No sound with m4b-files (audiobooks)

For some time I have not heard any more audiobooks. Now I suddenly realize that with m4b files no sound can be heard.
The files are okay - I can play them via other music servers.

I couldn’ t find anything wrong or missing in mpd.conf:

plugin "ffmpeg" enabled "yes"

Any ideas what´s wrong?

Regards

Black Senator

Hello all together,

the problem still persists. I can play my m4b-File with every other music server/-client - but not with volumio!
For sure: I was able to play these files months ago (Releases). Right now with the current release, I can not even add the albums / audio books to the playlist anymore.

I can not believe that no one else but me has the problem

Regards

Black Senator

Release 2.296
Raspberry Pi 3+
HifiBerry Amp+

I solved my problem: https://forum.volumio.org/post73920.html#p73920