input level when encoding CD's

Ian Malone ibm21 at cam.ac.uk
Tue Nov 2 16:03:41 UTC 2004


Matt Morgan <minxmertzmomo at gmail.com> wrote:

 > I have a problem with a lot of my CD's. I'm sure this is familiar to a
 > lot of people-the sound levels don't match. There's always that one CD
 > that's a lot louder than the others, so you can't put it on mixes,
 > etc.
 >

I'm not sure, but I think many CDs use the full digital sample range
(which is a good thing if you think about it).

 > It looks like grip's "calculate gain adjustment" (encoding config,
 > options tab) will be a step to fixing this problem for new tracks.
 > Right?
 >

Exactly, though it doesn't do the peak volume tag needed for
clipping protection.

 > And then, what about existing .ogg and .mp3 files? Can I fix them, or
 > should I just re-rip and re-encode?

Google for replaygain and vorbisgain.  They add tags specifying
a preamp adjustment based on the perceived loudness of a track/
album (using acoustic modelling, similar to that used for audio
compression).  These values can be calculated at any time, and
do not destroy information on the track (it's a lossless
process).  So you can apply it to your existing tracks.  The
current version of XMMS can understand the tags (I think it's
down to the input plugin), not sure about the Jukbox or whatever
it's called.

To use grip to rip to vorbis, you're going to need to modify the
command line it uses.  I don't have an example here, but the
places to look for info are: man oggenc (for the options to set
custom tags when encoding), the grip help docs (for the variable
containing the calculated adjustment), and probably the vorbisgain
docs for the correct tag names (or just vorbisgain some existing
tracks and use vorbiscomment -l).  I prefer using vorbisgain
however, because grip does not produce all four tags (album gain,
track gain, track peak, and album peak).

-- 
imalone




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