Explaining 4K 60Hz Video Through USB-C Hubs #Video #Displays #Computing
BMOW (Big Mess o’ Wires) has a great article explaining getting high pixel rates through USB-C hubs. We’ve all experienced the hassles of trying to wire up monitors with some combination of HDMI, DisplayPort, Lightning, etc. along with Mac and PC compatibility.
Forget About HDMI
Lesson 1 is to focus on DisplayPort video connections, and forget about HDMI. You’ll never find a USB-C hub that offers better video capabilities through its HDMI port than through its DisplayPort, but you will find hubs that offer better DisplayPort resolution and refresh rates. I strongly suspect most hubs with an HDMI port are actually implemented internally as a DisplayPort, with an integrated DisplayPort to HDMI converter. This is because DisplayPort video can be carried more efficiently on the USB-C connection than HDMI for the same resolution and refresh rate.
The other method of supporting external monitors with zero dedicated lanes is DisplayLink. This technology compresses the video data on the host side, sends it over a USB 3.1 connection as generic data, and reconverts it to video on the other end using a special chip like the DL-6950. Conceptually it’s like a remote desktop connection for sharing your work computer’s screen when you’re logged in from home, except everything happens locally on your desktop.
DisplayLink is nice for squeezing high-resolution video over a lower-bandwidth connection like USB, or for supporting multiple high-res external monitors without Thunderbolt. But if you have any alternative, I think DisplayLink is best avoided.
What are the Options?
Putting all this knowledge together, we can group USB-C hubs into four categories based on how they treat video.
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