This post was published more than a few years ago (on 2004-11-18) and may contain inaccurate technical information, outmoded thoughts, or cringe takes. Proceed at your own risk.
Referencing my original post on the subject, I finally found a solution to removing a 4:2 pulldown from a 30i clip, to get back to a 25p clip. It’s not pretty, but if you’re interested in the tech stuff, read on…
The solution did, indeed, involve Windows (in my case, running on Virtual PC 7) and the freeware apps AviSynth and VirtualDub. These steps assume that you’re working with a QuickTime file from which you need to remove this pulldown.
- Prep your Windows machine (real or Virtual PC) by downloading AviSynth, AVSEdit (at the bottom of the AviSynth downloads page) and VirtualDub from the links above, and install them.
- Make sure that your clip starts on an “A” frame, where the cadence is “AA BB CC CD DE EE”.
- Open your movie in QuickTime Player, and File > Export… with Movie to AVI. Make your video settings Compression: None; Depth: Millions of Colors; Quality: Best. I didn’t bother with exporting sound, as my clips didn’t need it I’m not sure how the audio would fare through this process, but I’m betting not well. If you have audio, I’m guessing it would be better to strip it out here, and sync it back up later.
- Bring the AVI onto your PC, or on the same Mac that’s running Virtual PC. You’ll want to note the full pathname of your clip, from whatever random letter VPC has assigned the drive your clip is on.
- Open up AVSEdit, type this code and save
|
1 2 3 4 |
SeparateFields DoubleWeave SelectEvery(12,0,2,4,7,10) |
- Open VirtualDub, and open the AVS script that you just saved, then select File > Save as AVI… (F7) and save your new clean AVI.
- Bring your AVI back into QuickTime player, and File > Export… as a QuickTime Movie. You’re done!
- One additional step for me, since I needed to get back to a 24fps clip for inclusion in a 720p24 show I’m working on—- Bring the new QuickTime clip into After Effects, and File > Interpret Footage > Main… and set Conform to frame rate: 23.976
It’s pretty convoluted, but it works. What amazes me is that there’s no tool like this that exists for the Mac. Guess it’s time for me to get back to my programming class, eh?
A quick ‘n’ dirty solution that works without VMware silliness:
In After Effects, interpret the footage with “Separate Frames”. Place the footage into a comp at 59.94 and render out the progressive frames, including duplicates. Take this rendered file, replace it in a new comp at 25 and apply the “Timewarp” filter to the clip at 100% speed. This does a cleaner job of interpolating the frames down to 25 fps and avoids the ghosting that would otherwise result.
I did try just doing this with nesting the 59.94 comp into the 25 one, but After Effects wanted to resolve back to the original frame rate instead of keeping the 59.94, even if I checked “Preserve frame rate when nested” in the Advanced Comp Settings in the 5994 comp. Your mileage may vary.
Obviously, this isn’t perfect pulldown removal, but it worked well enough for some re-cre footage that was going to look at little dreamy anyway.
On the project I’ve been working on today, I discovered another pulldown pattern for 25p footage: a 3:3 pulldown. The pattern takes on this cadence “AA BB BC CD DE EE.” This is easy enough to fix with the same process— just substitute this line into the script:
SelectEvery(12,0,2,5,7,10)To clarify, this should really be called 2:2:3:2:3 or 2:3:2:2:3 pulldown, and not 4:2 or 3:3. The number should refer to the number of fields each original progressive frame takes up, not the ratio of progressive to interlaced frames. My mistake.