Mixing Unit

The M/E. Same job as a vMix Mix Input, a TriCaster or ATEM M/E, or a Kairos scene.
This is the core switching desk. Preview holds the next shot; Program holds the picture in use.

No per-session cap. Add as many as the machine will take.
Each unit has its own resolution and output frame rate.

Overlays sit on that unit’s Program. One unit’s Program can feed another unit or an Output.

The switching buses are Preview and Program.
A Switcher UI shows Preview and Program, so it uses 2 slots of the video output destination window limit. Closing it frees those slots.

Add Input can wrap this unit’s Preview or Program as a Mix Input. That Input reads the existing FrameDelay ring (1–8 frames) and does not add a swapchain. Put it on another Mixing Unit for a nested M/E. Wiring it back onto the same unit is refused. Mix audio is a delayed copy of one selected Audio Bus, or silence if None.