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The secrets of CCTV.

RECENT BREAKTHROUGHS IN closed-circuit video equipment (CCVE) provide security managers with options for greater programming flexibility and high-quality picture images required to identify suspects and win convictions. Among the more significant of these developments are the varied uses of digital-processing technology.

CCVE has come a long way since its inception in the 1970s. In the early days of camera-based surveillance, images were stored on helical, or spiral, scan 1/2 inch reel-to-reel recorders that were modified to allow extended-duration recording. The recorder turned on and off with a twenty-four to one reduction, which allows twenty-four hours of recording on a one-hour reel of tape. Planetary pulleys and acetate belts were used to achieve this goal. As one can imagine, the propensity for mechanical failure was high, as was the need for both preventive and corrective maintenance.

In 1979 VHS cassette technology replaced reel-to-reel tapes. Video cassettes were far easier to handle than tape reels. In addition, the 300-line resolution provided by commercial grade time-lapse VCRs far exceeded the image clarity provided by previous solutions.

Time-lapse video recording has continued to absorb technological advances from both the computer and television industries. Today, image resolution as high as 400 television lines can be achieved with standard VHS tape and even better color resolution is achievable with Super VHS (S-VHS) tape. S-VHS was introduced a few years back to provide higher resolution capability and still retain backward compatibility with VHS tapes. An S-VHS VCR will produce higher resolution color pictures because the format allows for increased bandwidth, or space, for the monochrome portion of the signal, as well as a higher frequency band. The bandwidth of the color signal remains essentially unchanged. The net effect is that when these two signals are combined, the user gets around 400 lines of horizontal resolution when recording monochrome or color images.

Digital processing is improving both picture resolution and system flexibility, and digital-image storage is on the horizon. While digital-image storage will eventually become integrated into security installations, the price to performance ratio of these devices is not yet at a realistic level for most businesses. Full-frame video requires 238.8 kilobytes for one video frame. This means that a 120-megabyte hard drive holds more than 500 pictures at a cost of approximately $7 per image.

While video compression techniques increase the storage capacity of the hard disk, decompression of video data decreases resolution, rendering the images unusable for most security applications. Ultimately, video compression advances being made by the television broadcast and cable industries--such as transmission of digitized video images over copper wire--are expected to benefit the CCTV industry.

The court admissibility of images stored on disk is still unclear because of the potential for digital-image manipulation. Until these issues are resolved, the best application of digital-image storage is access control where quick availability of a specific photo can be enhanced by a disk-based system.

Digital processing, on the other hand, is providing significant improvements in CCVE equipment today and will continue to enhance the price and performance for a long time to come. Digital-image processors include features such as 400-line resolution, 256 levels of gray, built-in digital quads and switchers, and the ability to enlarge a section of a scene during either record or playback.

Digital-image processing is bringing flexibility to almost every aspect of closed-circuit video surveillance. Take, for example, the developments in video motion detection where digital-image processing techniques have almost eliminated false alarm rates associated with analog systems.

Digital-image processing techniques, which incorporate specialized algorithms using both spatial and temporal statistical averaging techniques, add intelligence to video motion detection systems. This means that the motion detector can learn about or adjust to a changing scene.

With an intelligent video motion detector, the user defines the system's tolerances. The system can ignore small changes in the scene, such as leaves or snow blowing into the image area. It can ignore the motion of trees or grass in the video scene, or it can ignore slow or sudden changes of light. According to the user's desires, the system can be programmed to detect or ignore the smallest movement.

The ability to window or zone the detection scene is another useful tool provided by an intelligent system. In contrast with analog systems, which view the entire video picture as an alarm area, windowing allows the user to divide the monitored scene into small areas, each with its own set of security levels. For example, in an antiterrorist application, one might want to monitor a person who stands in front of a window for more than five minutes but ignore someone who walks by it quickly. This is easily achieved by setting a detection window with a five-minute alarm pattern.

Another benefit provided by the ability to window is the ability to monitor motion or nonmotion. For example, the user can define a window tightly around an object and tell the system to ignore passersby but to signal an alarm if the object moves. Referred to as museum mode, this technique can be used in a variety of applications, ranging from guarding art objects to ransom pick-ups.

