gdigrab does not get correct monitor resolution on hidpi device when grabbing desktop

[umansky]

Summary of the bug: On a hidpi device such as a touchscreen tablet, running Windows 7, attempting to grab the desktop when the DPI setting is set to a number higher than 100% in Control Panel\Appearance and Personalization\Display results in a cropped video and does not grab the entire desktop.

If I set the DPI setting back to 100%, gdigrab correctly gets the right resolution, but this is undesierable as text is practically impossible to read.

How to reproduce:

% ffmpeg.exe -f gdigrab -i desktop video.mp4 -report
ffmpeg version N-68881-ga79ac73 Copyright (c) 2000-2015 the FFmpeg developers
  built on Jan  5 2015 22:02:22 with gcc 4.9.2 (GCC)

This reports the resolution of the tablet as 1280x800, when the actual resolution of the screen is 1920x1200.

If I give it the -video_size flag to be the actual resolution of the monitor, it says I've gone out of bounds.

[umansky]

Full ffmpeg report output from the command.

[umansky]

Also, just as an extra bit of info, 150% of 1280 is 1920, which points directly to this being related to the DPI setting.

[Cigaes]

Why do you talk about percentages and DPI setting together?

[umansky]

This is the setting that fixes/breaks gdigrab on the hidpi device. At 100%, it works, at higher values (the tablet where I'm having the issue is on 150% by default) it reports an incorrect resolution.

[Roger Pack]

Hope to still get to this :) ​https://www.mail-archive.com/ffmpeg-devel@ffmpeg.org/msg20334.html

[Roger Pack]

OK hopefully fixed in ​https://github.com/FFmpeg/FFmpeg/commit/e82883aa88bfccf2669e914eab9deef6cecfd0db please report back and reopen if not.