[Spice-devel] Spice console pixelated noise on display changes

[Christophe Fergeau]

On Tue, Jul 17, 2018 at 09:15:05AM +0200, Mitja Mihelič wrote:
> 
> 
> On 12/07/2018 18:01, Christophe Fergeau wrote:
> > Hey,
> > 
> > On Wed, Jul 11, 2018 at 10:45:08AM +0200, Mitja Mihelič wrote:
> > > Answering the question for posterity.
> > > We found a temporary solution to the described problem.
> > > We had an oVirt development cluster with a working SPICE console. By
> > > comparing packages we have established the differences between working and
> > > not working SPICE setup. We have isolated the spice-server package.
> > > The installed version was spice-server-0.14.0-2.el7_5.3.x86_64
> > > We downgraded the package to spice-server-0.12.8-2.el7.1.x86_64 and rebooted
> > > the nodes in sequence.
> > > Now the SPICE console works again.
> > Hmm so this is an interesting report. This indicates a regression
> > between 0.14.0 and 0.12.8, which we want to avoid. I was able to
> > reproduce without ovirt on a fedora 28 host/guest/client, and to bisect
> > it to spice-server commit f401eb07 "dcc: Rewrite dcc_image_compress".
> > 
> > This commit introduced a behaviour change, where in some cases images
> > which were previously compressed with QUIC would be uncompressed. These
> > uncompressed images have an image stride which is bigger than the image
> > width, and spice-html5 does not seem to be handling image strides at
> > all, giving this pixelated look. So in the end, it's a spice-html5 bug,
> > but it's good there was this bug, as this pointed out a spice-server
> > regression ;)
> > 
> > I think you should be able to avoid the problem if you manage to force
> > the compression to quic
> > (<graphics> <image compression='quic'/> </graphics> in your VM XML).
> > This is hopefully possible with a ovirt hook (?)
> > 
> > Christophe
> Thank you for looking into it.
> Currently it does not make sense for us to introduce such fixes into our
> environment. I assume that altering the XML will require a reboot of each
> VM, which we cannot do at our leisure.

Yes, the suggested workaround requires a shutdown/restart of the VM.
Alternatively, you could look at adding support for 'preferred
compression' to the spice-html5 client, or fix that issue with
uncompressed bitmaps and a stride.

Christophe
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/spice-devel/attachments/20180719/99e3db86/attachment.sig>