When you select a transition effect from the Effect Palette and not enough source media exists to apply the effect, the Insufficient Source dialog box opens.
The dialog box shows a graphical display that indicates whether the source that has insufficient material is Media A (outgoing footage), Media B (incoming footage), or both.
The Avid editing application sets the duration of the effect to fit the available media. If you have selected an alignment, the application attempts to preserve it.
To change the alignment or duration of the transition effect, see
Creating a Dissolve in Trim Mode.