NoMachine mutes audio on Fedora when “Mute audio on the server” is enabled

[najanaja89]

Hi everyone,

I found what appears to be a reproducible issue related to NoMachine audio forwarding on Fedora Linux using SOF (Sound Open Firmware).

It took me several days to debug because at first it looked like a PipeWire, ALSA or kernel problem.

## System

**Laptop**

– HP ProBook 450 G10

**Audio**
– Intel Raptor Lake cAVS
– Realtek ALC236
– Driver: sof-audio-pci-intel-tgl

**OS**
– Fedora 44
– PipeWire
– WirePlumber

## Problem

Everything works correctly until I enable:

**Audio Streaming**

☑ **Mute audio on the server**

After enabling this option:

– local speakers become completely silent;
– disconnecting NoMachine does not restore audio;
– reinstalling NoMachine reproduces the problem again.

The issue is 100% reproducible on my machine.

## What I found

After comparing ALSA mixer controls I noticed that several SOF PGA controls are changed to:

Playback 0 [0%] [-99999.99 dB]

For example:

PGA1.0 1 Master
PGA7.0 7 Master
PGA8.0 8 Master
PGA9.0 9 Master
PGA30.0 30
PGA31.0 31

The value **-99999.99 dB** completely mutes the SOF DSP pipeline.

## Workaround

Running the following commands immediately restores audio:

bash
amixer -c0 sset 'PGA1.0 1 Master' 32
amixer -c0 sset 'PGA7.0 7 Master' 32
amixer -c0 sset 'PGA8.0 8 Master' 32
amixer -c0 sset 'PGA9.0 9 Master' 32
amixer -c0 sset 'PGA30.0 30' 32
amixer -c0 sset 'PGA31.0 31' 32

Audio returns instantly without rebooting.

## Why I believe this is related to NoMachine

The issue only appears after enabling:

**Mute audio on the server**

Every time I enable this option, the PGA controls become muted again. If I restore those mixer controls manually, audio immediately comes back. This suggests that either:

– NoMachine directly changes ALSA mixer controls, or

– NoMachine triggers a mixer state that is not restored correctly on systems using SOF.

## Temporary workaround script

bash
#!/usr/bin/env bash
CARD=0
CONTROLS=(
"PGA1.0 1 Master"
"PGA7.0 7 Master"
"PGA8.0 8 Master"
"PGA9.0 9 Master"
"PGA30.0 30"
"PGA31.0 31"
)
for control in "${CONTROLS[@]}"; do
amixer -q -c "$CARD" sset "$control" 32 2>/dev/null || true
done

## Question

Is this expected behavior?

Should **Mute audio on the server** modify low-level ALSA SOF mixer controls?

It looks like the previous mixer state is not restored after disconnecting, leaving the SOF audio pipeline permanently muted until the PGA controls are manually restored.

[jakdud1]

Hi najanaja89,

Yes, the Mute audio on the server option operates at the ALSA server level.

We will try to reproduce the issue in our lab environment and investigate why the audio was not properly unmuted.

Kind regards,
Jakub

[Author]

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