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I am struggling to get surround sound from my 2020 MacBook Pro (Intel version).

I also have a 2015 MBP that has an HDMI port which I connect to my Denon AVR and it gives me glorious Dolby/DTS 5.1 whilst passing the visuals to my TV. So I know my media is fine.

My 2020 MBP only has USB-C ports. So I first tried with this USB hub that has an HDMI port. My AVR only sees 2 channel audio and the Midi app in MacOS only shows 2 channels being available.

I have also tried this USB-C to HDMI cable and get exactly the same results.

The manufacturer of the 2nd cable couldn't get it working either and issued a full refund.

So how can I get HDMI surround sound from my 2020 MBP?

I've read it could be an issue with how the USB-C signal is being converted and maybe using DisplayPort as the middle man, but is this a quirk of the MBP or the adapters?

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  • With everything connected up, check you have 5.1 assigned in AudioMIDI Setup [Apps/Utilities]. If the Mac can see the output as 5.1, you should be able to set it there.
    – Tetsujin
    Commented Nov 28, 2021 at 11:26
  • That's the problem, the Mac only gives me the option of 2 channels in the Midi setup. (I'll add screenshot above)
    – Darren
    Commented Nov 28, 2021 at 11:29
  • I don't have the appropriate device connected to show this properly, but check in the drop menu if you can set to encoded output. the Mac itself cannot decode 5.1 so you need to send it still encoded to the Denon - i.sstatic.net/aKrW5.png If you can't set that in AudioMIDI you may still be able to set it in an app such as VLC.
    – Tetsujin
    Commented Nov 28, 2021 at 11:41
  • Every option in the drop down only lists 2 channel options. On my old MBP it has multi channel options, but not on my 2020 MBP.
    – Darren
    Commented Nov 28, 2021 at 11:42
  • i can only see 5.1 as a choice if I connect a specific 5.1 USB device. To stream to my TV I use the facility in VLC over the digital out. [I can use either/or & it works. I choose this method because I pre-process my cinema sound first inside the Mac - & that only works if I treat it as stereo. You won't have that issue.] i.sstatic.net/vri2k.png
    – Tetsujin
    Commented Nov 28, 2021 at 11:45

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I believe your problem is that the HDMI adapters you tried so far only support stereo audio, to get 5.1 audio requires an HDMI adapter that supports it.

In these USB-C HDMI cables is a small system-on-chip computer that does the conversion from the native DisplayPort (or "DP") to HDMI. That computer in the cable will have to tell the Mac what kind of audio and video to output, then do the conversion, and if the chip in the cable was programmed only to handle stereo audio then it's not going to provide a data path for the six audio channels needed for 5.1 surround sound. DP supports 5.1 audio, HDMI supports 5.1 audio, but that doesn't mean every adapter from DP to HDMI supports 5.1 audio. Look in the specs of the adapter cable for the number of audio channels it supports, if it doesn't tell you then assume it supports only two channel stereo.

I was curious if I could find a DP to HDMI adapter that specified the number of audio channels it supports, and that the number supported was more than two channel stereo, and found this: https://www.startech.com/en-us/audio-video-products/cdp2hdmm5mh

I have no affiliation with StarTech other than being a customer in the past, most of all they just happened to be near the top of my search results when looking for examples.

If your display has DP input then maybe you should use that instead. By using the DP input there is no protocol conversion in the cable, the cable should be less expensive and not limit your audio options.

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This is extremely useful as I'm having the exact same issue. I changed HDMI to USB-C cables connecting my MacBook to my tv/5.1 sound system and could only get stereo sound. All connections in the MIDI audio setup and VLC player are telling me 5.1 is enabled and yet only stereo plays.

My Denon receiver also confirms the existence of only a stereo connection on the display when. It is connected. So I assume my (rather expensive) new HDMI to USB cable is stereo only. It is this model. It doesn't specify the number of channels it supports so I think you're right in that being a smoking gun for a stereo-only signal.

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