Solved - No audio as service but sudo -u mopidy works (DietPi)

General
1

I’m running Mopidy as a service on Diet Pi with pHAT DAC.

I can access the web interface but I cannot get sound. The error I’m seeing in /var/log/mopidy/mopidy.log is

WARNING [1211:MainThread] mopidy.audio.gst: GStreamer warning: gst-resource-error-quark: Could not open audio device for playback. (6)

The service is running as user mopidy, I’ve checked this like so

$ ps -aux | grep mopidy
mopidy    1211 19.5 10.9 282556 53904 ?        Ssl  17:19   0:22 /usr/bin/python /usr/bin/mopidy --config /usr/share/mopidy/conf.d:/etc/mopidy/mopidy.conf

The mopidy user belongs to the following groups

$ groups mopidy
mopidy : audio spi i2c gpio dietpi

The audio section of /etc/mopidy/mopidy.conf is as follows

[audio]
output = autoaudiosink

I have tested that autoaudiosink works using the following command (as root), I heard the beep.

gst-launch-1.0 audiotestsrc ! audioresample ! autoaudiosink

Now the weird part… if I start mopidy with the following command instead of as the service, it works fine, I can hear sound. Also works fine without the debugging.

sudo -u mopidy GST_DEBUG=3 mopidy -v

I’m running out of ideas now, except maybe sudo -u mopidy is actually running with root credentials and that’s why it’s OK?

I wondered if the audio device is not in the audio group, is that even possible?

$ find /dev -group audio
/dev/snd/pcmC0D0p
/dev/snd/controlC0
/dev/snd/seq
/dev/snd/timer
2

Not sure if it’s relevant in your case but from the docs
" If you used the Raspbian Desktop image you may also need to add the mopidy user to the video group. Run sudo adduser mopidy video to do this."

3

Adding video alone didn’t help. I have managed to get it working by adding the following groups.

dietpi adm tty dialout cdrom sudo audio www-data video plugdev games users input netdev gpio i2c spi

So to re-cap, in case anyone else find themselves scratching their head running Mopidy on DietPi with pHATDAC the following groups were not enough

audio spi i2c gpio dietpi

I added all the groups that the dietpi user has

$ usermod -a -G dietpi,tty,dialout,cdrom,sudo,audio,www-data,video,plugdev,games,users,input,netdev,spi,i2c,gpio mopidy
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