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Time Remapping in After Effects

What's with the turkey, you say? It's from the video we're using to introduce you to the concept of Time Remapping, a very powerful but somewhat obscure feature in Adobe After Effects that lets you keyframe the timing of a video track to change its speed selectively.

We're only going to offer the briefest overview of Time Remapping here, but we can go into some greater depth at a later time. For now though, let's get started.

Step 1 - Add Audio and Video

For this example, we're going to be using a rhythmic music bed and a video of a wild turkey banging on my front window. We, for some reason, want to sync the banging of the turkey to the music bed. Here's the original un-synced video and music:

Step 2 - Spot Your Audio Track

Next, using the realtime audio spotting method I showed you in the recent Quick Tip: Spotting Audio in After Effects, add markers to the audio track at the strong beat points:

You can also add markers visually by locating the beats in the waveform, moving the Current Time Indicator to that point, and hitting * (multiply or asterisk) on your keypad (Mac and Windows) or Control-8 (Mac only).

Step 3 - Mark the Video Track

Next, add layer markers to the video track at the points where the turkey is striking the window - you can see those peaks in the waveform, and see the actual strikes in the video:

Step 4 - Enable Time Remapping and Add Time Remap Keyframes

With the turkey layer selected, enable Time Remapping (Layer > Time > Enable Time Remapping). Now, with Time Remapping enabled, add Time Remap keyframes at all the positions where you marked the turkey strikes.

Step 5 - Remap Time!

Next, drag the Time Remap keyframes you just made and them line up with the strong beats you marked in the audio track.

Note that I've dragged the yellow Time Remap keyframes away from their original marker locations so that they're now aligned with the beat markers in the audio layer. What this will do is force the turkey frames at those keyframe locations to remap to the new time locations aligned with the audio beats.

After Effects will speed up and slow down the video clip as needed to make the new frames happen at the correct points in time, so now our turkey banging on the window is in sync with the music:

You'll notice that the turkey audio has slowed down as well - I left that in to make the changes clearer, but if you simply disable it, you'll hear only the beats audio, if that's what you'd prefer.

And that's the absolute basics of Time Remapping in After Effects. Drop us a comment below. We'd love to hear from you!

Richard Lainhart

Richard Lainhart | Articles by this author

Richard Lainhart is an award-winning composer, filmmaker, and author. His compositions have been performed in the US, Europe Asia, and Australia, and recordings of his music have appeared on the Periodic Music, Vacant Lot, XI Records, Airglow Music, Tobira Records, Infrequency, VICMOD, and ExOvo labels. His animations and short films have been shown in festivals in the US, Europe, and Asia, and online at ResFest, The New Venue, The Bitscreen, and Streaming Cinema 2.0. He has authored over a dozen technical manuals for music and video hardware and software, served as Contributing Editor for Interactivity and 3D Design Magazines, and contributed to books on digital media production published by IDG, Peachpit Press, McGraw Hill, and Miller Freeman Books. Previously an Adobe Certified Expert in After Effects and Premiere, a demo artist for Adobe Systems, and co-founder of the official New York City After Effects User Group, he was, from 2000-2009, Technical Director for Total Training Productions, an innovative digital media training company based in New York and California.


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