Ã¢â‚¬Ë˜ Constant motion. Fountains, revolving doors, escalators and bodies of water all create constant motion. To the old systems, motion was motionÃ¢â‚¬â€there was no discrimination. If it moved, it created a disruption to the video signal and therefore created an alarm.
The net result of the early days was that video motion detection, for the most part, was kept indoors, locked away in chambers or areas where there was little or no chance for alterations.
The Birth of a Giant
Sometime in the very beginning of the '80s, digital video motion detection was born. The first digital system I was aware of was called the DAVID by the Senstar Corporation of Kanata, ON, Canada. For the most part, DAVID was developed for government applications. Think about this: DVMD was available before computers were available to the general public. Expensive? Yes! Accurate to the extent that it could be used outside effectively? Not by today's standards, but given the options of 25 years ago, yes. Multi-camera input, multiple zones per input, with limited motion discrimination and individual contrast sensitivity per zone pushed DVMD up to the plate and hit a home run. The only major drawbacks were cost, limited market acceptance, technical and theoretical acceptance, and false alarms.
The next 24 years would prove to be quiet in the world of digital video motion detection. Things were happening, but no one was bragging about them. Then, suddenly, so many improvements and so many new applications happened at the same time that we had to look. I have been promoting DVMD for more than 15 years. However, it seems that just lately, people are starting to ask how this technology applies to them. I have a simple answer. This technology applies to every application that you can dream of, from visual alarm monitoring, to access control, to traffic control, to wide-area protection, to temporary and flexible on-site demand coverage.
Now, let's apply modern digital technology to our four spooks of video motion detection mentioned earlier.
Ã¢â‚¬Ë˜ Contrast change due to fluctuating light or sudden lighting changes. The beauty of digital technology is that it gives us the ability to monitor each pixel of every image individually and/or as a group. Because of this, we now have the ability to monitor and filter harassing lighting or contrast changes. If the sun goes behind a cloud, the system stays calm and determines that the area of surveillance is still visible and real and that the contrast change is scene-wide and so must be a shadow. If lightning strikes or a headlight or flashlight sweeps across the scene, the same logic is applied in reverse. It comes down to the quality of the system you are working with. In essence, a snapshot image is taken at different intervals and is used as a comparative study for all future shots. By constantly updating and comparing, the system detects only actual, physical changeÃ¢â‚¬â€not light. On the other hand, we are able to detect even the subtlest of changes since we can check pixel by pixel. This solves our black or white man dilemma as discussed before.