Specifications

Chapter 1: Introduction 9
Frame-Accurate Video Editing
and Sample-Accurate Audio
Editing
Media Composer and Symphony edit with frame
accuracy. This means that in a 30 fps project,
you can edit at 30 different locations for every
one second of video. Pro Tools edits with sample
rate accuracy. In a 48 kHz session, there are po-
tentially 48000 locations to edit for every second
of audio.
When Pro Tools exports an AAF or OMF compo-
sition destined for an Avid application, it must
ensure that the audio files line up on frame
boundaries. To do this, it might have to split an
existing audio clip into three clips. For example,
the following illustration shows a 5-frame video
clip and a corresponding audio clip. In
Pro Tools, the audio clips might not line up on
video frame boundaries.
In order to export frame accurate audio clips,
Pro Tools splits the audio media on frame
boundaries and fills any gaps with silence. The
following illustration shows the resulting audio
clips that are exported to Media Composer.
When you use Export Selected Tracks as
OMF/AFF to export tracks from Pro Tools with
Enforce Avid Compatibility enabled, a number
of additional media files labeled Sample Accu-
rate Edit appear in the Avid bins. These are the
additional media files that Pro Tools creates to
ensure that Media Composer receives frame-ac-
curate audio. You also see the sample-accurate
edit media files if you zoom in on the imported
audio in the Timeline.
Figure 1. Original audio clip
One Pro Tools audio clip
5 frame video clip
The original audio clip does not line up on video frame boundaries
Figure 2. Exported audio clip
Three exported audio clips
5 frame video clip
Exported audio clips line up on video frame boundaries
New audio clip with
padded silence
New audio clip with
padded silence