The difference is digital
The difference is digital

Jun 1, 1998 12:00 PM

The digital CCTV revolution is upon us. Will you be dragged kicking and screaming, or are you prepared? Digital CCTV is all the buzz in the security industry. But do you really understand whatdigital is all about? There are many functions of digital technology - digital cameras, digital enhancement, digital zoom, digital transmission, digital storage, digital manipulation - to name a few. You can't just "go digital" because the entire world of CCTV is going digital. You must give it serious thought. Whether to use a digital camera, for example, is not such a serious decision, but whether to use digital transmission, storage, or manipulation requires investigation and planning because of the costs involved and differences in the equipment. It is important to understand the implications of this new, enhanced digital technology.

Analog vs. digital Digital technology is a finite form of information manipulation and storage that opens up infinite possibilities. To illustrate the difference between analog (the previous and current video format) and digital (the current and future video format), picture a single wave of light that is 750 nanometers long. A wave of light this length represents a shade of red. The objective is to recreate this particular color red perfectly during the creation of a video image - not just once, but every time we recreate the scene, either live or played back off a recording. With analog, there are infinite shades of red between 749 and 751 nanometers, and that is the problem. It is virtually impossible to recreate the exact same shade of red, time after time. With digital, on the other hand, there is only one possibility when recreating our 750 nanometer color red, because digital is like an electronic morse code. When a digital camera sees a 750 nanometer shade of red, it translates it into a series of electronic dots and dashes that will always represent that exact color. Such digital precision can be applied to virtually anything. Want a perfect reproduction of the same note in a piece of music? Want to zoom your lens to the exact point each time? Want to come up with the exact hour, minute, second, or frame of video information from a particular situation with a simple keyboard stroke? Want even more control in our world of best-guess? If your answer is "Yes," then you want to go digital. If your answer is "Who cares?" then you are about to be run over as the digital revolution gains more speed. The recreation of a color or black-and-white image is, however, only a small part of the problem with analog systems. A second problem has to do with transmission of the video signal. The current analog video signal is so fragile and sensitive to things such as frequency shift, radio frequency (RF) interference, amplitude drop and electronic magnetic inductive (EMI) fields, that it is continuously plagued by interference, which can cause a video image to appear flat, wobbly, noisy, dark, washed out or otherwise indistinguishable. In the world of digital, however, we are not transmitting a fragile, multi-frequency wave of information. We are transmitting an electronic code of finite definition. We can still have RF or EMI interference with digital transmissions, but they are more easily filtered out of our "electronic morse code." The cost of transmission can actually drop, and the accuracy of transmission can rise to new heights. A third problem with analog video is storage and retrieval of image information. We have been using the magic of magnetic tape for more than 30 years, but storing analog information in any format is a clumsy and dying technology. Bulk is part of the problem. How much room do you have to store several hundred video tapes? And in our fast-paced world, are you willing to wait a couple of hours or days while someone manually searches through files and files of recorded video information, all in hopes of finding a simple sequence of images? I have spent as many as 12 hours trying to find a single frame of video image on a time-lapse video recording for the purpose of evidence. Enter, stage right, digital storage and retrieval. With this simple, yet complex and precise form of information storage, we now have the ability to request precision searches of our video library at the push of a couple of buttons. We now can find and display the exact hour, minute or even frame of visual information that we need to review in less than two or three minutes - all this while the camera system continues to store and display information.

Then and now It is also important to consider manipulation of the various signals associated with multi-camera systems. For the first 30 years of our industry, we were restricted by sequential switchers to recording only one or two images from individual cameras at a time. Then came multiplexing, a new and greatly improved form of high-speed switching and information retrieval. Suddenly we are able to have two, three, four or even 10 times as much information stored for each camera. Review of information from individual cameras was also enhanced dramatically. Now, instead of having to review an entire videotape, frame by frame, to find our image, we simply say we want the pictures from camera 1 or 2, and the image is before us. However, we are still faced with making decisions about what information we are willing to lose in the end. Think now about the world of digital in which, suddenly, each camera within a system becomes totally independent of all other cameras. That is, if you only need camera 1 to record activity, go for it. Camera 200 takes a picture every 10 seconds - no problem. Camera 75 is set up for 24-hour real time - sure, why not? In other words, losing information because of priority setting is gone. How much information you can record from a camera is limited only by the needs of your application. How many cameras can you manipulate within a digital system? Well, how many do you want?

So close and yet so far The trouble is that we are not really ready to go fully digital. We're on the brink, but there is still a lot of work to do. Consider that we have had advanced multiplexing technology available for more than seven years now. Yet system after system around the world is still designed with inferior sequential switchers and quad splitters - all because of a few wives' tales and the fear that a multiplexer will cost 10, 20 or even 50 percent more. If it takes more than seven years to educate an industry about a simple concept such as multiplexing, I can only hope that we are able to move into digital in the next millennium. It is time to start educating ourselves about digital technology - what can be done, what is available, and what we can afford. To properly design a fully digital system, we must rethink roughly 50 percent of everything we have learned about CCTV system management over the years. The revolution is here, and it is time to act. Those who do will be profitable and thriving in five years; those who do not will not be in business in 10.

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