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View Full Version : MP3 quality poor due to low volume levels, notcompression.



Eric Lyons
2004-01-01, 13:25
Just to throw in my philosophical .02 on this first day of 2004...

I guess it's a good thing that people have used mp3gain and are
satisfied with the results -- I'm surely aware of the "problem" of
widely different gain/compression structures used in recording and
mastering CDs. This problem was virtually unsolvable (without
significant audible compromise) in the analog domain of multi-disc
carousel changers of recent past; although consumers of those devices
may have been just as dissatisfied with random play, there was nothing
they could do about it.

And I suppose if we're all satisfied with the coloration inherent in
MP3 codecs, some of us are probably happy to add a little more
coloration through level equalization. By "coloration" here I mean
anything that changes what the performance/recording/mastering process
went through to get the bits the way they are on the disc in the first
place. If you don't like it that your Green Day sounds 300% louder
than your Trip Shakespeare, that's fine, but that's how they put it on
the CD.

Having said all that, I looked at the theory behind mp3gain (or its
proposed 'replay gain' standard, as yet unimplemented), and have the
following comments.

First, this statement on the home page of mp3gain.sourceforge.net is a
fallacy:

"Also, the changes MP3Gain makes are completely lossless. There is no
quality lost in the change because the program adjusts the mp3 file
directly, without decoding and re-encoding."

It may be that the changes MP3gain makes are *reversable*, but they are
surely not *lossless*; in either a mathematical or musical sense. In
point of fact, the purpose of MP3gain is to *change the gain structure*
of the music coming from the original source (generally, lowering it
for "loud" music), and this can in no way be considered "lossless".
What you *lose* is average loudness in the bits going to the DAC.
While that subjective loss may be small (perhaps even inaudible,
depending on what's downstream of the bits after they've been decoded),
I would consider it strictly incorrect to call this process lossless
(unlike, say, FLAC encoding where the bits going into the codec are
exactly the same as the bits coming out).

When I reach over to turn down (or up!) the analog volume control on my
stereo when Green Day comes on, I'm doing something entirely different
than changing the bits going into the DAC that comes from the MP3
decoder (or directly from my CD player). The entire gain/response
structure of my analog preamplifier, power amplifier, speakers -- and,
indeed, my ears -- is being changed in the analog domain. Green Day
doesn't sound the same at 80db out of my speakers as it does at 100db
from them. Perhaps this is the essence of my argument.

Personally, I can't imagine "compensating" my entire collection to some
theoretical normal or average loudness level. Those loudness levels
are part of the music! If, at any given time, I feel like the
transition between songs results in a dissatisfying or abrupt loudness
change, I've got good analog recourse available easily. For me, it's
part of enjoying the music. To have all my precious music normalized
to a permanent "background listening" level would lower it to the
status of elevator music in some sense.

So, viva la difference!

And happy new year!

Eric.
--- Rod Savard <rodney (AT) savard (DOT) org> wrote:
> > I am perplexed that there are not many others who have the same
> problem
>
> I've run my entire collection of MP3s through MP3Gain and am pleased
> with
> the results. They sound just as good as they did before; I have no
> issues
> with volume on my SLIMP3 or Receiver. Actually now the SLIMP3 plays
> at
> volume level similar to my other devices (TV, DVD, etc). BTW, I
> have the
> SLIMP3 volume set at 11.
>
> -Rod
>
>