[audacity4blind] Re: Normalizing Versus Amplification Versus Gain
- From: Robert Hänggi <aarjay.robert@xxxxxxxxx>
- To: audacity4blind@xxxxxxxxxxxxx
- Date: Mon, 8 Dec 2014 16:56:51 +0100
2014-12-08 12:55 GMT+01:00, Robbie <tickleberryfun@xxxxxxxxx>:
> Hi Robert!
> Thanks a lot for these very insightful explanations. There are some
> interesting bits of info there. To use a project mix as a volume gauge
> before export is a brilliant piece of advice. I also didn't know that
> Amplify could be repeated regardless of the dBFS value. With Audacity,
> there's always something more under the surface. :D
> Just out of interest, why is the sample format important when using gain?
>
Do the following for instance:
generate a chirp tone (it has -1.9 dB)
Set gain to 6.
Mix and render
Open amplify.
It proposes -4.1 dB, which is correct.
You can repeat the whole procedure after setting the project format to
16 bit (preferences->quality)
Amplify will propose 0.0 dB because all above this value is cut away
after rendering.
Only Float representations (32-bit float) can go higher than 0 dB.
Thus, our normalization procedure for multi tracks wouldn't work wit a
project format of 16 or 24 bit integer because the sum of the tracks
would go over 0 dB (or 1.0 linear).
Amplify would always show 0.0 dB or less for these cases.
However, it will work when you're individual tracks are 16/24 bit
integer and the project format is 32-bit float.
The only thing you can't do with such a track is to
use amplify or normalize directly on it such that the peak exceeds 0 dB.
The gain slider doesn't matter for a single track because it is
virtual and the samples are only calculated on demand (playback, mix
down) and you can change this value at will before that.
There are very few occasions (and I recall none) for which changing
the format for the project or one track would bring anything but
regret.
My advice is to work with 32-bit float and to keep the peak under 0 dB
for any kind of export.
Lossy formats can raise the level by as much as 3 dB in some cases.
It's adviceable to re-import such files in order to see the new peak
(per amplify).
Robert
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