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3:2 pulldown? 29.97fps to 23.976
I have the JVC Everio GZ-HD7 camcorder and I believe it films in (60i)
or 30fps (I’m not sure if there’s a difference) is 60i different from 30fps?but back to what I was saying-
It films in that high frame rate and i am trying to convert it to 24p but then everybody keeps telling me about 3:2 pulldown but doesn’t bother to explain it.
What is 3:2 pulldown and how do i know when to or if to use it? what does it even do?
And lastly- if exporting 29.97 footage in 24p will that change it at all?
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1 Reply
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To fully cover pulldowns would require a lengthy explanation. I’ll try to be concise here and link to further information.
60i is different and ‘the same’ as 30fps. Really 60i should be thought of as 60 fields per second. Two of these fields form the full frame of video, so there are 30 ‘frames’ per second.
The reason I say ‘frames’ per second is because each ‘frame’ is made up of two wholly different fields that were recorded at different instances in time (1/60th of a second apart from one another). Where as in film and progressive video the smallest unit of time is a frame, the smallest unit in interlaced video is the field.
Many camcorders these days will record in 24p or 24pA, which generally means that they will record 23.976 full frames of video every second and add a pulldown to them to make the video 29.97 frames (59.94 fields) per second.
In NTSC land a pulldown is a method for translating 4 full frames into 5 ‘full’ frames of video. What is in fact happening is that the 4 full frames are being recorded as 8 interlaced fields, then 2 of those fields are duplicated and combined in such a way to create 10 interlaced fields.
If your original frames were:
A B C DThen your interlaced 8 fields would be:
A1-A2 B1-B2 C1-C2 D1-D2And your 10 fields after a pulldown is added could be:
A1-A2 B1-B2 B1-C2 C1-D2 D1-D2Notice that you now have 5 ‘frames’ but that two of them have fields from different source frames. To get back to 23.976 full frames the pulldown must be removed by combining “B1-C2” and “C1-D2” to create “C1-C2.”
Read more about pulldown here:
https://en.wikipedia.org/wiki/3:2_pulldown
After Effects has a feature in the Interpret footage dialog to do this, but you must first make sure that your footage had a pulldown added at some point (either by the camera during recording in the case of video, or during telecine for film):
https://livedocs.adobe.com/en_US/AfterEffects/8.0/WS3878526689cb91655866c1103906c6dea-7f33.html
Darby Edelen
Lead Designer
Left Coast Digital
Santa Cruz, CA
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