Lights by night and shadows

Forum for questions and support relating to the 1.34.x releases only.
Post Reply
aliban
Posts: 2
Joined: Fri Sep 04, 2020 2:06 pm

Lights by night and shadows

Post by aliban »

Hello

I'm using zoneminder with detection on Modtect, during the day all works as expected, but during the night due to the camera be near the road I'm getting alerts every time a car passes, I've defined the road as an exclusion zone, and it works, but the change of light on the zone triggers the motion detection event. There are any way to prevent this?

I've tried Overload Frame Ignore Count to 3 but this not work, even with the shadows of the light of the morning.
Size of the zone it's 9070 with Alarmed Pixels detection mode set to 10

Any advice on how to fix this?

Thanks
tommisgr
Posts: 23
Joined: Mon Aug 31, 2020 6:28 pm

Re: Lights by night and shadows

Post by tommisgr »

You could try to reduse the "Max Alarmed Area" & "Max Filtered Area "pixels to about half the area (or whatever is reasonable to ur case)
another tweak is to increase the "Min Pixel Threshold"

Any changes need to be retested during the day.
Min/Max Pixel Threshold (0-255)

In the AlarmedPixel layer of analysis, each individual pixel of the image is compared to the current reference image. Pixels that are different from the reference image are considered alarmed pixels. However, small aberrations in lighting or auto exposure camera adjustments may cause the explicit value of a pixel to vary by small amounts from image to image. This parameter allows you to set the limits of what will be considered a changed pixel. For example, if your camera points to a blank white wall, and you raise a black colored item into view, then the change in any one pixel will be great, indeed, extreme. If however, you raise a white piece of paper, then the change in an individual pixel will be less.

The minimum pixel threshold setting should be high enough to cause minor lighting, imaging, or compression changes to be ignored. Setting the minimum value too high, may allow a white cat to walk undetected across the view of the white wall. A good starting point for the minimum pixel threshold is 40, meaning that the difference in pixel value from must be greater than 40. A good default for the maximum pixel threshold is 0 (indicating that all differences above the minimum threshold are considered a change.)
Min/Max Alarmed Area
The count of alarmed pixels (or percentage of alarmed pixels relative to the pixel area of the region if in percent mode) is used in this first layer of analysis to determine if an alarm is triggered. If the count or percentage is above the minimum alarmed area, but less than the maximum alarmed area, an alarm is triggered. These settings depend on the size of the object you are trying to capture: a value too low may cause false alarms, while a value too high might not detect small objects. A good starting point for both the minimum and maximum are 0 and 0, indicating that any number of alarmed pixels (or any percentage) greater than 0 will trigger an alarm. The frame scores from logged events can then be used to bring the minimum up to a reasonable value. An alternative starting point for the minimum alarmed area (in percent) is 25% of the area that an object of interest takes up in the region. For example, if you approximate that a subject moving through the frame takes up 30% of the frame, then a good starting minimum area is about 7.5%.
Post Reply