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23.976fps to 25fps wierd problem – Anyone Else?
I’m having a really annoying new problem, basically the workflow is ntsc animation built and rendered at 23.976fps from which we then need to deliver 25fps pal animation. My standard workflow for the last couple of years is simply to nest the final 23.976fps comps into 25fps comps and apply a stretch of 95.904% which results in playing every frame without any duplicates, I’ve been doing this for years without any problem but now it’s not working any more.
When I apply the stretch and render the results are duplicate frames in the render, basically every fifth frame is duplicated but the duration is correct so it must be dropping every fifth frame also.
It works correctly if I place the 23.976fps comp in a 25fps comp that I know is the right duration and then stretch the out to the playhead at the last frame, this results in a stretch of 95.904% and it does work but why doesn’t the other way?
I’ve noticed that when I type 95.904% in the stretch box and then click back into it the number there is actually 95.903999, after effect is round the number down for some reason and I think that might be causing it by making the speed more or less correct but no longer falling correctly on the right frames.
Has anyone else come across this too? If any of you have a couple of minutes to spare I’d appreciate it if you could do a simple test, make a 23.976fps comp with some basic animation, nest it in a 25fps comp, apply a stretch of 95.904% and tell me if it plays every frame correctly or duplicates frames, also click back in the stretch box and let me know if it’s still 95.904 or something else.
Sorry for the long post, this is completely killing my workflow right now and I’m about to pull my hair out.
GlennserPS Dual 2GHz Power PC G5 with OS 10.4.11 and after effects 8.0.2.27 and QT 7.4.1 although I got the same results in an Intel/Leopard box
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6 Replies
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Thanks Dave, I appreciate your advice and if it was just footage I’d do that but I’m versioning pretty heavy comps with footage and camera moves along with text that needs to be versioned for multiple languages, I don’t want to waste time and space rendering everything at 23.976fps just to bring back in and convert to 25fps.
It’s really driving me nuts, I’ve been doing this for years and I just don’t understand why AE is changing the stretch value now, I’ve tried changing the project settings to 25fps and frames along with changing the nested comps settings to preserve frame rate when nested but it didn’t help.
If you have a second can you try and replicate what I’ve described (23.976fps comp nested in a 25fps comp), try to apply a stretch value of exactly 95.904%, I can type it in but when I check it afterwards AE has changed it to 95.903999%, it’s a tiny difference but I think it’s resulting in the duplicate frames in the render.
Projects that I set up months ago and rendered fine are now messed up so I know I’m not imagining it, at first I thought I was doing my maths wrong but that’s not the case, this workflow should be fine, I don’t know how common it is but I’ve been using it for years without any problems. I’ve trashed my preferences and had a look through the interpretation rules file but can’t find anything.
Thanks again,
Glennser -
If re-rendering isn’t an option could you possibly drop your final comp into a new 23.976 comp and apply Andrew Kramer’s framer rate converter to go from 23.976 to 25? Maybe just render a small portion as a test to see if it still gives you the duplicate frames you’re seeing with the speed adjustment. Have you upgraded your version of after effects recently or changed something else in your OS?
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my first question is if you are delivering 25 fps pal, why are you working in 23.976 fps, why not work in a pal preset?
if you are delivering both an ntsc and pal version, i think i’d work in a pal preset, then render that out with a post render action to import the render. re-interpret the footage to 23.976fps, take that to a 24p ntsc preset, make the scale adjustments and render that as the ntsc version (you could add the pulldown if necessary in the render settings).
but none of that helps you now… if you take a comp that has now footage into a comp with a different frame rate, the keyframed animations will get recalculated to the new frame rate, unless you have the ‘preserve frame rate’ option selected for that comp (compsettings>advanced tab). so make sure that is set correctly for your nested ntsc comp.
if you have footage in your comp that is 23.976 then you will get duplicate frames when that get stretched to account for the frame rate difference, unless you enable frame blending for the footage. you have 2 choices, frame mix and pixel motion… pixel motion will usually produce more natural results unless your footage has cuts, frame mix will render much faster…
Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW -
actually, after playing with you numbers, i’m not seeing you problem.
i created a comp at 23.976, created a white solid and set it to turn on every other frame. dropped that into a 25 fps comp, stretched it the 95.904 (ae turned that into 95.903999), but i’m not seeing any duplicate frames, or any re-interpolated data (where the white solid would appear a value other that 100% or 0% opacity).
thinking about it… the minor rounding of the value would not be enough to account for a duplicate frame every 5th frame, nor would something like a drop-frame/non-drop-frame discrepancy.
Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW -
Thanks for the suggestions guys.
I know this workflow mightn’t be familiar to you guys but it really is a great way to produce ntsc and pal from the same builds without worrying about keyframes slipping, (esp. roto or tracking) and all the other problems you run into if you try to convert all the framerates of the projects. Of course if we didn’t have to version text I’d just render oversized at 23.976fps and then speed that up to 25fps but that’s not the case. It’s the same technique they use for feature films and I’ve never heard anyone complain about the pal versions playing too fast? (There was a Panasonic white paper by David Wiswell back in 2000 which advocated 24p workflow which is still worth a read, it’s still available at panasonic)
I was playing around with it yesterday and Kevin you’re right that the slight rounding difference shouldn’t make a difference but it does, when I trick AE into actually keeping 95.904% (the only way I can do this is to put the 23.976fps comp into a 25fps comp that is the correct final duration, place the playhead at the last frame and use Cmd+Opt+, to time stretch the last frame to the playhead, then everything works as it should and did before. To replicate the problem you need to have 23.976 footage or pre-rendered elements nested at least two comps down and not starting at the first frame, I think the fact that they don’t start at the first frame is the problem, it’s as if AE is trying to “snap” the frames into alignment but it results in things being slightly off and repeating/dropping frames.
Thanks again for taking some time on this, as I said it used to work and now I have to find some workaround, right now I’m forcing it using time remapping instead of stretch but it’s a couple of extra steps and I find I need to tweak and check it a few times to get it to work right.
GlennserPS Mike, I thought about using Andrew’s preset but there really isn’t a need to reinterpolate new frames using Timewarp or frame blending, I can’t pin the changes down to any upgrade either.
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Actually I’ve just been contacted by a couple of friends who use the same workflow and have the same problem so it’s not just me, they had no idea why a workflow they’d been using for years was suddenly broken, I hope CS4 fixes it because the workaround is a real bitch.
Glennser
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