Motion Detection Explained

Motion detection may seem like a complicated technology, but it’s actually a very simple issue. Recorded video is nothing more than a series of snapped image stills, or pictures, played fast enough to where it appears there is motion. Each still picture equals one frame of video.  The DVR, or the camera, keeps a number of frames in memory. Frames will be dropped from memory as new frames enter into the memory. The DVR or camera will compare frames as they come into memory, and if there is a big enough difference detected between frames, a motion event will be triggered.

motion detecting cctv cameraUnfortunately, since pixels are being compared, there will be many false positives. Something as simple as lighting can cause the camera to detect motion and start recording. There are, however, a number of ways to reduce the number of false positives.

For starters, there is the option of masking areas. Masking an area comes in handy when you have a bush or a fan that is always moving causing your DVR to constantly record video. In this instance you can block the areas around the fan or bush to tell the camera / DVR to ignore that area and focus elsewhere. An alternate solution to this situation is to block everything but what you’d like to monitor, like a door or window.

Another option is to control the sensitivity. This defines how much of a change can occur before a motion event triggers the DVR to start recording. The higher the sensitivity, the less change is needed to cause a motion event. Conversely, the lower the sensitivity, the greater change in pixels will be needed to cause a motion event. An example of this would be if something as small as a bird flying outside a window was constantly triggering an event, then you could slightly decrease the sensitivity to measure only larger moving objects, like cars or people.

Motion detection is a very cool feature found on many security cameras and DVR systems, and it’s actually a very simple concept – just a series of still images that get compared to one another. It might take a little playing around with your DVR system, but with enough time, you can eliminate a good deal of false positives and enjoy the benefits of motion detection on your security system.


2 Comments on Motion Detection Explained

  1. Eric Nauta on Wed, 7th Mar 2012 4:25 pm
  2. Thanks! I knew that it worked but didn’t know why!

  3. KD on Tue, 13th Mar 2012 4:20 pm
  4. Since I have ben working in the CCTV industry, motion detection has always been a point of interest. End users are now starting to find out that it also saves hard drive space as well. Thank you for this insght on how it is activated and is triggered. This was very useful information and has enhanced my technical knowledge as well.

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