[FFmpeg-devel] [PATCH] doc/filters: Add double-pass example for loudnorm

[Carl Eugen Hoyos]

2018-08-19 21:33 GMT+02:00, Marvin Scholz <epirat07 at gmail.com>:
> ---
>  doc/filters.texi | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
>
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 32c95b591c..2078ee0f6f 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -3659,6 +3659,29 @@ Set print format for stats. Options are summary,
> json, or none.
>  Default value is none.
>  @end table
>
> + at subsection Examples
> +
> +For double pass processing you need to first run the filter with
> + at code{print_format} set to either @code{json} or @code{summary}, then read
> +the values in the output and pass it to the next run of the filter:
> +
> + at example
> +$ ffmpeg -i file.mov -map 0:a -af loudnorm=I=-13:TP=-1:print_format=summary
> -f null -
> +
> +[...]
> +Input Integrated:     -9.0 LUFS
> +Input True Peak:      +1.5 dBTP
> +Input LRA:             9.4 LU
> +Input Threshold:     -19.5 LUFS
> + at end example
> +
> +Then pass the input measurements to the next run that produces the result:
> +
> + at example
> +ffmpeg -i file.mov -af
> loudnorm=I=-13:TP=-1:measured_I=-9.0:measured_TP=1.5:measured_LRA=9.4:
> measured_thresh=-19.5:print_format=summary out.mov

I believe it should be "ffmpeg -i input"
Why does the first run output to null but the second to mov?

Carl Eugen