Re: pkg/54409: ffmpeg4 cannot capture video via X11grab

[coypu%sdf.org@localhost]

The following reply was made to PR pkg/54409; it has been noted by GNATS.

From: coypu%sdf.org@localhost
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: pkg/54409: ffmpeg4 cannot capture video via X11grab
Date: Mon, 5 Aug 2019 18:52:25 +0000

 The upstream discussion, including more context, is
 http://ffmpeg.org/pipermail/ffmpeg-devel/2019-July/246930.html
 
 I have encountered an error in libavdevice/xcbgrab.c that prevents NetBSD from
 using X11grab.  When xcbgrab_frame_shm calls allocate_shm, it creates a private
 shared memory region, attaches to that memory, sends the id to the server, but
 then removes the shared memory ID.  On NetBSD with xorg, this causes the
 subsequent call to xcb_shm_get_image to fail with BadShmSeg.  The fix is to keep
 the ID valid until the memory is know to be shared, after the call to
 xcb_shm_get_image_reply.  The following patch fixes the issue on my system.  It
 is untested on others.
 
 It looks like upstream expects you to send the patch with corrections as
 [PATCH v2] ...
 
 patch to mailing list development is weird, but patches do sometimes get
 applied in the end.