need help with 7.1 (3:10 to yuma)

[hagaf22]

this is what i have,

playstation 3 as a blu ray player with optical out for audio hdmi out for video
str-de897 receiver (no hdmi in) with the optical in to the tv/sat opt slot since there are not video slots aside from the one on the front for video 3 which doesn't seem to work.
samsung 52 in lcd 1080p tv


this is my problem, i know the ps3 doesnt decode 7.1 dts-ma but it should the 7.1 pcm which is the audio out for 3:10 to yuma.
i just watched it and couldnt get 7.1, i had it on auto detect and would only play in 2.1 so i chose the movie option which plays it in surround, but not 7.1.
i switched the audio on the ps3 options from bitstream to pcm which set it back to 2.1, if i put the movie on 5.1 dolby it worked like it was supposed to, but when i went back to 7.1 nothing.

please somebody help me figure this out.