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

We also tried running

- HDMI out from PS4 -> passive cable with HDMI at one end and mini displayport at the other (because it is passive we assume it is bidirectional) -> ASUS Thunderbolt EX 4 converter card -> thunderbolt cable -> LG Ultrafine

This, also, did nothing (blank black port)

Trying to figure out which combinations of device to solve the problem we have not yet tried, short of randomly ordering ANOTHER cable like the Club3D which claims to be an active HDMI to USB-C converter.

It sure is a frustrating failure mode that searching Amazon for "hdmi to mini displayport" turns up result after result of mini displayport to hdmi adapters (the opposite). Every other store site I try has the same failure. I realize tech products only improve when they're in expansion phases, but you'd think after like 25 years of being in this business someone at amazon would have thought that the order of words might sometimes matter in a product search.

Okay. Here's what we're concluding.

- The cable we bought is probably doing Displayport-protocol-over-USB-C. The monitor we have is probably thunderbolt-protocol-over-USB-C only.
- Our best bet, at present, is probably to use the ASUS Thunderbolt EX 4 to convert mini displayport to Thunderbolt. To do this, we need an *active* HDMI to mini displayport converter (or active HDMI-to-displayport, as we have a passive displayport-to-mini-displayport cable)

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