QuickTime 4 Reference

Specifying a Duration for a Tween

You can specify the duration of a tween operation by including an optional kTweenDuration atom in the kTweenEntry atom for the tween. When a QuickTime movie includes a tween track, the time units for the duration are those of the tween track's time scale. If a tween component is used outside of a movie, the application using the tween data determines how the duration value and values returned by the component are interpreted.