Re: [Qemu-devel] Re: Spice and legacy VGA drivers

[Izik Eidus <ieidus@redhat.com>]

On Sat, 12 Dec 2009 11:35:24 -0600
Anthony Liguori <anthony@codemonkey.ws> wrote:

> Izik Eidus wrote:
> > What you mean? how can it compress it? or what method?
> >
> > When there is no driver installed, we use compression that based on
> > LZ...
> >   
> 
> Okay, that's what I was asking.  I'm curious because during guest 
> installation, I assume that even if you're using QXL, you are still 
> stuck in VESA mode.


Correct.

> 
> I'm curious if LZ on it's own is significantly different than some of 
> the vnc encodings.  Both ZRLE and Tight have some pre-encoding 
> techniques that introduce a palette and in the case of Tight, also 
> support efficient gradient encoding.  The idea is that you end up
> with much more compressable data this way.
> 
> It's the sort of thing I think would be interesting to measure.  I
> think being able to use VNC style encodings could also be interesting
> for Spice in order to improve this "legacy mode" use-case.


That specific area in spice will be changed very soon due to new
requiments that the offscreens will add.
Windows direct draw allow modifying offscreen (or even primary)
surfaces using a pointer giving to the user, this mean we can`t know
what parts of the surface was changed... (In some modes the primary
screen can be changed without we know about this)

We already thought about few algorithems we might want to add to spice
to better address this "changed without notifications surfaces", But it
is still not in a state I can confirm in what direction we will go in
the end (We still need to test most of the cases to know what fit us
best)

Thanks.

> 
> Regards,
> 
> Anthony Liguori
> 
>