Here is a question about DIGITAL VIDEO

My wife has a monitor with Thunderbolt 3 input *only*. That's the "USB-C shaped" Thunderbolt.

She wants to plug a device with HDMI output into it.

She has, already, a card that can convert Mini Displayport to USB-C. But that means we must convert HDMI to Mini Displayport. We have lots of Mini Displayport to HDMI cables, but not the other way around.

Cheapest HDMI to Mini Displayport cable we're finding is $60.

Is this surprising? How should we do this?

I appreciate all the responses to this question but I cannot help but notice that they are a more or less even split between "the thing you want is impossible", "the thing you want is possible but you can't get it for less than $60 CAD because it is very hard", and "there is a cable on AliExpress that does that for $15"

Let me back up and ask the question again.

We have:

* An LG Ultrafine 4K monitor. The resolution is 3840 x 2160. It appears there are multiple monitor models fitting this description. We don't know how to find out which she has. The only input is USB-C shaped.

* A "ASUS ThunderboltEX 4" converter card in a PC.

* A device that outputs HDMI only.

Can we get the HDMI device to display on the LG monitor? Can we do it without introducing lag? How much should we expect to pay?

Several of the responses I got revolve around the idea that there are "active" and "passive" converters, where passive appears to be "switching between different physical cable types" and active means "converting different wire protocols". It appears there are at least 3 wire protocols the various cable types could be speaking, and *some* of them allow HDMI protocol over displayport cabling, or displayport protocol over USB-C cabling. I don't at present know how to find out what supports what.

As an update:

- We wanted to display a device that outputs HDMI on a 3840 x 2160 LG Ultrafine 4K monitor
- We got this cable https://www.amazon.ca/dp/B09JSYP8VR?psc=1&ref=ppx_yo2ov_dt_b_product_details which several people in the reviews claimed worked with what we think is the exact same monitor (unfortunately there are 3 very different LG monitors with the same name)
- We plugged in the cable from the HDMI at the Playstation end to the USB-C-shaped plug at the LG monitor end
- It does nothing. Black screen

@mcc I almost can't bear to scan the other replies for a mention of HDMI "alt-mode" compatibility

@protman Several people mentioned it but were not quite able to explain what to do with it.

@mcc I've made sure all three of my past and current laptops support HDMI alt-mode over usb-c. It's how I get dual external HDMI displays working with a single usb-c port. No other display ports provided. I do not have much insight into the display's usb-c input though. Is there a chance it's meant to be "portable"? In that regard? Maybe even supports a software display driver over usb? 😬 https://arstechnica.com/gadgets/2023/01/hdmi-to-usb-c-spec-axed-as-displayport-alt-mode-reigns-supreme/