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.
Using Key on Layer
Compositing these three feeds will require four layers on two mixes.
- Capture the Key Fill and Key Cut feeds on an external mix. Best practice is to capture live feeds onto a separate mix (ideally mix 1 to reduce latency) and to leave that mix capturing at all times.
- In this example, on the capture mix, Layer 2 is the Key Cut, Layer 1 is the Key Fill
- On the output mix layer 2, play the background clip and use inverse key from Mix 1, Layer 2. Set the layer to mix mode alpha.
- On the output mix, set source to relay and use layer 1 from the capture mix as the source
The result will be that layer 1 of the output mix will be visible through the cutout of the key on layer 2.