Digital video, particularly digital video recorders (DVRs), is the most exiting CCTV technology to come along since the introduction of CCD chip cameras. With the speed of modern microprocessors and networks in the gigahertz range, along with dropping prices on 100GB+ hard drive storage, this market is just beginning to explode.

On the surface, digital appears easier and more versatile than older analog CCTV technology. However, as with many new technologies, looking below the surface shows it necessary to learn some valuable tips and resources to make life a bit easier for all of us.

Chart Helps in Testing and Evaluating CCTV Performance

Currently, there are hundreds of new and exciting digital cameras and recorders on the market, all making claims that they have the best product with the best features. So how does one go about knowing if a camera or recorder performs as claimed?One valuable evaluation and testing tool a dealer or technician can use is a CCTV test chart.

Many of the chart measurements can be applied to DVRs as well as cameras, as follows:(A) Camera resolution can be determined by the sets of four triangulated horizontal lines.
(B) Video signal bandwidth can be checked with these sets of black lines. The higher the bandwidth the better the quality of the picture. This includes DVR recording.
(C) Camera focus and back-focusing adjustments can be made from the small square target of concentric lines in the middle of the chart.
(D) The large bars on the left can test for correct line impedance matching and sufficient human details for hold-up cameras and recorders.
(E) The tilted small white and black bars on the right give more detailed information on the recognizable human information for specifying security camera/lens combinations and DVR playback.
(F) On the right, the picture of the three children is used to check colors, such as human flesh, which is one of the most difficult for color cameras to get correct. Be aware that this will change depending on the light source (tungsten, florescent, etc.) used at the actual CCTV installation.

I encourage experimenting with a chart and some evaluation equipment to better understand the products you are installing. You may want to check with various manufacturers to see if they have test results from using similar charts. Some BMP samples of product tests and the CCTV chart instructions can be viewed at www.cctvlabs.com.

You Don’t Have to Be a Network Expert, But …

CCTV installers and dealers do not need to be a network information technology (IT) specialist, but should be familiar with working in a computer network environment.

While many DVRs currently use analog camera inputs, more and more full digital systems will be used. Network addressing terminology such as subnet masking and static IP addressing should be understood (for more on this topic, see October 2002’s “Tech Talk”).

When coordinating a CCTV installation with an IT manager, the dealer may run into some new terms, such as quality of service (QoS) and cabling certification. Because so many products, such as DVRs and digital IP cameras, are now being tied into computer networks, IT managers need additional performance guarantees. They need to know that the products and services connected to their network, and the network itself, will perform reliably, and as specified by manufacturers and installation companies.

Compression Method Affects the Resolution

In the United States, real-time video is typically 30 frames per second (FPS). However, a strategy of compressing digital video/audio data is needed in order to get the best picture with the storage medium available.

So what are some good guidelines for compressing this data and what are the consequences if not followed? Here are some suggestions:• Keep compression rates at 20:1 or lower
• Use a full-frame resolution of 720 X 486 pixels
• Keep frame rates above 10 FPS for a single camera and 20 FPS for a four-camera application.
Several compression standards are currently being used by DVRs. Keep in mind that

Work Hand in Hand With Law EnforcementWith all of these compression schemes, a dealer must always keep one thing in mind: What is the final product and what are we going to do with it?  Let’s use a convenience store application as an example. We want to end up with a good viewable image of a robber, which can then be used to identify the perpetrator and then possibly serve as evidence in court.

The first thing to do would be specifying camera and lens placement. It should allow a person’s features to fill as much of the frame and monitor as possible. Having to drastically enlarge a digital image of a subject can have serious effects on picture quality.

Mike Fergus, executive vice president of the Law Enforcement Video Association (LEVA) suggests the following:• Have a DVR that can easily convert compressed proprietary digital video to a common format (AVI) for investigative purposes.
• High compression ratios can lose valuable data and make video useless to an investigator.
• Plan CCTV systems carefully. Simply adding a DVR in place of an analog VCR will not work. Look at the whole system.
I suggest you pay a visit to your local law enforcement video investigator or the forensic expert in your installation jurisdiction and see what they like working with. This is the person who may eventually be reviewing and trying to digitally enhance your customer’s video footage after a holdup.

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