22 May 2009 Comments Off

What to look for when purchasing a DVR for your Security Camera System

Deciding to go Digital is easy. By now you probably already know all the reasons for switching to Digital Video recorders, such as: the ease of locating events without having to slog through hours of recordings, excellent storage quality that does not degrade after repeated viewings, their ability to multi-task and do several things at once, and smart monitoring that allows multiple recording speeds based on motion or other events.

The hard part is figuring out what type of DVR to use, and how to end up with a good quality recorder that will give you what you expect and is reliable over the long haul. Many times, it’s what you’re NOT told that causes you grief, so to help you to understand the myths and learn to ask the right questions, here are some helpful tips and things that you need to look at before jumping into Digital Video.

PC-based Systems

Digital recording can push any system to it’s limits, and this is especially true with pc-based DVR’s. Most desktop PC’s are not designed to operate long term in harsh electrical and un-conditioned environments found in many industrial businesses or in the attics of homes. However, when I started putting pc-based DVR’s at my businesses, I started having all sorts of problems. At first my problems were mostly due to buying cheap DVR cards and software. Poor performance, frequent crashes, fuzzy pictures and hardware failures were a constant pain.

Finally I was able to get high quality cards and software and my performance improved greatly, and the pictures were excellent. The system was still too maintenance intensive though, and had several inherent problems that I had to deal with regularly. The most frequent problem was lock-ups and reboots. The problem it seems, was that the Windows operating system and the main processor did not tolerate being worked at near full capacity non-stop day in and day out. A good system is capturing and digitizing as many as 480 pictures every second, while serving you and perhaps others remote video via the Internet, and allowing an operator at the DVR to be doing something simultaneously. That kind of intensive computing power can work a system to death, and software lock-ups and rebooting are the outcome. You will also need to de-frag the hard drives every month or so to keep the system operating at peak, or it will start to slow down noticeably, and performance will suffer. Then throw in the fact that most business environments are not air-conditioned very well, if at all, and this can lead to heat related problems that can severely shorten the life span of the hardware components. It may keep working, but for how long?

Compounding these problems was the fact that my employees would get on the computer and surf the net and unknowingly pick up viruses that would constantly slow the system to a crawl, or even worse, cause it to stop working altogether. One employee in particular would play games on the computer and even load his favorite games on it. Games are also very processor intensive and this was another contributor to loss of performance and system crashes.

Purpose-built Dedicated DVR’s -

All of my locations now have DVR’s that are not PC-based and have been designed and built to perform their tasks non-stop without lock-ups or rebooting. These stable systems are usually Linux-based but you never know that because you only see the graphic interface and menus, and never have to deal with the operating system or even see it. These types of systems are sometimes called stand-alone systems because they do not need a computer or any other devices to operate. Another common name is an embedded system because the entire operating system and software has been embedded on the processor chip. No software resides on the hard drives, those are reserved for archived footage. This arrangement allows the system to work much faster, and also makes it virtually immune to hacking or viruses. Thus, you can put it on the Internet without any worries about picking up a virus or allowing someone to hack into it.

Lately, however, there have been a lot of cheap stand-alone DVR’s come in from overseas. Unfortunately it is just as easy to get taken with a cheap knock-off as it is to buy PC cards that are junk. So I have compiled the following list of minimum performance parameters to look for when evaluating a stand-alone DVR. Again, if they try to hide some of the numbers or won’t give them to you at all, move on to another supplier.

Resolution: There is displayed resolution and recorded resolution, and you will need to ask questions about both. Many companies try to tell you that their resolution is 720 x 480. However, when pressed they will admit that number is only for live picture viewing and that the recorded picture size is much smaller, such as 320 x 240 or even less. The smaller picture size is hard to see, and lacks the resolution or clarity of the larger sizes, so you blow the picture up to try to make out some detail, and this causes the picture to “pixelate” or appear grainy and fuzzy. Therefore, look for a minimum recording or capture size of 640 x 480, and 720 x 480 is even better. If it is a IP-based system, look for much higher resolutions (I will cover these types of systems in a later series of articles).

Frame Rate: Once again there is two numbers to look for, display rate and recording rate. These numbers are usually stated as “global”, meaning that the frame rate number is divided by the number of cameras on the system. For example: a 60 frame per second system running 16 cameras will be recording the video from each camera at just over 3 pictures per second. At that rate the video will be jerky and many movements or actions will be missed entirely.

The display rate should be real-time. No exceptions. If the system can’t display pictures in real time, it likely won’t be able to record very fast either. Recording rate is very important as well. Real time is defined as 30 frames per second per camera. However, if you insist on recording that fast, you will fill up your hard drives in just a couple of days. So a compromise is in order. The human eye cannot really distinguish the difference between 20 frames per second and 30. In fact, I have found that on a quality DVR, I can record at 15 frames per second and it still looks near enough to real time that I can’t see much difference. So that should be your minimum recording rate: 15 frames per second times the total number of cameras the system can handle. (ie: 60fps on a 4 camera system, 120fps on a 8 camera system, and 240fps on a 16 camera system).

Compression ratio: Some systems tout very high compression ratios, such as 1000:1 or 2000:1, as if it were a benefit or feature. While that might sound impressive, higher compression means that the system is stripping more and more resolution out of each picture in order to make smaller file sizes. A better system of compressing pictures is “dynamic”, meaning that the amount of compression attained changes continuously, depending on the picture content or amount of movement within the picture. It’s the only way to give sharp, clear pictures all the time, with just the right amount of compression, and you shouldn’t settle for less! Because anything less means poor quality pictures that let you down when you try to play back an incident to see what happened. In fact, the newest compression format, labeled H.264 is a really good system, and I would look for this type over all others.

Most of the other handy features such as Internet monitoring, motion-based recording and event or sensor-based recording is standard in most DVR’s these days, but make sure that the system will let you do more than just monitor cameras remotely. Ask if the system allows you to look at pre-recorded archive footage remotely, lets you transfer files over to your own PC, and even record simultaneously on your PC at home or the office. Also ask if the system lets you change all the settings remotely, and generally lets you operate that DVR as if you were standing in front of it. All are hallmarks of a quality DVR.

Last but not least look at the Warranty the company provides. A reputable company should give you a “fix it or replace it” warranty for at least 2 years. Beware of the system that comes with a 90 day parts and labor, or 1 year parts only warranty. If they won’t stand behind your system, why should you buy it?

If you let the performance numbers listed above be your guide to choosing a good quality system, you will be happy with your system for years to come. Good luck and feel free to e-mail me with any additional questions you may have.

Written by: Allen Spears, Chief Engineer, Rugged CCTV, © Copyright

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