Apple Final Cut Express HD - Manual (Page 444)

444 Part VI Rough Editing
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 Express HD 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 Express HD 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.
Viewing an Audio Clip at Single-Frame Resolution
When you’re editing an audio clip in the Viewer, you can zoom in so far that the
playhead is the width of a single video frame on the waveform. You can use this single-
frame view, along with the subframe scrubbing function in Final Cut Express HD, to
match the beats of musical clips you edit together; or you can use it to set subframe
keyframes to eliminate pops or clicks that occur at the audio edit points you’ve chosen.
If you do not hear audio from the monitoring speakers while scrubbing, you may need
to turn up the volume, or you may have audio turned off (see “
Turning Off the Audio
Scrubbing Sounds ” on page 435).