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[Possible Bug] Issue with itunes soundcheck values for album gain

Repost, but unable to move original.

What I've observed is that the ReplayGain album gain is the same value for all tracks in an album (naturally as its the average).

I'm also using Foobar to calculate the equivalent itunes Soundcheck value for album gain.  However, when I look at the value (COMMENT ITUNNORM), even within the same album it can vary.  Should it, be uniform, as the ReplayGain value for album gain is uniform?

Edit:
If I use dbpoweramp to calculate the soundcheck album gain, it as I expect (maybe I am wrong) calculates a uniform value for all the tracks in one album.

Re: [Possible Bug] Issue with itunes soundcheck values for album gain

Reply #1
Pictures to clarify the issue.

Calculating replaygain & itunes soundcheck with dbpoweramp:

https://hydrogenaud.io/index.php?action=dlattach;sa=tmpattach;attach=post_tmp_126506_01695fd11b3a25affb7122209accdaff;topic=119872

Notice how the values are the same across the highlighted tracks (both itunes and replay gain).

Same calculation done in foobar:

https://hydrogenaud.io/index.php?action=dlattach;sa=tmpattach;attach=post_tmp_126506_7aa326b339e6c2ca6c163571863b22ca;topic=119872

Now because the value varies for the itunes soundcheck, you can see its no longer a static value but varies.

Re: [Possible Bug] Issue with itunes soundcheck values for album gain

Reply #2
Oh no! Classic noob error.  Did an update to recent September 2020 release and retested across a few more albums. It seems to now behave as expected.

The only anomaly left is this:

Soundcheck value calculated by dbpoweramp for -6.77 dB:
 0000128F 0000128F 00002E65 00002E65 00024CA8 00024CA8 00000000 00000000 00024CA8 00024CA8

Soundcheck value calculated by foobar for -6.77 dB
 0000128F 0000128F 00002E66 00002E66 00024CA8 00024CA8 00000000 00000000 00024CA8 00024CA8

I don't know if the difference is significant enough. I will have to test by importing to itunes and checking across more sets.

Re: [Possible Bug] Issue with itunes soundcheck values for album gain

Reply #3
It seems that dbPoweramp writes album gain to SoundCheck. In foobar2000 you can choose what to write to Soundcheck - track gain or album gain. File->Preferences->Advanced->Tagging->SoundCheck->Automatically write when writing ReplayGain.

Re: [Possible Bug] Issue with itunes soundcheck values for album gain

Reply #4
It seems that dbPoweramp writes album gain to SoundCheck. In foobar2000 you can choose what to write to Soundcheck - track gain or album gain. File->Preferences->Advanced->Tagging->SoundCheck->Automatically write when writing ReplayGain.

Thanks I was careful to watch for that. dBpoweramp's plugin has options to choose as well between track/album etc.

One more update:
So I did a bunch more testing. It looks like there is virtually nonsignificant difference between the values computed by dbp or foobar for the soundcheck value (either track or album).

However, if you import tracks to itunes WITHOUT any gain tags/info, itunes will then calculate values for you if sound check is enabled in your preferences.
The values iTunes calculates on its own is significantly different from foobar/dbpoweramb.
The gain change is much smaller. So an example, dbp/foobar might apply -4.42 dB. iTunes on its own will apply -1.3 dB for the same track. (The difference persisted when testing at both -18dB LUFS and -16dB LUFS).
Testing done on Win10, foobar 1.6, dbpoweramp 17.1, itunes 12.10.8.5

Clearly iTunes is doing something different for how it normalizes volume but I'm not sure there is much info out there detailing that.

 

Re: [Possible Bug] Issue with itunes soundcheck values for album gain

Reply #5
iTunes doesn't use the same gain scanner. There is no way to calculate 100% identical values to iTunes without using the same gain calculation algorithm as iTunes.

 
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