Hi Folks,

Just about to insert 'COMMENT ITUNNORM' to my .MP3's and had a quick question; have already reviewed the various threads I could find ... most notably:

After running MP3GAIN, it creates various tags of which one is REPLAYGAIN_ALBUM_GAIN and REPLAYGAIN_ALBUM_PEAK. The value in REPLAYGAIN_ALBUM_GAIN typically formatted as '+#.#### dB' whereas the REPLAYGAIN_ALBUM_PEAK is formatted as '#.####'.

The threads suggest using REPLAYGAIN_ALBUM_GAIN (or track); what I'm wondering is if $RG2SC automatically strips out non-numeric data before performing the conversion ... or, should I be using REPLAYGAIN_ALBUM_PEAK.

Advance thanks,

I've gone ahead and applied $RG2SC using REPLAYGAIN_ALBUM_GAIN as the source value to my entire library. Programmatically speaking, I'm assuming that the non-numerical portion of the field is stripped prior to the calculation.

Prior to applying $RG2SC, an iTunes SoundCheck value on a file was (+2.7 dB) whereas the ReplayGain on the same file was ALB: +0.48 dB and TRK: +0.49 dB. Understanding that calculations might vary slightly, why there is such a significant disparity between iTunes SoundCheck and ReplayGain remains a mystery to me ... even after a fair bit of reading on the web.

I can't really tell the details on how iTunes SoundCheck is working internally and most of it is just speculation. Some assume that it only samples the files and produces the values from those samples, other say it gets easily confused by files with bad quality. Short: I can't explain the difference either.

However, using REPLAYGAIN_ALBUM_GAIN as the source value is the correct way of using the feature.

If you're unsure about the produced values by Mp3tag, you can also double-check with another program. AFAIK, dBpoweramp also has means to compute the SoundCheck values from ReplayGain values.

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Hi Florian,

Thank you for making time to reply; dBPowerAMP is my defacto tool for ripping/transcoding audio with MP3Gain as my RG processing tool.

I've read that iTunes SoundCheck is essentially a track analysis but as with all things Apple ... it's a black box. :slight_smile:

MP3Tag makes it easy to manage the metadata and as I use WMP, KODI, and iOS/macOS (iTunes) devices, I was looking for a "consistent" and "predictable" listening experience - hence the Album RG <-> SC.