[FFmpeg-user] Audio normalization using "volume" and "compand"filters

[Thierry Lelegard]

> De: "Paul B Mahol" <onemda at gmail.com>
> On 11/27/13, Thierry Lelegard <thierry.lelegard at free.fr> wrote:
> > Le 27/11/2013 21:49, Paul B Mahol a ecrit :
> >  > On 11/27/13, Thierry Lelegard <thierry at lelegard.fr> wrote:
> >  >
> >  >> Second problem: The usage of the filter "compand" is extremely
> >  >> obscure.
> > Its
> >  >> documentation (http://ffmpeg.org/ffmpeg-filters.html#compand)
> >  >> can hardly
> > be
> >  >> understood if you do not already know the meaning of each
> >  >> parameter.
> > See
> >  >> below some tests I made without deeply understanding what they
> >  >> mean.
> >  >>
> >  >> [....]
> >  >>
> >  >> Could someone please explain how to use "compand" and its
> >  >> parameters?
> >  >>
> >  >> More precisely, how can we compress an input audio with the
> > characteristics
> >  >> in_rms and in_peak into a given target out_rms and out_peak?
> >  >
> >  > compand filter is port of sox effect filter of same name.
> >  > I really doubt that its documentation is obscure.
> >
> > This is of course a subjective matter. To make it more objective,
> > the
> > following
> > is a complete copy/paste of the "compand" documentation from
> > http://ffmpeg.org/ffmpeg-filters.html#compand
> 
> Why are you pasting documentation? To show you can copy & paste?

No, it was to show you the documentation because when you wrote
"I really doubt that its documentation is obscure" it was obvious
you did not read it.


> > Honestly, how can you get an answer to the above question ("how can
> > we
> > compress an input audio with the characteristics in_rms and in_peak
> > into
> > a given target out_rms and out_peak?"), using this when you are not
> > an
> > expert in audio engineering?
> 
> rms and peak are calculated using whole file, so whatever you are
> trying to do you are doing it wrong.

I know that what I am doing is wrong. Otherwise I would get the expected
result and I would not have posted on the list in the first place.

Considering that my question was somewhat specific ("how can we
compress an input audio with the characteristics in_rms and in_peak
into a given target out_rms and out_peak?"), it would be more
constructive to provide an answer. Simply replying "you are wrong"
brings no information since we all already know that.

-Thierry