The HiFiBerry Digi user “Pretender” has written a very good guide how to use the board to output Dolby Digital and DTS to an external home theater system. This will output the plain AC3/DTS data stream without decoding it on the Raspberry Pi. Check out his guide.
P.S. We expect that this should work out-of-the-box in Raspbmc soon.
Dom Cobley was again working on XBMC and the HiFiBerry Digi. There is now an experimental build that supports AC3 and DTS bitstream output. That means you can now send Dolby Digital and DTS soundtracks to your home theater amplifier over an coax or optical link.
The OpenElec build can be downloaded from here: https://dl.dropboxusercontent.com/u/3669512/temp/OpenELEC-RPi.arm-devel-20140308190048-r17871-g8a2f22b.tar
Note that this is again a very experimental setup. It needed a hack in the XBMC code. This must be fixed in the ALSA driver. While we will work on this, we can’t say, when we will be able to change this.
Check out this article how to configure it. Note that for the HiFiBerry Digi you need the following module configuration:
cat >/storage/.config/modules-load.d/hifiberry.conf <<EOF snd_soc_bcm2708 snd_soc_bcm2708_i2s bcm2708_dmaengine snd_soc_wm8804 snd_soc_hifiberry_digi EOF