If you run mythfrontend 0.22 from RPMfusion, it will automatically try to disable pulseaudio and use the default ALSA output instead. This leads (in most cases) to no audio output at all.
Changing mythtv’s audio output device in the frontend (Utilities/Setup -> Setup -> General -> Audio System -> Audio Output Device) from ‘ALSA:default’ to ‘ALSA:spdif’ worked for me, but then the volume control (internal as well as external) was broken.
But you can easily tell mythtv to stop disabling pulseaudio by setting EXPERIMENTALLY_ALLOW_PULSE_AUDIO=1 in your environment before running mythfrontend.
For example, add an export statement to your .bashrc
echo "export EXPERIMENTALLY_ALLOW_PULSE_AUDIO=1" >> ~/.bashrc
(Of course, if you use another shell, YMMV!)
Set mythtv’s default audio output device to ‘ALSA:default’ and the volume control to Master (instead of PCM) and voilà, sound!