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
There are three main differences between constant and variable speed changes.
Â 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.
Â 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.
Â 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.