PAL Inverse Telecine?

[Anakin]

Been reading about how you take a NTSC interlaced video and turn it back to its source with Inverse Telecine. Is there any way to do this with PAL?

[gadgetguy]

In short, no. NTSC is telecined to compensate for the vast difference in frame rates between film and broadcast/DVD. PAL frame rate is close enough to film to be able to do a simple speed adjustment without noticeable difference.

[manono]

Been reading about how you take a NTSC interlaced video and turn it back to its source with Inverse Telecine. Is there any way to do this with PAL?

What gadgetguy said. However, I'm curious as to what prompted that question. Are you actually seeing interlacing in your PAL DVDs? Are you noting that your DVDs are usually encoded as interlaced? Unless you see the interlacing artifacts (the combing), it's not interlaced, even though it may have been encoded as such. Even if you do see interlacing, the fields have often been phase-shifted and can be easily fixed without deinterlacing. And even if they really are interlaced, as often happens from a poor NTSC2PAL conversion, an unblender can usually straighten them out again. Only if shot using video cameras is the source truly interlaced.

If you have a source you can't handle properly, upload somewhere a small 10 second untouched piece and we can have a look.

[Chris K]

Even if you do see interlacing, the fields have often been phase-shifted and can be easily fixed without deinterlacing.

This phase-shifting (I think you mean mixing odd and even fields of two frames in one frame)
was popular in older days for PAL. I could remove that with reasonable success in vdub using the telecide filter.
However, occasionally duplicate frames are inserted at irregular intervals.

[manono]

This is phase-shifting. Where the capital letter is the top field and the small letter is the bottom field, ordinarily the fields are lined up so:

A B C D E F
a b c d e f

When phase-shifted, they go like so:

A B C D E F
b c d e f g

They appear to be interlaced but it's a simple matter to realign them again using the field matching component of an AviSynth IVTC, such as Telecide() (from Decomb) or TFM() (from TIVTC). We use different terms to describe it, but I think we're both referring to the same thing.

However, occasionally duplicate frames are inserted at irregular intervals.

You seem to be describing one way to convert film to PAL - by inserting a duplicate frame every second in the form of a duplicate field every half second. That's also an easy matter to fix using an AviSynth IVTC.

[Chris K]

You seem to be describing one way to convert film to PAL - by inserting a duplicate frame every second in the form of a duplicate field every half second. That's also an easy matter to fix using an AviSynth IVTC.

No that's not what I meant. It's very irregular, lets say only 20-30 times in a whole 90 min movie.
I have the impression that it are mistakes by the telecide filter with frames that have none of very little combing.
I also encountered sources that are mainly progressive but use the by you described phase-shifting occasionally
only on fast moving scenes.

EDIT: Note that I'm reffering to the vdub telecide filter (by Donald Graft).

[jagabo]

No that's not what I meant. It's very irregular, lets say only 20-30 times in a whole 90 min movie. I have the impression that it are mistakes by the telecide filter with frames that have none of very little combing.

Yes, all the automated IVTC filters do this on occasion. They occasionally let interlaced frames through, and they occasionally duplicate and drop frames (ie, whenever a frame is accidentally duplicated another frame has to be dropped, and vice versa).