HD300 only providing Stereo Out instead of 5.1/DTS

[hackzaw]

My audio receiver is about 9 years old (Sony STR-DA333ES) which has optical in for a variety of inputs (it does not have HDMI in).

The receiver has a mode which I leave it on for the most part which is Auto Format Decode (AFD). It will adjust to whatever signal is being delivered to it. For instance, playing a Blu-Ray from my PS3, I'll get DTS 5.1 surround.

With the HD300, all I can seem to get is Stereo output. I've gone into the settings and tried all the different Audio options (Digital Bitstream, Digital PCM, HDMI 1.3 Bitstream), but they all perform the same with just stereo output.

If I hit the Info button when watching a particular program, it says something to the effect of "stereo audio", but then a little lower in the info it'll say "Mpeg-2..... 5.1 audio" (or something like that - sorry writing from work and going by memory).

Is there another setting I need to change in the HD300's detailed setup? I looked but couldn't find anything in the menus.