About time-remapping
In After Effects you can easily expand, compress, play backwards, or freeze a portion of a layer's duration using a process known as time-remapping. For example, if you are using footage of a person tearing a movie ticket, you can play footage of the tearing, freeze the motion as the ticket is torn halfway, and then play a few frames backwards to make the ticket appear whole again. ![]() Footage is usually displayed at a constant speed in one direction. ![]() Time-remapping distorts time for a range of frames within a layer. You can also time-remap layers containing audio or both audio and video. When you apply time-remap to a layer containing audio and video, the audio and video remain synchronized. You can remap audio files to gradually decrease or increase the pitch, play audio backwards, or create a warbled or scratchy sound. You can remap time in either the Layer window or the Timeline window. Remapping video in one window displays the results in both windows. Each window provides a different view of the layer duration: ![]() A. Current-time marker B. Remap-time marker C. Time-remap value D. Navigator bar ![]() A. First frame B. Last frame C. Active frame D. Top speed E. Current speed F. Lowest speed When remapping time in the Timeline window, use the values represented in the Time Remap graph to determine and control which frame of the movie plays at which point in time: Time Remap This value indicates which frame plays at the current time. As you drag a Value graph marker up or down, this value changes accordingly. You can click this value and type a new one. The Time Remap value also appears in the Layer window next to the Out point value. Value: Time Remap The top value represents the last (highest) frame in the layer, and the bottom value represents the first (lowest) frame. Velocity: Time Remap The top value indicates the layer's fastest speed. The bottom value is always a negative of the top value. The middle value indicates how fast the video is playing at the current time. Normal speed is 100%, slow-motion is less than 100%, and fast-motion is greater than 100%. When you turn on Enable Time Remapping, After Effects adds a Time Remap keyframe at the start and end points of the layer in the Timeline window. By setting additional remap keyframes, you can create complex motion effects. Every time you add a Time Remap keyframe, a Value graph marker appears on the graph directly below the keyframe. As you move this marker up or down, the Time Remap value changes to the frame of the video set to play at the current time. After Effects then interpolates intermediate frames and plays the footage forward or backward from that point. The speed at which remapped video plays depends on the number of frames you are remapping and the amount of time allocated in the timeline for the changes. For example, if you freeze a frame for one second and do not increase the duration of the layer by one second, the footage following the freeze frame must play faster than normal to play all frames in the limited time remaining. The original duration of the source footage may no longer be valid when remapping time, because parts of the layer no longer play at the original rate. If necessary, set the new duration of the layer before you remap time. See Understanding trimming. If you remap time and the resulting frame rate is significantly different from the original, the quality of motion within the layer may suffer. Apply frame blending to improve slow- or fast-motion effects; see Using frame blending. Related Subtopics: |