Rockbox mail archive
Subject: Re: output level equalisation
From: ten Velde family (tenvelde_at_xtra.co.nz)
At 18:22 29/11/2003, you wrote:
> > The question is: should I use the files as they are and assume that
> > MP3Gain would distort the real levels, or should I normalise using
> > MP3Gain to get a true evenness of levels? Also, since I have processed
> > all the music files through MP3Gain, and if that has "adjusted" the
> > frequency response of these files, would I be better off to process my
> > test tones the same way?
>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.
> > Only one can be right, surely - and a level variation of some 40dB over
> > the audio spectrum is rather too large to ignore.
>Either could be considered "right" unless you discount weighted dB
>measuments as a "real" measurement. The human ear is not a linear
> > John ten Velde
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