%composer% & %writer%


I have an irritating problem with mp3tag (tested with 2.39k but also occured some months ago with previous beta).
My library is in AAC format (*.m4a) and was tagged with foobar2000.

The problem comes from %composer% and %writer% confusion. I have both on my m4a files (plus artist field).
Each time I edit a file with mp3tag the %composer% tag is erased and its content is put into the %writer% field.

before mp3tag:
• composer=Bach, Johann Sebastian (1685-1750)
• writer=Goebel

after any mp3tag operation:
• writer=Bach, Johann Sebastian (1685-1750);Goebel

I don't know if it's a bug or an intended feature (cf. here). But I can edit my m4a files with foobar2000 and iTunes (embedded coverart) without changing anything to both composer and writer fields. So I suppose that both can coexist without conflict with the MP4 tagging specification.

Any comment about this? Thanks.

The problem starts with the tag mapping of foobar, because it displays the official composer atom as WRITER and not as COMPOSER
If you add a COMPOSER tag, it will not show in iTunes.
The internal atom name is ©wrt which might be an abbreviation for writer, but it is displayed in the iTunes GUI as composer and the same gui field uses the TCOM frame for MP3 so I'm confident its mapping name must be Composer and foobar should change its mapping name.