If you have problems bitstreaming or decoding audio via XBMC from Version 12 Frodo then please try and use the below fault finding steps to try and establish the problem and then fix.
XBMC Frodo (version 12) introduces a new audio subsystem called AudioEngine. While this introduces a better quality audio subsystem for stuff like HD Audio it does mean that previously working system might no longer work upon upgrade.
Typical problems introduced by incorrectly configured audio
No DTM-MA audio
No TruedHD audio
Slow frames per second ( FPS) when playing video
WASAPI crackling or distortion