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

[Paul B Mahol]

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?

>
> 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.

>
> The description of the function transfer using the "points" is not clear.
> Especially when the experimentation gives results which seem inconsistent.

I can not find where you posted valid proof of such statement.

> I do not mean that the filter does not work well. I mean that the way it
> works using the parameters is far from clear. This is why I am looking for
> help in this list.
>
> Thanks,
> -Thierry

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