Does Mac Mini M4 Support DP Alt mode?

den.thed wrote:

Just because that USB-C to DisplayPort adapter works with a PC and an Intel MacBook Pro, doesn't mean that it will work with a cable picky silicone Mac.

What I would do, is test a short high speed 8K Thunderbolt 3/USB-C to DisplayPort cable.

for example: https://www.amazon.com/dp/B08B3SB5VC/ref=sspa_dk_detail_4?

Agreed, it would be worthwhile to test the setup with a different adapter.

The strange thing is that in the OP's present setup the M4 mini recognizes the Benq monitor as an audio output device (which would seem to indicate the adapter is doing its job) ... but the audio level sliders in Audio MIDI setup are at their zero position and the OP is not able to adjust them.

I'm going to suggest that the OP also try using an HDMI connection between the Benq & the mini. If audio also doesn't work via HDMI then a hardware problem in the mini becomes suspect.

Check Audio MIDI Setup. You may need to route the audio output to the DisplayPort device (may be identified as your Benq monitor). The default audio output is "Built-in Output" (the built-in speaker & headphone jack). In Audio MIDI Setup, select the DP/Benq device, then click the gear icon and select "Use This Device for Sound Output."

btw, the M4 mini supports both DP 1.4 and DP 2.1.

Let's check a few more things ...

1. Which USB-C port are you plugging into? On the back of the M4 mini, use the rear left or right USB-C port, not the one in the middle. The middle one is also the DFU port, so let's eliminate that as a possible concern.
2. What USB-C to Displayport adapter are you using? Make & model.
3. Shut down & restart the mini. Then try things again.
4. In Audio MIDI settings the Primary & both Channel sliders should be available to move. In your screenshot, next to those sliders, the MUTE button is not checked. Try checking it, then uncheck it (MUTE/UNMUTE). See if that enables the sliders.
5. In Audio MIDI setup, for the Benq monitor, click Configure Speakers and make sure that Left & Right are set to Channels 1 and 2.

In the right pane, raise the levels for Primary, Channel 1 & Channel 2. In your screenshot they are all at zero. That's effectively turning the volume all the way off. Take them up all the way for your Benq. For format you should keep it at the default 44,100 KHz 2ch 24bit.

If you want audio output to more than 1 device then you must create a Multi-Output Device. Click the "+" at the bottom of the left panel to do that. That way audio out can go to both the Benq & the Mac mini speakers.

I notice you created an Aggregate device. Reason?

Also, FYI, the USB-C ports on the front of the M4 mini are USB 3.0 only. The USB-C ports on the back support TB 4, USB 4 & Displayport; on the M4Pro version they supports TB 5, USB 4 & Displayport

Yes, the M4 and M4 Pro Mac minis support DisplayPort Alt Mode – on the rear-panel USB-C / Thunderbolt ports.

The front-panel USB-C ports are USB-only and will not provide a DisplayPort Alt Mode signal.

Just because that USB-C to DisplayPort adapter works with a PC and an Intel MacBook Pro, doesn't mean that it will work with a cable picky silicone Mac.

What I would do, is test a short high speed 8K Thunderbolt 3/USB-C to DisplayPort cable.

for example: https://www.amazon.com/dp/B08B3SB5VC/ref=sspa_dk_detail_4?

den.thed wrote:

I suggested testing a single cable, instead of an adapter and cable.

Just FYI there is adapter circuitry built into the DP head end of the cable, so it not just a plain cable. It's effectively an adapter + cable.

According to Apple it supports DP1.4. I assume you have set your audio output setting to the monitor ?

Long shot but try one of the other TB ports.