Re: [gentoo-user] Re: [OT] ogg/mp3 volume

[luis jure]

el 2012-05-20 a las 21:48 Nikos Chantziaras escribió:

> On 20/05/12 12:41, Jesús J. Guerrero Botella wrote:
> > Just for sake of correctness, what the op wants is called
> > normalization, in the world of sound edition.
>
> Actually, no.  That's not what he wants.  Normalization simply adjusts
> to 0db.  How loud something sounds however is not a simple matter of
> what the maximum peak of a waveform is.  ReplayGain actually analyzes
> the music to tell how loud it *sounds*, not how loud it actually is.

[...]

> Normalization makes audio equally loud for hardware.  ReplayGain makes
> audio equally loud for humans. :-)

 
actually, that isn't quite correct either... that's not the difference
between normalization and replaygain, you are mixing different things.

- normalization is process that modifies all the data in a file to adjust
  it to a reference level. as such, it only works in uncompressed audio;

- replaygain is an algorithm that tries to estimate the perceived loudness
  of a sound file, and calculates the gain level needed during playback
  (hence the name) to adjust it to a reference loudness level. this gain
  level is written in the metadata of the file (not all file formats
  support it), and has to be understood by the playback device. it does
  not modify the actual audio data (that is, it does not normalize).

now, normalization does not "simply adjust to 0dB", you can of course
normalize to whatever level you want (usually, *not* 0dB). 

moreover, normalization doesn't necessarily mean peak level normalization,
there's also loudness normalization. RMS normalization its most basic
form of loudness normalization, but there are more complex algorithms
that take into account the response curve of the human ear (like the
replaygain algorithm).