scan converters

Jason Leigh spiff at
Wed Jul 5 21:30:35 CDT 2000

	Cray is an IR Onyx with a Sirius option. I don't believe the Sirius option
was necessary for what we did as the IR's have composite out. In any case
the video control panel (vcp) has a tool that lets you either deliver
regular NTSC rez images or scan convert the entire screen down to NTSC. We
did not have it scan convert the full screen. Instead we ran in CAVE
simulator mode at 640x480.
The video tool also has an anti-flicker option (which we turned on) so that
single pixel horizontal lines do not flicker when displayed in NTSC.

During the demo we tried as little as possible to move around or else the
graphics would particalize into boxes. I recall when we did the same thing
at the Corridor1 meeting several months before the Chautauqua we also had to
turn transmission rate/quality up on our AG node or else the image would
lose a lot of its color at the receiving end.


Jason Leigh, PhD
spiff at              Electronic Visualization Lab (M/C 154)
EVL Phone (312) 996-3002         University of Illinois at Chicago
EVL FAX   (312) 413-7585         851 S. Morgan St. Room 1120 SEO     Chicago, IL 60607-7053

> -----Original Message-----
> From: Allan Kenneth Spale [mailto:aspale1 at]
> Sent: Wednesday, July 05, 2000 12:21 PM
> To: Michael Grobe
> Cc: ag-tech at; ag-tech at
> Subject: Re: scan converters
> Michael,
> During the June Chatauqua, EVL displayed a video stream that
> ported video
> directly from a Cray to the video capture card.  We did not have any
> serious trouble related to capturing and maintaining the video stream.
> The video quality was good, too.  Maybe someone else at EVL would
> be able to comment more on this subject as I am only a node operator.
> Allan
> On Tue, 4 Jul 2000, Michael Grobe wrote:
> > hello:
> >
> > the various complexities of using VNC for screen-sharing demos
> > got me to thinking about alternatives.
> >
> > has anyone tried using scan converters for these demos?
> > that is, in more detail:
> >
> >    use a scan converter to take the VGA signal from a laptop
> >    or workstation and convert it to composite video for the
> >    video capture card for normal broadcast over the grid.
> >
> > this would be MUCH simpler than the VNC approach (especially the
> > bi-level VNC approach invented by eric).  i suppose it would
> > be considerably lower resolution, so it would be unusable for
> > some demos or PPT slide sets.
> >
> > i have found a cheap scan converter...well, relatively cheap...
> > $495 list price...i have a call in to see about an edu discount.
> > for similar quality (VSC-75 or VSC-100) the Extron edu price
> > appears to be about $1000.
> >
> > the product is the CORIOscan Select from (
> > (up to 1024x768, composite, s-video, and RGB output, ntsc and pal
> > switchable, scan rates up to 100KHz, etc.)
> >
> > if nothing else this MIGHT make a reasonable backup tool for VNC
> > and dPPT, if it isn't good enough for general use.
> >
> > :michael grobe
> >

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