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View Full Version : Re:Re:RE: Proper ReplayGain with Madplay



Andrea Minini
2005-04-05, 08:19
******************
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?
******************

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 :)

Marc Sherman
2005-04-05, 08:38
Andrea Minini wrote:
>
> 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

Another difference is that there are (rare) cases where mp3gain is
destructive. From the man page:

> So now the default behavior of mp3gain is to _not_ wrap gain
> changes. In other words,
>
> 1. If the gain change would make a frame's global gain drop below 0,
> then the global gain is set to 0.
>
> 2. If the gain change would make a frame's global gain grow above
> 255, then the global gain is set to 255.
>
> 3. If a frame's global gain field is already 0, it is not changed,
> even if the gain change is a positive number.

However, mp3gain is much more widely supported than the replaygain tags,
and I've never seen an mp3 that actually had a frame with the volume low
or high enough for that destructive effect -- I think it's more of a
theoretical than a practical problem.

- Marc