With time remapping, you can change the timing of a layer in After Effects. Specifically, the process allows you to adjust the timing of “footage” of some kind: an image sequence and/or video file, for example. You could remap a particular section of a layer to slow it down, add a hold, speed up a phrase, make another part play in reverse, etc. Or, all of the above.
It is possible to perform the same by editing layers in a Composition, but remapping allows you to adjust the timing of a single layer. This works well for drawn animation sequences; for instance the kind that you would have drawn and shot on animation paper.
To explain things further, the “current time” in a Timeline always ticks along at a standard rate, like 24 frames per second. We cannot slow the tempo down. A movie player will always run at 24 frames per second, unless you stop the player by enacting the stop button.
With remapping however, you can instruct After Effects to expand and compress timing and play certain frames within “current time.” For example, let’s imagine an image sequence that is 120 frames in length. As AE plays from frames 1 to 70, you could make the software run through drawings/frames 1 to 90 in the 70 frames of “current time.” As a result, the timing of the sequence will be faster. Similarly, from frames 71 to 80, you could tell the software to hold on frame 90, while current time plays from 91 to 110. You could then instruct it to play frames 89 to 54 in reverse.
These are useful features in a variety of ways, one being that you could slow the timing of an action to synchronize to a particular section of music.
To accomplish remapping, After Effects sets keyframes, which you could subsequently shift and adjust, to continue to adapt the timing.
Straightforward Ways to Make Timing Changes to a Video File or Image Sequence
- Time Stretch: Select and click a layer in the Timeline and then go to the Main Menu > Layer > Time Stretch. In the Time Stretch dialogue box, under Stretch Factor, enter a percentage amount. More than 100% will make your animation slower and the sequence will be longer in duration. Less than 100% will be quicker and shorter. When you enter and amount in Stretch Factor, under New Duration, you’ll see what the new lenght will be.
- Time Reverse: Select and click a layer in the Timeline and then go to the Main Menu > Layer > Time-Reverse Layer. Doing so, the segment will simply play in reverse.
Time Remapping with the Layer Window
This is a more complex ways to make timing changes to a video file or image sequence.
Open the Layer Window / Panel for the layer you plan to remap (i.e., referring to the Timeline, double-click on the layer and then refer to its Layer Panel. The Layer Window / Palette usually tabs with the Composition Window. You can flick back and forth from one window to the other).
To set remapping on the layer, go to After Effect’s Main Menu and choose Layer > Time > Enable Time Remapping.
Similar to other effects, Time Remapping will appear as part of the layer in the Timeline, along with the default Transform Effects, like Position, Scale, Rotation, Opacity and Anchor Point.
By default, when you choose Time Remapping, After Effects will place two linear key frames with the layer, a start-point at the beginning of the layer clip, and an end-point at the tale of the clip. You can move the keyframes to remap time. For example, if you click and drag the end keyframe along the Timeline to the right, you therefore extend the timing and duration of the sequence, not only making it play longer, but slower as well. Similarly, move the end keyframe to the left, you will shorten the duration and make the animation/movement sequence speed up and move quicker.
Back to activating remapping, once you have set it (i.e., Layer > Time > Enable Time Remapping) when you look at the Layer Window, you will probably notice that a second Time Ruler appears in the Window, situated above the main time ruler and navigator:
- Upper Ruler = Remap-Time Indicator / Marker
- Lower Ruler = Current-Time Indicator / Marker
Let’s use an example where we choose to adapt the timing of a 120 frame sequence.
To remap, use the Time Locator on the Lower Ruler — the Current-Time Indicator — to locate the first frame where you want a particular change to occur (e.g., frame 40).
You will find that the Time Locator on the Upper Ruler — the Remap-Time Indicator — follows along and is currently mapped to the time indicated on the Lower Time Ruler.
You would then use the Remap-Time Locator to set a different time to what is indicated on the lower ruler. For example, if the Current -Time Indicator (lower ruler) is at 40 and you then move the Remap-Time Marker to 60, the result will be that After Effects will adjust the timing so that drawings/frames 1 – 60 will quickly play in 40 frames.
To Freeze a Frame or Make a Hold
Set the Remap-Time Marker to the frame you want frozen or held (e.g., frame 40), and then add a linear keyframe, using the Add/Remove Keyframe toggles in the Timeline. Move the Current-Time Indicator (lower ruler) to the last point in time where the frame will appear frozen (e.g, frame 60). The Remap-Time Marker will follow along. Then, move the Remap-Time Marker back to the frame you want frozen, e.g., 40. Doing so will set a keyframe in the Timeline and the Current-Time will play Frame 40 for the duration of 20 frames.
To Make a Section Move in Reverse
We’ll follow the steps listed about, to cover the first parts of the remapping process.
Use the Current-Time Indicator and Remap-Time Marker to locate a position where you would like to shift the movement direction (e.g., at frame 50). Add a linear keyframe, using the Add/Remove Keyframe toggles in the Timeline. Move along the Timeline to the last keyframe in the sequence and then move the Remap-Time Marker (upper ruler) to the point where you want the sequence to end, in reverse (e.g., frame 10). Doing so will set keyframes in the Timeline and part of the phrase will play backwards.