Video Asset Length Changes
If you have changed the length of a video asset that is used in a track, there could be
audio sync problems if other assets are used in the same track. For example, making the
asset shorter would cause all video assets in the timeline that are placed after it to shift
earlier because the V1 stream cannot have any gaps in it. The corresponding audio does
not shift though, because audio streams can have gaps.
Making the QuickTime video asset longer does not change the clip in any tracks that use
it. You have to manually change the clip’s duration in the tracks to use the added video.
When used as backgrounds in motion menus, you may need to adjust the menu’s duration
to better fit with the asset’s new length.