bad image quality with tigervnc server

[Miroslav Vadkerti <th...@vadkerti.net>]

Hi,

I am experiencing bad image quality when connecting to my TigerVNC server
via guacamole. With the TigerVNC viewer the image is sharp. Any idea what
could be wrong? Could be that the guacamole vnc client is using wrong
encoding or jpeg transport?

Thanks,
/M

Re: bad image quality with tigervnc server

[Miroslav Vadkerti <th...@vadkerti.net>]

Hi Mike,

Thanks very much, I applied your SQL and we now have a sharp image in
guacamole :) I also found out that we see the best performance with
ultra encoding, which seems to be also what tigervnc is using.

Best regards,
/M

On Mon, May 23, 2016 at 10:07 PM, Mike Jumper <mi...@guac-dev.org> wrote:
> Hi Miroslav,
>
> It's likely that TigerVNC is using JPEG to encode the updates it send to
> Guacamole, hence the artifacts / poor quality. This will also lead to
> performance degradation, as the JPEG artifacts will decrease the efficiency
> of the PNG compression used by Guacamole for most images.
>
> You can change this behavior by explicitly setting the "encodings" parameter
> of the VNC connection(s) to a space-delimited list of encodings which does
> NOT include the "tight" encoding (the VNC encoding that uses JPEG). A
> known-good value is:
>
>     zrle ultra copyrect hextile zlib corre rre raw
>
> If you are using the database auth, I have a SQL script which updates all
> VNC connections, setting the "encodings" parameter to the above value:
>
>     https://gist.github.com/mike-jumper/35987e86c64cac389e8b
>
> This shouldn't be a problem going forward, as the default for "encodings"
> has been changed to exclude the "tight" encoding. If you're OK with building
> from git, that should solve things as well:
>
>     https://github.com/apache/incubator-guacamole-server
>
> If you follow the current version of the manual for building from git,
> beware that the manual still refers to the version of Guacamole prior to its
> migration to the Apache Incubator, so the names and URLs of the git
> repositories will be incorrect. The new repositories are all of the form
> "https://github.com/apache/incubator-guacamole-*".
>
> Thanks,
>
> - Mike
>
>
> On Mon, May 23, 2016 at 12:43 PM, Miroslav Vadkerti <th...@vadkerti.net>
> wrote:
>>
>> Hi,
>>
>> I am experiencing bad image quality when connecting to my TigerVNC server
>> via guacamole. With the TigerVNC viewer the image is sharp. Any idea what
>> could be wrong? Could be that the guacamole vnc client is using wrong
>> encoding or jpeg transport?
>>
>> Thanks,
>> /M
>
>

Re: bad image quality with tigervnc server

[Mike Jumper <mi...@guac-dev.org>]

Hi Miroslav,

It's likely that TigerVNC is using JPEG to encode the updates it send to
Guacamole, hence the artifacts / poor quality. This will also lead to
performance degradation, as the JPEG artifacts will decrease the efficiency
of the PNG compression used by Guacamole for most images.

You can change this behavior by explicitly setting the "encodings"
parameter of the VNC connection(s) to a space-delimited list of encodings
which does NOT include the "tight" encoding (the VNC encoding that uses
JPEG). A known-good value is:

    zrle ultra copyrect hextile zlib corre rre raw

If you are using the database auth, I have a SQL script which updates all
VNC connections, setting the "encodings" parameter to the above value:

    https://gist.github.com/mike-jumper/35987e86c64cac389e8b

This shouldn't be a problem going forward, as the default for "encodings"
has been changed to exclude the "tight" encoding. If you're OK with
building from git, that should solve things as well:

    https://github.com/apache/incubator-guacamole-server

If you follow the current version of the manual for building from git,
beware that the manual still refers to the version of Guacamole prior to
its migration to the Apache Incubator, so the names and URLs of the git
repositories will be incorrect. The new repositories are all of the form "
https://github.com/apache/incubator-guacamole-*".

Thanks,

- Mike


On Mon, May 23, 2016 at 12:43 PM, Miroslav Vadkerti <th...@vadkerti.net>
wrote:

> Hi,
>
> I am experiencing bad image quality when connecting to my TigerVNC server
> via guacamole. With the TigerVNC viewer the image is sharp. Any idea what
> could be wrong? Could be that the guacamole vnc client is using wrong
> encoding or jpeg transport?
>
> Thanks,
> /M
>