Video taping a UNIX sreen. How?

Video taping a UNIX sreen. How?

Post by Olav Bertels » Fri, 10 Jun 1994 21:32:20



Hi Everybody

We are currently trying to do some videobased evaluation of some of the
systemdevelopment tools constructed in the DeVise project.

The problem we have is that our video equipment interfere with the screens on
our UNIX stations in a vrey bad way.  We have earlier made video recordings of
Mac and PC screens without problems with the same video equipment.

We are using the VHS video system and the UNIX stations are SUN-SPARC and
HP9000. The problem is that 2/3 of the screen is black, and that the only thing
it is possible to see is how many windows the user opens.

Does anybody know how we can solve the problem?

Any help will be appreciated.

                /olav

PS: For info on the DeVise project see:
WWW URL: http://www.daimi.aau.dk/~kgronbak/deviseIndex.html
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Video taping a UNIX sreen. How?

Post by Tim Sh » Sat, 11 Jun 1994 19:11:10



>The problem we have is that our video equipment interfere with the screens on
>our UNIX stations in a vrey bad way.  We have earlier made video recordings of
>Mac and PC screens without problems with the same video equipment.

You need a scan converter. It converts the signal sent to the screen
display to a video signal suitable for recording. They cost anywhere
from $10,000 to $25,000 US (last time I looked), depending on the
features that you get (flicker filter, zoom, etc.). You may be able to
rent one.

Another option is to see if you can change the scan rate of your display
or change your display to something which doesn't interfere so badly.
The main problem is the mismatch between the scan rate of the display
(probably 70 Hz or so, non-interlaced) and video (60 Hz, interlaced, 30
frames per second) (at least in the US).

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Video taping a UNIX sreen. How?

Post by Archer Sul » Sun, 12 Jun 1994 02:49:29



;
; Another option is to see if you can change the scan rate of your display
; or change your display to something which doesn't interfere so badly.
; The main problem is the mismatch between the scan rate of the display
; (probably 70 Hz or so, non-interlaced) and video (60 Hz, interlaced, 30
; frames per second) (at least in the US).
;

The other way to use a camera directly is to rent a Sony "Computer camera":
these things detect the rate of the screen that they're pointed at and sync
to it.  I don't know the model number off hand, sorry.

-- archer

 
 
 

Video taping a UNIX sreen. How?

Post by Alex Madara » Sat, 11 Jun 1994 18:25:03



> We are currently trying to do some videobased evaluation of some of the
> systemdevelopment tools constructed in the DeVise project.

> The problem we have is that our video equipment interfere with the screens on
> our UNIX stations in a vrey bad way.  We have earlier made video recordings of
> Mac and PC screens without problems with the same video equipment.

> We are using the VHS video system and the UNIX stations are SUN-SPARC and
> HP9000. The problem is that 2/3 of the screen is black, and that the only
> thing it is possible to see is how many windows the user opens.

I assume you were running the PC and Mac systems at about 640x480 and using
a relatively cheap VGA/Mac->NTSC converter.

The same converter won't work on higher-res systems like Sun/HP/...
workstations unless the workstations have a way to change their video
output to VGA/Mac resolution and timing (on many SGI workstations you
can change the video output format using the /usr/gfx/setmon command).
Ask your sysadmin (or read your manuals) to see if your workstations'
video output can be changed.

If they can't, you need something called a "scan converter", which can
down-sample high-res RGB video (1024x78, 1280x1024, ...) and convert it
to NTSC/PAL/S-Video/... output.  The high-end scan converters will
auto-synch to just about any video source, give you lotsa options for
adjusting the quality of the video output, and allow you to pan and zoom
the scan-converted video "window" around the workstation screen.  I've
used a top-of-the-line Folsom "Otto" and found it to be an excellent
solution for recording 1280x1024 SGI workstation video.

Of course, the problem with scan converting high-res video down to NTSC
resolution is that you're throwing away a lot of pixels and a full-
screen shot of a lot of small objects will lose a lot of information and
can have some aliasing.  Again, the better scan converters have features
like anti-aliasing and filtering to prevent some of these artifacts.

Call around to video production houses and ask if they can rent you a
scan converter.  I rented my Folsom Otto from a Folsom dealer.

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Video taping a UNIX sreen. How?

Post by Alex Madara » Sat, 11 Jun 1994 18:37:42



> We are currently trying to do some videobased evaluation of some of the
> systemdevelopment tools constructed in the DeVise project.

> The problem we have is that our video equipment interfere with the screens on
> our UNIX stations in a vrey bad way.  We have earlier made video recordings of
> Mac and PC screens without problems with the same video equipment.

Oh, and another thing ... when you're dealing with this kind of video-
taping, the quality of the recorder and the recorder format make a lot of
difference.  I used S-VHS and it was OK, but Betacam (while expensive) is
much better for mastering tapes, which can then be re-recorded on any
format you want by most any video production house.

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Video taping a UNIX sreen. How?

Post by Matthew David ALDO » Tue, 14 Jun 1994 15:07:23




>> We are currently trying to do some videobased evaluation of some of the
>> systemdevelopment tools constructed in the DeVise project.

>> The problem we have is that our video equipment interfere with the screens on
>> our UNIX stations in a vrey bad way.  We have earlier made video recordings of
>> Mac and PC screens without problems with the same video equipment.

>> We are using the VHS video system and the UNIX stations are SUN-SPARC and
>> HP9000. The problem is that 2/3 of the screen is black, and that the only
>> thing it is possible to see is how many windows the user opens.
>I assume you were running the PC and Mac systems at about 640x480 and using
>a relatively cheap VGA/Mac->NTSC converter.

Do what I do. Amiga has direct NTSC/PAL video output, and the newer
models have SVHS output as well. There's a programme called DAGGEX
that runs an Xserver on the machine, etc. So you can do all
your normal unix stuff, and dump straight to video.
 
 
 

Video taping a UNIX sreen. How?

Post by John Atwo » Wed, 15 Jun 1994 01:21:55


Quote:>I assume you were running the PC and Mac systems at about 640x480 and using
>a relatively cheap VGA/Mac->NTSC converter.
>  >> Is this a correct assumption?  I read it that you were just videotaping t$
>  >> screen.  I've gotten satisfactory results doing this, though I had to find
>  >> a fast enough monitor or i'd get flicker.  I'm using Hi8.  One problem
>  >> I had was that I couldn't zoom in on a particular area of the screen;
>  >> I'm looking into close-up lenses.

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Video taping a UNIX sreen. How?

Post by Jonathan Inn » Thu, 16 Jun 1994 20:54:33


Re: Scan converter prices "They cost anywhere from $10,000 to
$25,000...", this is not true.  While the cost of a scan converter
that will work with most Unix workstations is higher, PC and Mac scan
converters can now be had for less than $1000, and as little as $300.
Actually, in the New Media magazine review of scan converters a
product called HyperConverter from PC Video Conversion claims that it
will work with some Unix ouputs and lists between $1400 and $3200
dependent on model.  I'm sure that units in the price range you
mention have additional features, but I'm sure that much usability
testing could be accomplished with the cheaper versions.  Maybe you
could use an Xterm emulator on a PC for your study and use a cheap
(under $500) scan converter...

Jon Innes
Dept. of Psychology
New Mexico State University
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