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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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