Grass Valley EDIUS Pro v.7.20 - Manual (Page 364)

Applying Effects
342 EDIUS - Reference Manual
6 Composite the clips by laying them on the timeline.
[Track Matte]
Generate alpha (transparency information) from the clip placed on the timeline as a matte clip, and multiply it by alpha
of the clip placed as a source clip. In addition, you can place it overlaying the background image.
1 Place a clip to use as a matte clip on a track.
2 Place a clip to use as a source clip on a track on the matte clip.
3 In the folder view of the [Effect] palette, click the [Keyers] tree.