bear in mind that if you have the old fat ps3 in the audio settings you must set the audio to linear pcm it doesn't display the hd codecs but will send the audio as hd.
and if you have the ps3 slim set the audio to bitstream once you have done that you will be able to get hd audio.
That's TOTALLY WRONG!! If you own a B&O TV, you MUST choose linear PCM everytime, with every blu ray player (PS3 fat/slim/oppo/kikinoko)!!
If you select bitstream as output, you will simply get the core audio signal, which is DTS/DD, not HD signal, as there is no B&O electronic that can decode HD signal.
As fl4f says, no matter which device decodes the HD signal into PCM, as it's lossless, which is exactly like unzipping a .zip file : if you do that on a cheap PC, you will get the same result as with a glamour-unibody Mac... The multichannel PCM is then converted to analog 5.1 audio via the excellent B&O D-A converters.
Always go for linear PCM out from a BD player, until B&O give us some up-to-date TVs that can decode HD signals.