HDMI recognized as "unplugged", after installing drivers

The only thing that worked for me was changing the monitor scan rate from 60 to 25Hz (I am in a 50Hz country)

You might try forcing a restart of pulseaudio, which you can do by running killall pulseaudio.

In the last month when I boot and first login, or when I recover from suspend, I see "HDMI/DisplayPort (unplugged)" or sometimes the HDMI output is not even listed; killall pulseaudio solves the problem each and every time: pulseaudio restarts itself, rescans devices, finds all the existing devices, and it works as expected, with no need of any other action.

I have struggled with many solution but the only solution that worked for me was set audio on with xrandr as below:

xrandr --output HDMI-1 --auto --set "audio" on

and then HDMI device changes to plugged in in pavucontrol panel.

Here is how I solved mine.

My motherboard is AMD Rs780 and my Ubuntu is 20.04.LTS, kernel 5.4.0-42

In my case, ALSA could use the HDMI sink, as I could prove by this command (it leaked sound on HDMI):

aplay -D plughw:[card],[device] /usr/share/sounds/alsa/Front_Center.wav

If you want to test as well, you can get the values for [card] and [device] with this command:

aplay -l

But Pulse still insisted that the HDMI is unplugged.

After a lot of digging, the only solution that worked for me was running the 2 following commands:

pacmd load-module module-alsa-sink device=hw:[card],[device]
pacmd set-default-sink alsa_output.hw_[card]_[device]

Here is where I found this solution: https://gist.github.com/bassmanitram/495fd35b76083f0c4a79777b8ab470fd

Unfortunately I have to run it on every logon, since I haven't find yet how to set the init file.

The link below brings more technical details of the bug, looks like there are two parameters for the HDMI card, one for the video and other for audio, and the audio parameter (eld_valid) is wrongly set to 0.

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1827967

Thank you! Running this command mostly solves the problem:

pacmd set-card-profile 0 output:hdmi-stereo

If not, pressing Ctrl+Alt+F1 and then Ctrl+Alt+F7 solves it.

I have the same issue. Each time I suspend the system and wake it up, pulseaduio says HDMI is unplugged. I do the following:

1. Press Ctrl+Alt+F1 to go to a terminal log in.

2. Then press Ctrl+Alt+F7 to go back to the GUI.

After that, pulseaudio says HDMI is plugged in (under Output Device).

I had the exact same thing with an old Radeon 6900 Series.

To see info on pulseaudio devices:

pacmd list-cards

Look for the card's index and, under that, profiles. For instance, I had:

2 card(s) available.
   ****index: 0****
    name: <alsa_card.pci-0000_01_00.1>
    driver: <module-alsa-card.c>
    owner module: 6
    properties:
        alsa.card = "1"
        alsa.card_name = "HDA ATI HDMI"
...
    profiles:
        ****output:hdmi-stereo****: Digital Stereo (HDMI) Output (priority 5400, available: unknown)

Those bits of info are then used to set the output profile:

pacmd set-card-profile 0 output:hdmi-stereo

Note that the set-card-profile parameters are the card index (0) and the output (hdmi-stereo).

After that, things just worked.

Queues came from here mostly: PulseAudio reports HDMI Audio is unplugged from the Nvidia MCP79 device

You cant do this on the default sound properties you need pauvcontrol

sudo apt-get install pavucontrol
pavucontrol

go to the configuration Tab

find your device

choose a profile that is plugged.

updated: fixed typo in pavucontrol

I will try to help you. It sounds like your HDMI is working ok, but try this if you haven't already.

1. First, plug in your HDMI cable.

2. Go to settings and click on Displays.

   

3.Now click on Mirror Displays.

4. Finally, click on apply.

That does it for the video. Now you'll want to adjust the audio so that you hear it from you television.

1. Click on the volume control on the top right hand corner of the monitor.

2. Now scroll down to Sound Settings. You should see this screen:

3. Click on the HDMI menu in your sound settings and you are good to go.

I hope this helps.