When I stream my M4A files using Jellyfin, Jellyfin correctly handles files with multiple artists in their web client. The meta data is handled correctly in Symfonium as well when connected to my Jellyfin server.
When I remove the streaming indirection and directly store the same M4A files on my Android device, Symfonium (which now needs to read the meta data itself as opposed to getting the meta data fed from the streaming server) does not handle multiple artists correctly. It just displays a single artist. The track details have no mention of other artists apart from the first one.
I edit my local M4A files using MusicBee. When using an external tagging tool such as Mp3tag, I can observe multiple ARTIST tags in the Extended Tags.
Fwiiw I have not really seen any Android music player that correctly handles M4A files. Before I used BlackPlayer, which has the same behavior. Furthermore, the Navidrome web client has the same behavior too. It is possible to work around the latter by using one ARTIST tag with multiple artist names separated by one of the recognized delimiters, but this is quite inconvenient. Especially given that MusicBee is my core music player (but unfortunately only handles the “local Windows” part of the equation). It would be great if Symfonium (“local Android” part) could handle these M4A files correctly/consistently too.
My bad. Didn’t enable the Debug Mode. Should be uploaded now via the app.
I am not sure what is included in the log file. But I just played a M4A track with multiple artists and opened the details if that would be useful.
Uploaded the sync as “matt77hias multiple artists M4A 2”
I also added another M4A file (should be part of the sync too) with 2x ARTIST and 2x LANGUAGE tags, because the issue is the same for multiple LANGUAGE tags. The Jellyfin client does not show any languages, though.
It is worth noting that multiple genres seems to work fine everywhere (MusicBee, Jellyfin, Symfonium local & streaming). MusicBee does not seem to write multiple tags for the GENRE tag.
Ok so MP4 tag format does not officially allow to have duplicated atoms, so taglib ignore the duplicates as expected and most software will do the same.
Globally speaking the fact that there is a way to do something does not mean it’s used and should be done.
You can write your ratings in a tag named MyPrecious with a 0-1000 range. It will work but no one will be able to use but you.
That why there’s standards, and people trying to have everyone doing the same.
In this case there’s none and the library chose to support the logical cases, since the format support multi valued data, people should write multi valued data. This is more efficient too.
I do regret having a 100% M4A (AAC) library now. FLAC (and Vorbis comments) would have likely be the better choice. Now I cannot really convert to some other format anymore (to lossy would decrease the quality, to lossless would keep the quality at a multiple of the file size).
Just re-tag your files using the latest mp3tag beta as @655321 suggested you, I’m a Musicbee (stable), M4A library and Symfonium local provider user too, enable it here: