can VNC transmit pc- television pictures?

Seak, Teng-Fong tfseak "at" futurmaster.com
Mon Mar 8 11:17:00 2004


> -----Message d'origine-----
> De : vnc-list-admin "at" realvnc.com [mailto:vnc-list-admin "at" realvnc.com] De
la part de
> Jonathan Lennox
> Envoye : mercredi 3 mars 2004 21:40
> A : vnc-list "at" realvnc.com
> Objet : RE: can VNC transmit pc- television pictures?
> 
> On Wednesday, March 3 2004, "Seak, Teng-Fong" wrote to
"<vnc-list "at" realvnc.com>"
> saying:
> 
> > 	The highest ADSL rate I know of is just 2Mbps while the usual
> > entry-level is just about 128 kbps.  And even at 2Mbps, nothing can
> > guarantee a constant rate.  I don't know how much VNC can compress,
but
> > since it has to be a lossless compression, it can't be very high.
> 
> It doesn't *have* to be.  TightVNC has a JPEG mode.

	Really!?  That's interesting.  But I suppose it has to use the
lowest compression rate or the displayed screen would become quite ugly.
OTOH, compression is efficient only when there are a lot of data.  But
VNC updates squares of pixels (is it 32x32 ?).  With this small size,
and in order to keep a relatively neat result, it seems that a
compression rate of about 40% is needed.  This is, moreover, based on a
24-bits images.  Jpeg is applicable high or full colour images, right?
So, maybe compression could just partially help to reduce network
traffic.

> It'd be an interesting research project to try to auto-detect
on-screen
> video, and use a real-time video codec to transmit over VNC.
Presumably not
> going to happen any time too soon, though.
> 
> --
> Jonathan Lennox
> lennox at cs dot columbia dot edu