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Nested Comp of Different Framerates - Preserve Framerate - No Effect

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Kieran Hanrahan
Nested Comp of Different Framerates - Preserve Framerate - No Effect
on Jun 24, 2014 at 10:29:20 pm

Hello,

I have a 48 frame 25fps sequence. I have turned on Preserve Framerate in the Advanced tab of the Composition Settings. When I nest this comp into a 23.98 comp, the length of the nested comp is now 46 frames.

Do I not understand what Preserve Framerate is supposed to do? I expected the 48 frame comp to still be 48 frames in the new comp.

Additionally, this result is observable whether I turn Preserve Framerate on or off. No difference.

After Effects 12.1.0.168
Apple 10.9.3

Thanks in advance for any replies.


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Brian Charles
Re: Nested Comp of Different Framerates - Preserve Framerate - No Effect
on Jun 24, 2014 at 10:58:52 pm

Are they both 1 second 22 frames long?



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Todd Kopriva
Re: Nested Comp of Different Framerates - Preserve Framerate - No Effect
on Jun 24, 2014 at 11:10:04 pm

> Do I not understand what Preserve Framerate is supposed to do?


You seem to misunderstand what this setting does. I'll explain.

The Preserve Frame Rate When Nested setting determines how many times per second the nested composition will be sampled.

Consider an example: You have a composition (comp_jerky) with the frame rate of 1 frame per second. It is 10 seconds long. When you play this composition by itself, it plays 1 frame each second, for 10 seconds, for a total of 10 frames. This gives a very jerky animation, which might be what you want for some reason.

Now, you nest comp_jerky into a composition that is 10 seconds long that has a frame rate of 30 frames per second (comp_smooth_master).

If you do _not_ use Preserve Frame Rate setting, then comp_jerky will be sampled at 30 frames per second when played back within comp_smooth_master, and the result will be smooth. If you do use the Preserve Frame Rate setting, then comp_jerky will be sampled at its own frame rate, and the result will be jerky.

In both cases, the compositions are still 10 seconds long.

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Todd Kopriva, Adobe Systems Incorporated
After Effects quality engineering
After Effects team blog
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Walter Soyka
Re: Nested Comp of Different Framerates - Preserve Framerate - No Effect
on Jun 24, 2014 at 11:13:42 pm

Two items of the same length of time but different frame rates will not have the same number of frames.

Consider: 1 second at 24 fps is 24 frames. 1 second at 25 fps is 25 frames. They are both the same length of time, but a different number of frames.

In your case, 23.796 / 25 = ~95%. 95% of 48 is 46.

Preserve frame rate forces the comp to be rendered at its nominal frame rate when nested in other comps or when rendered through the render queue. This may result in repeated or skipped frames if the containing frame rate is not the same.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Kieran Hanrahan
Re: Nested Comp of Different Framerates - Preserve Framerate - No Effect
on Jun 25, 2014 at 1:46:03 am

If I here correctly it sounds like AE is more time-centric, not frame-centric.

One workaround is to render out the 48 frame 25fps sequence, then re-import and interpret the footage to 23.98. Voila, 23.98 48 frame sequence.

Explanation: I am making 23.98 and 25fps versions of an animation. The edit is different for each, 48 frames for 25fps, 46 frms for the 23.98. So in both, this shot will be 1.92secs. I was hoping to nest the 25fps in a 23.98 comp and trim the last 2 frames.

Maybe my explanation helped. Just looking for the correct/cleanest was to do this. Rendering out and re-importing seems silly.


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Walter Soyka
Re: Nested Comp of Different Framerates - Preserve Framerate - No Effect
on Jun 25, 2014 at 9:42:53 am

[Kieran Hanrahan] "If I here correctly it sounds like AE is more time-centric, not frame-centric. "

Yes, this is correct.


[Kieran Hanrahan] "Explanation: I am making 23.98 and 25fps versions of an animation. The edit is different for each, 48 frames for 25fps, 46 frms for the 23.98. So in both, this shot will be 1.92secs. I was hoping to nest the 25fps in a 23.98 comp and trim the last 2 frames."

They don't have to be different versions. You could render the same version at both 23.976 and 25 fps and get identical timings. Your keyframing will be smoothly recalculated upon render for the new frame rate.

But if you really want to, in the 23.976 comp, select the 25 fps layer. Layer > Time > Time Stretch and enter 48 for the new duration. Trim off the last two frames by adjusting the out point.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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