Unable to output via DisplayPort

cgreentx · May 21, 2019, 3:20pm

I have a 2018 Mac Mini with three monitors attached. All three are DisplayPort and support audio. One of them has my audio system attached to it. The system and all other apps present no issues outputting audio in this setup, however Audacity doesn’t output any sound when this method is selected. If I choose my headset or the internal Mac Mini speakers I get audio without issue. I have tried all three instances of DisplayPort in the output drop down.

Diagnostics follows:

==============================
Default recording device number: 3
Default playback device number: 1
==============================
Device ID: 0
Device name: DisplayPort
Host name: Core Audio
Recording channels: 0
Playback channels: 2
Low Recording Latency: 0.01
Low Playback Latency: 0.0024375
High Recording Latency: 0.1
High Playback Latency: 0.0117708
Supported Rates:
    8000
    9600
    11025
    12000
    15000
    16000
    22050
    24000
    32000
    44100
    48000
    88200
    96000
    176400
    192000
    352800
    384000
==============================
Device ID: 1
Device name: DisplayPort
Host name: Core Audio
Recording channels: 0
Playback channels: 2
Low Recording Latency: 0.01
Low Playback Latency: 0.0024375
High Recording Latency: 0.1
High Playback Latency: 0.0117708
Supported Rates:
    8000
    9600
    11025
    12000
    15000
    16000
    22050
    24000
    32000
    44100
    48000
    88200
    96000
    176400
    192000
    352800
    384000
==============================
Device ID: 2
Device name: DisplayPort
Host name: Core Audio
Recording channels: 0
Playback channels: 2
Low Recording Latency: 0.01
Low Playback Latency: 0.0024375
High Recording Latency: 0.1
High Playback Latency: 0.0117708
Supported Rates:
    8000
    9600
    11025
    12000
    15000
    16000
    22050
    24000
    32000
    44100
    48000
    88200
    96000
    176400
    192000
    352800
    384000
==============================
Device ID: 3
Device name: Jabra Engage 75
Host name: Core Audio
Recording channels: 1
Playback channels: 0
Low Recording Latency: 0.008375
Low Playback Latency: 0.01
High Recording Latency: 0.036375
High Playback Latency: 0.1
Supported Rates:
==============================
Device ID: 4
Device name: Jabra Engage 75
Host name: Core Audio
Recording channels: 0
Playback channels: 2
Low Recording Latency: 0.01
Low Playback Latency: 0.00335417
High Recording Latency: 0.1
High Playback Latency: 0.0126875
Supported Rates:
    8000
    9600
    11025
    12000
    15000
    16000
    22050
    24000
    32000
    44100
    48000
    88200
    96000
    176400
    192000
    352800
    384000
==============================
Device ID: 5
Device name: HD Pro Webcam C920
Host name: Core Audio
Recording channels: 2
Playback channels: 0
Low Recording Latency: 0.26125
Low Playback Latency: 0.01
High Recording Latency: 0.28925
High Playback Latency: 0.1
Supported Rates:
==============================
Device ID: 6
Device name: Mac mini Speakers
Host name: Core Audio
Recording channels: 0
Playback channels: 2
Low Recording Latency: 0.01
Low Playback Latency: 0.0125
High Recording Latency: 0.1
High Playback Latency: 0.0218333
Supported Rates:
    8000
    9600
    11025
    12000
    15000
    16000
    22050
    24000
    32000
    44100
    48000
    88200
    96000
    176400
    192000
    352800
    384000
==============================
Selected recording device: 3 - Jabra Engage 75
Selected playback device: 2 - DisplayPort
Supported Rates:
    8000
    9600
    11025
    12000
    15000
    16000
    22050
    24000
    32000
    44100
    48000
    88200
    96000
    176400
    192000
    352800
    384000
==============================
Available mixers:
==============================
Available recording sources:
==============================
Available playback volumes:
0 - PCM
==============================
Recording volume is native
Playback volume is emulated

Any suggestions to try something else? I’ve never had issues getting Audacity to output on any system, Windows or Mac, simple audio or complex interfaces. This is a first.

Thanks!
Chris

steve · May 21, 2019, 4:30pm

From the audio device info, you can see that Audacity recognises 3 display port stereo outputs (ID 0, 1 and 2). What happens when you select each of those as the playback device in the device toolbar?

cgreentx · May 21, 2019, 8:59pm

I’ve flipped between all three in the bar with no change. Interestingly, no matter which is picked in that chooser the one in preferences is always the third one. Wondering if I’ve found a bug?

steve · May 21, 2019, 9:02pm

Imagine that we can’t see your machine, and that we only know what you tell us.
What happens when you select each of the “display port” options as the playback device in the device toolbar?

cgreentx · May 21, 2019, 9:14pm

Image attached. There is no errors or popups when selecting them. The checkmark moves to the one I’ve selected. Playing the audio shows playback in the meters but no sound exits the system.
Screen shot.png
screen shot 2.png
I can do a screen recording if you’d like to see it in action… Definitely no errors or anything informational.

steve · May 21, 2019, 10:46pm

It looks like Audacity is sending the audio correctly. Perhaps it is muted somewhere else on your system (?)
I don’t have a DisplayPort device, so I’m not able to make further suggestions. Perhaps someone else on this forum has experience of DisplayPort devices.

cgreentx · May 21, 2019, 11:19pm

The same audio device is used by the system for all sounds. There is no further routing in Core Audio to be muted. All other application including system sounds, youtube in Chrome, etc. are playing audio properly even if I do them at the same time this is being attempted. That’s why I’m here. Audacity appears to be generating audio but failing to get it to the output if I use DisplayPort audio. I’m at a loss.

billw58 · May 21, 2019, 11:27pm

So what happens if you go to Audacity Preferences and choose different display port options there?
– Bill

cgreentx · May 22, 2019, 1:00pm

Took this all the way down to the basics…

Clean boot, nothing else running, same issue…
unplugged all three displays and just plugged in a single display (the one I’m using audio out on) and audio worked.
Brought the other two up and it continued to work.
Rebooted and restarted app multiple times and can no longer reproduce.

