Deinterlacing an online video with comb artifacts?

[Master Tape]

Basically i want to download a few old shows i used to watch that are online, but annoyingly have not been deinterlaced as they still show all combing artifacts. So how do i turn this progressive source back to it's original interlaced format to then run QTGMC on it?

[jagabo]

That clip was already deinterlaced. You can clean it up a bit with QTGMC(InputType=1).

[hello_hello]

I'd also suggest QTGMC, and enabling it's denoising will probably help. It can be kept fairly low.
ie QTGMC(InputType=1, EzDenoise=1)
You'll lose some fine detail, but hopefully it'll smooth it out a bit. I'd follow QTGMC with GradFun3()

I wonder if the problem's not that it wasn't de-interlaced, rather it was de-interlaced when it didn't need to be. Your sample looks like film, although it's all outdoor scenes. Is the inside stuff any better?

[killerteengohan]

Doesn't really look interlaced to me. QTGMC is one option like the above 2 posts said. You could also try santiag(strv=0)

[ItaloFan]

The OP knows the clip is progressive and has been deinterlaced.

In the fade-in of the supplied clip there are some ugly lines which do suggest deinterlacing has happened, but as far as I can see, none of the things in motion are showing any hint of residual combing, nor are there vertical or diagonal lines showing any mismatch in horizontal alignment. The only issue I can see which he may be having a problem with is the blurry, ugly edges of the titles, especially the solid orange rectangles.

If that's what it's about, I suspect it has more to do with the low vertical resolution of the clip (it is 576p, maybe a DVD rip) and the 4:2:0 chroma subsampling (color info is provided at half resolution vertically & horizontally), and maybe also issues with limited gamut in the red/orange end of the spectrum (subtle gradations in those colors are difficult to achieve, for whatever reason). There's no way to undo this.

To answer the OP's question, if you have something that did not deinterlace to your liking, you can't really undo it. I mean, you could try interlacing it again, so that you could re-deinterlace it with a better algorithm, but at best you would just get back exactly what you started with.