I use SMPlayer / Mplayer2 / PulseAudio in Kubuntu 12.10 (upgraded from 12.04.)
PulseAudio supports ac3 passthough; if you sink an ac3 audio stream to it it should send it out to the DD receiver. This works in VLC on my setup.
But I prefer SMPlayer
If SMPlayer is set up to use pulse as the audio output, and also SPDIF passthrough, does this work for other folk in sending a raw ac3 stream to the receiver?
If I suspend pulseaudio and use the right alsa device for spdif passthrouh, dolby digital works great.