[FFmpeg-trac] #8744(avdevice:new): Transparency problem when capturing a window with gdigrab

FFmpeg trac at avcodec.org
Thu Jun 18 20:50:03 EEST 2020

#8744: Transparency problem when capturing a window with gdigrab
             Reporter:  sacereda     |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:  avdevice
              Version:  git-master   |               Resolution:
             Keywords:  gdigrab      |               Blocked By:
  alpha                              |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |

Comment (by sacereda):


 If I open the attached copy-rawvideo.bmp file with xnview or similar, most
 of pixels have alpha component to zero. Format is detected as BGRA, but
 some parts of the window are "covered" (alpha 0) and doesn't reproduce the
 original content (check gdigrab-transparency.jpg)

 You can reproduce it both with ffplay and ffmpeg:

 % ffplay -f gdigrab -i "title=Documents"

 % ffmpeg -f gdigrab -i "title=Documents" -vframes 1 output.png

 In our software (using ffmpeg 4.0), we handle alpha channel and the
 behaviour is the same as in ffplay.

 Let me know if you need further info, or if I can help in any way.

Ticket URL: <https://trac.ffmpeg.org/ticket/8744#comment:7>
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