Using HDMI passthrough on the Elgato 4K X

The short answer

HDMI passthrough on the Elgato 4K X sends the incoming HDMI signal out to a second display while the card captures that same signal for your computer. When a DSLR or mirrorless camera is your webcam, passthrough lets you watch the camera feed on a separate monitor without routing it through the computer. It is a monitoring path, not an audio-processing path. Passthrough does not improve, clean up or otherwise change the speech your computer captures. One condition limits this answer: the evidence available for this guide did not include confirmed passthrough resolutions, refresh rates or latency figures, so check Elgato's current specifications and firmware notes before matching the card to a particular display.

What passthrough means

A capture card with passthrough has an HDMI input and an HDMI output. The signal entering the input is copied to the output so a display can show it, and the card sends a version of the signal to the computer over USB at the same time. The display connected to the output gets the picture without waiting for the computer to decode and redraw it. That is why passthrough is mainly used for monitoring. In a camera-as-webcam setup, the camera's own screen is often small or flipped away from you, so this is useful for checking framing and focus.

Where passthrough fits in a camera-as-webcam chain

• Camera HDMI output to the 4K X HDMI input. Enable the camera's clean HDMI output, if it has one, so on-screen overlays are not sent along with the picture.
• 4K X HDMI output to a monitor or TV. This is the passthrough connection.
• 4K X USB connection to the computer, where the card appears as a video source for conferencing or streaming software.
• In the conferencing app, select the capture card as the camera. Then choose the microphone deliberately rather than accepting the default.

What passthrough means for speech capture

HDMI can carry embedded audio, meaning sound sent inside the same cable as the video. If your camera passes audio over HDMI, that audio reaches the 4K X along with the picture. Capture cards typically present it to the computer as an audio input. The same embedded audio also goes out through passthrough to the connected display. The audio source is whatever the camera hears: either its built-in microphone or an external microphone plugged into the camera's mic jack.

Passthrough does not decide how good your voice sounds. Microphone choice and placement do. A camera's built-in microphone is usually positioned for general pickup on the body of the camera, not close to your mouth. In a typical desk setup it can capture more room sound and less direct speech than a dedicated microphone placed nearer to you.

Audio route | How it reaches the computer | What to check

Camera's built-in mic | Embedded in HDMI, through the 4K X | Distance from mouth, room echo, and whether the camera sends audio over HDMI at all

External mic into the camera | Embedded in HDMI, through the 4K X | Camera input level settings, and whether the camera supplies power if the mic needs it

USB or interface-connected mic | Directly to the computer, bypassing the camera and card | Lip sync, because the video may arrive later than the audio

Lip sync deserves attention when the microphone connects straight to the computer. In that case the video travels through the camera's processing and the capture card, while the audio takes a shorter route. The voice can then arrive slightly ahead of the picture. Streaming and recording software such as OBS usually includes an audio sync offset to correct this. Many conferencing apps do not, so audio embedded in the camera's HDMI signal can be the easier way to keep speech and video aligned. This guide has no measured delay figures for the 4K X, so judge sync by watching a test recording.

Watch out for the passthrough display's speakers. If the monitor plays the embedded audio aloud during a call, your microphone can pick it up again. That can cause doubling or feedback. Mute the display's speakers, or monitor with headphones.

Gaps to close before relying on it

The evidence for this guide contained no confirmed specifications, measurements or test results for the Elgato 4K X. Treat the following as open questions to confirm with Elgato's documentation or your own test recording:

• Which resolutions and refresh rates passthrough supports, and whether these differ from the capture limits.
• Whether passthrough keeps working when the computer is asleep or the capture software is closed.
• What name the card's audio input uses in your operating system and conferencing apps.
• Whether your specific camera sends audio over HDMI, and at what level.
• How much delay you see between a directly connected microphone and the captured video in your own setup.