SUMMARY `©mvi` (Movement Number) tags are saved incorrectly – as text, rather than as integers. STEPS TO REPRODUCE 1. Use Kid3 to add an ©mvi tag to an MP4 file. Set the value to a number. (Note that the field name has to be entered as `©mvi` – for some reason, “Movement Number” can’t be typed in even though that’s what it displays as. If you type in “Movement Number”, it’s saved as a `----` user text frame.) 2. Open the file in, say, Mp3tag. 3. Look at the “Movement” tag in the extended tags. (Correct `©mvi` tags also parse incorrectly.) OBSERVED RESULT The tag is garbled. EXPECTED RESULT The tag should show up as the number entered. ADDITIONAL INFORMATION This result is only observed using the Mp4v2 plugin – not the TagLib plugin.
Unfortunately, these new atom types introduced by Apple for classical music are not supported by mp4v2. You have to disable the Mp4v2Metadata plugin so that TaglibMetadata is used for MP4 files, TagLib supports more atom types, however, it does not support MP4 chapters, which is probably the reason why you have Mp4v2Metadata activated. That is also the reason why "Movement Number" can't be typed in - it is not supported. You can type in anything, but then you will get a free form atom, as you experienced. So this is not a bug in Kid3. If you want to see support for more atoms in mp4v2, you will have to file a bug or pull request at https://github.com/enzo1982/mp4v2.