Negative sensitivity area in motion detection to suppress recording

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Harald Klein

• July 21, 2018 08:29

I have a camera in a staircase which always triggers motion detection when the staircase lighting turns on and off. Back when using zone minder I did solve that by using a "negative" zone. When pixel changed there, it did ignore motion in the other zones of the image. By using a small area up the wall that nobody would reach, I got perfect results. Hence it would be great if NX Witness could implement the same. On the motion page, one could introduce a -1 sensitivity, which would then show the same behaviour.

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• Official comment

  

  Norman Graafsma

  • September 10, 2018 10:22

  Hi Harald, 

  Great suggestion to improve our VMS. 
  I submitted your ticket to our support portal to share your suggestion with our dev team. 

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  Tuli Dem

  • July 24, 2018 14:23

  Harald,

   

  You can acheive that just by selection that area in the motion menu and setting it to 0.

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  Harald Klein

  • July 24, 2018 14:32

  no, that wouldn't achieve the same. I can't set a sensitivity of 0 to the whole image, because then no motion would be detected. But if pixels change in that specific "negative" area, it is for sure the ceiling light switching on or off, and not somebody walking in front of the camera. 

  From the Zoneminder Wiki:

  But hey what's that preclusive zone in your image at the start of this article?
  
  ZM allows us to specify a zone where should an alarm occur, it suppresses alarms in that zone and all other zones in the monitor. I've set it to cover my recess lights. So if someone turns our lights on, I won't get an alarm.

  That worked a treat with ZM for my use case. Now I'm searching for the same feature in NX Witness. A negative sensitivity would allow to define such preclusive areas. Movement there would suppress movement detection in the other areas.

   

   

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  Tuli Dem

  • July 24, 2018 15:02

  You didn't "read" what I wrote... I said that you could set 0 sensitivity to a "specific" area. That should achieve what you are requesting.

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  Harald Klein

  • July 24, 2018 15:07

  I did read what you wrote. But I'm unsure if you do understand the objective. The ceiling light, when being turned on, will change *all* pixels in the image. So just having a specific area set to 0 sensitivity, will not prevent motion detection to trigger. You can try that on your own system. Enable motion detection for a specific area, and then turn the light on at night. It will trigger. Having a specific area high up on the wall - where usual motion does not occur -  set as "preclusive" area, e.g. by sensitivity -1, would prevent motion detection in other areas set with different sensitivity. Did that explanation clarify things?

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  Glen Harrison

  • October 29, 2018 19:13

  Hi Harald

  yes I agree , mobtotix cameras have this option , to qualify a small region somewhere where motion is not expected.

  Great for controlling motion when sun goes behind clouds and rain etc . 

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  Sergey Bystrov

  • February 18, 2019 00:22

  Harald, 
  
  Here is another idea. 
  So there are false positive based on lights on/off or camera goes to day/night.

  Based on our observation, such events trigger luminance(brightness) change across all image. 
  So would it be better if we ignore MD if luminance changed across all image?

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