Apple Final Cut Pro 6 - Manual (Page 1126)

Chapter 17 Changing Clip Speed and Time Remapping 341
II
Constant and Variable Speed Settings
You can make two kinds of speed changes to a clip—constant and variable. Additional
options allow you to control the timing and improve the look of clips when you apply
speed settings.
There are three main differences between constant and variable speed changes.
 First, while a constant speed change applies a single speed percentage to the entire
clip, a variable speed change can have as many speed percentage changes
throughout a single clip as you want. Unlike clips with constant speed changes
applied, which may require rendering at higher speeds, variable speed clips can play
back in real time regardless of how fast the clip plays back.
 The second difference is that while a constant speed change automatically affects
the duration of the affected clip, a variable speed change leaves the duration of the
clip unchanged. You can manually shorten or extend the duration of a clip with
variable speed applied using the Final Cut Pro trimming tools (just as you would with
any other clip), but no change you make involving a variable speed setting changes
the duration of the affected clip.
Note: After applying a variable speed effect to a clip, you can still modify the
duration of the clip by entering a new value in the Duration field of the Speed dialog.
Changing the duration of a variable speed clip in this way changes the Out point of
the clip but has no effect on the keyframes and duration of that clip’s time
remapping keyframe graph.
 Last, variable speed settings applied to a video clip item are not applied to the audio
items linked to it. After making a variable speed change to a clip, audio and video
sync is lost.
Constant Speed
Applying a constant speed change to a clip alters the entire clip’s playback speed by
the same percentage. For example, applying a speed setting of 25 percent to a clip
makes the entire clip play in slow motion. Constant speed changes are useful when
altering a clip’s timing to fit a larger or smaller gap in your sequence, or when trying to
achieve a consistent speed change across an entire clip (making a car seem faster or
slower, for example).
Constant speed changes also alter the duration of a clip. If a constant speed change
causes the duration of a clip in a sequence to become longer or shorter, all clips
coming after it ripple forward or backward according to the ripple editing rules in
Final Cut Pro. For more information about rippling clips in a sequence, see Volume II,
Chapter 18, “Performing Slip, Slide, Ripple, and Roll Edits.”