Using the Speed Parameter in the Motion Tab

While the various speed adjustment methods allow you to make speed adjustments to clips quickly, you can also make very precise adjustments to a clip’s speed using the keyframe graph in the Speed parameter in the Motion tab of the Viewer. In particular, editing the keyframe graph is the only way to customize keyframe velocity, easing the transition from one keyframe to another using smoothed keyframes with Bezier handles. For more general information about settings in the Motion tab, see Adjusting Parameters in the Motion Tab.

Figure. Motion tab showing the Speed parameter.
  • Speed % field: This field displays the speed percentage at which the clip plays back. If a constant speed change is applied, this percentage represents the speed for the entire clip. If speed keyframes (and speed segments) are applied, this field displays the speed of the clip at the current playhead position.
  • Speed keyframe graph area: Use this area to apply and adjust speed keyframes. You can ease the transition from one keyframe to another using smoothed keyframes with Bezier handles.

    For specific information about the Speed keyframe graph area, see About the Speed Keyframe Graph Area. For information about adding and adjusting keyframes in any Motion tab keyframe graph area, see Adjusting Parameters for Keyframed Effects.

About the Speed Keyframe Graph Area

This section provides some background information on how to use the Speed keyframe graph area.

The Y Axis

The y axis represents the frame numbers of a clip’s media file. For example, if a clip’s media file contains 300 frames, the y axis ranges from 0 (the first media file frame) to 299 (the last media file frame).

Note: This is true regardless of the In and Out points you set for the clip. Even if the clip has an In point at frame 100 and an Out point at frame 200, the y axis of the clip starts at frame 0 of the media file and goes to frame 299.

When you choose a value for the keyframe on the y axis, you are choosing a frame from the clip’s original media file. When you drag a speed keyframe up and down on the y axis, a tooltip appears that displays which media file frame you are assigning to that point in time in your clip. As you move the keyframe up, you choose a later frame in your clip’s media file; when you move the keyframe down, you choose an earlier media file frame. The top of the y axis represents the last frame of your clip’s media file, and the bottom represents the first frame.

Figure. Motion tab with the Speed parameter showing a graph of the length of the clip's media file in frames.

The X Axis

The x axis represents a clip’s playback time. Frames are always played back at the frame rate of the clip. You can set a keyframe at any point on the x axis to specify which media file frame you want to see at that moment in the clip.

For example, suppose you want frame 100 from a clip’s media file to appear 2 seconds into the clip. In this case, you set a speed keyframe at 02:00 in the clip. Then you vertically adjust this keyframe to the value 100.

Speed and the Keyframe Graph

The following illustrations show how changes to the keyframe graph affect the speed of a clip in the Timeline. In each graph, the vertical axis represents media time, where each tick mark up is a successive frame of your video clip. The horizontal axis represents the Timeline, where each tick mark represents the duration of one frame playing at the sequence frame rate.

  • Linear time (100 percent speed): This is represented by a straight, upward-sloping diagonal line, in which one frame of a video clip plays in the space of one frame of the Timeline. This is real time.
    Figure. Diagram showing the upward slope of linear time.
  • Slow motion (less than 100 percent speed): Slow motion is represented by a line with a more gradual slope, in which one frame of a video clip may play over perhaps three frames of the Timeline.
    Figure. Diagram showing the upward slope of slow-motion time.
  • Fast-forward (greater than 100 percent speed): Fast-forward speed can be seen as a steeper line, in which several frames of a video clip play in the space of one frame of the Timeline.
    Figure. Diagram showing the upward slope of fast-forward time.
  • Freeze frame (0 percent speed): So far, all these graphs have illustrated forward-playing clips, represented by a line that slopes upward. A freeze frame, represented by a flat line, may also be created with the keyframe graph.
    Figure. Diagram showing the horizontal line of freeze frame time.
  • Reverse speed (less than 0 percent speed, or negative speed): When a clip plays in reverse, previous frames of the video clip are mapped to successive frames of the Timeline. Reverse speed is represented by a line that slopes downward.
    Figure. Diagram showing the downward slope of reverse-speed time.
  • Acceleration/deceleration: Finally, the most powerful feature of the keyframe graph is the ability to adjust the transition in a clip from one speed to another, at whatever velocity you require. Gradual changes from one speed to another are represented by curves. For example, a gradual transition from slow motion to fast-forward might look like this:
    Figure. Diagram showing an upward curve representing acceleration.

Note: Bezier curves in the Speed parameter are constrained so that any value along the curve is limited by the minimum and maximum values of the surrounding keyframes.

For more information on using Bezier handles to smooth keyframes, see Smoothing Keyframes. For more information on working in the keyframe editor of the Timeline, see Working with the Timeline Keyframe Editor.

Making Speed Adjustments in the Speed Keyframe Graph Area

You can add speed keyframes and make precise speed adjustments in the Speed keyframe graph area of the Motion tab.

To add a speed keyframe in the Speed keyframe graph area
  1. Open the clip in the Viewer.

  2. Click the Motion tab.

  3. In the Speed keyframe graph area, do one of the following:

    • Option-click anywhere along the line in the keyframe graph.

    • Select the Pen tool from the Tool palette and click anywhere along the line in the keyframe graph.

To adjust the position of a speed keyframe
Do one of the following:
  • Drag the keyframe up or down to choose a frame from the clip’s original media file.

  • Drag the keyframe left or right to set the timing for the specific frame from the clip’s original media file.

Tip: The Speed keyframe graph area of the Motion tab can be resized vertically, allowing you to have a more detailed view of the keyframe graph you’re editing. For more information, see Resizing the Keyframe Graph Area.

To adjust the transition from one keyframe to another using Bezier handles
  1. Control-click a speed keyframe.

  2. Choose Smooth from the shortcut menu.

    Bezier handles appear on the keyframe.

  3. Drag the Bezier handles to adjust the shape of the graph line on either side of the keyframe.

    For more information on using Bezier handles to smooth keyframes, see Smoothing Keyframes. For more information on working in the keyframe editor of the Timeline, see Working with the Timeline Keyframe Editor.