Re: mp3gain vs madplay

On Fri, 2004-04-02 at 10:57, Bruce Fitzsimons wrote:
> I see the trick. It's linked off replaygain.org, and uses the 
> *algorithm*, but doesn't write the standard replaygain mp3 tags. It 
> *does* write some custom tags in the APE standard though.
> 
> I'll see what improvements I can come up with.

I've only come across this message today.
The replaygain.org site hasn't been updated for years, it's very
misleading.. 

the 83dB reference, the kind of tag to use.. have never reached much of
real use. By the time replaygain really was implemented into tools, the
de-facto standard evolved into :

1/ APEv2 tags, put at the end of file, easy to parse. Those are 
key=value kind of tag, for the replaygain keys (case-insentive) it gives
something like :
replaygain_track_gain=-4.36 dB
replaygain_track_peak=1.042839
replaygain_album_gain=-5.19 dB
replaygain_album_peak=1.085183
The only replyagain aware tools I came across (mp3gain, foobar, and also
the musepack xmms plugin for mpc files)  use those tags.

2/ "89dB reference level" instead of the SMPTE-200 _83dB SPL_ calibrated
reference.
that's better suited to POP music levels (since under the original
reference, all POP files' gain were below -6dB, and by large).
Note that the name "89dB reference" is rather misleading, unless you
consider 89dB to be an abstract value, the "expected loudness obtained
by playing on an SMPTE-200 calibrated system" for the music you expect
to be playing.

The whole point is : we don't expect the user to actually *listen* to it
at 89dBSPL (much too loud !). in fact it is still assumed he will listen
to it at 83dB. (i.e., we assume the sound system amplifies 6dB less than
a SMPTE-200 calibrated. -> we assume some kind of 77dB-calibrated
sound-sytem)
The value 83+6="89dB" is purely virtual. The new standard's reference's
physical basis is in fact : it assumes a 77dBSPL (=83-6) calibrated
sound-system.


Recent projects planning to support replaygain will likely be using
those de-facto standards, since these are the only ones currently in
use.
For instance, the C++ TagLib library is currently adding "APE tags in
mp3" support. And then will read replaygain tags from those tags as well
as the other mentionned tags.

IMO working on modifications for mp3gain to support other tags, or any
other work aiming at better conformance with the outdated replaygain.org
specs is somewhat a waste of time..

-- 
Sam