Hi, and Welcome to Audioholics.
On the audio setup menu from your PS3, for the digital optical Out, you just Select "Bitstream". And:
DD = Yes.
DTS = Yes.
LPCM 2-ch. 44.1 khz = Yes.
LPCM 2-ch. 48 khz = Yes.
LPCM 2-ch. 88.2 khz = Yes.
LPCM 2-ch. 176.4 khz = No.*
* Your Sony STR-DG820 A/V receiver should be able to handle all these resolutions. But the higher numbers of resolution don't really matter from the digital Optical output. You can say Yes to all of them, and it would not matter.
Cheers,
Bob