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Optical flow jittery? Useless?

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Alan Langdon
Optical flow jittery? Useless?
on Dec 26, 2017 at 1:29:47 pm

I have footage shot in 60p, and am slowing it down and applying Optical Flow. No matter what speed I use (25%, 3%), I don't get smooth motion but rather stuttery footage, with repeated frames every so often, etc... Motion is smooth for several frames, then pauses, then goes forward, making the effect useless... Any advice?
I have converted footage to ProRes, and the timeline is 29.97 fps 1080p.

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Jeff Kirkland
Re: Optical flow jittery? Useless?
on Dec 27, 2017 at 8:17:04 am

Not every bit of footage works well with optical flow. Have you tried the other options? One of those may look better.

Jeff Kirkland | Video Producer & Cinematographer
Hobart, Tasmania | Twitter: @jeffkirkland

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Robert Olding
Re: Optical flow jittery? Useless?
on Dec 27, 2017 at 7:03:01 pm
Last Edited By Robert Olding on Dec 27, 2017 at 7:04:22 pm

Depending on the cut you're attempting to smooth out, you may have to try a variety of "optical flow" workflows. Give MotionFX's mMorphCut a try, it works great. If that doesn't do the trick, here's a tutorial that shows you how to do it manually;


Robert Olding
Minneapolis, MN

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Doug Suiter
Re: Optical flow jittery? Useless?
on Dec 27, 2017 at 10:49:12 pm

It sounds to me (could be wrong) that you are introducing Optical Flow unnecessarily. Try this:

1. Create a new 29.97 timeline (be sure to NOT use automatic settings or the moment you bring in 60p footage the timeline will change to 60p)
2. Drop in the 60p footage
3. Select it and choose Modify->Retime->Automatic Speed. This used to be known as Conform.

That will give you perfectly smooth footage because it is simply playing back at a slower rate than it was shot.

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Jeremy Garchow
Re: Optical flow jittery? Useless?
on Dec 28, 2017 at 12:49:35 am

Use "automatic speed" to get your footage to playback 60p over 30.

Then use optical flow and wait for the clip to finish analyzing. It shouldn't really repeat frames, the results should be more mushy/warpy if optical flow isn't working. But if the clip isn't finished analyzing (you can check the progress by open the background tasks window with command-9) you will see stutters frame until it's complete.

That being said, optical flow is very often magical, but sometimes it's not and it doesn't work very well. It's wholly dependent on the footage.

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