That said, when listening to hairy_hen’s purist mix for Harmy’s despecialized ROTJ, I noticed a significant amount of bleeding of dialogue from the centre channel into the front left and rights. I say significant because, if I play the 1993 mix through my receiver in Pro Logic II mode, this bleed is much reduced. I thought that the 5.1 mix was created from a Pro Logic II upmix in software, so this is surprising.
Most FREE DPL decoders in software are of the passive consumer non-steering type :dolby surround: , which are inferior to the PRO PL1 (with primitive allband steering), & obviously all inferior to PL2. I’m guessing he used PL1/DS things.
As of now, there are FREE PL2 things, only one I know of is freesurround (the foobar implementation being easiest to use imo), which should have much less C ch bleed. (hint, use old defaults preset for maximum discreteness)