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14 Nov 2020
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TOPIC: Help with retiming

Help with retiming 15 Jun 2020 17:00 #107909

  • manoucho
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Dear friends,

I hope you are all well.

After editing and picture locking my new film, we noticed in the Color Grading room that 3 clips where I had applied a speed-up ramp were looking very jittery.

I have two questions:
- does Optical Flow do anything for speeding up clips ? (it should't, I guess, but you never know)
- one clip only has a 10% speed up ramp but it looks jittery and unnatural. I don't know if it's expected behaviour. Would doing the speed up in Baselight bring better results ?

PS: I'm also dealing with the infamous "Analizing for Optical Flow" bug, where the message stays and never leaves...

Thanks a lot for your help

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Last edit: by manoucho.

Help with retiming 16 Jun 2020 04:57 #107925

  • Redifer
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Yes Optical Flow absolutely helps speed increases. I always notice a difference unless you speed it up by 200%, 300% or other round increments like that. Otherwise FCP is just playing the nearest frame which may not be the frame you actually need. Give it a try. However keep in mind you may need to render for smooth playback as I've found that FCP will play back slow motion footage done with optical flow in real time, but not so much fast motion footage with optical flow.

As far as the "analyzing" bug goes, I'm not sure if I've ever experienced that. Have you tried buying controlling shares in Apple and then forcing the FCP team to look into it? That would be what I'd try next.

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Last edit: by Redifer.

Help with retiming 16 Jun 2020 08:49 #107929

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Thanks a ton Redifer. Long time no talk.

That's good news, so Optical Flow is helpful in that case, thanks !

Unfortunately I'm dealing with the infamous Optical Flow bug, with has been running around for as long as I remember. Basically FCPX says "Analyzing for Optical Flow" forever, nothing happens. And if I want to export, it says those renders are missing. And deleting all render & optical flows files won't do much either.

It is happening almost every time I use it, but sometimes only later in the project.

I read in the past that it had to do with Speed Transitions, but I'm not sure.

In the meantime I had to to the retimings in Resolve. That's so sad :)

Controlling shares in Apple, what a brilliant idea !!

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Last edit: by manoucho.

Help with retiming 16 Jun 2020 12:27 #107932

  • joema
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manoucho wrote: ...deleting all render & optical flows files won't do much either...

Here are some possibilities: as you may know, the optical flow files cannot be deleted within FCPX, only at the Finder level within the library or designated cache location. If you haven't done that, manually delete them. Make sure background rendering is disabled so you can control the render by selecting clips and doing CTRL+R.

It could also be a manifestation of the general problem with tracking and re-using valid render files. Yes it seems more often seen on optical flow, but there is a broader problem. In some cases the render dots never go away, in other cases they vanish but the render files are not used. Either way, if render files were not used it could make optical flow ranges jerky.

To investigate, make a snapshot duplicate of the project, then on the problematic clips use Edit>Delete Attributes and delete all effects *except* for optical flow and retiming. The above-mentioned render problems are associated with certain combinations of effects in the stack. This test may help differentiate between that problem vs one unique to optical flow analysis.

Also I've observed optical flow analysis is very sensitive to UI actions while it's in progress. After deleting the optical flow and render files, while in the analysis phase do not touch the keyboard or mouse.

There have been some optical flow fixes in more recent versions (although I still see some problems on 10.4.8). If you are not on 10.4.8 then consider using that.

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Help with retiming 16 Jun 2020 13:23 #107937

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Thanks a million Joema. That's super informative.

I've sent feedback to FCPX, for what it's worth...

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