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Techniques for Independent Production
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Old May 12th, 2008, 12:55 PM   #1
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24p and HDV?

Are there any advantages to converting 60i to 24p? I have to deinterlace my footage in after effects anyway, so that I can properly green screen etc... I'm trying to decide what the final frame rate should be if I de-interlace, which I guess means it is progressive.

Last edited by Aric Mannion; May 12th, 2008 at 02:10 PM.
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Old May 23rd, 2008, 09:59 AM   #2
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Hi Aric,

the answer depends on where you are sending your footage.

that advantage of 24p is that is easily cross converts between NTSC compatible 29.97fps (insert a 2:3 pulldown) and PAL compatible 25fps (by speeding it up 4%) I know HD isn't strictly PAL/NTSC but the frame rate thing still applies for those areas.

Converting 30p to 25p is MUCH harder to do well, or even acceptably.

If you're not distributing to PAL/SECAM countries then 24p might not matter.

if you're distributing only over the internet there are other caveats. 24p still compresses and play back better at higher resolutions. 30p is a bit of a strain for some older computers (or with Flash, at HD, even for some newer computers). Over at vimeo.com they had a hell of a time with this.

An then many feel that 24p retains that "film look" a little better than 30p with the increased frame rate 30p may start to look a little more videoy, but that's a personal choice.
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Old June 16th, 2008, 10:07 AM   #3
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If you're editing 24p, the computer only has to apply effects and process 24 frames per second. If you deinterlace 60i, it's still 30p and that's 6 extra frames per second so it will take longer to render and edit.
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Old July 30th, 2008, 01:27 PM   #4
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hmmm. In a word.. not much. If you get the plug ins, you can maybe get the timing right going from 60i to 24p. Better to shoot 24p from the get go.

IF 24p/24f is not an option, only 60i.... then what is your destination? DVD? internet? IF you don't know yet, deinterlace at 60fps to keep your options open. How much better is chroma keying with deinterlaced video vs interlaced video (same source)? probably better... both will be time consuming. Again, better to shoot 24p... However chromakeying software gets better and faster every year.

biggest issue with going from 60i to 24p is the shutter speed. 60i is usually 1/60th, 24p is usually 1/48th. So movement (even with plug ins fixing the repeating frames) is at the wrong shutter speed. This starts to give the video a SAVING PRIVATE RYAN look. 1/100th is extremely choppy and harder to use.

So basically keep the final project at 60p (assuming the deinterlacing looks better for chroma keying than the interlaced image does.... it did in the past, today the software is better, so it may not be necissary) Then you can go back to 60i if you need to, or use the plug in/software to make a decent looking 24p if you have to later.
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