Key on Layer

Key on Layer replaces Matte Mix mode to use any other layer as key source

Keying is commonly used in broadcast applications to composite a live feed onto a background.

Often times, the key source is presented as two live feeds a Key Cut and a Key Fill which is mixed onto a Background.

Example Media:

Key Fill

Key Cut

Background

Using Key on Layer

Compositing these three feeds, Key, Fill and background can be done following these steps:

1) Have your key and fill on the lower z-order layers and the background above.
2) Level of the fill needs to be above 0, whereas cut can be set to 0.
3) On the background layer set layer mode to Alpha.
4) Apply key on the background layer and select the key cut Mix/layer.

The background now has the key cut filled with the key fill and overlayed.

The result will be that layer 1 of the output mix will be visible through the cutout of the key on layer 2.

*If you are using Key & Fill content with different aspect ratio than the mix then you will be required to create a second mix which you can then select the Mix Master as the key cut Mix/layer