Re: 7.1 with PowerDVD 8.0.2217. Tested it further, and having weird results with 2 different discrete 7.1 DTS-HD MA samples. One of them seems to mix sides with rears, but progressively (for ex. rear-right sounds louder when the rear-right channel is played, but there are "traces" of the sound in the rear-side). This is with a sample of an airplane flying, which is more like a sweep across the 4 surround channels. With another sample, an actual discrete sample, there is no mix whatsoever, and every channel plays just like it should.
I don't know if this should still be discussed here, but if anyone wants to test the difference between PDVD 8 and 12, I can upload the samples.