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

[Mitja Mihelič]

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.
We will keep the current working setup and wait for an update.

Kind regards, Mitja