Today while setting up a raspberry pi to be used as an airplay audio server I came across an error message which started,
unknown pcm cards.pcm.front
As I knew that the audio output was working fine normally I suspected a permissions issue.
In creating a new user under RPI Debian Wheezy, which I tend to do all the time for security reasons, the users is not add to the audio group, which is required.
So this command adds the user bob to the group audio,
sudo usermod -a -G audio bob
So if you have an audio problem that is fixed by running the application as sudo then checking the user is withing the audio group is a good starting place.
You can check what groups a user is in by just typing,