M4A files won't play with Navidrome (Subsonic Provider)

[DrDagless]

What version of Music Assistant has the issue?

2.4.0b18

What version of the Home Assistant Integration have you got installed?

No response

Have you tried everything in the Troubleshooting FAQ and reviewed the Open and Closed Issues and Discussions to resolve this yourself?

• Yes

The problem

When I play a M4A track in MA with Open Subsonic provider, the track fails to play. I press play, the button flashes to pause for less than a second, and then "stops". These are tracks I've encoded from FLAC to aac with FDK AAC specifically. I'm using beets to automate the encoding/tagging process.

This has been an issue with this particular setup since I started using MA last year. I've recently had some more time to test things out on my end. What I've discovered is that the same files play perfectly in Music Assistant using either the local filesystem provider or the Jellyfin provider. No issues at all there.

MP3 files also work flawlessly with the subsonic provider, so it seemingly is something specific to the filetype. I have no idea where the problem is coming from though. The same m4a files (most of my library) work fine with other clients like Symfonium and also the navidrome web client.

Absolutely love Music Assistant and the work being done on it. Please let me know whatever additional information I can provide.

How to reproduce

Play a M4A track encoded with FDK AAC using the navidrome provider.

Music Providers

Open Subsonic Media Server Library

Player Providers

Chromecast

Full log output

music-assistant.log

Additional information

Here's the mediainfo of an encoded track:

What version of Home Assistant Core are your running

2025.1.2

What type of installation are you running?

Home Assistant Supervised

On what type of hardware are you running?

Raspberry Pi

[OzGav]

@khers

[khers]

This is almost certainly a miscommunication between the provider and ffmpeg. When I try and run just such a file through my own development instance, ffmpeg complains that no audio data is delivered.

The web client and symfonium are poor comparisons because the subsonic client is also the process that will decode the audio stream. In MA, the API client only makes the encoded stream available to another process. So something about how we are populating the streamdetails object for these files is leaving ffmpeg confused about what it is seeing.

[khers]

I am sorry this bug has lingered so long, I had hoped that the ffmpeg update work would fix this for us but alas.

[khers]

Here is my understanding of the problem (if anyone is better versed in the detail of mp4/aac please correct me.

MPEG-4 supports storing file metadata at the end of the file. I am sure the decision maker there had reasons but it feels like an incredibly dumb decision to me. The up shot here is that because we do not offer ffmpeg the URL from which to read the file (so it cannot seek to the end) and instead we have a generator that yields chunks, ffmpeg cannot find the file metadata.

The reason that Symfonium can play it is that Symfonium will cache the entire file locally and then play back from the cache (allowing the audio decoder it uses to fine the necessary metadata).

This is not going to be fixed in the provider without significant changes to the subsonic API. These changes are being worked on but I don't expect them to be in Gonic/Navidrome any time soon as the specs around working authentication are still being discussed.

The OP has several options:

1. Don't use this format. If you need lossy compression, go with ogg, mp3, or if there is a way to force your m4a/aac encoder to put the moov atom at the front of the file this might also work.
2. Force the subsonic server to transcode all m4a files before serving to a format that works
3. Don't server these file from a subsonic server.

[OzGav]

Docs updated with limitation

[DrDagless]

Thanks very much for the detailed explanation and I'm glad that it's at least been figured out finally. Had I known I definitely would not have encoded flac to aac (which was actually recommended to me ages ago by the navidrome community, hah!).

In terms of the alternatives, as mentioned thankfully the jellyfin provider works without a hitch. I've tried encoding the m4a files from within navidrome, but typically one track will play in MA and then the next track will not start. The logs mention a ffmpeg timeout error.

The latter (encoding) would actually be my preferred approach. Would it make sense to create a new issue and attach logs?

Again, thanks for all the help. You're all amazing putting this together and happy to support your work.