Digital Video Motion Detection

If you've considered video motion detection in the past and passed it up, you might want to look again.


It seems like just yesterday that I was in the process of trying to convince a customer that there was nothing wrong with his video motion detection system. He had 15 outside cameras, each on a pan/tilt system, each in auto-pan mode, each connected to the analog video motion detection system. He was told that the system would detect the motion of someone walking while the cameras were panning back and forth. What a hoot! Can you imagine? There was already motion in the image, due to the auto-panning of the camera, and yet he wanted to be able to detect a man walking independently at the same time. Couldn't be done! At least not 26 years ago.

Enter advanced digital video motion detection (DVMD). Twenty-six years in the making and the explosion is getting louder. Now I realize that the entire industry has been pumping the heck out of digital video recorders. Want one? Go to the corner and buy one—God knows there are enough of them out there. On the other hand, I don't hear a lot of fuss being made over DVMD, and I feel like I should. This stuff is hot. Between IP cameras and DVMD systems, the CCTV industry is stepping boldly to the forefront of electronic security design. Little or nothing that we have produced in the last 50 years compares or competes with the new face of CCTV. So let's talk DVMD.

Where We've Been
First, I always like to discus the history of a process. This helps me to understand how we got where we are and, more important, where we are going. Video motion detection started with analog systems some 25 or 30 years ago. The technology was simple: Monitor the video signal coming from the camera and look for any disturbance within a specific section of it. This was the beginning of the four VMD false-alarm nightmares.

• Contrast change due to fluctuating light or sudden lighting changes. Flash a headlight across a dark room and you have contrast change. Streak it across the area that you are monitoring and you have motion. At least, this is how we had to perceive motion in the beginning. The problem is obvious: Not all disturbances are motion. Many are fluctuating light—sweeping headlights, room lights turning on or off, lightning, cigarette lighters, flashing neon signs, the sun passing behind a cloud. The opposite side of contrast change detection also caused a problem. If a black man dressed in black walked past a dark or black wall, or a white man dressed in white moved past a bright or white wall, did either man produce enough contrast change to be detected? It depended on the sensitivity setting, which was almost always set to minimum.

• Flying garbage. A piece of paper on the wind passes through your secured area and bingo, you have an alarm. A legitimate alarm. An object, in motion, passed through your protected zone. What about a rainstorm, snowstorm or dust storm? No, you don't have to be in the desert. I have seen dust storms in every state in the U.S. and in many other countries. High, playful winds across open plains open the day to dust storms. Same with snow and rain. The result of such natural interference would be an alarm. Such storms could create a problem serious enough to disable your entire system for a while.

• Animals. Birds and other critters don't let your motion detection problems get in the way of their daily business. Hello false alarms. I always get excited when I see a robin redbreast in my yard. It is a living symbol of spring. It is also a living nightmare for video motion detection systems. But, you say, it's so small. True, but the original systems didn't differentiate between small things and large things. On the other hand, what if I needed to detect an object moving that were only two or three pixels in size? Couldn't be done with analog. Just a bit too small and precise.

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