I think some DD 2.0 mono soundtracks put the same signal into both left and right channels, leaving the center, surrounds, and LFE channels empty. Halloween's been released on DVD several times, and with perhaps one exception they've all had a DD 2.0 track on them; they may also have a separate mono track, but it's hard to tell from my bit of poking around Amazon.com and looking at the Digital Bits review of three versions . Other discs (including The Omega Man, according to Amazon.com) use a DD 1.0 mono track; I've already interpreted the "1.0" to mean that it decodes to the center channel only and leave everything else empty.

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