Even when considering a relatively small scale system, the cost of a set of cameras and a DVR is still fairly substantial, so when picking out equipment, many a tech-head has contemplated building his or her own DVR as a means of saving money, and with good reason. Since more and more DVRs are using PC platforms, if one is already familiar with a PC and how to build one, it might seem like a cakewalk to put together a PC DVR from scratch.
Armed with past experience, many professionals and hobbyists have rushed headlong into surveillance projects by building or modifying existing PCs to function as the center brain of their camera system, and unfortunately the vast majority fail within a few months or a year, simply because they weren’t designed to be up to the task at hand. Though there are huge similarities between a normal PC and one that functions as a DVR, there are also large differences that must be accounted for in order for the system to function properly, and to successfully build a PC DVR, the system has to be built with its workload in mind.
One big difference between a standard PC and a PC DVR is that a standard PC (like the one you’re probably on now) is built with the intent that the system will be able to take a break every so often. A PC is able to go into sleep mode, or someone might turn it off when it’s not in use. When this occurs, not only does the hard drive stop spinning, every part of the machine gets to take a rest. The video and sound cards stop work, the processor gets some time off, and the motherboard gets to stop handing out instructions to the rest of the computer. More important than that, though, the computer’s memory clears out and the pent up heat that naturally collects inside the tower is allowed to dissipate, cooling the components and allowing them to start fresh later.
A PC DVR, though, will never have that kind of luxury. Even if using motion detection or scheduled recording to minimize the amount of data that’s being written, as the brain of the system the DVR has to be on and running all the time in order to analyze the video that comes in. This not only means the system can’t be turned off, that means it can’t hibernate, sleep, or stand by, either. The hard drive has to constantly be in motion, meaning all the other components of the PC have to constantly work as well. In terms of the construction of the DVR, this not only means that the hard drive, processor and cards have to be spec’d to work 24 hours a day, it also means that the PC must have sufficient RAM to keep the system working at top efficiency. Above all, though, as a matter of functionality and of safety, it is crucial that the heat sinks and fans that go into the system be able to be able to keep up with the workload and the heat put off by all those components; too much heat pent up in the tower doesn’t just degrade the system, in extreme cases it can be a fire hazard.
Considering all that, building a PC DVR is no small order, and as such, it’s usually best to build one from scratch instead of trying to customize an existing PC to do the job. Pre-built PCs, even ones in great shape, usually have proprietary drivers and other software that runs in the background and affects the performance of the DVR, and a system working in a surveillance capacity can’t afford to split its memory like that. For your home computer, it’s great to have a Media Center and a few free games, but your DVR’s processor has more important things to be working on. Even if those types of software aren’t always running, they usually have small update managers and support wizards that turn themselves on whether you use them or not, and all of that takes up memory. Removing these programs is one option, however this can be very difficult, especially for older computers that have seen a lot of use.
A brand new, custom-built PC, though, not only would have a clean sheet in terms of drivers and software, but one that was built from scratch with a new copy of Windows wouldn’t have any update managers or proprietary drivers that might clog up the memory of the system. In fact, it wouldn’t have anything that the person who built it didn’t personally put there, and this scenario is ideal since only what’s needed will be present on the hard drive. Still, this prevents unfamiliar territory to some. A simple trip to Best Buy or Circuit City will reveal literally hundreds of options for processors, hard drives, and every other component in a computer, and when faced with this even professionals might pause and scratch their heads a bit.
To help narrow options down, once one is ready to seriously begin building a PC DVR, the very first step should be to buy the DVR capture card or cards and get the manufacturer’s compatibility sheet, which lists all of the peripheral cards (or at least the specifications for each) that have been tested and are known to be compatible with the hardware and the software. With that information in hand, choosing the correct processor and video card to make up the rest of the PC should be a breeze, since the compatibility sheets will provide a road map. Additionally, a possible way of working backward with this same method would be to inventory the parts available, with their specifications, and pick a DVR card based upon that (this would be the best method if the aim was to make a “spare parts” computer that functioned as a DVR from components already on hand).
In either case, though, the spec sheets of the capture cards will be a DVR architect’s best friend, and should be followed to the letter in order to ensure that the machine will function to its full potential. Even at that point, though, no home built DVR will ever be able to match some of the non-tangible benefits of going with a professionally built one (such as one of the PC Witness Pro V\RT Series ). For example, a DVR built by a surveillance company will have a single, comprehensive policy for warranty and tech support, whereas a home built PC DVR could potentially have as many different warranties and support policies to keep track of as there are parts of the computer. Additionally, there is also the benefit of experience that even an experienced engineer would be somewhat lacking in; there are certain tricks and hang-ups to expect and be ready for with any system, and a professional would be familiar enough with surveillance territory to quickly and simply diagnose these issues before they become problems, either during the construction of the system or after the fact.
In short, building your own DVR, though less expensive, is a serious piece of work to take on and should only be done by those with enough experience and confidence to handle the job, but even then, it’s an imperfect substitute.
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