[rescue] Video Creator

[joshua d boyd]

On Thu, Jul 12, 2001 at 10:23:49AM -0400, Big Endian wrote:
> >http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1254650585
> >
> >Has anyone ever looked at these things?  It seems to me that it takes a
> >video signal in via RGB BNC connectors, then converts it to YUV, makes in
> >the proper scale (via scaling or cropping), and then output to video.  My
> >theory is that this whole process is controlled via the SCSI bus, although
> >I wonder why SCSI (as opposed to serial) since it seems that it would only
> >need a few control commands, as opposed to constant bandwidth.  Can anyone
> >verify that this is correct?
> >
> >If that is correct, then couldn't a person use a couple of those to drive
> >multiple video displays from one AGP video card the way the MCO does for
> >the Onyx?  Shouldn't reverse engineering what passes over the scsi bus to
> >control the thing be fairly simple?
> 
> These are basically sgi video -> ntsc translators so that you can 
> take the output of a Power series machine and dump it to tape.  The 
> VLAN port is for controlling special (read EXPENSIVE) vcrs that could 
> be made to record at frame by frame.  This is from when machines were 
> too slow to render things in real time for tape.  The MCO is 
> something completely different.  It reads direct from the framebuffer 
> itself not the output of the card.  Theoretically one could build an 
> MCO to work with modern AGP video cards (2048x1152 or some other 
> insane resolution) by doing the same segmentation of the video signal 
> but it wouldn't be worth it. All Pentium II class PCs have the 
> ability to use multiple PCI video cards in addition to an AGP card. 
> The MCO came about because it was the only way to get multiple lower 
> rez signals out of an onyx in a cost effective manner.

So, we've established that the MCO reads from the frame buffer and splits
the framebuffer for additional images.  Already knew that.  

You are not saying anything terribly new about the Video Creator.  What
does commenting about it's VLAN port have to do with anything?  The
question was, is SCSI used only for controlling the settings, and I guess
also the frame advance, stop, etc, VLAN features.  If so, any ideas why
SCSI instead of serial.  Also, if Matrox cards can be used to drive old
SGI monitors, why couldn't a matrox card with a few video splitters and a
few of these boxes be used to get the same end effect of the MCO.  IE,
split the matrox output out to each box.  Then, use the cropping features
of the Video Creator boxes to pick out a different part of the 1280x1024
video signal from the matrox for video output.

Now, why do this instead of PCI video cards?  Because PCI sucks.  And
having multiple video cards sucks.  If you need 64megs for textures, then
each PCI card needs 64megs for textures, but the chances are that these
textures are the same (assuming that the multiple video streams are
something like different views of the same scene), so why not have the
textures all on one card?  Further, to get the same bandwidth for moving
stuff from memory or the CPU to the video cards, you would need 4
different PCI buses to be able to drive 4 different PCI cards as well as
one AGP bus can drive one video card rendering to four displays (which is
why a multihead AGP card is far better than a single AGP and a single
PCI).

OK, so maybe it would be over kill to use these boxes.  After all, you can
buy quad head g200 cards and run it in low resolution.  But, quad g200s
cost a furtune, and G200s don't have much texture memory, and I don't
think that a G200 can drive a 640x480 display as well as an NVidea
Geforce2 can drive a 1280x1024 display.

-- 
Joshua D. Boyd