ATEM Lower Thirds: How They Work and What They Mean for Webcam Audio

The short answer

On a Blackmagic Design ATEM switcher, a lower third is a graphic, usually a name and title bar, laid over the bottom of the live picture. In typical workflows, the switcher does not generate the text itself. You design the graphic in other software, load it into the switcher's media pool as a still image with transparency, and place it over the program output with a keyer, most often a downstream keyer. Lower thirds are purely visual. They do not change how speech is captured. The audio question only comes up when the ATEM's output is used as a webcam source on a computer, which is covered below.

No model-specific evidence was supplied for this guide. The number of keyers, media pool slots, supported file formats and software features varies between ATEM models and software versions. Check those details against the manual for your unit.

How ATEM lower thirds differ from other overlay methods

A key is the switcher function that cuts out part of one image and places it over another. Where the key sits in the signal path determines how the lower third behaves when you change shots.

Method | How it behaves | Typical use

Downstream key | Applied after the main mix, so it stays on screen when you cut between cameras | Persistent lower thirds, logos, bugs

Upstream key | Part of the main mix and can be included in or excluded from the next transition | Graphics tied to a particular shot, picture-in-picture

External graphics source | A computer running graphics software feeds a switcher input, which is then keyed | Animated or frequently changing titles

Software overlay after the switcher | Added on the computer, for example in streaming or virtual camera software | Setups where the graphic is not needed in the switcher's own output

Preparing and showing a lower third

• Design the graphic at the same resolution as the switcher's video format so it is not scaled.
• Export it with an alpha channel (transparency). PNG is a common choice. Confirm which formats your model accepts.
• Keep text away from the frame edges so it is not cropped on some displays.
• Load the file into the media pool using ATEM Software Control, then assign it to a media player.
• Set the downstream keyer's fill and key sources to that media player.
• If edges look dark or fringed, change the pre-multiplied key setting so it matches how the graphic was exported.
• Use the keyer's On Air control to cut the graphic in, or Auto to fade it in and out.

Where speech capture comes in

ATEM Mini models can connect to a computer over USB and appear as a webcam. The switcher's audio mix can travel over the same connection. In a conferencing app, you will usually select the ATEM as the camera. Choose the microphone separately and deliberately.

• If your microphone plugs into the ATEM, or you use a camera's audio on an ATEM input, select the ATEM as the microphone so sound and picture travel the same path.
• If you select a separate microphone, such as a laptop's built-in mic, the sound skips the switcher while the picture passes through it. This can cause a lip-sync offset. That is an inference from the signal path, not a measured result.
• A typical USB webcam cannot plug into an ATEM Mini's HDMI inputs. Its built-in microphone goes straight to the computer, so it bypasses the switcher's audio mix entirely.
• Select only one microphone path in the conferencing app to avoid doubled audio or echo.

What this guide cannot confirm

• Keyer counts, media pool capacity and supported formats for specific ATEM models.
• Feature changes in particular ATEM Software Control versions.
• Measured audio-to-video delay for any particular setup.
• How specific conferencing apps handle ATEM audio and video devices.