mixed timebase

I was given a project timeline with mixed timebase: some 23.98 some 29.97, all in codec DVCPROHD 1080p30 according to the Analyze Clip function (1280X1080 aspect shot on P2s). It played through the editing with no problems or stutters (though got fussy with more than 8 audio tracks, requiring lots of audio renders), but output is another story. The timeline timebase was 29.97 despite the fact that more of the clips are 23.98 (previous editor's decision). The 29.97 footage has very noticeable interlacing on the computer monitor screen, but when output to SD DVD via compressor it still has very strong interlacing. I suspect that this footage was miscaptured.
1)Anybody know if interlacing on 29.97 even on DVD playback means that it should have been captured and excess frames removed by reverse T or advanced pulldown removal?
2) anyone know a way to convert a mixed 29.97 timebase timeline to a 23.98 timebase without rebuilding the entire timeline clip by clip (if I copy and paste All into the new timebase timeline the audio goes totally out of synch since some of the tracks are being shrunk and others are being expanded (I guess) to fit the new timebase)?
3)for future ref: is there a "best way" to mix different timebase clips for optimal results?

All help appreciated. Ron

First things first, the "solution" to fixing mixed frame rates from multiple cameras is called a reshoot. There are some exceptions where you need to work with mixed frame rates (eg. historic archival footage, etc..).

Removing pulldown from footage shot at 60i is not possible, simply because there is no pulldown to remove.

Also, interlacing is a video format. There is no such thing as "strong" interlacing. However, as you are working in 24p, the rest of the footage should be properly de-interlaced and converted to 24p.

>3)for future ref: is there a "best way" to mix different timebase clips for optimal results?

Yes. Firstly, reshoot. If it is not possible, you either convert the frame rates before you edit (either in Compressor or a hardware based converter), or you add a pulldown (in your case, without looking at the footage, I would work at 29.97 and add a pulldown to the 24p footage).

And golden rule: Do not use FCP to do standards conversion. It was not built for it (i'm seeing aliasing on some footage because the previous bunch of folks used FCP thinking they were working off a Teranex).



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Thanks for the info.

Followup questions:
"removing pulldown from 60i"---I was wondering if the 29.97 is not from 60i but from 23.98PA from which the pulldown was NOT removed during log and transfer. would that give footage with interlacing? (in this case, the problem wouldnt be in the shoot but in the ingest)

"de-interlaced and converted to 24p": that was my thought and planned to use Compressor, but in reading Ken Stone recs, he advises always going up to avoid dropping frames from 29.97. Thoughts on that?

re FCP and conversion: duly noted!

We need to make a distinction. There is 60i (29.97 fps), there is 24p (23.98 fps), and there are 24p footage with pulldown to make it 29.97 fps. 60i will not reverse telecine to 24p unless it was shot with a consistent pulldown.


>I was wondering if the 29.97 is not from 60i but from 23.98PA from which the pulldown was NOT
>removed during log and transfer. would that give footage with interlacing?

Well, check that. Go to the source clip, step through the frames. If you see repeated patterns every 5 frames, you're dealing with footage that was shot with a pulldown. Once you get that, count which are the jitter frames and which are the progressive frames, and check if it's consistent. Then you'll have your pulldown pattern. If it's a consistent pulldown, you may be able to remove that with Cinema Tools.



>he advises always going up to avoid dropping frames from 29.97.

Well, yes. Adding a pulldown to 24p would look better than doing a standards conversion from 60i to 24p and more importantly it's a lot faster, as the math is simpler.

But if you're going out to web, I'd say standards convert the 60i footage to 24p. You'll also go down to 24p if you have loads of 24p footage.



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