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From: ggm@dingo.cc.uq.oz.au (George Michaelson)
Newsgroups: comp.sys.ibm.pc.hardware.video,comp.windows.x.i386unix,comp.os.386bsd.misc
Subject: Re: Video output
Date: 25 Feb 1994 09:27:43 +1000
Organization: University of Queensland
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Message-ID: <2kjd5f$g32@dingo.cc.uq.oz.au>
References: <CLq9pt.Mps@cogsci.ed.ac.uk>
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richard@cogsci.ed.ac.uk (Richard Tobin) writes:
>I'm looking for some hardware that will allow me to record the display
>on a PC onto videotape (VHS/PAL). I will be running XFree under
>NetBSD.
>What are the options for doing this? Will I have to reduce the PC
>display resolution to that of the video? I'm willing to get either an
>external adaptor or a replacement video card, so long as it works
>under X.
Forgive me if this is wrong... Its my understanding...
You need either a card with an explicit video output akin to the
(very expensive!) Galileo board on the SGI, or a generic sync rate
converter, which is a black box that plugs into the monitor flyleads
and performs the decimation/rate conversion and provides flyleads for
input to suitable recording/mixing media. (SVHS plug, BNC RGB+sync, whatever)
VHS recorded tape and broadcast TV is around 15Khz. horizontal sync.
VGA is 35Khz, SVGA/Sun/Dec/Etc is 60, 65, 72, 100+ Khz. You can't get
from this to 15Khz without loosing information. Typically you either
select a zone of the screen for full pixel recording at the appropriate
width x height 1:1 or else do some kind of decimation. a 1024x768
window cut down to the VHS is going to look ok, but definately not
PIXAR quality. It beats the hell out of pointing a camera at the screen
mind you...
A sync rate converter for VGA->VHS is around $10k Australian. If you want
from 72+Khz its more like $40k Australian. I suspect a video toaster card
will be cheaper but quality will be an issue, as well as getting a NetBSD
driver. You can probably hire a sync rate converter from a mob doing
TV O/B production work, but you definately need to know the horizontal refresh
rate of the local monitor, and pinouts of the connectors. You can often
use Thinwire and T-pieces but remember Thinwire is 50 Ohm and TV is 75 Ohm
so you loose if the runs are too long.
Why not persuade SGI to loan you an Iris with Galileo, and use remote X
to get the NetBSD box to display onto the Iris which can then drive the
tapedeck directly? It'll only cost around $150k to buy the setup :-)
-George
--
George Michaelson
G.Michaelson@cc.uq.oz.au The Prentice Centre | There's no market for
University of Queensland | hippos in Philadelphia
Phone: +61 7 365 4079 QLD Australia 4072 | -Bertold Brecht