| IF I COULD TURN BACK TIME…
Sometimes you get a rendered animation or video clip that, for whatever reason, just doesn’t do it for you—or more importantly, for the client. The lighting looks great, the characters or other elements are fine, but there’s just something that needs changing. Turns out it’s the timing—the clip is too long, or too short, or would just work better if it could run at one speed, then suddenly take off faster, or slow down, stop, then run in reverse. Animations can always be sent back to the 3D guys for another expensive and time-consuming render, but video clips more often than not can’t be re-shot, and even if they can it may not do you any good, since you can’t say to the talent “Okay, start off at normal speed. At two seconds, ramp up to double, then at four pause, hold for two seconds, then do everything in reverse.” Well, you could say that, but you’re not likely to get anything you can use on broadcast television.
After Effects’ Time Remapping filter can do all these things and more. As the name implies, time remapping allows you to change the flow of time for a layer. Applying time remapping is a snap—select the layer, then head to Layer=>Enable Time Remapping (Alt+Ctrl+T). Controlling time remapping is a little trickier, but worth the effort.
One of the more obvious uses for time remapping is to put a hold frame on the beginning or end of a clip. Enable time remapping on ElbowDrop.mov and twirl down the transform mode arrow next to its name. Time remapping is the first value you can manipulate, and enabling time remapping automatically adds a keyframe at the beginning and end of the clip.
To add a hold frame at the beginning, just move the first key frame to a point in the timeline where you want action to start.
Do a RAM preview, and notice that the animation now holds until it reaches that first keyframe, and then starts playing. If you move the end keyframe in, you’ll see that the animation now holds once it’s through playing. You’ve probably noticed that the animation is now playing at a faster rate than its original render speed. That’s the tricky part of time remapping—using it can have unintended consequences, such as invalidating the original duration and playback rate of the layer it’s applied to. Put the keyframes back in their original positions, and the hold frames go away while the clip plays at its original speed again.
You can also use time remapping to reverse playback of a clip. Twirl down the time remapping arrow and notice that a line ramping up toward the right connects the keyframes in the Value: Time Remapping window of the timeline.
To reverse playback, just swap the beginning and ending keyframes—put the first keyframe in the position of the end and the last keyframe in the position of the first. Now the ramp slopes down from the left, and the clip plays backward.
Now, how about making the clip pause in the middle of playback, then play in reverse, then play forward to finish? No problem—reset your keyframes back to their original positions and grab the end handles of the animation. You can slide that puppy out to add length, and time, to the clip. Then go to, say, 20 frames in and set a keyframe. Now set two more keyframes—one at 25 frames and one at 1:10. When you did all that, little blue tics appeared on the ramp, and they allow you to manipulate the playback rate. Grab the tic at :25 and pull it down until the line between it and :20 is flat. That adds a pause in the playback. Grab the tic at 1:10 and pull down as far as you can. Now do a RAM preview—and the clip plays, pauses, then plays in reverse before quickly finishing. If you grab the handles on the tics in the Velocity: Time Remap window you can add bezier curves to the keyframes and smooth out the playback. And since you’re remapping the playback of the clip, you can spread out the keyframes as much as you want and not run out of frames. You might run into jerky playback since you’re forcing After Effects to make frames last longer than they should, but you won’t run out of frames. You can also smoothen playback some by enabling frame blending.
Time remapping also works on audio clips, and can create some interesting and useful effects. Combined use of time remapping on video and speech can make it easier to lip synch animations. Time remapping music clips can turn you into a house DJ.
Load up the cymbal.wav file. It’s just a garden-variety cymbal crash, but with time remapping you can make one of those weird Beatle-esque crashes-in-reverse, by enabling time remapping and then swapping the beginning and ending keyframes just like we did with the bodyslammers.
You can also turn this one innocent cymbal sound into a techie-sounding, other-worldly sound sequence. Doing this requires, even demands, that you play around. Put your keyframes back in their original positions, then add a bunch of keyframes in the timeline. Grab those little blue tics in the Value section and flatten, raise, lower and generally mess around with them. Do a RAM preview and listen to your madness—if you tweak it a bit, you can build your own rhythm section from one little cymbal sound. Here’s what I did to it:
Time remapping speech can add stutters and stops, and time remapping music tracks can let you add scratching, warping and other fun effects.
Time remapping is one of the most useful filters in After Effects, and knowing how to use it can turn any AE user into a power user. Time remapping can save you time and your client money, and can make you look like a genius in the process. Not bad for a free filter that comes with AE’s Standard version. (And yes, I know—I should be beaten with a sock full of quarters for making an obscure reference to a Cher song in this tutorial’s title. Sorry….)
--Bryan Preston
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