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Re: multiple webcams via one linux box

On Sat, Aug 24, 2002 at 10:51:02AM +1200, Dave Watkins wrote:
> At 18:00 23/08/2002 +0200, Nicolas Bougues wrote:
> >On Fri, Aug 23, 2002 at 10:06:40AM -0500, Bernie Berg wrote:
> >> Hi, I have a project that could potentialy have 85 webcams.  The easy
> >> thing to do would be to use an Axis network camera and just link to its
> >> own webserver from my linux web server (or whatever).  But these run
> >> about 300 bucks, that would be about 25 grand for 85 cams.  X10 on the
> >> other hand (I hate  their website, it looks like to is from 1994), has
> >> much cheaper cameras, and they are wireless.  You can get a usb adabpter
> >> to input them into a computer.  Ummm, anyone have luck linking 85 usb
> >> webcams into one linux box?  Anyother sugestions?
> >>
> >
> >USB can't have more than 63 devices per bus.
> FYI 127 is the max for USB, 63 is for Firewire

Thanks for the correction.

BTW, it's probably cheap and easy to add a few more USB buses, using
PCI boards. This would dramatically lower the number of devices per
bus, and thus avoid (some) problems when the number of cams increases
(bandwidth, latency, etc. caused by hubs chaining).

One question is how the USB cams send data to the host. If it is not
compressed at all, even a "small" 320x200x24 bit snapshot will be
192 Kb, and you won't be able to receive more than 3 such pictures on
a bus per second.

Axis cams send JPEG data, which is far smaller, and on a much higher
bandwith bus (100 Mbps Ethernet, which can be further
switched/aggregated to Gigabit on the host side), and you can easily
capture one picture every few seconds on tens of cameras without

Oh, one last thing : I don't know X10 products, but you'll probably
have some spectrum management issue when you run 85 wireless cams...

Nicolas Bougues
Axialys Interactive

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