kwag -
Have you actually done a listening test to compare HeadAC3he's "Surround" and "Surround 2" downmixing modes? I'd be interested to know how well they both work and if there's really that much of a difference on a Pro Logic II receiver.
I've been reading in newsgroups today that there is no special "Pro Logic II encoder" -- the magic happens in the decode phase, with regular Dolby Surround-encoded material, so I'm not sure what HeadAC3he's author means by "Surround 2" mode.
What would be really fun is to take one of those speaker test discs, pull off the AC3, and encode to MP2 with both "Surround" and "Surround 2" modes (also with any special preprocessing you might want to apply
). That way we could work out just how well the encoding maintains the channel separation...
I have one of those discs, so I'll see if I can pull the AC3 from it. Having totally separate channels like that would be very useful for testing audio.