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

[Rostislav Pehlivanov]

On 11 March 2018 at 22:41, Mark Thompson <sw at jkqxz.net> wrote:

> ---
>  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
>
> + at item
> +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:
> + at example
> +ffmpeg -f kmsgrab -i - -vf 'hwmap=derive_device=vaapi,
> crop=960:540:480:270,scale_vaapi=format=nv12' -c:v h264_vaapi output.mp4
> + at end example
> +
>  @end itemize
>
>  @section libndi_newtek
> --
> 2.16.1
>
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On a related note, deriving a vaapi device from kms has never worked for me:
libva: va_getDriverName() failed with operation failed,driver_name=i965