This has been mentioned a couple of times, but had no notice from any developers, so I hope that some information can now be given.

The ID3v2.3 mode in foobar2000 currently doesn't support user-defined metadata fields (i.e. those that do not have their own native frames), which are provisioned for in the (informal) specification through the use of TXXX frames - as I'm sure you know. Why is this so?

Thank you for your time.

Edit: spec. link - http://www.id3.org/id3v2.3.0.html#TYER

I am sorry to bump this topic but I would very much appreciate any reply from a developer in relation. Can you provide information about the lack of support for these custom fields when using the compatibility mode?

Maybe that's one of the reasons why the mode is called compatibility mode? Like, there are known bugs in some programs or devices' firmware, which surface when parsing those additional fields?

Just a guess.

No; it's named after the "compatibility" which it allows with devices/players which only properly support ID3v2.3, as opposed to foobar2000's default implementation of ID3v2.4.

Hakubo is right.

The compatibility mode was never intended to be a full ID3v2.3 implementation and has not been advertised as such. It was implemented as a compromise solution for those who need tags which are compatible with limited/flawed tag readers. This is explicitly mentioned in the option to enable it. Since most of those programs do not support TXXX frames anyway, and since it's preferred that the respective developers fix their bugs and update to the up-to-date standards, it was decided to put as least effort as possible into it.

However, I have verified that TXXX frames have been re-enabled for a future version.

I have no information about the release schedule though.

Edit: And I'm going to remove any whining post if it should not be present in the next version yet.

Thank you for your reply, Frank. Could you provide more information about that verification?

Now correct me if I'm wrong here, I assume TXXX frames are where a field such as Album Artist is stored. So based on that assumption, I would like to see support for that field in the compatibility mode, since I use Foobar2000 primarily but still need the tags to be readable by my iPod. So I use the Album Artist field in Foobar2000 but not on my iPod so it doesn't matter to me that TXXX isn't support by other tag readers.

foobar appears to write replaygain info to TXXX frames... go figure

I suggest making 2+ stages of compatibility. One that is like the current one, and one that fixes the boxes on itunes (which I expect is what many want).