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

[Cecil Westerhof]

Michael Koch <astroelectronic at t-online.de> writes:

> Am 02.06.2023 um 08:39 schrieb Cecil Westerhof via ffmpeg-user:
>> German Geraskin <german.geraskin at gmail.com> writes:
>>
>>>> I have videos where the audio is mostly reasonable good, but sometimes
>>>> the wind creates havoc. Is there a way to dial the volume a good deal
>>>> down for those parts only?
>>>> It would be even better if that could be down in say half a second
>>>> instead of at once.
>>> Hi, Cecil
>>>
>>> You can use the volume audio filter.
>>> Example for Linux version of ffmpeg:
>>>
>>>    -af volume=0.5:enable='between(t\,26.12\,28.64)'
>>>
>>> It means - set volume to 0.5 between 26.12 and 28.64 seconds.
>> Thanks, I will try it out. I can do this several times?
>> This is abrupt, there is no possibility to do it smooth?
>
> I have added an example with start and stop ramps in chapter 3.5 of my book:
> http://www.astro-electronic.de/FFmpeg_Book.pdf
>
> If someone finds a simpler solution, please let us know.

This is abrupt. (It is better as nothing.) I would prefer it to slide
to for example 25% and a the end slide back to 100%. Something like:
    -                        -
     -                      -
      -                    -
       -                  -
        -                -
         ----------------

I understood I should do something with:
    http://ffmpeg.org/ffmpeg-all.html#Expression-Evaluation

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof