[jpsdr]

Passthrough is not dependent on the channel settings, it is "passed through" as is, encoded as it originally was, which is why it plays fine even though channels detected are only two.

I know what passthrough is, but also non passthrough (FLAC) is played in 5.1.

The AAC button does nothing at this point. As mentioned earlier "AAC will not play unless your device decodes it natively. If it's playing then obviously it does.

Ok.

Little question : Is DTS-HD MA supported on passthrough ? If i ask, it's only because i have a file with DTS-HD MA (well, at least it's what's xbmc said when i ask codec info), but my receiver isn't displaying "DTS-HD MA" as it usualy does when i play Blu-Ray with DTS-HD MA.
So either it's not supported, either it's still the same EDID issue...
Google search doesn't give me true results (hard to search in an ocean)... Except that if it's the receiver wich is wrong, i'm screwed unless Pioneer update the FW.... I don't beleived on it. If it's the nvidia drivers... a little hope...