bt-speaker crashing when using dmix with other sources

[barde]

When running on a Raspberry I encountered following problems with bt-speaker: the service crashed with a python stacktrace and ceased working. The connection between bt-speaker and client was still running. Only restarting bt-speaker fixes the issue.

How to repeat:

• use alsa dmix plugin
• start mpd and bt-speaker
• connect to bt-speaker with client
• start playing music on mpd and stop it

Bt-speaker crashes with this messages repeatedly.

I used it with dmix for multiple sources and combined both stereo channels to mono on each output channel. Config