ddulmage@cdp.UUCP (12/31/90)
>I need some help with converting RGB (sync signal on G) video output >from some frame buffers to some composite (NTSC most likely) signal >and then distributing the composite signal to various locations on >our building. Please, do yourself (and your facilty) a big favor... Run fiber optic instead of coax. There's no reason not to run fiber these days, and it will give you tons of room to grow and save you a lot of grief as well. I do contract eng. for a comp. that builds video walls, and I finally talked them into running fiber on some of their installations. They run both baseband composite as well as RGB and also rs232 and audio over the fiber. They used a system from: Math Assc. 2200 Shames Dr. Westbury, NY 516-334-6800 If you like to tinker, Signetics has just about all the IC's for the stuff you want (including very complete app. notes) in the linear and video books. I've used a chip that does exactly what you want, rgb>composite and it was painfully simple. The chip was made to do the conversion for consumer video cameras. If you want to stick to pro-broadcast grade gear, try Grass Valley group in CA. or Sigma Elec. in Fl. G.V. has both fiber and coax, (very pricey) and Sigma has coax only. If you decide to run coax, keep in mind that you will need line equalizers, possibly D.C. clamps and all that other voodoo.. And be prepared for ghosts and hum as well, and don't skimp on the cable and connectors, and don't leave stuff unterminated, and ... anyway, I think you get the idea. Doug Dulmage
sheasby@dgp.toronto.edu (Michael C. Sheasby) (01/03/91)
ddulmage@cdp.UUCP writes: >Please, do yourself (and your facilty) a big favor... Run fiber >optic instead of coax. There's no reason not to run fiber these >days, and it will give you tons of room to grow and save you a lot >If you decide to run coax, keep in mind that you will need line >equalizers, possibly D.C. clamps and all that other voodoo.. >And be prepared for ghosts and hum as well, and don't skimp on >the cable and connectors, and don't leave stuff unterminated, and >... anyway, I think you get the idea. Foo. coax is nice stuff. Cheap, installable by volunteers who work for pizza, connectible without modification to every piece of equipment under the sun, and best of all, multipurpose. We ran 8 cables to each office node we created, and can now use the extra cables to run anything we want (not just audio and video) to each office (ie signals from motion detectors, commands to motorized camera platforms, you name it) we haven't had to use equalizers or clamps or any other 'voodoo' :) ... The only thing we had to be careful about was crossing power lines at 90 degrees. Our motto is to Do smart things with stupid technology. We've remained conspicuously humble technically (except for some truly groovy switch control software, borrowed from EuroPARC) and have built a good network on the strength of our interface. Doing it all with fibre optics would have been a real chore. >Doug Dulmage ---Mike.
ranma@noc.arc.nasa.gov (Robert Michael Gutierrez) (01/06/91)
c.graphics is the wrong place for this...BUT... ddulmage@cdp.UUCP writes: > Please, do yourself (and your facilty) a big favor... Run fiber > optic instead of coax. There's no reason not to run fiber these > days, and it will give you tons of room to grow and save you a lot > of grief as well. And will cost you tons of money also. Seriously, why can't he use coax, especially since it will be limited to one building. There is absolutely no need to expend multi-year loans on fiber, and there is NO video fiber distribution standard at this point [point: I said VIDEO, not data!]. If he were to distribute to different buildings, even then I would think twice about fiber, unless you get into a co-op agreement to share it with others (ie: data). > I do contract eng. for a comp. that builds video > walls, and I finally talked them into running fiber on some of their > installations. And what if they want to expand. They have only once source (essentally). And the technicial labor expense of having fiber maintained...ugh! Definitely not for the staff boiler room 'engineer'. Splice fiber breaks: Time Domain Reflectometer, $2,000+ Fiber fuser/splicer, another $2-4,000 Fiber splicing training, $1,000+expenses Splice coax breaks: Carpenters knife, $2.49 at Home Builders Supply. BNC connectors and butt connector, $10.00/all. Cordless Soldering Gun, $49.95 at Fry's Electronics. Coax Splicing training, Good Chinese restraunt for lunch. No comparison. [Yes, I took lots of liberties here, but the point is the same] > If you like to tinker, Signetics has just about all the IC's for > the stuff you want (including very complete app. notes) in the > linear and video books. I've used a chip that does exactly what > you want, rgb>composite and it was painfully simple. The chip was > made to do the conversion for consumer video cameras. ie: No ready plug-'n-play stuff available. Or at least, cheaply. Seriously, even here at NASA Ames Research, our main video net is on 440mhz RF modulated cable, and we have tons of room to expand on it, and it's even a split run (two-way)! Fiber is perfect for these ever-expanding data networks (FDDI) that would otherwise be a nightmare on coax based runs, but it's just overkill for a simple video distribution system. robert gutierrez