My Video Capture Passthrough application is meant to be the ideal application for using a capture card to turn your Mac into an external monitor.

Background

I purchased an Elgato Cam Link to allow me to use my iMac as an external monitor for my Nintendo Switch and my work MacBook Pro. I wasn't interested in recording the video, I just wanted to pass it through with as little latency as possible.

Initially, I used the Elgato software that came with the device. This worked great for my Nintendo Switch at 1080p, but when I tried to use it with my MacBook Pro at 4K, I noticed a significant amount of latency. I was able to work around this using QuickTime, but I would have to disable my screensaver otherwise the iMac would turn off its display. Also, with QuickTime, the cursor would always be visible. After living with this for a few months, I decide to build the solution I wish existed.

I wanted to optimize a capture application for passthrough. By removing any type of recording, I was able to combine the lowest latency possible, even at 4K, along with code to disable the screensaver from turning on. As a plus, I was able to add controls to set the volume of audio coming into the capture card.

Features

The first feature is the ability to select your video source. You can see all the available video sources from the menu bar and select the source you want to pass through to your Mac. The application will remember your selection from the last time you used the application.

Next, you can select the audio source different from the video source. This is useful if the best input for the source's audio is different from the video. This selection is also remembered between sessions.

Next, you can select the volume level of the source. You can select anything from 0% to 100%. This selection is also remembered between sessions.

The last two minor features are cursor auto-hiding and screen keep awake. The cursor auto-hiding feature detects when the cursor stops moving over the application window and hides the cursor after a few seconds. Lastly, when the application is open; the screen will be kept awake and the screensaver will not be triggered.