Single-frame video recording from an Iris

[sabbagh]

In article <1990Nov12.193845.11889 at cs.umn.edu> slevy at poincare.geom.umn.edu (Stuart Levy) writes:
>It *might* be possible to live without the genlock board altogether.
>We run the Iris as the master sync generator, and as far as I can tell,
>the genlock board isn't giving us much except a separate sync output.
>We should be able to use the Iris' built-in video generator -- the one
>that's switched by ``setmonitor(NTSC);/setmonitor(HZ60);'' and have the
>sync-on-green signal drive the rest of the video equipment.  The Sierra Video
>transcoder has a (solderable?) jumper option to use sync-on-green, and the
>other hardware might work with it.  I haven't tried this however!

We here at the Courant Institute have successfully made single frame recordings
without a genlock board.  Our equipment consists of:

	SGI Personal Iris
	Lyon-Lamb Color Encoder
	Vas IV video controller
	Sony 3/4" video tape recorder.

I do not know any of the prices; I am just a mere graduate student and
am listed as a peripheral myself :-).  

The basic technique is as follows:  we take the RGB output from our personal
Iris and plug it into the Lyon-Lamb's RGB input.  This encoder supports 
sync on green without no jumpering or anything; just don't plug in a sync
signal. Any IRIS using the suggestively named (???) de3 board to generate
its video output for the monitor may be used in this fashion.  Note that 
there is no way to view images on the video monitor and send them to the
equipment at the same time.

To switch from 60 hz hi-res to RS-170, with sync on green:

	setvideo(DE_R1,(long) DER1_170 | DER1_SYNCG);

To switch back to 60 hz (so you can use your monitor again):

	setvideo(DE_R1,(long)DER1_60HZ | DER1_SYNCG);

This works, and produces better picture quality than the composite NTSC
output from the genlock board (suggestively named cg2).  

According to the documentation (???) provided by Silicon Graphics, the
best possible output ("broadcast quality") is obtained by using the genlock
board to receive an sync signal generated by your encoder.  We have not
tried this; when we do, we will post our results.

The single frame recording is accomplished by treating the VAS IV controller
as a tty; you send ASCII character sequences as commands, and it sends them
back as status indications.  This is connected through an RS-232C connection
from serial port 2;  make sure to chmod ugo+rwx /dev/ttyd2 for this to work.

Hadil G. Sabbagh
E-mail:		sabbagh at cs.nyu.edu
Voice:		(212) 998-3125
Snail:		Courant Institute of Math. Sci.
		251 Mercer St.
		New York,NY 10012

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