Complex Change of Amplitude

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Complex Change of Amplitude

Sebastian Schumacher
Hey guys!

I need to change the amplitude (-v volume) of a mp3 file. That is not really a challenge, but I need to change the amplitude in one file at several "points". Is there a solution for that? Can I say, for example, that the change of volume should take place at 0:45, the next at 0:55 and so on?

I tried to trim the file to edit its segments apart, but it does not really work, because the merged output has a strange and unexpected "zero amplitude" of about approx. 0.060 sec. between the "merge points", caused by sox. 

Thank you for your help!
Sebastian

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Re: Complex Change of Amplitude

Ari Moisio-2
Hi

One solution is to split the file with mp3splt or similar into parts of
different amplitudes, then apply mp3gain for each part and then  join
all the pieces back to one file.

This avoids audio deteration due of  uncompress and recompress cycles.



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  Sebastian Schumacher kirjoitti

> Subject: [SoX-users] Complex Change of Amplitude
> Date: Fri, 21 Aug 2015 08:03:48 +0000 (GMT)
> From: Sebastian Schumacher <[hidden email]>
> To: [hidden email]
>
> Hey guys!
>
> I need to change the amplitude (-v volume) of a mp3 file. That is not really
> a challenge, but I need to change the amplitude in one file at several
> "points". Is there a solution for that? Can I say, for example, that the
> change of volume should take place at 0:45, the next at 0:55 and so on?
>
> I tried to trim the file to edit its segments apart, but it does not really
> work, because the merged output has a strange and unexpected "zero amplitude"
> of about approx. 0.060 sec. between the "merge points", caused by sox. 
>
> Thank you for your help!
> Sebastian

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Re: Complex Change of Amplitude

Fmiser
> >  Sebastian wrote:
> >
> > I need to change the amplitude (-v volume) of a mp3 file.
> > That is not really a challenge, but I need to change the
> > amplitude in one file at several "points". Is there a
> > solution for that? Can I say, for example, that the
> > change of volume should take place at 0:45, the next at
> > 0:55 and so on?

Unless it's silent at the volume change, or the change is
small, a change in volume that doesn't ramp, or slope, won't
sound very good.

Ecasound is another capable command line audio tool that
focuses more on multi track mixing and so it might have the
effect/command you are looking for.  I'm not sure.

> Ari wrote:
>
> One solution is to split the file with mp3splt or similar
> into parts of different amplitudes, then apply mp3gain for
> each part and then  join all the pieces back to one file.
>
> This avoids audio deteration due of  uncompress and
> recompress cycles.

That won't work because mp3gain does not change the audio
itself - is is simply a value in a tag that the playback
software may or may not honor.  And I'm not aware of a way to
tag only a portion of a file, so the join process would
result in loosing all but one tag.

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