How to Connect an ATEM Mini Switcher to Live-Captioning Software for Hybrid Services

Hybrid worship services demand accessibility for both in-person attendees and online viewers. Providing real-time subtitles improves comprehension for deaf and hard-of-hearing members, language learners, and viewers watching live streams in noisy environments. Integrating the Blackmagic Design ATEM Mini video switcher with modern live-captioning software creates an automated, high-definition captioning pipeline for your entire hybrid production.

Here is the step-by-step guide to connecting your ATEM Mini switcher to live-captioning software, configuring clean audio feeds, and overlaying synchronized lower-third captions onto your live broadcast.

1. Route a Clean Audio Aux Feed to the Captioning Computer

Live-captioning software relies on real-time speech recognition models that require clear, isolated vocal audio to maintain high transcription accuracy. Running house program audio that contains background instruments, congregational singing, or ambient room reverberation degrades caption quality.

To supply clean audio:

• Assign an auxiliary (Aux) send or dedicated direct output from your digital audio console containing only the spoken vocal channels (such as the pastor's wireless lavalier and pulpit microphones).
• Connect this Aux output to a USB audio interface plugged into the computer hosting your live-captioning software.
• Set the speech recognition software input directly to this dedicated USB audio interface.

Properly isolating the speech signal from the ambient house mix prevents music bleed from generating incorrect or garbled transcriptions during worship transitions.

2. Generate a Keyable Live-Caption Video Output

To overlay subtitles onto your video broadcast without expensive SDI hardware, use live-captioning software capable of outputting a full-screen display with a solid black or solid green background. Modern platforms like Kairos, WebCaptioner, and OBS-integrated captioning tools offer customizable lower-third display modes.

Configure your caption display settings with the following parameters:

• Font Size and Weight: Choose bold, sans-serif typography (such as Arial, Helvetica, or Inter) set between 36pt and 48pt.
• Contrast: Set text color to pure white (#FFFFFF) with a subtle black outline or semi-transparent backing box.
• Background Canvas: Set the output canvas background to solid pure black (#000000) for Luma keying, or pure green (#00FF00) for Chroma keying.
• Display Position: Position caption text within the lower 20% of the display frame to stay clear of speaker lower thirds and graphic title cards.

3. Connect the Caption Computer to an ATEM Mini HDMI Input

Connect an HDMI cable from the secondary display output of your captioning computer directly into one of the four HDMI inputs on the ATEM Mini (for example, Input 4).

On your captioning computer:

1. Configure your display settings to Extend Desktop rather than mirror.
2. Set the resolution of the secondary HDMI output to 1080p at 60Hz or 59.94Hz to match your ATEM Mini project frame rate.
3. Drag the full-screen caption display window over to this extended monitor feed.

Because the ATEM Mini features built-in hardware frame synchronizers and format converters on all inputs, it will automatically scale and sync the computer's HDMI output to your broadcast resolution.

4. Configure the Luma or Chroma Keyer in ATEM Software Control

To layer the live captions over your active camera shots without obscuring the video feed, configure the Upstream Keyer (USK) or Downstream Keyer (DSK) inside Blackmagic ATEM Software Control.

Follow these configuration steps for a clean Luma Key overlay:

1. Open ATEM Software Control on your production computer.
2. Navigate to the Palettes tab and expand Upstream Key 1 (or Downstream Key 1).
3. Set the key type to Luma.
4. Set the Fill Source and Key Source to your caption computer's input (e.g., Camera 4).
5. Check the Pre-Multiplied Key box. If using a custom black level, adjust the Clip slider to approximately 50% and the Gain slider to 100% until the black background disappears completely, leaving only sharp white text.
6. Toggle the ON AIR (USK) or AUTO (DSK) button to activate the caption overlay during sermon segments.

Using a Luma key with pure white text on a pure black background eliminates the green edge halos often created by chroma keying.

5. Align Video and Speech Latency

Real-time AI speech transcription introduces a slight processing delay, typically between 800 milliseconds and 2 seconds depending on engine complexity. If captions appear before words are spoken or lag significantly behind, adjust your audio delay settings inside ATEM Software Control.

Under the Audio tab in ATEM Software Control, select the microphone or line input receiving your broadcast sound. Blackmagic ATEM Mini switchers provide up to 8 frames of audio delay on analog 3.5mm inputs. If higher delay compensation is needed, adjust the global audio delay in your streaming encoder (such as OBS Studio, vMix, or hardware streaming boxes) to ensure spoken words, camera video, and on-screen text arrive simultaneously to online viewers.

Elevate Your Hybrid Accessibility

Pairing the Blackmagic ATEM Mini with automated live-captioning software eliminates technical barriers to worship accessibility. By combining isolated vocal routing, dedicated HDMI keying, and precise latency sync, your AV ministry can deliver professional, barrier-free service broadcasts every Sunday.