No sound from Monitor Speakers on DisplayPort

Hello all,

For a few months now, I have had no sound come from my built-in monitor speakers. I just now switched out the monitor cables and found the issue, but I am not sure how to fix it. The sound from the monitor works when I plug my graphics card into the HDMI port of my monitor. However, upon switching to a DisplayPort cable, there is no sound from the monitor. I have tried fiddling with AlsaMixer, and when I select the AMD GPU as the sound device, every parameter is set to zero and I cannot change it. My GPU is an AMD FirePro S10000 and I am using the default AMDGPU drivers. I am not sure if the DisplayPort cable itself is the issue, because the HDMI cable was very cheap, but the DisplayPort cable is made by Club 3D and is VESA-certified. Please let me know how I should go about trying to fix this issue, as I am running out of ideas on what to do. I cannot use HDMI since I have a 4K monitor, and only on DisplayPort can I run it at 60Hz; HDMI maxes out at 4K 30Hz.

I also tried turning off DisplayPort 1.2 capability in my monitor, but that did not do anything.

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Do you have multiple GPUs or audio devices? You can check using lspci. If you do, then try switching away from hybrid mode. For GPUs it shows up as options in BIOS called Discrete/Hybrid but I don’t know what they would be called for audio.
But based on your own troubleshooting, my guess is also the cable.

Update - Not your issue but here it seems kernel+driver combination did it: https://www.kubuntuforums.net/showthread.php/71925-Sound-though-HDMI-Displayport-not-working-nVidia-audio/page2?s=37a832c8f632db4ea064a9a997c04920

Thank you for the information!

When I typed lspci into the Terminal, I found these listed in the output:

00:1b.0 Audio device: Intel Corporation C610/X99 series chipset HD Audio Controller (rev 05)

05:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Tahiti PRO GL [FirePro Series]

05:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Tahiti HDMI Audio [Radeon HD 7870 XT / 7950/7970]

06:00.0 Display controller: Advanced Micro Devices, Inc. [AMD/ATI] Tahiti PRO GL [FirePro Series]

I only have the onboard audio chip and the GPU audio. Since I do not have integrated graphics, I cannot plug my monitor into my motherboard. I’m not sure what you mean by a “Discrete/Hybrid” mode. The FirePro S10000 is a little weird in that it has two graphics processors on one board. It appears that the OS uses one at a time during normal usage, with the other GPU only kicking into action when I play certain Steam games. I can try looking around in the BIOS, but I have a strong feeling that I won’t find anything since it is pretty barebones (my motherboard is a Huananzhi “X99” motherboard made from recycled server chipsets).

I also noticed when looking at my monitor specs that the HDMI ports are version 2.0, meaning that they support 4k at 60Hz. However, I just now realized that my HDMI cable uses version 1.4, which does not support 4k60Hz. With this in mind, I am guessing the solution to my problem is to buy a mini-DisplayPort to HDMI 2.0 which should theoretically have working audio.

Some machines call it “Discrete Graphics” under the BIOS but the typical term is Hybrid Graphics. Some links on that on the last post here: Asus Zenbook Laptop Brightness not changing - some people prefer turning off that optionality in BIOS. But my intent was to focus on the sound cards - if there is a similar issue with them.

Sorry for the late reply; I got busy with other things and I forgot to check back on the forum. I also bought an HDMI cable that supported 4k60Hz, but the issue is still present.

Unfortunately, my motherboard does not have any graphics settings in the BIOS, as it is meant for Xeon CPUs that don’t have integrated graphics. The only way to get a display output is through a separate graphics card. I also found out that the sound does not work with an HDMI 2.1 cable at 4k60Hz or 1080p. The only time the monitor sound works is when I use an HDMI version 1.4 cable that supports up to 4k@30Hz (so have to run the monitor at 1080p 60Hz).

Not only that, but when the sound does not work, video playback has extremely odd behavior (but the weirdest part is that games and system animations are not affected at all). 60fps videos play at the wrong frame rate in VLC, mpv, and Totem when outputting audio via DisplayPort or HDMI 2.1. It almost appears that they are capped at 30fps. When I try to switch to the headphone jack on my computer, videos play at the correct framerate, but there are random micro-freezes and intermittent stuttering when playing 60fps videos. I have tried three different Linux Distros via Live USB (Ubuntu 20.04, Manjaro with XFCE, and KDE Neon), but they exhibit the exact same thing. This happens across both Google Chrome and Firefox, as well as local videos. I’ve tried turning on and off TearFree with xrandr as well as trying as many fixes I could find on the internet but I have not found a solution to output audio at 4k60Hz without affecting video playback.

If only local videos were impacted and not online, I would have thought codecs. But given that is not the case and that lspci listed two sound cards, my guess is that the problem lies with there being two sound cards. Your games are somehow picking the correct sound card.
Can you see if paprefs helps you fix this issue as shown here? pulseaudio - Play sound through two or more outputs/devices - Ask Ubuntu