[LAU] keeping same perceived level on mp3 files

[Fons Adriaensen]

On Sat, Oct 06, 2012 at 01:08:43PM +0200, Atte André Jensen wrote:
 
> I tried it on a couple of files:
> 
> atte at blokhus:~/music/bands/eldorado/mp3$ ls *.wav | xargs -iarg ebur128 arg
> Integrated loudness:     13.7 LU
> Loudness range:           3.8 LU
> Integrated loudness:     13.0 LU
> Loudness range:           2.2 LU
> Integrated loudness:      6.0 LU
> Loudness range:           3.6 LU
> Integrated loudness:     10.8 LU
> Loudness range:           4.5 LU
> Integrated loudness:     12.9 LU
> Loudness range:           3.2 LU
> 
> Ok, so it seems the third file is softer than the rest, which is
> very true. But how do I interpret those values, and how do I call
> sox for a gain adjustment?

A 'Loudness Unit' (LU) is the same as a dB. So if you want a loudness L
and a file measures M, then you need to adjust by L - M dB. Beware of
clipping if you apply positive gain. Future releases of ebumeter and
ebur128 will measure peak level as well to make this easier.

The basic sox command is IIRC:

  sox infile outfile gain value-in-db

See the sox manpage for details.

Ciao,

-- 
FA

A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)