xiambax@raspberrypi ~/shairport $ sudo amixer cset numid=3 1
numid=3,iface=MIXER,name='PCM Playback Route'
  ; type=INTEGER,access=rw------,values=1,min=0,max=2,step=0
  : values=1
xiambax@raspberrypi ~/shairport $ ./shairport.pl -a AirPi
Established under name '7F827F25C26E@AirPi'
Audio StreamTEdcOatbdZ0FCq38v9mYMAALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.front
ALSA lib pcm_hw.c:1401:(_snd_pcm_hw_open) Invalid value for card
FATAL: Could not open ao device