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Old March 21st, 2005, 10:11 AM   #1
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From 24FPS FILM to 30FPS DVD?

Here is one for you editing gurus:
All movies sold on VHS and originated on film (24fps) have the first original four frames from film and the fifth one same as fourth; end result is 30 fps video.
Now, I saw "I robot" in theatre. It was shoot Panavision 24fps. I have the DVD. I was amazed to see 30 DIFFERENT frames every second. How is that possible from a material that originated as 24fps?????...Shed some light please.
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Old March 21st, 2005, 12:27 PM   #2
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Re: From 24FPS FILM to 30FPS DVD?

<<<-- Originally posted by Dan Diaconu : Here is one for you editing gurus:
All movies sold on VHS and originated on film (24fps) have the first original four frames from film and the fifth one same as fourth; end result is 30 fps video.
Now, I saw "I robot" in theatre. It was shoot Panavision 24fps. I have the DVD. I was amazed to see 30 DIFFERENT frames every second. How is that possible from a material that originated as 24fps?????...Shed some light please.
-->>>

I'm not sure why you're asking this in an HDV editing forum...

Feature film DVDs are usually recorded at 24fps (which you're seeing when you play back frame by frame).

The DVD player itself converts the signal to the same frame rate that VHS uses (30fps) by repeating some fields, though it's a little more complicated and subtle than simply repeating frame 4 (it may appear this way as when you play through the VHS tape frame by frame, the VHS deck only plays back a single field).

It's called a 2:3 pulldown and basically it's how film has been transferred to NTSC video for decades.
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Old March 21st, 2005, 12:49 PM   #3
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Sorry, but I did not find a "film / video" forum and since the question relates to editing, you guys are most likely to provide an answer.
As I understand, the DVD player "fills in the gap" and smoothens out what the VHS does not. Thank you.
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Old March 21st, 2005, 02:25 PM   #4
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<<<-- Originally posted by Dan Diaconu : Sorry, but I did not find a "film / video" forum and since the question relates to editing, you guys are most likely to provide an answer. -->>>

I guess it's OK, but the admins seem jumpy today, a whole thread got pulled this evening. ;-)

<<<---As I understand, the DVD player "fills in the gap" and smoothens out what the VHS does not. Thank you. -->>>

Yes, the DVD player does convert the disc's 24fps to 30fps, however with VHS, the same 24-30 fps conversion is done when the film is first transferred to videotape.

On an NTSC TV set, the VHS frame rate is no different to the DVD, regardless of what you see when examining frame by frame.
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Old March 21st, 2005, 03:07 PM   #5
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Dylan, thank you for your explanation, I've got it now.
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Old March 21st, 2005, 03:47 PM   #6
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Dan,

It may look like 30 unique frames, but it is likely variations on the original 24 frames, combinations of fields from various frames. It's 2:3 pulldown, and it's a standard process. On VHS tape, it's hardcoded. On DVD, it's done on the fly (saves space on the disc).

If you have seen a VHS with the 4th frame repeated, it's a really lame conversion, and you'd be able to see stuttered motion on playback.

Josh
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Old March 21st, 2005, 04:26 PM   #7
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Thanks a lot Josh,
I was just settled with the previous explanation, but now comes another "head scratching" question:
If the damn DVD player will "mix and match" and ruin all the hard work and expense to shoot 24P, then why bother with 24P to begin with? (if it does not show the jitter as VHS used to...?) I keep scratching my head to find a decent answer/reasoning
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Old March 21st, 2005, 04:49 PM   #8
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Dan,

I say "mix and match," but there is a method to it. You need to read up on 2:3 pulldown. Here is a link:

http://www.zerocut.com/tech/pulldown.html

It is a necessary evil to fit 24 progressive frames into 60 interlaced fields without too many headaches.

Why go to all the work of shooting 24p? Because regardless of the trickery involved in getting it to play back, capturing 24 progressive frame of video will have similar motion characteristics to film. 24fps originated film goes through the same on playback, as well.

Josh
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Old March 21st, 2005, 07:43 PM   #9
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Thank you.
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