Frame-rates, interlacing, and variable speeds

Zander

Zander

Well-known member
I understand that with the DVX100 you can record 24pA and when you import your footage FCP (or another NLE) will pull frames and deinterlance. I'm wonder if there is a way to do that with 30p. For some videos I prefer the feel of 30 frames over 24. My problem is when I import 30p the footage it is interlaced. Does FCP or another Mac compatible application offer some sort of pull down for 30 frames?

Also, I used to think the best method to get a nice slowmotion clip out of the DVX would be to record 60i, deinterlace, and time stretch. Now after reading a lot about interlacing and framerates I think I've come to the understanding that deinterlacing blends back to back frames into a clean progressive video. Is my understanding correct? If so what would be a better way to make slowmotion clips with the DVX?

Quick breakdown of what I have: DVX100a, Final Cut Studio 1, and a PowerMac G5 running Leapoard (10.5.1).
 
There should be a way to setup a 30p timeline. In Vegas, I can set my framerate to 30 and then choose progressive under "Field Order." I'm not sure about FCP, though.
 
24p footage isn't deinterlaced. It isn't interlaced to begin with -- the only reason it's recorded with pulldown is because the codec requires it. When you remove the pulldown, you end up with the original progressive frames. It's not a process of making interlaced footage into progressive -- it's a matter of removing the necessary interlacing from footage that's already progressive.

30p doesn't require a pulldown cadence like 24p, because it's easy to split the frames into field pairs and record them in a 60i stream -- each field pair represents a frame. You shouldn't actually see any interlacing at all, even if you're viewing on a 60i timeline.

As for the slo-mo method, you mention the correct one. If you slow 60i footage to 40% on a 24p timeline, you'll get a 1-for-1 matching of each 60i field with a 24p frame. Then, when rendered, the fields will be interpolated -- each field will be made into a whole frame using the information in that frame. It'll be about 50% resolution, of course.
 
When you capture via FCP, make the capture preset for 24pa have the 48khz advanced 2:3:3:2 removal, when you want 30p capture with the reg. 48khz NTSC. the way to see that you have progressive clip is that it will have no half frames when going threw the clip one frame at a time. 60i and 30p will be labeled the same as 29.97 fps, but one will be interlaced, the other will be progressive. So in short if you shoot 30p, FCP will automatically do the pull down. At least it does it for me :) The only reason that 60i gives you smother slow motion because it has 60 fields of video, It will be less quality, but you can go slower and smoother with it. This all can be found in Berrys book.
hope that helps!
Jon
 
David Jimerson said:
30p doesn't require a pulldown cadence like 24p, because it's easy to split the frames into field pairs and record them in a 60i stream -- each field pair represents a frame. You shouldn't actually see any interlacing at all, even if you're viewing on a 60i timeline.
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I have shot 30p before with my DVX and edited in FCP with a 29.97 timeline. During the edit I did not see any interlacing but when I exported there was interlacing. This has happened with multiple projects, it was not a one time thing. When I applied the de-interlace filter to all my clips the exported video was then clean.
 
You should never deinterlace progressive footage. You're just throwing away half your resolution.

What were your render settings when you got the interlacing? What type of file? What were you playing the footage on?
 
Got it. My sequence set up was Field Dominance - Lower instead of none. Problem solved. Thanks for the help!
 
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