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[FFmpeg-devel,v2,7/7] doc/indevs: Add example using cropping to capture part of a plane

Message ID 20180321231236.3024-7-sw@jkqxz.net
State New
Headers show

Commit Message

Mark Thompson March 21, 2018, 11:12 p.m. UTC
 doc/indevs.texi | 8 ++++++++
 1 file changed, 8 insertions(+)
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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 capture
+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