fullscreen video cropped on high-dpi screen

[Andreas E.]

On high-dpi screens when the global scaling factor is set to 2, a fullscreen video is records only a fraction of the screen. Kazam does not read the real screen dimensions in device-pixels (1600×900 instead of 3200×1800), but it sets the coordinates of the recorded area in device pixels (1600×900 = one fourth of the screen).

org.gnome.desktop.interface.scaling-factor = 2
kazam: 1.4.3-0ubuntu1
operating system: Ubuntu 14.04 / Unity

[Jose Gómez (adler-dreamcoder)]

As a consequence of this issue, image screenshots are saved in low resolution (1600x900 instead of 3200x1800), so they look blurry.

[David Klasinc (bigwhale)]

Hi, thanks for your report. Right now I don't have such screen available for testing, so if you could run kazam with --debug switch and attach the output here, I'll greatly appreciate it.

[Andreas E. (andreas-e)]

Thanks for looking into the issue.
I believe there is nothing special about the display that could not be simulated by setting the UI scale to 2 in Ubuntu control center.

Attached is a log from doing a full screen capture (only the upper left screen quarter was recorded).

[Andreas E. (andreas-e)]

Indeed, screenshots take the whole screen, but with half resolution (like gnome-screenshot 3.10, but unlike gimp 2.8.10 which takes full resolution).

[ALinuxUser (buntulongername-new)]

I thought Kazam was really good - until I encountered this problem. It makes the video recording unusuable on HiDPI systems, sadly. I tried Kazam on Linux Mint 19.1.

[Michael Zanetti (mzanetti)]

So... It doesn't look like this is ever going to be fixed, seeing this bug report is 6 years old now... Anyone aware of an alternative? Simplescreenrecorder has the same issue sadly...

[Sergio Llorente Romano (sllorente)]

The problem is easily solved by using the function "get_monitor_scale_factor" from Gdk.screen object of the Gtk library.

I have stored the value returned by that function in the elements of hw.screens. Then i have used that value in the funciont "setup_video_source" in gstreamer.py for fix the values of startx, starty, endx and endy.

Please, see the patch attached.

[Joseph (joeyave)]

Any updates?

[nymea (nymea)]

Confirming that the patch by sllorente is working fine. Thanks a lot.

[Mohan (vivek-mohanraj)]

the patch by sllorente is working and was helpful to me. thanks.

[Sergio Llorente Romano (sllorente)]

Updated patch (the previous patch caused an error when trying to capture "all screens"). Now it is only necessary to patch the file "backend/prefs.py"

[Ubuntu Foundations Team Bug Bot (crichton)]

The attachment "Patch for taking into account scale factor in HiDPI screens" seems to be a patch. If it isn't, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are a member of the ~ubuntu-reviewers, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issues please contact him.]

[Christopher Field (volks73)]

I did not use the patch from sllorente because I found this blog post, https://mlisi.xyz/post/kazam/, before finding this issue, but it appears to do the same fix. I modified both the `gstreamer.py` and `prefs.py` files. This worked for me after experiencing the exact same problem.