Going to have to write this one off as a non reproducible issue. I suspect that Audacity wasn’t actually selecting the output I wanted, but it is definitely working now.

Thanks for the

billw58 · May 22, 2019, 3:30pm

OK, but what happens if you go to Devices Preferences and change the output, then change it back, or do the same in the Device Toolbar? Which of the three “Display Port” options is shown as selected when it is working?

What happens if you go through the above procedure but first plug in one monitor that is not being used for audio? Then plug in the monitor that is being used for audio and try to switch to it?

This may, in fact, be an issue where having three devices with the same name causes a problem.

Or, if you’re happy it’s working and don’t want to mess with it, that’s fine. This does seem to be a very rare problem.

– Bill

cgreentx · May 22, 2019, 3:43pm

Give me a bit and I’ll gladly try it. Would love to help if this is in fact a bug.

Chris

tzengyuxio · January 8, 2025, 6:10am

I encountered the same issue, which has been troubling me for a long time. Today, I happened to find this post, and thanks to the hint provided in cgreentx’s report, I believe I’ve identified the cause of the audio playback bug.

TL;DR:

Root cause hypothesis: In the “Playback Device” selection menu, if there are options with the same name, switching between them does not work properly (the action has no effect). This might be due to using the name as a key.

Affected UIs:

Main Screen → Audio Setup → “Playback Device” menu
Preferences → Audio Settings → Playback → “Device:” dropdown menu
Other menus, such as the “Recording Device” menu, might also be affected, but I couldn’t test this due to a lack of devices with duplicate names.

My Environment:

I’m using a Mac Mini 2018, with two monitors connected to the machine via Mini DisplayPort. A speaker is connected to one of the monitors via the “Audio In” port.

In Audacity, I see two playback devices named “DELL U2515H.” One outputs sound (connected to the external speaker), while the other does not.

When I launch Audacity, most of the time, selecting either “DELL U2515H” device results in no sound, regardless of the selected option (as they have the same name). However, the software operates normally, and the playback volume meter shows activity.

Occasionally, after launching the software, selecting “DELL U2515H” will allow playback with sound. In this case, switching between either device both output sound, not work as expected (one output sound and the other silent.)

Test Steps

Main Screen Audio Setup Menu Switching

Open Menu -> Help -> Diagnostics -> Audio Device Info... to view the following information (I have three playback devices):

==============================
Default recording device number: -1
Default playback device number: 1
==============================
Device ID: 0
Device name: DELL U2515H
Host name: Core Audio
.
.
.
    352800
    384000
==============================
Device ID: 1
Device name: DELL U2515H
Host name: Core Audio
.
.
.
    352800
    384000
==============================
Device ID: 2
Device name: Mac mini的揚聲器
Host name: Core Audio
.
.
.
    352800
    384000
==============================
No recording device found for 'DELL U2515H'.
Selected playback device: 1 - DELL U2515H
Cannot check mutual sample rates without both devices.

Note that the second-to-last line reads:
Selected playback device: 1 - DELL U2515H
Switch playback devices in the main screen’s Audio Setup menu.
After switching, reopen “Audio Device Info” and check the second-to-last line. If a “DELL U2515H” device (either of the two with the same name) is selected, the device ID always reads 1 (the monitor without the external speaker), which results in no sound.
If the playback device is set to “Mac mini的揚聲器,” sound playback works as expected and the second-to-last line in Audio Device Info changes to:

Selected playback device: 2 - Mac mini的揚聲器

Preferences → Audio Settings → Playback Dropdown Change

Same “Audio Device Info” here with previous test.

Step 1: The Playback dropdown list in “Preferences → Audio Setting” contains three options:
1. DELL U2515H
2. DELL U2515H
3. Mac mini的揚聲器
Step 2: After launching Audacity, the dropdown initially points to the second item (“DELL U2515H”).
Step 3: Switch to the first item (“DELL U2515H”) and close Preferences to return to the main screen.
Step 4: Open “Audio Device Info” and observe the second-to-last line. It shows:
"Selected playback device: 1 - DELL U2515H"
Step 5: Reopen Preferences. The dropdown is still pointing to the second item. The previous switch to the first item had no effect.
Step 6: Switch the dropdown to the third item (“Mac mini的揚聲器”), close Preferences, and return to the main screen. Playback works correctly, and the second-to-last line in “Audio Device Info” updates appropriately. Reopening Preferences shows the dropdown set to the third item.

cgreentx · January 8, 2025, 5:10pm

That is definitely the behavior that I experienced in the long-ago time. I solved the problem by moving to a different audio interface method since it didn’t seem to be getting resolved.