In ordinary Timeline editing, a video clip and the original audio that was captured with it are treated as a unit. Their special relationship is symbolized in the Movie Window by the line connecting the video track indicator with the original audio track indicator, showing that the latter is dependent on the former.
The track lock buttons make it possible to deal with the two tracks independently for operations like insert editing, which typically means replacing part of a clip on the video track while the original audio track continues uninterrupted.
Note: Insert editing may also be carried out on the overlay video and audio tracks, using analogous methods to those described here.
For instance, in a sequence that shows someone recounting a story, you might wish to insert a shot of an audience member smiling (or sleeping!) without breaking away from the main audio.
To perform an insert edit on the video track:
1. In the Timeline view of the Movie Window, click the original audio track’s padlock button to lock the track.
The lock button is highlighted, and the track itself is grayed to show that its contents will not be affected by editing operations.
2. Clear space on the video track for the video clip you want to insert. Position the Timeline scrubber at the point you want the insertion to start and use the Split clip/scene button. Now move to the point where the insertion should end and again split the clip. Finally, delete the portion of video that will be replaced by the insertion.
Because the audio track is still intact, having been locked, the video to the right of the insertion point does not move leftwards to fill the gap you have made in the Timeline, for the video and audio would then no longer be synchronized. If you were to preview your video now, you would see a black screen as the gap portion played back, but the soundtrack would be normal.
3. Now all that remains is to place the clip you want to insert. Drag the clip (whether from the Album, the Project Bin, or elsewhere on the Timeline) into the hole in the video track that you’ve just opened up.
If the inserted clip is too long for the space you created it is automatically trimmed to fit the space. You can adjust the trimming with the Clip properties tool.
The converse insert-editing operation, in which a sound clip is inserted into the original audio track over unbroken video, is needed less often but is also readily performed in Studio.
The procedure is analogous to the one for inserting video: simply reverse the roles of the two tracks at every step.