timeremapping

Time remapping is a technique in video and animation that alters the playback timing of a sequence by mapping input time to output time. It enables non-linear pacing, allowing footage to be sped up, slowed down, frozen, or reversed. A time remapping system assigns a time value to each frame or sample along the timeline, with keyframes marking desired time values and interpolation generating the in-between frames.

In practice, time remapping provides a range of effects, including speed ramps where speed changes gradually or abruptly, frame holds that freeze a moment on screen, and reverse playback. It is commonly implemented as a property on a layer or clip in composition and edited with keyframes or expressions. When audio is involved, remapping can desynchronize sound unless the audio track is separately re-timed or replaced.

Quality considerations include potential artifacts from insufficient frame sampling, such as stutter or blur. To improve smoothness, some workflows use frame interpolation or optical-flow techniques, which can be computationally intensive. Velocity graphs or bezier handles are often used to control the pacing curve, enabling precise acceleration and deceleration.

See also: speed ramping, time warping, frame interpolation.