Subject: Re: [linux-audio-user] Fwd: [Jamin] Re: soft clip: Achieving Gain, inconsequential overloads
From: Anahata (anahata_AT_treewind.co.uk)
Date: Tue Apr 13 2004 - 16:53:22 EEST
> > What I mean by destructive is the outfile replaces the
> > infile. With Ardour undo can revert but the original
> > file is destroyed
Nothing to stop you copying the file and normalizing the copy, of
course...
> Somebody else noted, I think it was Jan, that there is 'rms'-normalization
> also. In my mind that sounds more destructive.
If we're talking about the command line normalize program, its default
action is RMS normalization. It sets the level so that the average RMS
value is -12dBFS. It also "limits" (I'm not sure exactly what this means in
the context) any samples above -6dBFS (50% full scale). Depending on how
'peaky' the file is, varying amounts of peak material will be thus
limited.
It has the option of peak normalization, which is a very simple
operation of scaling every sample up by a constant value chosen so that
the biggest peak is exactly 0dBFS. That's non-destructive in the sense
that no dynamic range compression happens - the only impairment is
the usual rounding errors inevitable with any audio processing.
However I suspect that what the original poster wanted is far more
sophisticated than either of these, and the comments about multiband
compression and the dangers of squashing out all the dynamics are much
more relevant.
Other techniques that help (where possible) are:
- compressing the individual tracks before or while mixing
- cascaded compressors with different settings, as simulated
by the "super nice" mode of the FMR Audio RNC (Really Nice
Compressor!). By applying slow and gentle compression first, then
successively faster and harder stages, you can get higher compression
with less audible pumping than a single compressor.
Personally I'm quite happy with running an album through normalize and
leaving it at that, but I'm definitely not in the pop music business :-)
-- Anahata anahata_AT_treewind.co.uk Tel: 01638 720444 http://www.treewind.co.uk Mob: 07976 263827
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