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Digital Video
Recording
There are presently over 200 manufacturers of digital video recorders
worldwide with products on sale here in Ireland having prices
ranging from a few hundred Euro to a few tens of thousands of
Euro. Some of these products we would consider inappropriate due
to functional deficiencies or issues of reliability, but the majority
of the products on sale are appropriate for specific markets and
are priced suitably for these markets.
Quite commonly, a client will be presented with an innappropriate
choice of DVR for their specific application, and as a result,
they may feel that the solution they are being offered is either
over-priced or under-spec'd.
Jade choose to try to understand the true requirements of an end
user in order to match the requirements with the specification.
As we all know, you cannot compare apples with oranges.
A more expensive machine will have a high price tag for a reason.
Find out why. You should expect your CCTV system to have a life
span in excess of 8 years, make sure that the company you buy
from and the parts they use are properly supported in Ireland
by at least one other vendor. Don't let yourself get tied in with
a company who may inflate prices at a later date or hold your
system's support to ransom on the basis of an expensive maintenance
contract.
The details of how a digital video recording system are quite
technically complex, but your requirements for a CCTV system are
not. You want a system that records images from cameras at a quality
you specify for a period you specify and allows you to retrieve
these images in a way you specify.
Make sure you get a system that does what you want it to. How
it does it is not important.
It's not about "The Gigabytes".
Too often the amount of hard disk storage included in a DVR becomes
the only piece of information used by vendors and users upon which
to judge the value of a machine. Of course the amount of storage
included is important, but only once it is understood what the
information is that is to be stored on the hard disk.
Choosing a DVR first involves deciding what information you want
from each of your cameras. Is a camera's purpose that of monitoring,
detection, recognition or identification? This determines the
camera specification, the lens to be used, the position of the
camera and the recording resolution/frame rate.
Once this has been determined for each of your cameras you can
work out the overall frame rate requirements of the DVR and how
much storage you will need based on:
* The file size for each camera achievable with the required video
capture resolution
* The frame rates you have chosen for your cameras
* The estimated level of motion (as a percentage) you expect at
each camera
* The recording scheduleSome simple arithmetic can now be used
to calculate how much storage you'll need per month.
The kind of events you expect to be searching for should also
have an influence on your choise of DVR. Different DVRs come with
different software, some of which is better suited to event searching
than others. If you expect to be spending a lot of time looking
for video events then you'll save yourself a lot of time by chosing
a machine with more powerful search tools. The extra cost may
well pay for itself in the long run. |
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