18 fps to 29.97 fps, DGPulldown Question

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18 fps to 29.97 fps, DGPulldown Question

Post by BaronVitelius »

Hello, Forum,

I have Googled the topic that I'm about to ask about, and I haven't seen an answer that I like, so I'm trying here.
I have used AVISynth and DGPulldown a number of times to help convert film-based PAL DVD's to NTSC, so I'm
a little bit knowledgeable about what I'm asking, but still rather a novice. I've been using CCE basic for MPEG2

I have just gotten some home movies (the film kind) scanned to (720p) .AVI files. The 18 to 60 conversion was
accomplished by, for lack of better terminology, 3:3:4 pulldown (at the frame level). Therefore, for every 10
AVI frames, there are 3 progressive film frames. I want to author to DVD at 29.97 fps. I know how to use AVISynth
to resize and to select every third, sixth, and tenth frame from the AVI to get the18 fps progressive source. Then,
the trail goes "cold".

Here's what I think I can do to proceed:
1) Use AVISynth to perform a hard telecine to go from 18 fps (/1.001) to 29.97 fps, and encode
2) or, forget about trying to reproduce 18 fps, and go with 20 fps, encode, and use DGPulldown to add "3:3" pulldown
3) or, use AVISynth to repeat every 3rd 18fps frame, essentially turning it to a 24 fps film, encode, then use DGPulldown to add "3:2" pulldown, and live with the jerkiness
4) or, my preferred but maybe non-implementable solution, use AVIsynth to repeat every 3rd 18 fps frame (as above), encode,
then use "miracle occurs here" product to apply what I'll call 3:3:2:2 pulldown in which only the first and second (and fifth and sixth, etc) frames
have an extra field displayed, yielding a cadence of 3 fields, 3 fields, 4 fields. Assuming that this would be a valid application of
flags, it seems conceptually that DGPulldown could do this, but it would have to synchronized with the underlying frame structure so that it
would know to only touch TFF / RFF flags of the first and second frames of every 4-frame "cluster".

Whew. So, does any product that you know of do what I've described in (4) above?


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Re: 18 fps to 29.97 fps, DGPulldown Question

Post by admin »

#1 is not possible per the definition of hard telecine.

DGPulldown can't implement #4 as it stands. I couldn't think of a way to do it with Avisynth but I didn't try for long.

If you just dgpulldown your cluster ABCC 24->29.97 (your #3), how does it look?

I don't think you should bother with field pulldown, given that modern displays are natively progressive. Just decimate it progressively and be happy.
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