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What's the benefit to replaygain vs. mp3gain? You implied it was more
accurate but I don't know the details of this. Is it simply more
accurate because it relies on the decoder to know about the special
replaygain tags, whereas mp3gain actually adjusts the volume in the
mp3 frames directly? How bad is this latter technique?
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The benefit is that mp3gain is able to adjust volume in 1.5 dB steps,
whereas with this approach you are achieving 0.1 steps of precision.

Foobar actually gives you even more accurate results, going to the second
decimal of precision (0.01). Madplay approsimates that to the first decimal.
But it's still a lot more precise than 1.5

Andrea

PS
Yes, it was a lot of work... in convincing people to help me, more than
anything else