I’m using an ATV2 with the most up to date Firecore software installed on it. I downloaded an MKV with a Polish audio track as the primary audio source and an English audio track available. When I play the file using VLC on my laptop or XBMC on my ATV2 I can select the English track and it works.
I’d like to use the Media application instead, because I find XBMC has to buffer constantly, but can’t hear anything when I switch to the English track. I’ve gotten mutli-track audio to work previously, so I’m stumped.