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After Effects export frame rate issue
I am using Keylite 1.2 in After Effects to key out green screen shots that I am then bringing into FCP 7 to composite over backgrounds. The keying turned out well, but the problem is when I bring the new Alpha channeled Quicktimes back into FCP and lower the opacity on these shots, I see they are not quite in synch with the original green screen footage on the layer beneath. Seems like a frame rate issue. The original footage is 23.98 fps. When I imported the source footage into AE, the program defaulted to 23.976 fps. I did a new composition of the same footage at 23.98 setting, hoping this would solve the problem, but it didn’t. The other curious thing is that when I nudge the newly keyed footage (23.976 fps) to the left in the timeline by 1 frame, it seems to synch up. But I have to trim off the first frame. The bigger issue is that I am losing a frame at the end of the clip, creating a one frame gap before the next shot.
In terms of my AE render export:
To get a good key with no rim or halo around it, I have unchecked Unpremultiply Results. I’m rendering out at Apple Pro Res 4444 (same as source footage), same frame rate as composition (23.98), Channels: RGB + Alpha, Depth: Millions of Colors +, Color: Straight (Unmatted). These settings are giving me a great key, but maybe these settings may be causing the synching issue?Sorry for such a long post, but I wanted to provide all the detail I could in hopes of finding a solution. Any advice appreciated.
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1 Reply
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FCP rounds the real 23.976 frame rate to 23.98 for display. Do not be fooled by this into thinking that the frame rate is 23.98 fps.
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Todd Kopriva, Adobe Systems Incorporated
After Effects product manager and curmudgeon
After Effects team blog
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