some Qs re 24 vs 23.98

hi there

im working on a 24fps (film based) project,
but occasionally i've accidentally cut footage in to 23.98 sequences.
i would have expected a render bar of some sort, but FCP lets me do this.
it;s like there's no difference between them as far as FCP is concerned.

however, if i bring a 24fps sequnce as a nest into a 23.98 sequnce, (or vice-versa)
i get the behaviour i expect:
render bars all over the place!


this confuses me a little, (i'm from PAL land, the whole 23.98 thing is confusing!)
and it;s a bit of a worry.
FCP is letting me do something that may get me in trouble down the track.
(that's FCP for ya.. freedom to anything you want.. even mess up!)
or is it nothing to worry about??

one manifestation of this:

we had some 24 clips in a 23.98 timeline
wen we made some subclips from the timeline,
the subs had a 23.98 vid rate.
then i found out i could fix this by dragging the subs into a 24 timeline, and back to the browser again!


so my real question is this:
how much of a worry is this behaviour if i can fix it this easily?
or this this quick fix covering up some bad thing that could get me in trouble down the track?

(i've since made the vid rate column a sandard part of my column layout so i can spot these problems up front)

thanks,
nick

I would expect you to get burned later.

Somehow, usually about once a minute, a frame is going to be doubled-up or dropped to make up the difference. It's possible that the dropped frame is in the sound.

At the risk of plowing old ground, 23.976 has a direct 4/5 relationship to NTSC's wacky frame rate and 24 doesn't. The various pull-downs (3:2 and 2:3:3:2) only work when that 4/5 relationship exists.

Koz

Hi Nick,

How's the shoot going?
-------------------------------------------------------
> im working on a 24fps (film based) project,
> but occasionally i've accidentally cut footage in
> to 23.98 sequences.

Back when I was testing Cinema Tools and film workflows for FCP I also noticed this. I kept trying to find an answer whether it would muck things up, but it seemed that somehow it all worked out. All my lists matched the timeline just fine and it never skipped a frame.

> however, if i bring a 24fps sequnce as a nest into
> a 23.98 sequnce, (or vice-versa)
> i get the behaviour i expect:
> render bars all over the place!

I experienced that too. It was sort of like nesting would somehow make the total length fixed while cutting clips into a slightly mismatched timeline would make the length "give" a little.

Of course we're talking about a computer counting frames and time so it doesn't really make sense--at least I can't explain it in any rational manner!

> we had some 24 clips in a 23.98 timeline
> wen we made some subclips from the timeline,
> the subs had a 23.98 vid rate.
> then i found out i could fix this by dragging the
> subs into a 24 timeline, and back to the browser
> again!

Humm--so you made new subclips? I suppose these subclips will behave pretty much like a 24fps clip in a 23.98 timeline.

> so my real question is this:
> how much of a worry is this behaviour if i can fix
> it this easily?
> or this this quick fix covering up some bad thing
> that could get me in trouble down the track?

I don't know if what you are doing could be considered a "fix." The real fix would be to get all of your clips and timelines at the same frame rate.

I may be wrong about these assumptions but it seems to me that all your original clips are 24fps and some of the sequences started out as 23.98 and of course once you start adding clips to the timeline you can't change the frame rate. Is that right?

The fix is very simple, for each of your 23.98 sequences, make a 24fps sequence. Now don't just nest the 23.98 sequence into the 24fps timeline, what you need to do is to copy your 23.98 sequence into the clipboard then paste from the clipboard into the 24fps timeline. That should do the trick.

Now what if my assumption is wrong and you have some 23.98 clips mixed in with your 24fps clips? That's a possiblity if you exported one of your 23.98 sequences to QuickTime then brought that clip back into the project--talking about getting your self into trouble making a film cut list out of that! In any case, what you can do is to run the 23.98 clips through Cinema Tools and batch conform the clips to 24fps.

By the way, if your clips were synced with sound in telecine and you conformed the clips to 24fps, the audio sampling rate will be "pulled up" to 48.048 kHz. This can cause "unrendered red bars" on the timeline if there are enough audio tracks and/or the playback audio is set to high quality. That's because FCP is doing sample rate conversion on the fly and it can only handle so much before it has to give up and render to disk.

I do believe that last time we exchanged messages you were syncing from imported audio files so the audio pull up shouldn't be an issue with your project.

Finally:
(i'm from PAL land, the whole 23.98 thing is confusing!)

I found some PAL related messages we exchanged from a couple of years ago. Yeah, NTSC is confusing, PAL is in many cases even more confusing and filmmaking in general would probably be much simpler if we didn't have to deal with these wacky television standards.

--Dan