doc/indevs.texi | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/doc/indevs.texi b/doc/indevs.texi
index 6951940a93..02d1cb3d86 100644
--- a/doc/indevs.texi
+++ b/doc/indevs.texi
@@ -462,6 +462,14 @@ Capture from CRTC ID 42 at 60fps, map the result to VAAPI, 
convert to NV12 and e
 ffmpeg -crtc_id 42 -framerate 60 -f kmsgrab -i - -vf 
'hwmap=derive_device=vaapi,scale_vaapi=w=1920:h=1080:format=nv12' -c:v 
h264_vaapi output.mp4
 @end example
+To capture only part of a plane the output can be cropped - this can be used 
to capture
+a single window, as long as it has a known absolute position.  For example, to 
+and encode the middle quarter of a 1920x1080 plane:
+ffmpeg -f kmsgrab -i - -vf 
'hwmap=derive_device=vaapi,crop=960:540:480:270,scale_vaapi=format=nv12' -c:v 
h264_vaapi output.mp4
+@end example
 @end itemize
 @section libndi_newtek

ffmpeg-devel mailing list

Reply via email to