Yes and no. HDMI CEC works pretty decent these days, all the kinks have been worked out over the years and the only time it bugs out is if you use Chinese brands (looking at you, TCL) that write horrid firmware and never fix any bugs found after release.

Displayport has DDC/CI, which allows you to adjust things like brightness, volume, etc. remotely. This has existed since the DVI era (!) which means Displayport has a huge headstart. But they never formalized and enforced the DDC/CI spec, which means every monitor has extremely weird quirks. Some will allow you to send and read data. Some will only allow you to send data and crash when you try to read. Some will update only once every few seconds.

Although in this specific case, one wonders why Valve didn't just use two Displayport 1.4 ports and and stuck an onboard HDMI converter in front of one of them, sourced from a company that would be amenable to having Valve work on the firmware of said converter. Make the entire firmware of the converter open source except for the binary blob that handles the Displayport 1.4 -> HDMI 2.1 bits.

Hopefully Valve does this but sells it as a external, high quality converter. It would be a nice little plus even for non-Steam Machine owners, same way like Apple's USB-C to 3.5mm convertor is the highest quality mini DAC on the market for the low price of €10.

> HDMI CEC works pretty decent these days, all the kinks have been worked out over the years and the only time it bugs out is if you use Chinese brands

I don't know. I have an LG TV and it does not support turning the display on/off with HDMI CEC. Everything else seems to work but it intentionally ignores those commands.

Have you turned off SIMPLINK? (LG's older name for CEC).

Option 1 (Hidden Menu Method)

* Press the Mute button repeatedly until the hidden menu appears; ensure Auto Power Sync is enabled.

* Go to General → Devices → TV Management and disable Quick Start+.

* Go to General → System → Additional Settings → Home Settings and turn off both options.

Option 2 (Settings Menu Method, webOS)

* Press Settings on the remote and open All Settings.

* Navigate to General → Devices.

* Turn SIMPLINK (HDMI-CEC) ON. (webOS 6.0+, enabling SIMPLINK automatically enables external device control).

No, it is enabled. Other CEC commands like changing the active input work.

[Older] LG TVs do not implement CEC Standby command. You need a hardware mod: https://github.com/Pulse-Eight/libcec/issues/363#issuecommen...

That's too bad. It's only about five years old now. Old but not unreasonably old.

Brightness control on external monitors has never been supported in Windows though, partially due to issues with displays that have poor write endurance on internal storage.

Monitor brightness is controlled over CEC which is just i2c. Windows most certainly supports this on an OS level.

Yes, I've used this in the past:

https://learn.microsoft.com/en-us/windows/win32/api/highleve...

I change brightness all the time with a little tool called Monitorian.

It might not be an "internal windows" tool, but I have controlled an ancient monitor (I think over VGA?) using a 3rd part app on windows. The buttons had broken, but software control worked just fine.

Funny enough... HDMI CEC is still not perfect in my experience. For the longest time, if I powered on my Mac mini and not power on the TV manually, it would actually cause the TV to crash and force a reboot. It was really strange behavior.

Is there any reason CEC can't be implemented over DisplayPort?

There shouldn't be. DP already is a half-duplex, bidirectional AUX channel running at 1 Mbps.

As long as you are okay with a 1-3m long cable.

Unfortunately, for longer runs, DisplayPory is kind of a nightmare. HDMI tends to "just work" as long as you use fiber optic construction.

nothing stops cable makers from making the same for DP

In fact I’ve used a 100 foot fiber optic DisplayPort cable that I “just bought” on Amazon, admittedly for a LOT of money (like, I think it was about $100 USD, 3 years ago or so).

That's not actually such a bad price. I didn't know they even made these - cool!

Huh, I thought I had mine earlier. Mine was from May 2021. They were very very new and had very few reviews, and it was $56. For a 100' fiber optic cable that promised 8k60 and was light.

This cable is absurdly long. I have no idea how to coil it nicely. At my last place I had three stories, and would sometimes just dangle most of it down to the ground then wind it up from the roof.

I just wish they sold the transceivers separately from the fiber. Being able to use any random length of cheap off-the-shelf SMF/MMF fiber would be so much more convenient than having to get a custom one-off cable.

They exist for medium-speed HDMI (see for example [0]), but I haven't seen them for modern high-speed DP yet.

https://www.amazon.com/Converter-Extender-Transceiver-module...

You say it's a LOT, but it's about the same cost as a much much shorter USB 4.0 cable. (Granted, it also has to be able to carry 240W.)

I hate noise from the PC, so I've sited my PC under the desk at the opposite end of the room to where I sit (so about 3.5m away). I have a pair of 5m DP cables running to my 2 ultrawide monitors without any problems at all, so it seems if you buy decent cables it just works with DP too.

The only potential issue is that they seem to be slow waking up from sleep. I've never been interested enough to investigate if moving the PC closer with shorter cables fixes that, or whether it's just an issue with having 2 monitors. I think the underlying cause is actually just because it's Windows and that one monitor (they're supposed to be identical) seems to wake up earlier than the other, so it briefly flashes on, then goes black while it reconfigures for 2 screens and then on again.

But anyway, my 5m cable runs seem fine. They weren't especially expensive nor especially cheap cables, IIRC around 10-15 GBP each.