Sometimes a blob remains from prior movement and never goes away (I end up with an outline of pants, for example, in my analysis images), which locks the alarm on. Dark colors seem to trigger this more than anything else, such as black pants or a black outfit. My cameras are all monitoring bright tan backgrounds, for the most part.
I haven't found any adjustments that cure it completely without ceasing capture altogether, from blob size changes, pixel threshold changes, reference image blend, etc.
This seems like a bug to me as I understand the algorithm to adapt to changes in the field of view over time, such as if someone leaves a cart behind and it stays motionless for a period of time the alarm should clear (depending on image blend). This is because there will cease to be change in the image from frame to frame, as I understand it. Am I misunderstanding the way the blob detection works, and if so, how do I deal with things moving around in the zones (not to mention the previously-mentioned outlines of people on a uniform background)?
[SOLVED] Ghost blobs keep alarms set
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superchicken
- Posts: 2
- Joined: Wed Sep 05, 2012 3:56 pm
[SOLVED] Ghost blobs keep alarms set
- Attachments
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- Person's ghost at Frame #41 (~18 minutes later)
- 7766-analyse.jpg (66.82 KiB) Viewed 969 times
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- Person at Frame #41 (fps 7)
- 041-analyse.jpg (68.24 KiB) Viewed 969 times
Last edited by superchicken on Fri Sep 07, 2012 4:23 pm, edited 1 time in total.
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superchicken
- Posts: 2
- Joined: Wed Sep 05, 2012 3:56 pm
Re: Ghost blobs keep alarms set
Aha, BLEND_ALARMED_IMAGES seems to be the key.
I believe the problem is that the alarms are ending while someone is still standing there somehow, obviously the number of pixels in a blob/filter/alarm no longer meet the requirements. Then when that person moves, they are now in the reference image and because the floor/wall/door/etc. is more uniform than whatever had moved into frame (be it pants, a shirt, a cart, etc.) it creates a large enough alarm area to keep the alarm going. Since ZM doesn't blend the frames from the alarmed image without the above-referenced setting, that alarm will thus never clear until someone happens to walk onto that spot (with similar enough pixels to whatever was there previously.) This will happen regardless of the settings for blend image in the zone, despite the text describing this option as somehow being a less desirable alternative.
I believe the problem is that the alarms are ending while someone is still standing there somehow, obviously the number of pixels in a blob/filter/alarm no longer meet the requirements. Then when that person moves, they are now in the reference image and because the floor/wall/door/etc. is more uniform than whatever had moved into frame (be it pants, a shirt, a cart, etc.) it creates a large enough alarm area to keep the alarm going. Since ZM doesn't blend the frames from the alarmed image without the above-referenced setting, that alarm will thus never clear until someone happens to walk onto that spot (with similar enough pixels to whatever was there previously.) This will happen regardless of the settings for blend image in the zone, despite the text describing this option as somehow being a less desirable alternative.