the basics of pull-up pull-down and Frame Rate

[joenovice]

I'm looking for basic information regarding Frame Rate variations. How does the video editing process manage these changes? After recieving a project what do I need to ensure proper sync to these variations?

In the past, and now, I will be recieving an OMF and QT mov file (MPEG4). I asked the editor about the projects frame rate during filming and editing.... his answer was confusing. Filmed at 24 (something)p, edited at 30/29.97.... (something like that)


At any rate.... I'm just hoping for some quick tips or education resoucres.... webpages, books, etc.

many thanks....

[joenovice]

ok.... so I just read this.....

Drop and Non-Drop time code serve different purposes for different people in different professions. I work almost exclusively in television and we use drop-frame constantly. The comment that it's "rarely used" is completely false. However, since it seems that the comment was made by someone working primarily in film, it makes sense. When I've worked in film, we've preferred Non-Drop.

It's just a way of counting after-all. It's like saying "In our country we use a leap-year-calendar even if you don't use it in your country." No matter which "calendar" you use... it still takes just as long to get from solstice to solstice (1/2 a revolution around the sun). Granted, the solstice wont always be in June or December. Eventually it will be in May and November (if you don't use Feb 29 as part of your calendar).

Same thing with Drop Frame time code. Without it, "one-hour" programs of 29.97fps media on television would not actually last an hour. The explaination above of why it even exists is accurate - it's to help make up for the fact that television (now) doesn't actually run at 30fps.

Heck - read this: http://www.csif.org/html/dropframe.html

Depending on your NLE, you might be able to use drop-frame TC with 30fps media. I'm not sure why you'd want to though. Likewise you could use Non-Drop TC with 29.97 media, but you'd want to be careful in doing so. Generally speaking, the counting method and the type of media have a reasonable correlation (but this is NOT required, nor does the type of time code necessarily indicate the frame rate).

But, none of that answers the pull-down issue. Pull-down is not a Drop/Non-Drop question. The two might overlap in some forums, but they are (overall) unrelated. Many cameras, like the HV20, record footage at 1080i/60-fields per second (or rather 59.97 fields per second). That's just how the camera works. There are cameras that record 24p/24 frames per second (or 24p/23.987 frames per second), but this isn't one of them. However, to compensate for that - and avail people (who want it) the "look" of 24p, the camera offers to record those 24 frames as 48 interlaced fields spread out over 60 fields. This is called 24psf and you can read about it (and the miriad of other HD formats) here: http://www.leitch.com/resources/whit.../Whatis24P.pdf .

The process of adding the 12 fields per second to make up the difference (60-48=12) is 3:2 pulldown and it adds images in the recorded media on the tape that are not part of the originally intended 24 frames. Unfortunately (for you - trying to remove the pull-down) it's not simply 2 bad frames for 3 good frames. And cutting out the bad frames (if that's what it were - which it's not) will not solve the problem, since the media won't last as long (because without the frames that you remove - it will be shorter) and you'll have audio sync problems.

The solution is to change the media from 59.97 fields/second to 23.987 frames per second (let's just say 60 and 24 from now on, even though it's not) - while not changing the overall length of the footage or the speed of the audio that accompanies it. In the 1080i source footage, each two-frames is 1/30 second. You need that to actually play as 1/24 second. So it's not just removing frames that solves the problem, but changing the rate at which the remaining frames play. And sadly (for you), it's not just a frame that has to go away, since the pattern for inserting pull-down is intrafield and it actually means removing 12 fields in various points throughout each second. What a pain?

Check this out (since it has a good illustration of where the numbers 3 and 2 play into all of this): http://www.projectorpeople.com/resources/pulldown.asp

There are some consumer products that do this, but I've had a hard time finding any. Pro products (like Avid Symphony Nitris, Film composer and certainly others) can handle it without a problem, but who has one of them sitting in the living room. I've found that FCP5 and Avid Xpress Pro both have limitations in this area. Rumor has it that FCP6 can handle it, but I've not tested it.

However, just yesterday, I finally stumbled onto a shareware program that will do it (remove pulldown from files captured on a Mac from an HV20) - and it does it flawlessly (after a bit of basic trial and error - me trying to outsmart the default settings, really)!!!! Finally, after months of searching....

http://www.xs4all.nl/~jeschot/home.html#DEI

which I found here (and they seems to have solutions for other OS-es):
http://eugenia.gnomefiles.org/2007/0...-24p-pulldown/

This takes 59.987 media and removes the pulldown fields, coverts the frame rate and maintains the audio sync as well as the the color depth and image quality. When you're done, you have clear, accurate 23.987 media without the added fields that plays in sync with its audio. Ta Da!

Then, import it into your favorite NLE (in a 23.987 project) and edit!!!!!

Why 23.987? Because, either
1) you're editing for completion on a SD DVD (in which case, upconverting to 29.97 will be a dream)
2) you're delivering on the web, so what's the difference?
3) you don't care - so why bother making it 24
4) if your project is 24, there's a chance (depending on the NLE) that the audio (recorded in sync with 23.987 media) will no longer play in sync with the video - since you forced it to play at 24 (faster than 23.987).

enjoy...

I understand a fair amount of what was said but still am unclear as to the information I need from the editor to ensure that our projects will match.

Perhaps I'm totally wrong for wondering about this?

[bignate]

What format was the original video that was shot in "24p?" Was this film or HD? Also, you mentioned receiving an OMF in the original post. Will you also be receiving the production audio masters, or will you just be receiving the audio from the editor in the OMF?

-Nate Bishop

[joenovice]

It was HD. He has since "removed the 3:2 pulldown" and sent me new OMF and Video Reference.

The OMF consist of Dialog Edits and was packaged to include the whole audio file. (not raw production masters)

I still am attempting to understand the 3:2 pulldown concept.

[bignate]

Please see this previous thread.

Why 59.97 or 60Hz?

There is a post I made in the first page that explains pulldown.

Hope it helps,

-Nate

[joenovice]

Wow.... thanks for the link. I had done a quick search before my post and didn't see that one.

case closed....