On ubuntu, using VLC I can play movies with DTS or AC3 audio through HDMI to my TV. When I play the same movies in XBMC, I get no sound.
The interesting thing is that when I play movies with 2.0 audio thru xbmc I get the sound normally to my TV.
Any ideas?
What is the settings status of your audio output? I.E. do you have DTS and AC3 capable receiver checked? If so, uncheck them, and see if that makes a difference. My guess is that you have them checked, so XBMC is passing through the DTS and AC3 signals. Your TV probably cannot decode the multichannel signals. I could be wrong, but that's my gut feeling.
If the TV was unable to decode the multichannel signals, wouldn't DTS audio not work through VLC either? I'm actually experiencing the same problem and have tried various solutions (like removing pulseaudio) with no luck. I'll give your suggestion a shot when I get home tonight. Thanks.
VLC is probably doing the decoding, not passing it through. I've not seen any TV capable of decoding DTS, the manufacturers need to license the functionality. My TV will do certain AC3 audio, but not all.
I tested what you suggested, and audio does work, but unfortunately it is only passed through the left and right speakers (2.0 instead of 5.1). Could it be that if DTS and AC3 capable receiver options are not selected, then xbmc does not pass those signals to the tv? I can tell xbmc to pass everything through as stereo, in which case I get sound out of all speakers, but the quality is awful. The other thing I noticed is that music will play fine out of every speaker, but I guess that's the same idea as converting the audio signal from a video file to stereo. Another thing I should mention is that the sound output device (my video card under the sound settings menu) does not show up as being 5.1 surround sound, but that kind of makes sense to me since it's hooked up directly to the tv through hdmi.
How is your audio system set up? It sounds as if you're going HDMI to your TV and then probably optical to your receiver. Is this correct? If so, there's not a whole lot you can do since you're going to have to pass stereo to your TV if it can't decode DTS or AC3 signals. Part of the HDMI handshake is end devices telling each other what they can support channel-wise. Since your TV is stereo only, doesn't matter if it passes through to something else, you're only going to get the option of two speakers.
The only way to get multi-channel audio would be to go from your XBMC box directly to your receiver.