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Subject: Re: output level equalisation
From: Chris Holt (amiga2k_at_cox.net)
Date: 2003-12-01


On Mon, 01 Dec 2003 23:02:45 +1300, ten Velde family wrote:

> MP3Gain does not adjust the frequency response in any way, (it simply
> adjusts the global gain variable on each frame) but it's analysis is
> based on perceived loudness, so it will not treat all frequencies the
> same (when it comes to analysis, not processing)
>
> But surely, when played back with these modifications, the result must
> be audibly different, especially when there's a difference of some
> 40dB. When you take into account that a difference of 10dB equates to
> a halving or doubling of the perceived volume, and if a "song" is
> treated the way the sin waves were, things would sound rather strange
> at the bottom and top ends of the frequency spectrum. So I assume that
> one adjustment is made to the entire "song" rather than varying
> adjustments depending on frequency.

Yes, it makes a single adjustment to the entire song based on the loudest
parts of the song (percieved loudness, rather than a simple peak analysis)
If I understand it right, your "songs" are simply a sine wave of a single
frequency. What I am trying to tell you is that a file like this is going
to totally screw up MP3Gain's analysis of the peak loudness. For one
thing, there aren't really any peaks, and for another thing percieved
loudness is frequency dependant.

 You should set MP3Gain to "Max noclip gain" setting so that the analysis
is based on actual and not percieved levels.

Chris



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