Go to Applications->Utilities->Audio MIDI setup. In the
dialog box, select your output. Then set the drop down menu
to 2ch-24 bit and 48kHz sample rate. What will then happen,
when you play back a video in iTunes with 5.1 Dolby, the encoded
Dolby track will then be passed through the the output and can
then be decoded by the device.
This is how I have my 2010 Mini setup connected to my Yamaha Rx
via HDMI and it happily passes Dolby and DTS quite happily to my Rx
from any app (personally use XBMC as my media app for movies as
iTunes had just too many problems with video quality). Dolby's
True HD and DTS-HD/Master Audio do not work however since
the video chip in the 2010 Mini does not have the required "protected"
Thanks Woodmeister50 but I have tried that, I understand that mac minis after 2009 should run 5.1, I am frustrated at how difficult it is proving to sort this. The Mac mini shows my system though some of the features are greyed out. I may take it to apple for them to sort, they have been quick to let me purchase software / hardware to sort this, so they can sort it for me.