for example, in the Iron Man blu-ray disc, the only way to get the Dobly True HD audio track on the PS3 is to have the PS3 decode that sound track and output it via PCM to your receiver. The PS3 does not output the "HD" audio codecs (Dolby True HD and DTS HD Master) via bitstream since it already has built-in decoding of the aforementioned HD audio codecs.

If you choose bitstream audio on the PS3, the only type of audio the PS3 will output is the core audio (stereo, dolby digital, core DTS). This would be fine if you only have a 2.1 channel setup or if your receiver doesn't have HDMI inputs for audio.

larryV