Re: [Qemu-devel] Sensible VNC encodings

[Johannes Schindelin]

Hi,

On Wed, 21 May 2008, Anthony Liguori wrote:

> Johannes Schindelin wrote:
>
> > On Tue, 20 May 2008, Anthony Liguori wrote:
> >
> > Clearly, you have never waited one minute for a full screen update 
> > from a machine half around the planet.
> >
> > That is what happens here with hextile + an compressed SSH tunnel, 
> > just in case you thought this was pure speculation.
> >
> > It is pretty obvious why, too: generic compression, such as SSH's, 
> > will never outperform specialized compression, such as tight 
> > compression.
> 
> Tight uses zlib compression in combination with a palette mechanism.  
> Hextile is a palette mechanism so adding zlib compression to it (via 
> ssh) makes it pretty comparable to Tight.

I'm awfully short on time, so this is only a hint to the explanation:

Tight compression can fall back to a Jpeg scheme which is lossy.  You 
obviously did not know that, and obviously this is what I have to use to 
make VNC usable.

Hth,
Dscho