Choosing the Right DVR

By Allan B. Colombo | Jan 15, 2009
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A pharmacist friend called about a couple of after-hours attempts to break into his establishment. In both incidents, the perpetrators were frightened off by the intrusion alarm system. Because he had a good shot of the criminals on video, he thought the police would have little trouble identifying them, but he was wrong.

When the police arrived on the scene and asked for a copy of the video, it was soon discovered that there was no way to remove it from the digital video recorder (DVR). He realized that there was no provision made to export digital images to a magnetic or optical storage device. The only way to share images with law enforcement using his DVR is to physically remove the hard drive from the machine. In this case, the hard drive is part of an assembly that can be pulled from a docking station within the DVR using a key—a solution that unfortunately did not simplify the process for the end-user.

Choosing a DVR begins with a close examination of what the buyer intends to do with his camera system. He must consider his current and future needs. In the pharmacist’s case, four cameras may have been all he needed when he purchased the system, but now he may need more. Buying with the future in mind not only saves money, but it results in a more integrated approach where camera control and image storage are carried out in a more efficient way.

DVRs come with as few as four or as many as 32 video channels. Starting with four cameras, the number of video channels doubles with each upgrade, for a maximum of 32. Network-based storage systems also are available, but we will confine our discussion to stand-alone DVRs, which dominate the market at this time.

Another issue end-users need to consider is how images are recorded. There are three basic methods used to store video images to a magnetic hard drive: quad, mux and full frame.

The quad method squashes up to four images into a single image frame.

“In quad, four camera images are recorded on a single frame [or image]. This gives the illusion that the machine is capable of recording 120 images per second (ips) when it’s really only recording 30 ips,” said Erron Spalsbury, account manager, of Boulder, Colo.

“And since there are four cameras sharing a single frame/image identifying a person or car in essentially (one-quarter) of a 640-by-480 pixel area means that the image quality will be rather poor. But a better quality DVR that uses full-frame mode is capable of truly recording 120 ips, which will give you a much better quality image,” Spalsbury said.

Using the mux method, images are recorded one after the other in a serial format with embedded data that defines each as camera 1 through 4.

The third method, and the best, saves full-frame images in folders or baskets that correlate to each specific camera.

Exporting images for police

When an incident occurs, there must be a way to export images for law enforcement. My pharmacist friend said he didn’t consider exporting images for law enforcement before the incident.

There are several ways to export images. Some of the most popular types of image export include the following:

• A read/writable CD-ROM burner

• A USB port

• An Ethernet port for integration to a local area network (LAN), an individual PC or to a modem for Internet connectivity

Unless the alarm salesman educates the client with regard to cost versus quality, the client likely will award the job to the lowest bidder. As in the case of the pharmacist, we have seen what can happen when price alone motivates a final buying decision.

Including a high-end DVR on each quote you give is perhaps one alternative. It’s also necessary to explain the difference between quad, mux and full frame, so the buyer fully understands the difference between each.

Another way to do that is to use the video tools made available on the Web sites of many DVR manufacturers, such as that of Spalsbury’s There are other DVR manufacturers in the marketplace that, similar to 3xlogic, offers graphic tools to illustrate these differences. For a list of video sales tools, go to

COLOMBO is a 33-year veteran in the security and life safety markets. He is director with and a nationally recognized trade journalist in East Canton, Ohio. Reach him at [email protected].

About The Author

Allan Colombo is a 35-year veteran in the security and life safety markets. He is director with and a nationally recognized trade journalist in East Canton, Ohio. Reach him at [email protected]





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