Deinterlaced or Source?

[Wicked_Al]

My source is supposedly Progressive PAL, but at every so often there appears to be interlacing...Not the whole screen kind, but the outline of a person who is moving appears to be interlaced! It only last for a few frames, then a few minutes or seconds go by and it comes back...just enough to irritate you.

My question is this: How can you tell if something is interlaced or the source was encoded with visible interlaced-like lines? I've tried pretty much everything except a manual IVTC, but nothing seems to get rid of the lines. Switching field orders and using all of the deinterlacing optins in TMPGEnc's deinterlacer, Auto IVTC, Smart Deinterlace, deinterlace - area based, and deinterlace - PAL frameserved via Vdub, yet the lines are there.

[D_Knife]

I was reading on www.100fps.com that some video can be transmitted in in both interlaced and progressive streams. Very informative site by the way.
There is also this filter
http://www.uwe-freese.de/vdubfilters.html
It's a time based de-interlacing filter, and being a german site there's a good chance that the filter is optimised for PAL as well.
Let me know how you go

[Wicked_Al]

Thanks for the link D-Knife. www.100fps.com described the interlacing as color interlacing, but that seemed to be the final result of an interlacing technique. I would think that simply deinterlacing again would remove the color interlacing, but its always there. I tried the time based filter and it seemed to make it truely interlaced! I've only been playing with it for a few minutes, but I'll look at it in detail later tonight. Thanks for the link! At least now I know what to call it and what to search for!