If you’re thinking about installing CCTV security cameras in your home or workplace, you may have a few questions about how it works, including how motion detection works. Read on to find out how these security services work…
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.
Unfortunately, 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
….More at Motion Detection Explained