Hi - Just wanted to know if iTunes recognizes the gain correction information stored by MP3Gain in mp3 files. Also, if I have already adjusted the gain using MP3Gain is there any point in turning on iTunes' SoundCheck?

Rgds,
Saugata

MP3Gain alters the file directly so there is no recognizing to do.

As far as I know SoundCheck does the same as MP3Gain.

iTunes does not modify the MP3 file directly for SoundCheck other than to add a tag to it. It scans the file for the average volume (using some method that is much faster, but not nearly as good, as ReplayGain) and stores this information in the file's tag (if it can) and also in the iTunes database.

The only reason I can find that it adds to the tag is that if you remove that file from the iTunes library and readd it, it won't need to scan the file again. It simply reads the tag. Other than that, the tag never appears to be accessed in any way. You can remove the tag and SoundCheck continues to work fine, as it's reading the volume from the database.

Soundcheck essentially uses the volume level and applies an adjustment to bring it to zero. So if it thinks the volume is -6.9dB, it'll apply 6.9 dB of gain to it. I do not know what it considers to be the base level. The applied gain is also transferred to the iPod's database when it syncs, and the SoundCheck option in the iPod Settings controls whether the iPod applies that gain or not at playback time.

To the original post:
MP3Gain modifies the file itself to adjust the volume, and so iTunes will use this data because it's not a matter of not using it. The actual sound data is modified when you MP3Gain it. *All* player programs work with MP3Gain. SoundCheck won't help you much because of this. Admittedly, it probably won't hurt either.

Thanks, Otto42. I presume the "iTun Norm ..." which shows up in the comment field is this "normalization" information!

Well, at least the first chunk of hex is. I still have no idea what the rest of the numbers in that tag mean.