If I edit a tag using mp3tag, mp3gain loses its ability to undo volume changes. The undo info is stored in an APE tag that mp3tag must delete.
I have experimented with various settings (read/write ape) and can't fix this.
Is there a workaround? Thanks.
Don't tick any of the APE boxes in Options > Tags > Mpeg
That's the easiest way to keep ape tags as they are.
Thanks, I tried that. Unfortunately, changing a tag with mp3tag still makes mp3gain undo not work.
Also, I noticed that changing a tag with mp3tag changed the cover art type from jpg to bmp (when it is really jpg), making the art not display any more in Godfather.
Uhm ... no (at least not with the current version).
Yes, it really does have both these problems in current version. However, one important detail: I'm working with itunes .m4a files (aac). I tested an mp3 and neither of these problems show up.
Huh? How are you using MP3Gain with M4A files? 
Great, you leave out the most important information and make everybody think you are using mp3 files. 
(Sebastian, he uses aacgain... )
What now - M4A or AAC since the two have different tagging standards - M4A cannot contain APEv2 tags AFAIK.
Must be m4a
Anyway I think I have figured out the problems and I'll write to Florian.
Both issues should be fixed in latest http://developer.mp3tag.de/ version.
You did fix it for me! Thank you.
And sorry not to give all the key info initially. It didn't occur to me this might be m4a specific until you couldn't reproduce the issue at all.
And yes you guessed correctly that I'm using aacgain with mp3gain, and that I'm using Apple m4a files (they call them aac but give them a m4a extension so I don't know the difference there).
John