ffmpeg, ffmpeg-devel: Please add x11grab

[egan@…]

Please add --enable-x11grab.

[dbevans (David B. Evans)]

The legacy x11grab indev is deprecated and disabled by default in recent ffmpeg releases. Instead, it has been replaced by x11grab_xcb which does X11 frame grabbing using XCB. This indev uses the same ffmpeg command line arguements but works much better.

Per your request, I have enabled x11grab_xcb when variant +x11 is asserted for both ffmpeg and ffmpeg-devel in r131259 and r131260.

Please note, however, that X11 frame grabbing does not work as expected when the target is an XQuartz display. This is due to the XQuartz design which uses Aqua to render what appear to be X11 windows on the OS X desktop. Consequently, x11grab appears to work without error but the video returned consists of a solid black image of the requested size. This is not an error in ffmpeg and I expect that using x11grab targeting a remote X11 display of more traditional design (e.g. a Linux X11 desktop) should work correctly.

I have discussed this issue with co-maintainer jeremyhu who has been intimately involved with the XQuartz project for some time and he agrees (unfortunately) that this is the expected behavior.

If you want to grab frames from the OS X desktop, use the new avfoundation indev which returns a faithful rendition including both Aqua and XQuartz X11 windows.

For usage details of both x11grab and avfoundation, see ​https://trac.ffmpeg.org/wiki/Capture/Desktop.