ZoneMinder Forums

I am new to Zoneminder and I have read this page
https://wiki.zoneminder.com/index.php/U ... or_Dummies
and this page
https://zoneminder.readthedocs.io/en/la ... ezone.html
over and over again
and done my best google to around to find the answers but at this point my best is leaving me feeling pretty stupid.

I cannot understand even the basics about how to set up the AlarmedPixels alarm check method. For starters the docs say to try
Min Pixel Threshold 40
Max Pixel Threshold 0
Min Alarmed Area 0
Max Alarmed Area 0
but when saving I get an error: "You must specify the minimum alarm pixel count"
So I'm totally lost: what is minimum alarm pixel count? is this the same as Min Alarmed Area?
How can Max Alarmed Area be zero? Surely Max Alarmed Area must be greater than Min Alarmed Area? And this will mean that there will never be an alarm?
I have tried many combinations of these 4 parameters but I cannot get my zone to trigger. That is, there are no triggering events associated with that camera.
[many more questions omitted]

Here are some details about my setup:
zm version 1.36.8 running under ubuntu 20.04
camera: Hikvision DS-2CD2087G2-L newly installed streaming 4 fps at 640x480 with modect and 3840x2160 with nodect
The modect camera has one active zone, one inactive and no others.
camera installation is outdoors looking at a tennis court with a road behind with cars going by all the time (but still no triggers!).

It would be great if someone could explain these parameters to me or at least provide a starter set that I can understand that causes lots of triggering. Then I can adjust these to tune the triggering to something that works best for this situation.

Best
Chris

Min/Max Pixel Threshold is the amount of change in color to consider a pixel changed. I use the to reduce cloud false alarms, it also helps with camera noise.
Min/Max Alarmed Area is how many pixels need to change to trigger the alarm.

Choose a preset and work your way from there. At first it requires a lot of tweaking to understand the how the values change the result.

tob-support wrote: ↑Wed Oct 20, 2021 4:29 pm So I'm totally lost: what is minimum alarm pixel count?

It's the minimum number of pixels that have to change in that zone for an alarm to be triggered by it.

It will be an actual number of pixels if you're in "Pixel" mode, or a percentage of that zone's area when in "Percent" mode.

is this the same as Min Alarmed Area?

Yes.

How can Max Alarmed Area be zero? Surely Max Alarmed Area must be greater than Min Alarmed Area? And this will mean that there will never be an alarm?

A Max Alarmed Area of zero means no maximum.

Min Pixel Threshold and Max Pixel Threshold

Pixels have a value ('brightness') ranging from 0 to 255. The thresholds are how much the current value has to change by to be considered as an alarm. These are never percentages but always actual values. A value of zero for Max Threshold means no maximum. I mostly use lowish values like 15 or 17, with no maximums (in most cases).

Try percentage mode. I find it a bit easier to work out the size of interesting objects that way - A person is at least 10% of that wall, for instance.

If you want the zone to trigger easily, set the Check Method to Alarmed Pixels; Min Pixel Threshold fairly low, say 10 or 12; Max Pixel Threshold to 0; Min Alarmed Area to a small percentage; Max Alarmed Area to 0. Movement or small changes in lighting should kick that off, but if it doesn't then try reducing the Threshsold and Area values (or walk around in a more-contrasting outfit!)

Perhaps also check the Reference Image Blend %ge and Alarm Reference Image Blend %ge on the Monitor's General tab to make sure they're set sensibly (whatever that may mean - With my outdoor cameras I use 12.5% and 6.25%)

Good luck!