Problems w/ 30P to 24P 80% frame rate conversion.

C

Christopher Julian

New member
Hi folks-
I've been shooting a project in 24P on a DVX-100, and working in an appropriate 23.98 timeline in Final Cut Pro HD (4.5).
I did intentionally decide to shoot a few selected scenes in 30P, intending to slow them down by 80% to give them a slightly/subtly dreamlike semi-slow motion effect without having to double any frames.
I had assumed that this could be handled easily by FCP. I imported the clips as 30fps (29.97), worked with the clips in a 29.97 timeline, and then once I was happy with the edit, I pasted the clips from the sequence into a 23.98 sequence, and changed the speed of each clip to 80%. (And rendered.)

BUT: instead of giving me the exact frame-for-frame clips in the 24fps timeline, FCP's rendering has skipped every 4th or 5th frame, and then doubled the next one. This causes a terrible jerkiness to the image--worse than if I had shot on 24P and slowed it down.
If I try turning frame blending on, then it merely composites multiple frames together, therefore losing the sharpness and quality of each individual frame.

I'm sure I'm NOT the only one who has tried this 30P-to-24P slowdown method before. How can I change the FCP settings to render each frame in its appropriate place, instead of the skipping/doubling pattern that it's doing?
Thanks for your help. This is my first posting here, and I'm glad to be involved!
-Chris
 
Hi Chris, I wouldn't let FCP do it. Export the edit as a self-contained movie and take it to Cinema Tools where you just conform the clip to 23.98fps. I suspect the reason it turns out so jerky is that FCP first tries to keep the speed of the clip on the new framerate and then renders the slomo. I guess it doesn't understand that all you want to do is change the framerate.
 
I just did precisely what moebius suggested--it totally works. The CinemaTools conversion of your footage from 29.97 to 23.98 is INSTANTANEOUS, and then dropping it into a 23.98 timeline means zero rendering.

Very, very cool subtle slomo with absolutely no rendering. The longest step in the process is making the clip a self-contained .mov file, which is negligible.
 
question? Did you apply the 80% speed adjustment before exporting as a self-contained movie file and then bring it into cinema tools to conform to 23.98? Or did you do the conform, and then bring the footage into a 23.98 timeline and do the speed adjustment then?
 
you don't need to do the speed adjustment at all. Conforming your 29.97 clip to 23.98 will do the job.
 
I did the speed adjustment in FCP without problems. I imported 30P onto a 29.97 timeline, then changed the speed setting, then exported. In that order, it worked for me.
 
I'm shooting a television show using the DVX 100a , and probably two or three POV cameras (DV). Obviously, the POV cameras will be shooting 29/30fps...how does this effect the edit? Do I need to use the Cinema Tools plugin to simply "convert" the POV footage to 24p - and I'm all good to go? Does that conversion take a long time (I'm thinking editing budget concerns...)? Any help or suggestions would be great...thanks
 
I suggest you edit in 29.97, so you don't need to take anything to Cinema Tools or conform anything. Just treat the DVX footy like all the rest (even if you shot it in 24p) but make sure to shoot 24p and not 24p advanced with DVX.
 
the problem is that its not an 80% speed change.. its a 75% speed change.

your thinking in terms of 30fps .. and in that case.. yes it would be a 80 % speed change... but in terms of 24fps.. its a 75% speed change.

heres the deal.. lets just talk in terms of real time so i dont have to type out as many frame numbers and math.. if you want i could do it that way as well , but lkets just stick to time for now..

30fps takes how long to display on a 30 fps timeline?
1 sec

and 24fps takes how long to display on a 24fps timeline?
1 sec

how many frames display in a 24fps timeline in 1 sec?
24

so how many frames of the 30 frames coming in from the 30 fps timeline should go into one second of the 24fps timeline?
24

so you have 6 frames left over.. which is what percentage of 24?
25%


the issue is that when you import a 30fps clip into a 24fps timeline. the NLE assume you want to keep time constant.. so it will play a one sec 30fps clip over one sec.. and drop the necessary frames to make that happen. if you do a rate chage to add 20 % worth of playback time it assumes you want to change the 24fps present for the one sec selected clip to play over 1 1/5th sec.. but of course 30 frames should take up 24 frames(one sec) and an additional 6 frames or 1/4 sec in the next sec which is a playback time increase of 25%. basically you need to think in frame rate terms of the timeline that you are working with.. not the framerate you brought in the other clip at.

try 75% ..or change the clip duration to 125% of its imported duration) or just manually stretch the clip over one and one fourth its imported time length (number of frames imported 30 fps clip takes up x 1.25 will give you new duration of clip)
 
danimalpower said:
Thanks moebius...

Does the 24p footage look the same if you edit in 29? The image doesn't lose anything, or become slower?
Click to expand...
No, since what you are essentially getting from the camera is 29.97 anyway. Just make sure you don't remove any pulldown.
 
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