I've just recorded a short film which was broadcasted in PAL. It doesn't seem to come from a digital source (according to the film-noise), so there shouldn't be any interlacing at all - BUT there is.
Now when I take a closer look at the frames, they're not interlaced equally:
Short: 20 interlaced1 - 20 interlaced2 - 20 progressive
Detailed:
interlaced1:
~20 frames are simply phase-shifted (after field swap),
interlaced2:
the next ~20 frames look better after the frame shift, but still contain interlacing lines.
progressive:
To make it worse, the NEXT ~20 frames are progressive.
What the hell is this?
[SOLUTION]
since I currently haven't found a way of deinterlacing "interlaced2", I cannot deinterlace it losslessly, but I'm planning to use a plugin for VirtualDub, called "conditional" (get it here) and then deinterlace every 20 frames differently.
Wish me luck.