Filtering: before or after IVTC?

[AlonP]

Hi,

From what I know things like Rainbows/dotcrawl if present should be handled before the IVTC process. But how about other filters? Say fft3d - it has an "interlaced=true" option.

Basically, in which cases, and what are the benefits of filtration pre-ivtc?

[colours]

If you're trying to clean up artifacts introduced during or after telecine, then the appropriate filter should be used before IVTC. Other than those cases, you should pretty much always filter after IVTC.

[AlonP]

What kinds of artifacts can be introduced? I know of rainbows and dot crawl, but besides that? Like, ghosting and what not - those are more like... "TC" specific things... But many filters, again, fft3d have interlaced=true switch... I always took it for "use if you can" kinda thing... I always figured, before you IVTC it -the video has more "information" or something, for the filters to work with...

I'd appreciate some examples.

[johnmeyer]

Colours post really says it all: artifacts that were introduced after the telecine should be removed first. These include encoding artifacts, like blocking.

That said, many of those artifacts change frame-to-frame, and so can be removed just as effectively after doing IVTC.

For any sort of film restoration (see the several extremely long threads on that subject, elsewhere in this sub-forum), you must do IVTC first. It is not even an option: the AVISynth restoration will not work at all on the telecined film.

So, for most things that I can think of, you should do IVTC as the first step.

[feisty2]

Separatefields()
Any filter you want
Weave ()

[feisty2]

And I don't see the point filtering before ivtc, even luma/chroma cross could be removed by denoisers after ivtc

[kuchikirukia]

Separatefields()
Any filter you want
Weave ()

Antialiasing is a fun one.

[AlonP]

Alright, thanks guys :).