OK, brief description of 2-2 and 3-2 pulldown. Let's take a regular, 24 frames per second film with frames 1, 2, 3 & 4.
For PAL, this is sped up to 25 frames per second so all that is needed is to split the frames into two interlaced fields, a & b. Hence, for PAL, the fields output (at 50Hz) would be 1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b. The key thing is that you have pairs of fields that correspond to the same frame, i.e. the cadence is 2 - 2 - 2 - 2; this is 2-2 pulldown and a player needs 2-2 pulldown detection to ensure that it combines fields 1a & 1b to produce frame 1, rather than 1b & 2a, which would produce an artefact called combing.
For NTSC, 24 frames per second are converted to 30 frames per second by duplicating some fields: 1a, 1b, 1a, 2b, 2a, 3b, 3a, 3b, 4a, 4b. Here you see the cadence is 3 - 2 - 3 - 2, or 3-2 pulldown. Again, 3-2 pulldown detection is needed to correctly recover the original movies frames without combing.
Note, the above only applies to cadence-based deinterlacers - like the Sony - which ignore the flags on the disc and try to spot the 2-2 or 3-2 cadence to deinterlace. Other players rely on the discs ahving the correct flags to allow the correct recombination of field to produce the original movie frames. This is easier to implement but leaves you completely at the mercy of the DVD author.
FWIW, my 730 seems to correctly detect 2-2 and 3-2 pulldown - included wrongly flagged discs that would comb badly on a flag reading player.
HTH,
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