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Fifth-frame stutter on ProRes files in After Effects

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Daniel McKleinfeld
Fifth-frame stutter on ProRes files in After Effects
on Oct 20, 2011 at 10:05:04 pm

Hello, all!

I've got some movie files that I want to bring into an After Effects project, where they'll be flown around the screen while various animated elements play.

The files are all Apple ProRes 422 (HQ) codec, 1920 x 1080, 29.97 fps.

The After Effects project is based on the HDTV 1080 29.27 preset, with the pixel aspect ratio set to Square and the frame rate at 29.97 (non-drop display).

The problem is that as soon as I drop the ProRes file into a composition, every fifth frame is a repeat of the fourth frame!

When exported, all the animated elements play normally. It's just the embedded ProRes files that have the odd stutter.

I usually associate this problem with a bad 3:2 conversion, but as every link in the chain is 29.97, I don't understand what's happening.

Does anyone have thoughts? Much appreciated!


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Walter Soyka
Re: Fifth-frame stutter on ProRes files in After Effects
on Oct 21, 2011 at 5:40:52 am

[Daniel McKleinfeld] "I usually associate this problem with a bad 3:2 conversion, but as every link in the chain is 29.97, I don't understand what's happening."

Are you sure the original ProRes footage didn't originate at 24p? If you step through the footage in AE outside of the comp, do you still see the duplicated frames?

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
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Brian Charles
Re: Fifth-frame stutter on ProRes files in After Effects
on Oct 21, 2011 at 1:01:15 pm

[Daniel McKleinfeld] "The After Effects project is based on the HDTV 1080 29.27 preset, with the pixel aspect ratio set to Square and the frame rate at 29.97 (non-drop display).
"


Rather than use a preset, drag the ProRes footage onto the New Composition icon at the bottom of the Project Panel.

This will make a composition that conforms to the footage dimensions and frame rate.

The only other thing I can think of is that the footage is 1080i not 1080p and the footage is not interpreted correctly.



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ben g unguren
Re: Fifth-frame stutter on ProRes files in After Effects
on Oct 21, 2011 at 4:05:59 pm

it sounds to me like your footage was shot with advanced 3:2 pulldown (2:3:3:2 pulldown, etc). Advanced 3:2 works in such a way that every fifth frame can be discarded -- this fifth frame has two fields from different images in it, so it looks very different from the others. However, my guess is that AE has recognized that your footage has fields, and is removing one of the fields. Thus, in the AE timeline, you don't see the interlaced fifth frame, and it looks like a duplicated frame. If this is the case, it is VERY important that any graphics that overlay your footage exhibit the same behavior. Here's how I do it:

- Remove the pulldown. (Now your 29.97 footage is 23.976)
- Do all your animating for that clip at 23.976.
- Re-add pulldown at render time (you can do it in the Render Settings of the render queue)

Of course, if your footage absolutely has do be 29.97, then you can use Timewarp or Twixtor to convert the 24 footage into 30, often with reasonable results. But having the stutter of a duplicated 5th frame along with the relative smoothness of non-duplication simply won't work.

Ben Unguren
Motion Graphics & Editing
http://www.mostlydocumentary.com


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Daniel McKleinfeld
Re: Fifth-frame stutter on ProRes files in After Effects
on Oct 23, 2011 at 1:20:51 am

Thanks for all the thoughts, y'all!

@ Walter and @ Brian:

Tried dragging the ProRes directly to New Composition, and I still had the extra frame problem. So that's out.

@ Ben:

Well, part of the weirdness is that the graphics run normally, but the video has the stopped frame. Which, frankly, I can't see during playback---it was only noticed by the QA people making the Blu-Ray masters.

But… sure enough, using Interpret Footage -> Remove Pulldown -> SSWWW, the doing everything in 23.976 removed the extra frame!

I am afeared of what this is going to do for timing, but at least I'm a couple steps closer. Thanks, everyone!


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