When shopping for an intelligent digital video motion detector, the user should look for features like a built-in quad. This will allow the user to see up to four camera views at a time. It does not, however, limit the number of cameras to four. Some systems allow up to eight terminating. video inputs. Also, the user should look for a high number of user-defined alarm windows that are individually programmable.

Because they are digital-based systems, intelligent video motion detectors can take advantage of on-screen menu-driven programming technology. This ability makes window definition or modification easier. Programming is typically done with buttons on the front panel of the system, and some systems feature an optional mouse.

The benefits derived from digital-processing technology are particularly applicable to multicamera installations, such as might be required at a bank. Bank theft falls into two categories, robberies and fraud, and a successful security system must be able to deal with both. This is further complicated by the fact that the average bank robbery takes place in seventeen seconds. Therefore, a bank's system must be flexible enough to keep up with the rapid pace of business inside the building, interface with ATMs, and provide a high-resolution picture.

Many financial institutions with multicamera needs are turning to time-lapse recorders with built-in multiprocessor-based switchers. When specifying this kind of recording device, a security manager should look for recorders that incorporate the most recent advances in time-lapse recorder technology. To aid in suspect identification and conviction, the recorder should feature at least 400 lines of horizontal resolution. Other helpful features include a direct-drive chassis, which will provide fast tape loading and reduced maintenance, and a selectable azimuth, which is a head selection process for playback of more than one VHS recording format.

Of particular importance for multiple-camera installations is the ability to handle a number of video cameras and alarm inputs. Connie Agresta, president of Grand Central Engineering and Security, recently went through such a selection process when he designed and installed CCVE security systems for Great Western Bank in Florida, which has more than 150 branches. Manufactured by GYYR, the time-lapse recorders selected by Agresta use digital processing to switch camera inputs in accordance with the user's sequential switcher, which enables one to view areas in a predetermined order, and dwell-time program. The dwell-time program makes it possible to display a particular image for a specific period. "With this system, any camera may be selected more than once during a switching sequence," explains Agresta. "The camera switcher may be programmed through either front panel controls or remote keyboard. The dwell time for each camera may be programmed from one to ninety-nine seconds or one to ninety-nine fields."

In addition, the recorder Agresta chose has a seven-day programmable timer with separate day and night sequencing. "I like this particular feature because for each day of the week, the user may program two time periods during which the switcher sequence is automatically modified," he says. This arrangement permits the bank to focus greater attention on certain areas during busy or

critical time periods.

According to Agresta, these features are important to the successful design of bank installations: "When specifying such a system, we have two major objectives that apply to most multicamera applications. First we need to increase the number of images taken of each person who enters the building. Second, we need to optimize tape consumption. While the two objectives appear to be in conflict, the resulting system accomplishes both."

Because they selected a time-lapse recorder with a built-in digital switcher, Grand Central Engineering was able to specify how the recorder captures pictures via alarms or dwell times. This provides maximum programming flexibility. The recorder was set up with a special turbo, which allows the recorder to capture an image from each camera on a single frame every time the VCR is programmed to record--25 percent more images than a standard recorder. The dwell time is dependent on the camera location, with an average of one image being taken every three seconds for more than 570,000 pictures (four to five days) on a standard two-hour tape. In other words, pictures of a person are continuously recorded as they walk through the bank.

This compares to older systems, which are often set up in twenty-four-hour mode with every camera recording an image every six seconds, more if a panic button was pushed at a teller window. In theory this is fine. However, if there is an eighteen-second robbery, some of the older systems are lucky to capture three images.

Users might also want to consider one of the other benefits afforded by digital technology, a portable storage transfer device (STD). These handheld devices provide an easy way to archive the complicated multiprogram sequences that are used with the sophisticated digital processing-based recorders, and with this feature, users can download the same program to other recorders.

The flexibility provided by digital processing-based time-lapse recorders can help the user obtain a system that meets his or her needs. When properly applied to CCVE products, digital-processing technology can make sophisticated security products easy to use and simple to program, even for the novice user.

Tom Pappageorge is director of sales and marketing for GYYR, a division of Odetics, in Anaheim, California. He is a member of ASIS and on the board of directors of the Closed-Circuit Television Manufacturers Association.
COPYRIGHT 1993 American Society for Industrial Security
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1993 Gale, Cengage Learning. All rights reserved.

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Author:Pappageorge, Tom
Publication:Security Management
Date:Aug 1, 1993
Words:1750
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