vnc-list-digest V1 #1272

Frank Evan Perdicaro frank "at" dsea.com
Fri, 14 Sep 2001 19:56:28 +0000


> We are trying to use Win VNC to view maps & info via a remote terminal, with
> this degree of complexity of information the update is very slow.
> What I would like to know is what is it that limits the VNC software from
> making the best available use of the bandwidth available. Our computers are
> connected via a 10MB network and yet the peak bandwidth used by VNC is about
> 11K p/sec.
> Also does anybody know how we can modify the software to make best use of
> the bandwidth available to the software.

For some time now I've thought about this problem with VNC. For a lot
longer (decade) this subject has interested me in the more general are
of human perception of computer-displayed information.

VNC, and TightVNC in particular, do a good job of squeezing information
across a pipe.  You can help the speed quite a bit by reducing the
information density of the scene (few colors, few color breaks) and
reducing the scene size (use VGA size).

To get better performance one needs to work on VNC so it prioritizes
the information _so the human on the far end gets the most important
information first_.  This is a hard problem, but the framework of VNC
permits solutions.  The brain already works this way, and the tiling
ability of VNC helps the solution a great deal.  One of my proposals
for VNC involves temporal-variable resolution and color depth.
Basically the "important" part of the screen gets drawn in lower
resolution black and white first.  Ignoring boundary conditions
associated with protocol overhead, when compared to full RGB, this
approach gives a 96:1 reduction in data volume before further
compression.

Coding this is, as they say, a tough row to hoe.  Can it be done?
Yes.  Would it work?  Yes.  
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