Subject: Hi res video on 100MB mbone.

From: [email-masked]
Date: Mon, 20 Jul 1998 21:02:29 -0500

I need to deliver full rate(around 30fps) full rez (640x486) 256 
     shades of gray video from one Octane, to several O2's on the same 
     physical 100BaseT network.  I have looked at VAT, but it's CIF max 
     resolution is not suitable for my problem.  Does anyone have any 
     knowledge about what it takes to do this?  Any hints are welcome.
     Somebody has had to have done this before.

     THanks,
     Doug

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From: "Christophe Tronche" <[email-masked]>
Date: Tue, 21 Jul 1998 22:46:55 +0200 (MET DST)

>      Somebody has had to have done this before.

I've done this with Linux PCs (at half your speed, but the Octane
should have no problem). This surely sounds crazy, but I used ANIMATED
GIF (produced by a specialized web server). The full (uncompressed)
image needs about 100 Mb/s. With the usual GIF compression ratio on
digitized image of 1/4 to 1/8, you should be able to feed 4 to 8
stations (if no-one else transmits)...

-- 
Christophe Tronche		[email-masked]
Tel: (33) 01 47 40 28 48	Fax: (33) 01 47 40 28 65

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From: Magnus Danielson <[email-masked]>
Date: Wed, 22 Jul 1998 00:44:18 +0200

>>>>> "DM" == DOUGLAS MASHEK <[email-masked]> writes:

Hi!

 DM>      I need to deliver full rate(around 30fps) full rez (640x486) 256 
 DM>      shades of gray video from one Octane, to several O2's on the same 
 DM>      physical 100BaseT network.  I have looked at VAT, but it's CIF max 
 DM>      resolution is not suitable for my problem.  Does anyone have any 
 DM>      knowledge about what it takes to do this?  Any hints are welcome.
 DM>      Somebody has had to have done this before.
     
Once upon a time in a galaxy not that far away we used to do similar
things with Indy's and Indigo 2's equiped with the Cosmo Compress
card(s). They did hardware JPEG compression/decompression using C-cube
CL-460 JPEG chip. Due to curcomstances (no spare slot in the Indy!) we
could not run more than 10 Mbps, but the cards where capable of more.

We had a special hack being cooked up that more or less only set up
things and transported the compressed data on and off IP/UDP
packets. There where also an rate adaption routine that kept the
transission rate to an acceptable level not to drop anything.

This was a research tool that where used in various transmissions and
it could do multicast as well. We ran in in PAL, but minor adaptions
would make it run NTSC as well. We are talking about full frame rate
in both cases.

Not being a close followers on SGIs hardware development I can't say
exactly which box that has appropriate hardware, but I guess that
there is suitable options for it. I know that there where some efforts
to transfer the research hack onto the O2 hardware but I don't know
what happend.

A few experiences from these exercises says that it is will matter
what kind of hardware one used, some didn't cut it but produced
mediocre output even if they where quite expensive, the Cosmo cards
where steady as a rock for us.

You should have the bandwidth, but somewhere below 10 Mbps it is worth
to reduce transfered resolution and interpolate at the output end, if
you give it some 30-40 Mbps it should not be much of a consideration.

The research hack was quite simple and most of the magic where in the
rate adaption. Much of the other code where collected bits and pieces
blended with quickies. I think I can dig it up, if necessary.

The user interface where very rough and left a lot of things to be
done (rude tty only control), but it was enougth for our purposes.

Cheers,
Magnus