Some people have issues with audio crackling or latency on Linux and that motivated me to write this guide as I’ve been doing some latency tests and came to very clear conclusions recently.
Pipewire docs: https://gitlab.freedesktop.org/pipewire/pipewire/-/wikis/Config-PipeWire
Pipewire-pulse docs: https://docs.pipewire.org/page_pulse_modules.html
Arch wiki: https://wiki.archlinux.org/title/PipeWire
Pipewire and Pulseaudio have countless settings, some of which directly affect your audio output latency as well as other issues such as audio crackling and CPU usage. This guide covers Pipewire specifically since the tendency is for more people to use it than Pulseaudio over time. This guide also covers pipewire-pulse a bit.
Audio latency formula and settings
In /etc/pipewire/pipewire.conf lies the primary configuration file for Pipewire, inside it you have multiple settings. Look for the ones inside context.properties, specifically the settings default.clock.rate, default.clock.quantum, default.clock.min-quantum and default.clock.max-quantum.
Your Pipewire system’s latency is defined by the quantum size and the sample rate. The quantum size serves as a buffer while the sample rate serves as a temporal resolution.
Sound latency (in seconds) can be calculated with this formula: quantum_size / sample_rate
To measure it in milliseconds, multiply the result by 1000: quantum_size / sample_rate * 1000
Note that your real sound latency is a bit higher than the calculated value because of extra software overhead.
Min, default and max quantum
I’m unsure about this, but based on my testing, the quantum size does not vary between min, default and max over time, instead each application chooses one of the 3 latency settings provided. Web browsers seem to use the maximum quantum size, while WINE seems to use the minimum quantum size.
Setting audio latency and fixing audio crackling
Based on the formula written above, your audio latency is defined by both the quantum size and the sample rate. Most of us use 48KHz or 44.1KHz sample rates and have no real usecase for higher sample rates than that, and so I will assume that you are using 48KHz.
Adjusting your audio latency is as simple as changing the quantum size. Lower values result in lower audio latency but also higher CPU usage and eventually audio crackling if the system cannot keep up. Audio crackling is very common if you are running an application that uses the lowest quantum size while also using a lot of CPU. It can also happen if you are multitasking or
just have slow and old hardware.
Setting a decently low latency that does not result in audio crackling requires that you do some tests, but I have some values I recommend. My general recommendation for audio latency is for it to be equal or lower to 60Hz, which is 16ms. Latency below 20ms is likely to be imperceptible, but just to play safe a latency below 16ms is very decent.
The default min, default and max quantum sizes are exaggerated, as the minimum value is way too low, the default value is a bit too high and the maximum value is also too high.
This is the configuration I currently use:
default.clock.rate = 48000
default.clock.allowed-rates = [ 48000 ]
default.clock.quantum = 256
default.clock.min-quantum = 256
default.clock.max-quantum = 1024
Since I don’t have a usecase for extremely low audio latency, I set the same value for the default quantum size and the minimum quantum size. For these, 256 results in ~5ms of latency (256 / 48000 * 1000 ms). I previously used 80 for minimum quantum, and while playing games and screensharing at the same time the game’s audio would crackle to very unsettling levels. 256 is a pragmatic value that provides a very low latency while giving room for the CPU and Pipewire to breathe, but remember that the best values for you will depend on your hardware and how much latency you can tolerate.
The maximum quantum value is usually used by applications that don’t require audio latency to be used properly, such as web browsers. Because of this, you can choose whatever high quantum size you want.
Change pipewire-pulse too!
Quantum size settings are also available in /etc/pipewire/pipewire-pulse.conf. Find the place where pulse.min.req and pulse.min.quantum are, and change the values to your liking. In this case, you provide not only the quantum size but also the sample rate. For example if you want a quantum size of 256 for pulse.min.quantum at 48KHz, set the value to 256/48000.