Not Running Dolby with PS3 Games. Help..

[Pelican170]

Ok, I have posted something like this before, but still have no solid answer so let me try to explain this to the best that I can. Hopefully someone can help me. I have an onkyo 804 (a lil older now but runs HDMI 1.1) so here is my problem. When i play games, and only games, my receiver seems to switch to a multichannel pcm instead of the Dolby Digital which it should be running. If i go to the settings and uncheck all the codec options, (5.1 pcm 48 hz, 2.1 pcm....) and only leave Dolby Digital and DTS checked, then the receiver will play the games in Dolby Digital. At first I thought that maybe the Multichannel PCM was actually a DD, but after playing with this for a bit, I can clearly hear a difference in sound, and the DD sounds much better. Can anyone help me so that when it comes to watchign movies, i dont have to go and recheck the 5.1 pcm...?