# Question: $RG2SC - \[REPLAYGAIN\] GAIN vs PEAK
**URL:** https://community.mp3tag.de/t/question-rg2sc-replaygain-gain-vs-peak/51574
**Category:** Support
**Created:** [January 14, 2021, 10:51pm UTC](https://community.mp3tag.de/t/question-rg2sc-replaygain-gain-vs-peak/51574 "2021-01-14T22:51:52Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@hgagne](https://community.mp3tag.de/u/hgagne)
#### Post date: [January 14, 2021, 10:51pm UTC](https://community.mp3tag.de/t/question-rg2sc-replaygain-gain-vs-peak/51574/1 "2021-01-14T22:51:52Z")
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:
> [@Convert replaygain values](https://community.mp3tag.de/t/convert-replaygain-values/8069):
>
> I have a mixture of mp3, mp4 and m4a files as correctly tagged as I can manage (the mp3 tagging is ID3v1 and ID3v2.4). I have used Foobar to replaygain all files. These files are going to be used for two reasons, to listen to at home using Foobar and on the road using iPod (which I don't have as yet!!) It is my understanding that iPods cannot read replaygain values but that MP3Tag can be used to convert the replaygain tags into a format which can be read by the iPod. Can somebody please help…
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,
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### Author:  [@hgagne](https://community.mp3tag.de/u/hgagne)
#### Post date: [January 16, 2021, 2:59pm UTC](https://community.mp3tag.de/t/question-rg2sc-replaygain-gain-vs-peak/51574/2 "2021-01-16T14:59:16Z")
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.
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### Author:  [@Florian](https://community.mp3tag.de/u/Florian)
#### Post date: [January 16, 2021, 3:51pm UTC](https://community.mp3tag.de/t/question-rg2sc-replaygain-gain-vs-peak/51574/3 "2021-01-16T15:51:03Z")
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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### Author:  [@hgagne](https://community.mp3tag.de/u/hgagne)
#### Post date: [January 16, 2021, 4:32pm UTC](https://community.mp3tag.de/t/question-rg2sc-replaygain-gain-vs-peak/51574/4 "2021-01-16T16:32:16Z")
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. 🙂
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.
Cheers,
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### Author:  [@system](https://community.mp3tag.de/u/system)
#### Post date: [February 9, 2026, 12:29pm UTC](https://community.mp3tag.de/t/question-rg2sc-replaygain-gain-vs-peak/51574/5 "2026-02-09T12:29:00Z")