Re: Advice needed on CCTV

["Philip Coombes" <philip.coombes@xxxxxxx>]

Hi Bruno,

> I'm very impressed with your software, especially as it is
linux-based
> and uses a browser frontend. But:
>
> 1. What sort of processing power do you need per camera for USB
cameras
> and BTTV-connected cameras (presumably less for the latter)?
>
Not being awash with cash I've not had access to loads of cameras to
play
with but my home installation is a PII-233 and that happily monitors 3
(usually) or 4 (occasionally) cameras with a load average of much less
than
1. It is designed so that it isn't trying to just go mad all the time but
to
go as fast as is sensible. The actual image capture and analysis isn't
really all that processor intensive really, currently I have two
cameras
being actively monitored for motion and one just being captured for a
feed
and my load average is .25 or so.

> 2. If you are using BTTV-connected cameras, how do you connect more
than
> a couple? Don't you quickly run into clashes and run out of slots
and
> IRQs for cards?
>
Well a good start is to get a multi-port card, you can get 4 or 8 port
cards
though I haven't tried the latter. Naturally the more cameras connected
to
it the lower your capture performance will be though. This is a
limitation
of the card rather than the software. I think you can get around 25fps
with
one camera on the card, about 8 with two, and 4 or less for more (I dread
to
think what it is with 8!). Obviously having larger screen dimensions
and
colour depths also has an impact. In general I think you'd have a
fairly
slimmed down box for running ZM on so IRQs shouldn't be an issue. If
you
want it to monitor 20 cameras you might find a problem or two as I
haven't
tried it with that many. (If anyone wants to send me 20 cameras I'll
check
though!)

> 3. If you are using USB cameras, how do you get round the
cable-length
> limitations? You don't really want to be limited to putting your
> security cameras within 5 metres of the computer.
>
Well if you really want to you can get USB extenders to put in line but
I
wouldn't recommend it for a serious installation. I've also had issues
with
wireless cameras getting mugged by my other wireless stuff (ie. 802.11) so
I
make sure everything is wired. However I have a USB camera covering the
room
where the machines are and if I didn't already have a camera outside I
could
easily put it in the window sill and use it to cover the garden if I put
a
hood on it to shield out the glare. It all depends on budgets and
preferences really.

> I had originally planned to do something like this for my barn
> conversion, but have resigned myself to the more expensive option
of
> using network cameras. If you have figured out how to do this without
a
> battery of linux computers, you could save me a lot of money.
>
It really depends on your own circumstances. I make no bones about the
fact
that ZM is pretty new and immature and as such has not been tried in a
lot
of different scenarios and may not be suitable for all applications.
However
the corollary of that is that it has been developed to be used (mainly
by
me!) and to actually be useful. I want to be able to see who's been
around
my house, I want to be able to check what's going on at home from my
browser
at work or on my phone, and I'd like to be able tie in my cameras from
the
alarm system or other HA entities.

Having said all that, all I got last night was several hours of
recordings
of a brightly IR illuminated spider carefully making a perfect web slap
bang
in front of one of the lenses...

Phil,







http://www.automatedhome.co.uk
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