The concept of video layers is central to understanding how the Switcher, M/E and Transition controls relate to one another, and how they combine to form the video seen on Program output.

• The Background layer (often shortened to BKGD) is always the base for the video composition displayed on Program output.

• DSK (Down Stream Keyer, or overlay) layers may appear above (in front of) the Background.

DSK layers are typically used for overlaying objects like graphics or titles, although they may serve other purposes as well. In addition to BKGD, up to five additional primary layers can contribute to the final Program output at any given moment:

• Overlay layers (DSKs) are composed above the BKGD layer on output. DSK 2 appears in front of DSK 1 on Program Output (closest to the viewer) and so on in order.

• FTB (Fade to Black) constitutes a final overlay layer – one that obscures all other layers when applied.

Recall, too, that the BKGD layer itself is often a composite of sub-layers:

• It may include mixed video from both the Program or Preview rows.

• Selecting an M/E as source on Program or Preview can add many sub-layers to the BKGD composition, including the M/E’s primary Inputs and dedicated KEY layers (which are similar to DSK layers but, being upstream of the main Switcher, appear composed in the background layer).