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25 Jan 2021
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Best strategy for de-telecining difficult 24PF footage? 14 Mar 2023 21:37 #124595

  • oxband
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So, I'm working on a project and some of it was shot 10 years ago on a Canon XA-10 with the dreaded 24PF format.I'm working on a film in FCPX that's 24fps. I took the footage and did Reverse Telecine in Compressor. This solved the issue for most of the footage, but some of it had people walking past the camera, and there is still some salight interlacing after the Reverse Telecine in Compressor.Any suggestions for what to try? I still have a backup of the original card I shot this on. Is there any way to somehow try to reverse it from the card rather than once it's been exported as 30i.I know FCPX has a way to stop the conversion in importing, but that only works if it's from the camera. That option is greyed out if I try to import again.

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Best strategy for de-telecining difficult 24PF footage? 14 Mar 2023 21:57 #124597

  • DaveM
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It seems that you have created two posts. To remove the other one, simply edit it and delete all your text, then click Submit.

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Last edit: by DaveM.

Best strategy for de-telecining difficult 24PF footage? 14 Mar 2023 22:02 #124598

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Sorry. It's 29.97i
The camera shot at 24fps but rewraps it. God, I hate the PF24 camera setting

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Best strategy for de-telecining difficult 24PF footage? 14 Mar 2023 22:27 #124600

  • DaveM
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I misspoke. I haven't done this in over ten years (and Compressor has changed a lot, as well)... ;-)

On looking at the manual, you're supposed to choose 29.97 in the Frame rate field of the Video Properties in the Video Inspector tab. It should be 23.976. In the Quality section of the Video inspector, click the “Retiming quality” pop-up menu, then choose Reverse Telecine.

Seems like you did this. Compressor is supposed to be able to handle cadence breaks automatically. That's about all I have to say, right now... sorry.

Addendum:
If the reverse telecine worked properly, you probably shouldn't see any actual "interlacing" issues, at all. You might possibly see some "strobing" or other shutter-related effects (depending on camera recording settings). If you posted a sample clip, before and after your reverse telecine, we could at least verify that we're getting the same thing, or maybe offer further advice...

(I see you have also posted on Apple Discussions. That's usually not a good idea, as it can cause you confusion and delay getting a proper answer. Also, most of us participate both here and there.)

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Last edit: by DaveM.

Best strategy for de-telecining difficult 24PF footage? 15 Mar 2023 23:11 #124603

Funny, I've been playing with some 24P footage in a 60i stream (Panasonic version) lately too, and this is what I've found.

Compressor can reverse telecine it. The manual:

https://support.apple.com/en-ca/guide/compressor/cpsr9b255c31/mac

has the steps to do it in the Perform a reverse telecine frame rate conversion section, but step 3 is wrong. Set your frame rate to 23.976 or 24, depending on your desired output. If the camera recorded in 3:2 pulldown and not in 3:2:2:3, Compressor should be able to detect it and reverse telecine it without issue. It's worked that way in the tests I've shot.

After Effects can also do it, via the interpet footage, but it seems to like standard 3:2 pulldown rather than anything advanced. It takes longer to do and you have to put each shot into a comp, output it and on and on. Might want to try Compressor first because of it's batch nature.

Hope that helps.

fsorvin

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Best strategy for de-telecining difficult 24PF footage? 17 Mar 2023 16:37 #124626

I also found this method, which I've never tried before:

The Optical Flow Method
This is currently the highest quality method of converting 60i footage to 24p. It involves using optical flow to extrapolate 24 frames of information from 60 frames while compensating for the time displacement between the two. For example, in one second of 60i footage, each image is captured at 1/60 second, which does not perfectly align with images that would have been captured 24 times per second. Simply "cherry picking" 24 images out of 60 does not present 24 frames with perfect temporal consistency, since more or less time may have elapsed between frames. The result is a slightly jittery picture, which appears to jitter in a cyclic fashion. Optical flow algorithms will analyze the footage and make corrections to the picture in order to better "fit" each frame into the new 24 frame sequence. The resulting footage is much smoother because it simulates equal exposure time between frames.
For best results, footage should be deinterlaced and frame-doubled to 60p. This preserves all of the footage's temporal information, which is key in determining what the "missing" points in time should look like when converting to 24 frame/s.
The last step is to compensate for the lack of motion blur in the 60i footage. Since the images were captured at 1/60 second, there is less motion blur between images than there would have been if shot at 24 frame/s with a 180° shutter (i.e. 1/48 second exposure time). Optical flow is used to introduce motion blur between frames, mimicking the motion blur present when shooting the standard 180° shutter angle. This method of creating motion blur is far more realistic than simple frame blending, which is simple to implement and usually a standard feature in most non-linear editing programs.
The optical flow method also works with 30p footage and is currently the best option for 30p to 24p conversion.

from: en.wikipedia.org/wiki/24p#Advanced_pulldown

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Best strategy for de-telecining difficult 24PF footage? 17 Mar 2023 20:34 #124629

  • DaveM
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I also found this method, which I've never tried before:

from: en.wikipedia.org/wiki/24p#Advanced_pulldown

Thanks for that info.

So, something the OP could try, in addition to the reverse telecine workflow in Compressor would be to do the optical flow method outlined in the wikipedia article and see if it makes any difference.

Following the workflow from the wikipedia article should be doable in Compressor. According to Apple's Compressor product info:

Pristine format conversions.
Compressor uses optical flow processing to perform format and standards conversions at exceptional quality. You can also take advantage of built-in image filters and tools for audio processing.


An example:
In Compressor, add a preset (say ProRes 422) and set the Video tab's Frame rate to 59.94 and the Field order to Progressive. Optionally, set Retiming quality to Best (I don't know if this will make a difference in the deinterlacing process). This will do the deinterlacing step.

Next, Control-click the setting in the batch, then select New Job With Selected Output. Add another instance of your output preset (ProRes 422, for example). In the Video tab for the second preset, you could set the Frame rate to 23.976, the Field order to Progressive, and Retiming quality to Best to use optical flow.

Compare the results with the reverse telecine method...

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Last edit: by DaveM.

Best strategy for de-telecining difficult 24PF footage? 18 Mar 2023 17:06 #124641

Yes, it's certainly something you can try with any 24p encoded footage in a 60i format with anything other than 3:2 pulldown on it (like 24PA, or 24PF possibly). It's kind of a hack, but it might just save your bacon.I just did a test on some 24PA footage I had that Compressor could not reverse telecine without getting interlaced tears. It was basically two steps.1. convert footage to 60P. Set for 59.97 and progressive. Under Quality, set it for Best (Motion Compensated). This turns on Optical Flow, which is key for this. Process the footage.2. take the resulting 60P footage back into Compressor and set for 23.976, progressive and for Quality -> Best (Motion Compensated). Let Optical Flow do it's magic and reconstruct frames for you into 24P.Unfortunately this doesn't do a true reverse telecine like Classic Final Cut Pro used to do all on it's on during injest of 24PA or 24PF footage, but it will make something workable. I just tried it out and the results were decent. fsorvin

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