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Comment by alin23 | Hacker News Reader

When the new MacBook Pro came out this year, everyone was puzzled as to why the newly included HDMI port was only 2.0.

Well it turns out they lied. It’s 2.1 after all! \s

Jokes aside, it’s actually only 2.0 because internally they transmit a DisplayPort video signal and convert it to HDMI using an MCDP2900 chip[0], which is the same chip usually seen inside USB-C hubs.

So the new MacBook basically got rid of the HDMI dongle by integrating it inside the laptop.

This also breaks DDC/CI on that port and now I get a ton of support emails for Lunar (https://lunar.fyi) because people can’t control their monitor brightness/volume and think that the app is broken.

[0] https://www.kinet-ic.com/mcdp2900/

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"So the new MacBook basically got rid of the HDMI dongle by integrating it inside the laptop"

Damn, that sounds like something a no-name 'made in China' brand would do, what is the possible justifucation for this on a premium device?

AIUI, Sony did the same with the PS4:

> If you query the GPU information, you actually get that it has an HDMI port and a DisplayPort port. [...] If you ask the GPU, it tells you that HDMI is not connected, DisplayPort is connected. OK. Yeah, they have an external HDMI encoder from DisplayPort to HDMI because just putting a wire from point A to B is too difficult

https://youtu.be/VpB49dhk2uQ?t=1665

How can I control screen brightness from my m1 max? Willing to pay for a solution.

Lunar can do that: https://lunar.fyi

It’s free for manual brightness adjustments.

Just make sure to use one of the Thunderbolt ports of the MacBook.

And if it still doesn’t work, check if there’s any monitor setting that could block DDC by going through this FAQ: https://lunar.fyi/faq#brightness-not-changing

Neat. I've been quite fond of Monitor Control: https://github.com/MonitorControl/MonitorControl

How does Lunar and Monitor Control get around the Tbolt -> HDMI dongle baked into the logic board problem?

There is no way to get DDC working on that port. It’s probably locked in the chip firmware.

All we can do is to provide software dimming using Gamma table alteration, or tell people to use the Thunderbolt ports instead.

Now I understand. There are two ways of dimming a screen. One is dimming the backlights in the display while the other is faking it via Gamma table alteration

They said use one of the Thunderbolt ports.

What problem? Is DDC not available?

Hey, I was wondering if there was a way to lower the minimum brightness of my M1pro built-in display. The minimum brightness at 1 notch is way too bright for working at night. I have to resort to apps like quickshade which just put a grey overlay on the display which kills contrast and colors.

I had found something on stackexchange to do this for previous gen macs, but was unable to replicate for current gen. This is something I would be willing to pay for. https://apple.stackexchange.com/a/179204

I figure with the HDR display there must be a way to control the actual backlight brightness.

Lunar can control the real backlight of the MacBook display by tapping into the private DisplayServices system framework.

The app only supports integer values between 0 and 100 but the framework supports floating point values between 0 and 1.

You can try installing Lunar’s CLI (https://lunar.fyi/#cli) and then running something like the following in a terminal:

    lunar display-services SetBrightness builtin 0.005

That will try to set the backlight of the builtin display to 0.5%. Then you can try lower and lower values to see if they make any difference.

If you don’t see much difference between 1% and sub-1% values then there’s no way to dim the backlight further, and the only remaining method would be Gamma dimming which Lunar can do if you disable the Apple Native protocol from the Controls menu.

Thanks for the reply, I tried this but it seems like anything below around 6% (.06) doesn't actually brightness anymore. This matches the behavior of when you press function+shift+option+F1, where if you set the brightness to anything below the first bar (1/16th = .0625), there is no difference.

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