Got the Firetv a week ago and have been playing around with it. Wanted it basically to play my movie collection from my PC over the network. I'm doing it with an xbox 360 right now but as you know the interface is....basic.
So FireTV is connected to my Pioneer vsk1120 via HDMI. I rented Walter Mitty from Amazon and it played fine and receiver indicated Dolby Digital Plus on the display the sound was good.
I loaded up XBMC. Pointed it to my PC and movies. XBMC is cool as it tell me the codec and audio it is. So I start Oblivion, receiver says Stereo. If I play it back via xbox, receiver will say Dolby Digital.
So Firetv only output digital on amazon content or any idea whats going on here?