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23.98 Timeline in a 30p World

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Bob Cole
23.98 Timeline in a 30p World
on Feb 16, 2013 at 11:58:09 am

This is a "should I take drastic action" post. I discovered, well into an edit, that the framerate in my sequence was wrong. Can I shift framerates in mid-stream? Should I even try?

I'm almost done editing a graphics-intensive, multi-video-layer 20-minute show destined for DVD playback on a big screen, using a variety of sources:

1. XDCAM EX footage shot at 1080 p30 (29.97)
2. XDCAM EX footage shot at 720p60 (59.94)
3. After Effects clips rendered 1080 29.97

On my MacPro 1,1 the renders were taking awhile, so I checked and found that the sequence was set as follows:

Frame Size: 1920x1080 Aspect Ratio: HDTV 1080i (16:9)
Pixel Aspect Ratio: Square
Anamorphic unchecked
Editing Timebase: 23.98
Quicktime Video Settings - Compressor: XDCAM EX 1080p30 (35 Mbps)

Note: the 23.98 framerate, which cannot be changed. (And no, I have no idea how that happened - that's one of my questions.)

I will try outputting a section to see whether the mismatch of 23.98 framerate has any effect on the final result. (UPDATE: I HAVE DONE THAT, AND IT LOOKS FINE, THOUGH I HAVE SOME QUESTIONS ABOUT WHETHER ONE PANNING SHOT MIGHT NOT LOOK BETTER AT 30FPS.)

I'd appreciate the collective wisdom on what happened, and whether it is something I should worry about.

I have already tried copying and pasting the whole timeline into a new, 29.97 timeline. A small error box appears: "Not Found." I was able to copy the soundtrack, but that process results in timing discrepancies; there are gaps between many of the clips, and the clip that appeared in the 23.98 original timeline at 01:09:31:06 is, in the 29.97 timeline, at 01:09:31:25.

Thanks for your help.

Bob C


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Dave LaRonde
Re: 23.98 Timeline in a 30p World
on Feb 16, 2013 at 7:31:30 pm

If the mention of 30P had not been made, the answer would have been simple: use Compressor to add 3:2 pulldown to the 23.976 clips (23.98 is a misnomer) to make 29.97 files. They would by necessity contain interlacing.

BUT.... you specify 30P.

You now need to open the wallet to the tune of some $600 for Twixtor, which is frame rate conversion software. It has capabilities beyond those of Compressor.

It can actually create the new frames required to go from 24p to 30p by looking at the surrounding frames, analyzing the motion within the frames, and inventing a brand-new frame containing the most likely position of the pixels. This is far beyond Compressor's meager capabilities.

Dave LaRonde
Former Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Bob Cole
Re: 23.98 Timeline in a 30p World
on Feb 16, 2013 at 7:55:52 pm

Thank you Dave. Very interesting! I'm glad to get your answer, because several hours ago I decided to bite the bullet and manually drag each shot of this 23.976 timeline into a new 29.97 timeline. A real painstaking pain, what with the software's confusion over timing the shots differently - especially as multiple layers of video were involved.

Any idea as to how FCP dictated using a 23.976 timeline? I sure didn't specify it on purpose. My SOP is to drag a clip into the timeline, let FCP adjust the timeline's setting, and go from there. I'm guessing it has to do with the use of 720p30 footage, which is not something I usually do.

When I use FCP's automatic sequence settings, here is what happens:

Footage that was shot 720p60 is characterized within the FCP bin both as 720p60 and as 59.94. The sequence auto-sets to XDCAM EX 720p60 with an editing timebase of 59.94.

Footage that was shot 1080p30 is characterized within the FCP bin both as 1080p30 and as 29.97. The sequence auto-sets to XDCAM EX 720p60 with an editing timebase of 29.97.

I've been trained to ignore this discrepancy; am I missing something critical?

Bob C


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Dave LaRonde
Re: 23.98 Timeline in a 30p World
on Feb 16, 2013 at 9:07:45 pm

I'm a bit confused, sorry to say: do you intend to deliver the final product at 29.97 or 59.94?

If it's 29.97, you will really want to use the frame rate conversion software on the the 23.976 stuff. If you place 23.976 footage in a 29.97 timeline, you'll see a 1-1-1-2 frame cadence as you step through the timeline frame-by-frame. The motion is both annoying and wrong. The 59.94 footage should be okay: FCP ought to see the first frame of it, and ignore the second one. It looks right.

If it's 59.94 and will always remain at 59.94, no exceptions, you've just hit the editing sweet spot: no frame rate conversion necessary! The 23.976 footage will show up as alternating between 3 frames and 2 frames in the timeline: it's built-in 3:2 pulldown. The 30p footage will have a constant 2-2-2-2 frame cadence as you step through it.

That's why I just LOVE 59.94p: it's just so flippin' versatile for people in NTSC-Land. Sure, the different frame rates display different kinds of motion, but the point is that they all play nicely together from an editing point of view.

Dave LaRonde
Former Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Bob Cole
Re: 23.98 Timeline in a 30p World
on Feb 17, 2013 at 2:04:41 am

[Dave LaRonde] "do you intend to deliver the final product at 29.97 or 59.94?"

It's headed to DVD.

That is very, very interesting about 59.94. Forgive the stupid question, but what about the whole issue of p30->29.97 and p60->59.94? Is that just a fact of NTSC life, or a choice?

If I understand it correctly, 29.97 and 59.94 are relics of interlacing, only here because of history. I need a refresher on all of this stuff.

Bob C


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Dave LaRonde
Re: 23.98 Timeline in a 30p World
on Feb 17, 2013 at 8:20:17 pm

[Bob Cole] "...what about the whole issue of p30->29.97 and p60->59.94? Is that just a fact of NTSC life, or a choice? "

In NTSC-Land, 30P can be either Standard-definition or HD 1080; the 1080 will contain two interlaced fields of the same identical frame. HD 720 can accommodate 30P: its 59.94 non-interlaced frame rate simply displays one frame twice.

60P can ONLY be HD 720.




[Bob Cole] "If I understand it correctly, 29.97 and 59.94 are relics of interlacing, only here because of history"

Actually, they're here because of the introduction of color TV in 1953. The NTSC signal needed to carry a tiny bit more information to broadcast color, but a TV channel's bandwidth was already full. Something had to give, and it was the frame rate: they changed it from 30 to 29.97... and many decades later, 59.94.

The frame rates have been grandfathered in. If they weren't, Aunt Emma's old RCA console TV from the '80's wouldn't work any more. Since Aunt Emma is NOT about to go out and waste money to replace a perfectly-good TV, this is not a minor consideration.

The United States could also assume the role of a dictatorship and mandate that henceforth all standard-def TV's will no longer be functional after a specified date, thus solving this frame rate untidiness.

And need I mention the decades of historic, archival and still commercially-viable material at 29.97?

Yeah, I wish someone could wave a magic wand and turn 29.97 into 30. It ain't gonna happen.

Dave LaRonde
Former Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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