
Blob Sizes: 23003 (22%)
Alarm Limits: 74,394-388,536
Score: 22

The pixel threshold is currently set to 30. I've had it at 40 but then it didn't seem to be triggering an alarm when people wearing light clothing came into the zone. Generally, when someone wearing contrasting clothing (like black) walks up or if they cast a shadow, the pixel diff is 60-70, but that's not guaranteed.

I'm wondering if others have experience with situations like this and do you just live with false alarms or have you found any tricks to differentiating them?
pimehexon
Posts: 7
Joined: Wed Jan 12, 2022 2:55 pm

Re: Trying to distinguish between lighting changes and people

Post by pimehexon »

If the reason is lighting change, you'll hardly tackle this false alarm and have to live with it.
Magic919
Posts: 859
Joined: Wed Sep 18, 2013 6:56 am

Re: Trying to distinguish between lighting changes and people

Post by Magic919 »

Or use ZMES for person detection.
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