[FFmpeg-trac] #9425(undetermined:new): x11grab fails to adjust to framebuffer resolution changes

[FFmpeg]

#9425: x11grab fails to adjust to framebuffer resolution changes
-------------------------------------+-------------------------------------
             Reporter:  Mykola       |                     Type:  defect
  Mokhnach                           |
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:

 OS: Linux vm 5.11.0-22-generic #23-Ubuntu SMP Thu Jun 17 00:34:23 UTC 2021
 x86_64 x86_64 x86_64 GNU/Linux

 ffmpeg version 4.3.2-0+deb11u1ubuntu1 Copyright (c) 2000-2021 the FFmpeg
 developers
   built with gcc 10 (Ubuntu 10.2.1-20ubuntu1)
   configuration: --prefix=/usr --extra-version=0+deb11u1ubuntu1
 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu
 --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl
 --disable-stripping --enable-avresample --disable-filter=resample
 --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-
 libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-
 libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig
 --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm
 --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-
 libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse
 --enable-librabbitmq --enable-librsvg --enable-librubberband --enable-
 libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-
 libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-
 libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack
 --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid
 --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal
 --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx
 --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883
 --enable-nvenc --enable-chromaprint --enable-frei0r --enable-libx264
 --enable-shared
   libavutil      56. 51.100 / 56. 51.100
   libavcodec     58. 91.100 / 58. 91.100
   libavformat    58. 45.100 / 58. 45.100
   libavdevice    58. 10.100 / 58. 10.100
   libavfilter     7. 85.100 /  7. 85.100
   libavresample   4.  0.  0 /  4.  0.  0
   libswscale      5.  7.100 /  5.  7.100
   libswresample   3.  7.100 /  3.  7.100
   libpostproc    55.  7.100 / 55.  7.100
 Hyper fast Audio and Video encoder

 How to reproduce:

 1. Install Xvfb and x11vnc on Ubuntu
 2. Configure the virtual framebuffer:
 % Xvfb :95 -screen 0 1920x1080x24
 % x11vnc -display :95 -forever -shared
 3. Add more supported resolutions to the framebuffer:
 % xrandr -d :95 --newmode "1024x768" 63.50  1024 1072 1176 1328  768 771
 775 798 -hsync +vsync
 % xrandr -d :95 --addmode screen "1024x768"
 % xrandr -d :95 --newmode "1440x900" 106.50  1440 1528 1672 1904  900 903
 909 934 -hsync +vsync
 % xrandr -d :95 --addmode screen "1440x900"
 4. Start ffmpeg recording on the created display:
 % ffmpeg -y  -f 11grab -framerate 4 -r 4 -i :95.0 -filter_complex
 "[0:v]split=2[ts][capture];[ts]setpts=time(0)*FR[ts];[capture]scale=1280:960:force_original_aspect_ratio=decrease:eval=frame,pad=1280:960:-1:-1:color=black[capture]"
 -map "[ts]" -vsync 0 -flush_packets 1 -f 'mkvtimestamp_v2 output_ts.txt
 -map "[capture]" -c:v libx264 -tune zerolatency -preset veryfast -fflags
 nobuffer -pix_fmt yuv420p -movflags +faststart -f mp4 output.mp4
 5. Change the display resolution while the recording is running:
 % xrandr -d :95 -s "1024x768"

 Actual result:
 ffmpeg quits recording. the following output is observed in the log:
 [x11grab @ 0x55bc5ca9c980] Cannot get the image data event_error:
 response_type:0 error_code:8 sequence:130 resource_id:23068672
 minor_code:4 major_code:130.
 [x11grab @ 0x55bc5ca9c980] Continuing without shared memory.
 [x11grab @ 0x55bc5ca9c980] Cannot get the image data event_error:
 response_type:0 error_code:8 sequence:131 resource_id:1294 minor_code:0
 major_code:73.
 :95.0: Permission denied

 If I set framebuffer resolution to a greater value than the inital one
 then the issue above is not being observed, although the video content
 does not get scaled properly and is cut off to the initial dimensions

 Expected result:
 The video must be properly scaled/padded after the resolution change, so
 the content of the full screen is always visible there.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9425>
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