iTunes Soundcheck tag, COMMENT ITUNNORM vs. ITUNNORM

[mville]

Can someone please explain the difference between the COMMENT ITUNNORM and ITUNNORM tags?

For years I have created the COMMENT ITUNNORM tag in MP3Tag assuming that iTunes and my iPod would use this tag for the iTunes Sound Check feature.

However, I notice that dBpoweramp is writing the ITUNNORM tag and not the COMMENT ITUNNORM tag for the Sound Check feature.

[Spoon]

Re: iTunes Soundcheck tag, COMMENT ITUNNORM vs. ITUNNORM

http://forums.mp3tag.de/index.php?showtopic=16926

From what I can see COMMENT ITUNNORM is a very old iTunes 6 tag.

[mville]

Re: iTunes Soundcheck tag, COMMENT ITUNNORM vs. ITUNNORM

http://forums.mp3tag.de/index.php?showtopic=16926

From what I can see COMMENT ITUNNORM is a very old iTunes 6 tag.

Spoon, that thread also suggests COMMENT ITUNNORM is the Sound Check tag for mp3, whilst ITUNNORM is the Sound Check tag for m4a.

From what I can gather, the issue with COMMENT ITUNNORM vs. ITUNNORM seems rather confused, so users often write both.

Does anyone have definitive knowledge on which tag to use and with which file format?

[Spoon]

Re: iTunes Soundcheck tag, COMMENT ITUNNORM vs. ITUNNORM

I think that is where the confusion is, it might have been true at one point in time, however I think Apple unified the tag name, that said iTunes 10 does not write it any more.

[mville]

Re: iTunes Soundcheck tag, COMMENT ITUNNORM vs. ITUNNORM

Just done some testing with iTunes v.11.1.3.8, Sound Check enabled in iTunes preferences.

1. Started with a new empty library and added an album with no Sound Check tags (COMMENT ITUNNORM or ITUNNORM):
iTunes scans the files and computes the normalization information (Determining Audio Volume progress appears at the top of iTunes). No tags are written to my files so I assume the data is stored in the iTunes Music Library database.

2. Started with a new empty library and added an album with the Sound Check tag ITUNNORM:
iTunes scans the files and computes the normalization information (Determining Audio Volume progress appears at the top of iTunes). No tags are written to my files so I assume the data is stored in the iTunes Music Library database.

3. Started with a new empty library and added an album with the Sound Check tag COMMENT ITUNNORM:
iTunes does not scan the files and no tags are written to my files.

So when NO tags OR the ITUNNORM tag is present, iTunes scans the files (Determining Audio Volume), but when COMMENT ITUNNORM is present, no scanning occurs.

This suggests that in dBpoweramp, COMMENT iTUNNORM should be used (for mp3) and not ITUNNORM.

[Spoon]

Re: iTunes Soundcheck tag, COMMENT ITUNNORM vs. ITUNNORM

Noted, will update for the next beta.

[garym]

Re: iTunes Soundcheck tag, COMMENT ITUNNORM vs. ITUNNORM

This suggests that in dBpoweramp, COMMENT iTUNNORM should be used (for mp3) and not ITUNNORM.

To confirm, I just did same test and got same results. Note that mp3 files need "COMMENT iTUNNORM" but m4a (aac) files need "iTUNNORM".

[Makaveli84]

Re: iTunes Soundcheck tag, COMMENT ITUNNORM vs. ITUNNORM

A quite late input, and this has probably been fixed, but just confirming what has been said here: ITUNNORM for aac/m4a and COMMENT ITUNNORM for mp3.

On a similar issue, the same concept applies for gapless tags, in theory. For example, iTunes checks mp3 files for COMMENT ITUNSMPB. In the case of LAME encoded mp3 files, it reads the LAME Tag for gapless playback and transforms it into a COMMENT ITUNSMPB. This means that for best compatibility with Apple hardware, encoding software (such as dbpoweramp) should do the same and apply a post encoding COMMENT ITUNSMPB tag to mp3 files. This is especially needed for the ability to transfer gapless mp3s to some (maybe all) Apple devices using third-party tools rather than iTunes (tools that may not mimic iTunes' behavior of transforming the LAME gapless tag into a COMMENT ITUNSMPB one).