Which feature can you use to speed up or slow down a video track in After Effects?

Time remapping is the correct answer because it is a specific feature within After Effects that allows users to manipulate the timing of their footage. This technique enables you to change the speed of a video clip by creating keyframes that indicate how fast or slow a segment of the video should play. By adjusting these keyframes, you can create effects like slow motion or fast-forward, allowing for precise control over the playback speed of your video.

Other methods, such as speed adjustment or frame rate change, do not provide the same level of flexibility. Speed adjustment is more generalized and may not allow for dynamic control over specific parts of a video. Frame rate change can affect the overall quality and smoothness of the footage but does not allow for selective speed changes. Keyframe interpolation, while useful for creating motion between keyframes, does not directly alter the timing of footage playback itself. Thus, time remapping stands out as the dedicated feature for controlling playback speed in After Effects.