The following instructions detail how to use Frame Interpolation in After Effects.
Create a new composition with the clip you’d like to apply slow motion to.
Create a “Null Object” layer on top of the input video that is the new length of the slow motion output.
2a. Example: a 2-second clip set to 3x slow motion would need a 6-second Null Object placed above it.
Pre-compose the two layers and apply “Frame Interpolation” from the Effects panel.
BTW, does it work with precomped sequences? Or does it have to be a video file? Say if I want to slow down a whole composition, rather than just a video file.
Perhaps you could export your comp using the lossless animation codec and then reimport it and slow that file down. I think it would be much faster than all the calculations needed to slow the contents of a composition down as opposed to a single mov layer. Just a suggestion. [quote=“michael.demetriou, post:4, topic:74062, full:true”]
BTW, does it work with precomped sequences? Or does it have to be a video file? Say if I want to slow down a whole composition, rather than just a video file.
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Yeah that’s the go. Also it seems to only like conventional video formats like .mov/.mp4/.avi … Image sequences dont work, anything else freezes up the viewport for anyone wondering.
Regardless of whether it’s a video or animation, AE simply passes the image data of the object with the applied effect to the plug-in. There is no need to pre-render unless you have other issues related to performance or memory limitations.
Having said this, any freezing issues are most likely performance issues and not related to the source of the image data (i.e. MOV vs. image sequences). Converting from one to another may solve the issue, but it is because you are solving your performance problem, not because a plug-in is sensitive to one or the other. The plug-in would have no way of knowing the source of the images.
The reason for the need to add a null layer is that AE will not pass anything when either the pre-comp has ended or there are no active layers in the pre-comp to pass on to the comp. By adding a null object you are forcing AE to behave as if the source comp is longer than it actually is.