Closed Circuit Video on Linux

[Charles Steinkuehler]

Jim Herrmann wrote:
> I have a friend that is building a professional music studio.  They are 
> considering eliminating the glass between the control room and the main 
> studio room to help with isolation.  Also no glass between the drum room 
> and the control room.  Probably still have glass between the drum room 
> and the main room.  Anyway, to accomplish this they are thinking about 
> using something like web cameras and monitors to see from one room to 
> another.  I was thinking this could be an excellent application of 
> linux.  I know some of you have experience with doing streaming video 
> with linux.  I thought I would get your ideas for the best way to go 
> about this.  I'm thinking something like a dual headed machine for 
> running the monitor in the drum room and the main studio room that could 
> be controlled remotely with a machine in the control room, which could 
> also be a dual head, I suppose.  All hooked together with 100Mbit 
> ethernet, of course.
> 
> Give me some ideas on a technical solution.  Anyone interested in 
> helping with this project as an interesting intellectual pursuit?  We're 
> looking to move on the design of this project right away, with 
> implementation coming just a few months from now.

Not that I don't like linux, but is there a particular reason you're not 
considering using plain video technology for this?  A couple points you 
might want to think about regarding the web-camera solution:

Resolution:  Will probably suck.  If it doesn't, you paid a lot for your 
cameras (a quality camera w/lens is several hundred $), probably with a 
"kicker" for a good video capture card.

Latency: You will have substantially more latency between "real life" 
and the viewed image when using web-cam/networking than if you just pipe 
raw video around.  This may or may not be an issue for you, but it's 
something to think about.  Remember it doesn't take too much delay 
between audio and video to start driving you nuts and create lip-sync 
problems.

Synchronization:  AFAIK, there are no genlockable web cameras, so each 
will be running off it's own timebase.  This may or may not cause you 
problems, but it can create issues if you're intending to work with 
multiple sources on the same system.

It's hard to make an exact recomendation with the limited information 
above.  The proper solution depends a *LOT* on exactly how you plan to 
use the system, but I think you'd be better off with plain video 
cameras, maybe some distribution amps or a routing switcher, and a bunch 
of coax.  It would probably be no more expensive than the webcam 
solution after you factor in computer and capture card costs, unless you 
really don't care about image quality.

Oh...and I'm not just trying to be a PITA.  My day job is designing 
professional video equipment, which I've been doing for the last 15 
years or so.  I'm not up on the latest gear for your sort of an 
installation, but I have yet to see a web-cam image that didn't suck 
compared to a quality baseband video signal.

-- 
Charles Steinkuehler
charles at steinkuehler.net