What is a video mixer?

A video mixer is the core of any modern video studio. It's a system (usually a dedicated "magic box" type device, but sometimes a computer program) for smoothly switching between multiple video sources and combining then with effects like green screening, overlaying, etc.

A couple important words:

  • Sources: These are the things that feed video into the mixer. Most of the time this will be a camera or a computer.
  • Buses: Places to put video
  • Program Bus: This is what's on air; your audience will see whatever's on the program bus.
  • Preview Bus: This is a place to queue things up for the program bus. To smoothly move something to the program bus, you'll put it on the preview bus first.

Connecting Sources

Modern video mixers almost always accept HDMI, SDI, or both.


You've probably used HDMI before. Computers, TVs, game consoles, and countless other things use it. It's a very consumer-oriented standard, but it's also common in the broadcast world.


You may have never seen this before. SDI is a broadcast/professional standard; you don't see it too much in the real world. It uses BNC connectors, and it's capable of 4K and higher video.

Example Mixer Connections:

As you can see, our mixer has connections for both HDMI and SDI devices, but it gives its final output in SDI.


See this video tutorial. The tutorial is shot on an older version of the ATEM video mixer, but the operation is still the same.