Apple Final Cut Pro 5 - Manual (Page 1099)

312 Part II Project Interchange
Differences Between Constant and Variable Speed Changes
There are three main differences between constant and variable speed changes.
 First, while a constant speed change applies a single percentage to the entire clip, a
variable speed change can have as many percentage speed 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 alone. 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 into 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
variable speed motion 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.
Frame Blending and Reverse Speed
Duplicating frames to create slow motion can result in a strobing, jittery effect. To
minimize this, you can turn on frame blending in the Speed dialog. When slow motion
is created, frame blending uses the two frames that appear to either side of duplicate
frames and creates new in-between frames that are a composite of both. By inserting
blended frames in place of frames that have simply been duplicated, slow-motion clips
appear to play back more smoothly. Speed changes can still play back in real time with
the Frame Blending option turned on.
Original Blended frame Original