Key And Fill
Key and Fill is a technique used to composite graphics in broadcast vision mixers - often for lower third graphics and overlays. Physical video signals (like HDMI and SDI) do not carry alpha information, therefore the alpha channel (Key) needs to be split into a separate video signal, with alpha being presented as luminance.
Media servers have the ability to split RGBA into RGB (Fill) and A (Key) signals, with no changes to your project’s configuration. Standalone offers this functionality by sending the Key & Fill to two different video monitors/outputs.
To enable this functionality in standalone:
- Run your Standalone Application.
- Enable Key & Fill from the launch dialogue, or from the Command Line.
- For Display choose the monitor you want the Fill (RGB) signal to be output to.
- For Display 2 (Key) choose the monitor you want the Key (Alpha) signal to be output to.
- Tick Full Screen to ensure both monitors are matched on frame output.
Both output monitors/devices need to support the same output resolution and refresh rate.
If your vision mixer requires that the Key & Fill signals be genlocked, you will need a workstation grade GPU to genlock the outputs together. Please refer to your GPU vendors documentation.
Make sure you have enabled alpha output on your composition, and checked that alpha is being generated in Builder.