SOLVED: mp4 songs are not appearing in the music library

[Nexusnui]

After creating a music library I noticed that non of my music saved as mp4 files appeared in my library, while other file formats like mp3 or flac where correctly found. I tried rescanning, but that did not change anything. I also tried searching with different search engines, the documentation and this forum for a solution. The only thing I could find was this stale GitHub issue wich would indicates that mp4 music may be unsupported.

Here is picture from the Metadata-Manager the first directory contains an album with one mp3 song and the second an album with several mp4 songs(wich do not appear):
   

Search terms I used(without the jellyfin part on this forum):
-Jellyfin mp4
-Jellyfin mp4 music
-Jellyfin mp4 music  not found
-Jellyfin mp4 songs
-Jellyfin mp4 songs not found

[Update]
Renaming my ".mp4" files to ".m4a" solved the issue.

[TheDreadPirate]

MP4 is a VIDEO container and is not supported in a Music type library. If these are Music Videos, there is a Music Video type library.

[Nexusnui]

No they are songs without any video, most audioplayers I used recognise them as music.

[TheDreadPirate]

Then you will need to repackage them into an audio specific container (mp3, flac, ogg, opus, etc.). Jellyfin will not read in mp4s since they are mainly used for video.

[Nexusnui]

Could changing the file extensions from ".mp4" to ".m4a" help to indicate that the files are audio files and not video?

[TheDreadPirate]

Give it a try. Pretty sure m4a is supported by the Music library.

[Nexusnui]

That worked and I will now write a small python script to rename everything.
I also created a pullrequest on GitHub and added as section about file extensions on the documentary page for music, so others are spared the search for a solution.

[Nexusnui]

After renaming 975 files everything appeared in the library.