vnc+vic=better relay?

Jeff Long long at
Mon Oct 9 16:55:54 CDT 2000

Michael Grobe wrote:
> rdo, et al.:
> i think vnc is a great AG tool, especially when coupled with the
> unix-based VNC relay, but it works with unicast and so generates
> beau coup net i was thinking it would be nice to
> modify it to use multicast... at least when running in listen-only mode.....
> but an unguarded moment...i thought...why not run a VNC client
> on a unix box and use the X11 "device" in vic to muliticast the VNC
> screen to the world....(this would be especially nice if the "raw"
> codec were used, but perhaps that's not necessary).
> the only problem with this is that the X11 device shows only that
> portion of the screen within 0,0 and 100,100 pixels (or so)...
> and even though the menu offers to change this region, it does not.
> i'm wondering if this region can be changed by some X magic i don't
> understand, or, if not, whether the source can be hacked to enlarge
> the area to something more useful...say 1240x800 or so....

As I work for Michael I was asked to look into this and here's what I
know and/or found:

The X11 grabber device can currently encode using the h261, h263+, h263,
bvc, and pvh codecs.

h261 max size is CIF (352x288) which is not big enough for Michael.

h263 max size is CIF16 (1408x1152) but vic only supports up to CIF :-(

I don't know what the bvc and pvh protocols are but pvh appears unusable
from my testing.

bvc doesn't appear to have size restrictions associated with it but the
source code for vic is not amenable for easily changing the amount of
display space captured by the X11 grabber device (perhaps the position
could be changed though?).

Also, the source code for vic does indicate that a developer was working
on adding support for allowing users to select regions of the X11
display to be captured along with picking entire windows to be
captured.  At this point I have no idea on how close they were to
obtaining this goal.


Jeff Long
University of Kansas

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