Wiping out tag fields

[poster]

@zerow

Second: MP3Gain do not change the raw data at all [in that "default" mode]. If it did I would not be able to undo the changes once a clipping occurs. And I tested this again, but this compared the original file with file-massacred-with-clipping-and-then-restored-to-that-original-state [with MP3Gain] not only with my ears but on spectrogram and in a waveform: not a pixel or line was different between them

You do not know the structure of a MP3-File and how MP3Gain does this, which is explained in the help-file of Mp3Gain:

[quote="Mp3gain Helpfile"]
The mp3 format stores the sound information in small chunks called "frames". Each frame represents a fraction of a second of sound. In each frame there is a "global gain" field. This field is an 8-bit integer (so its value can be a whole number from 0 to 255).

When an mp3 player decodes the sound in the frame, it uses the global gain field to multiply the decoded sound samples by 2(gain / 4).

So if you add 1 to this gain field in all the frames in the mp3, you effectively multiply the amplitude of the whole file by 2(1/4) = 119% = +1.5 dB.

Likewise, if you subtract 1 from the global gain, you multiply the amplitude by 2(-1/4) = 84% = -1.5 dB.
[/quote]

And to avoid futher misunderstandings:
This "global gain field" is not a tag field, that can we read or written by Mp3Tag. It belongs to the music part of the MP3 and not to the tag part.

There is another method to get gain changes than that done by MP3Gain. Foobar for example is able to store informations in tag fields and during play uses these informations to equalize the music for the hearer. But these informations are only use by Foobar and I think some other compatible players. If you want to apply these changes to be used by all players then you have to do it the way Mp3Gain does. Foobar can do the Mp3Gain-method too in addition to the tag-field method.

So to explain again:

Mp3Gain uses APE-tags to store the gain-informations only for analysis and undo-purpose. These tags are not used by a player to play a a mp3-file louder or less louder. But all players are able to play in the intended loudness because MP3Gain makes changes to the music part of the mp3-file.

There is another method not used by MP3Gain that indeed uses the content of tags after analysis to tell a compatible player, that can read and use these tag-informations, to decide how loud it has to play.

I think you are not aware of these different modes and constantly mix them up.