Working with Audio at the Subframe Level
While the smallest unit of video is a single frame, the smallest adjustable unit of audio
in Final Cut Pro is 1/100th of a frame. Audio level and pan keyframes, as well as the sync
between the video and audio tracks of a clip, can be set with an accuracy of 1/100th of
a frame.
Subframe Synchronization of Audio and Video
When you’re synchronizing audio and video, audio that’s as little as 300 samples
off perfect sync can be noticeable. For this reason, Final Cut Pro allows you to
resynchronize your audio in increments of 1/100th of a frame. There are several cases
in which this will come in handy:
 When editing music clips together, it’s essential that you edit them together precisely
on the beat. Even a subtle offset can upset the rhythm.
 Video and audio that were recorded from separate sources and resynchronized on
tape may be subtly out of sync.
 Audio that was recorded with a microphone far away from the audio source might
have an offset between the video and audio, since sound moves through the air
more slowly than images.
To navigate through a clip by subframe units:
1
Open a clip in the Viewer.
2
Hold down the Shift key while dragging the playhead within the duration of a single
video frame.
This allows you to move the playhead in increments of 1/100th of a frame. When you
set a new edit point in the clip, the clip’s audio item slips a fraction of a frame,
establishing a new sync relationship between the video and audio items.