Unleash Sonic Perfection: Configuring PipeWire with an RT Kernel for Low Latency Audio

For audio enthusiasts, musicians, and producers seeking the absolute pinnacle of audio performance on Linux, combining PipeWire with a real-time (RT) kernel is a game-changer. This dynamic duo delivers remarkably low latency, ensuring your audio experience is smooth, responsive, and crystal clear. Let’s dive into a step-by-step guide to unlock this sonic potential.

Why an RT Kernel and PipeWire?

• RT Kernel: Designed for time-critical applications, an RT kernel minimizes latency by prioritizing real-time tasks, crucial for audio processing.
• PipeWire: A modern multimedia framework that excels at handling audio and video streams, offering superior performance and flexibility compared to older solutions.

Step-by-Step Guide

1. Verify Your RT Kernel is Running:

Before anything else, confirm your RT kernel is active. Open your terminal and run:

Bash

uname -r

You should see “rt” in the output, indicating a successful installation (e.g., 5.15.0-xanmod1-rt).

2. Install PipeWire and Essential Packages:

Install PipeWire and its necessary components using your distribution’s package manager:

• Debian/Ubuntu:

Bash

sudo apt install pipewire pipewire-audio-client-libraries pipewire-pulse pipewire-jack wireplumber

• Fedora:

Bash

sudo dnf install pipewire pipewire-pulseaudio pipewire-jack-audio-connection-kit wireplumber

• Arch Linux:

Bash

sudo pacman -S pipewire pipewire-pulse pipewire-jack wireplumber

3. Grant Real-Time Privileges:

To allow PipeWire to operate in real-time, configure the audio group:

• Edit the limits file:

Bash

sudo nano /etc/security/limits.d/99-audio.conf

• Add these lines:

@audio   -  rtprio     95
@audio   -  memlock    unlimited

• Add your user to the audio group:

Bash

sudo usermod -aG audio $USER

• Log out and back in for the changes to apply.

4. Fine-Tune PipeWire Configuration:

• Create a custom configuration directory:

Bash

mkdir -p ~/.config/pipewire

• Copy default configurations:

Bash

cp /usr/share/pipewire/pipewire.conf ~/.config/pipewire/
cp /usr/share/pipewire/pipewire-pulse.conf ~/.config/pipewire/

• Edit ~/.config/pipewire/pipewire.conf:
  • Add desired sample rates to default.clock.allowed-rates (e.g., 44100, 48000, 96000).
  • Set default.clock.quantum to your preferred buffer size (e.g., 256 for low latency).
  • Set default.clock.min-quantum to your minimum buffer size (e.g., 32).

5. Optimize for Low Latency:

• Create a low-latency configuration file:

Bash

mkdir -p ~/.config/pipewire/pipewire.conf.d
nano ~/.config/pipewire/pipewire.conf.d/99-low-latency.conf

• Add these settings:

context.properties = {
    default.clock.rate = 48000
    default.clock.quantum = 256
    default.clock.min-quantum = 32
    default.clock.max-quantum = 8192
}

48000 Hz is perfectly adequate, 192000 Hz is generally only relevant in professional audio production or for audiophiles with very high-end equipment. Most people would not be able to tell the difference between the two.

6. Enable Real-Time Priority:

• Create a real-time priority file.

Bash

mkdir -p ~/.config/pipewire/pipewire.conf.d
nano ~/.config/pipewire/pipewire.conf.d/10-rt-priority.conf

• Add these setting.

context.modules = [
{   name = libpipewire-module-rt
    args = {
        nice.level = -11
        rt.prio = 88
        rt.time.soft = 200000
        rt.time.hard = 200000
    }
    flags = [ ifexists nofail ]
}
]

7. Restart PipeWire:

Apply the changes by restarting PipeWire:

Bash

systemctl --user restart pipewire pipewire-pulse

8. Verify Low-Latency Operation:

• Check latency settings:

Bash

pw-top

• Verify real-time priorities:

Bash

ps -eo pid,cls,pri,cmd | grep pipewire

Troubleshooting:

• Xruns (audio dropouts): Increase default.clock.quantum.
• High CPU usage: Use htop to identify problematic processes.
• CPU frequency scaling: Consider disabling it: sudo cpupower frequency-set -g performance.

Important Notes:

• Finding the optimal settings requires experimentation based on your hardware.
• For advanced usage, consider CPU core isolation, and the realtime-privileges package.

By following these steps, you’ll be well on your way to achieving exceptional audio performance with PipeWire and an RT kernel. Happy listening!