[FFmpeg-user] Dim audio in parts where there is a lot of wind

[Michael Koch]

Am 03.06.2023 um 11:49 schrieb Cecil Westerhof via ffmpeg-user:
>
> I did it with:
>      inputfile=00096.MTS
>      outputfile=00096.mkv
>      start=31
>      end=44
>      ramp=1.5
>      volume=0.05
>      volumeCmd="
>        '
>          lerp(1, ${volume}, (t - ${start}) / (${ramp}))
>          *
>          between(t, ${start}, ${start} + ${ramp})
>
>          +
>
>          lerp(${volume}, 1, (t - ${end} + ${ramp}) / (${ramp}))
>          *
>          between(t, ${end} - ${ramp}, ${end})
>
>          +
>
>          ${volume}
>          *
>          bitand(gt(t, ${start} + ${ramp}), lt(t, ${end} - ${ramp}))
>        '
>        :enable='between(t, ${start}, ${end})'
>        :eval=frame
>      "
>
>      ffmpeg -i ${inputfile}           \
>             -vcodec copy              \
>             -af "volume=${volumeCmd}" \
>             -y ${outputfile}
>
> The distortion by the wind was very loud, so the volume needed to be
> set very low.
>
> I think it is not necessary at the moment, but what if there are
> several parts in the video where the audio has to be dimmed?
>

That's very easy with the other solution with sendcmd, where the times 
and ramps are defined in a text file.

Michael