HDMI Projector Flickers

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Level 1

6 points

HDMI Projector Flickers

I have an M1 MacBook Pro (13 inch, M1, 2020) running the latest Mac OS 12.2.1. I like this machine.

I give lectures to students. Yesterday was the first time I used a certain lecture room, which uses a ceiling mounted projector for which the only connection to the podium is via an HDMI cable. I connected my Mac to the HDMI using an Anker USB-C hub. The projector mirrored my screen, then the projector display started to flicker, worse and worse until it finally just turned black. My computer display was fine.

A student brought me his Windows laptop, we connected the HDMI directly to his laptop and the projector worked fine. Obviously not a problem with projector or its cable. Luckily I had my PowerPoint on a thumb-drive and could give the talk using his computer. I was embarrassed feeling as if I was somehow unprepared, and it certainly made Mac and Apple look bad. Students were snickering that I had a Mac.

I thought maybe my hub had developed a problem. At home I used the hub to connect to my monitor by HDMI and it seems fine, no flicker at all.

Is this a known bug, just affecting M1 to projector via HDMI? Is there a workaround? I need to give another lecture next week and I'm afraid the same will happen. Dare I say I might just go out and buy a Windows computer?

MacBook Pro (2020 and later)

Posted on Mar 3, 2022 7:24 AM

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Answer 1

Best reply

Grant Bennet-Alder

Level 10

127,843 points

Mar 4, 2022 8:22 AM in response to rsx50

On closer examination, it appears the overwhelming issue here is that the adapter you are using uses a very old version of HDMI. It appears to support only HDMI 1.2. HDMI 1.4 is common, 2.0 is available, and 2.1 is possible, but rare.

The USB-C Digital AV Multiport Adapter supports HDMI 2.0, and should have no such issues. It also keeps you solution, "all Apple"' so that getting official support (if needed can be simpler and more consistent.

USB-C Digital AV Multiport Adapter - Apple

Apple has a liberal return policy -- try it and see if it works for you.

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Answer 2

Mar 3, 2022 7:49 AM in response to rsx50

Like soccer and basketball, when it goes out of bounds, the fault is attributed to the last guy who touched it in any way.

You used the output of an Anker Hub, but did not post its model or a link to its specs.

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Answer 3

rsx50 Author

Level 1

6 points

Mar 3, 2022 5:31 PM in response to Grant Bennet-Alder

Sure, thanks. It's an Anker Premium 5-in-1 USB-C Hub 1H2A1S1M Model A8334.

https://us.anker.com/products/a8334?_pos=1&_sid=be6b011ad&_ss=r

I cannot detect any problem with the hub connected to a monitor. The flickering was only when outputting to the projector.

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Answer 4

Mar 3, 2022 5:49 PM in response to rsx50

Whatever adapter you use, it needs to take a 3 Volt DisplayPort family signal and pump it up to a 5 Volt HDMI signal. The Anker Hub you listed has no separate POWER input, and that could be a lot of the problem. The Anker Hub is also only speed-rated at "2K" (2560 by 1440) @ 60 Hz. Your built-in display is 2560x1600, so if the projector says it can go at least that high, the Mac will send it that as its signal, but the signal may collapse because the adapter cannot keep up at that pace.

You might be able to get it to work by reducing the resolution.

I would recommend a more powerful Converter Hub.

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