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Comment by shmerl | Hacker News Reader

> ALSA is the core layer of the Linux audio stack. It provides low-level audio hardware control, including drivers for sound cards and basic audio functionality.

> ...

> Ulike PuleAudio and JACK, PipeWire does not require ALSA on a system, in fact if ALSA is installed the output of ALSA is very likely pushed through PipeWire

I don't get this part. If ALSA represents the kernel level hardware drivers for audio, how does Pipewire bypass it? Does it implement an alternative set of kernel drivers? I assumed Pipewire still relies on ALSA base.

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ALSA had both kernel-space drivers and a user-space API layer.

I think what they're getting at is that PipeWire speaks the ALSA API, so an app or game that linked against ALSA will connect to PipeWire and should Just Work, without needing to be rewritten to target PipeWire's API.

PipeWire does the same trick with the PulseAudio API as well. on my PipeWire-using NixOS box, for example, I can connect through the `pavucontrol` GUI, my `pactl`-based keybindings work the same, etc. it's a clever design that allows them to avoid what would otherwise be a nasty pile of backwards-compatibility issues and poor desktop user experience.

That part is simply wrong. Pipewire uses Alsa to drive the soundcard. Alsa is a hard requirement.

This. Also, how does PulseAudio not support videoconferencing?

May be it's about a higher layer of ALSA API, not about actual hardware drivers.

yeah I think there are two ALSAs, one in the kernel as drivers and one as a userspace library.

Well. PulseAudio is a plain sound server. It does not handle video at all.

This is probably wrong. ALSA is a low-level API that allows direct access to audio hardware, but only for one application at a time. ALSA has a kernel component and an userspace library that can be configured.

Pipewire uses ALSA to interface with audio hardware. But Pipewire also adds a plugin to an ALSA userspace library so that audio from apps that use ALSA API is rerouted to Pipewire. Pulseaudio did the same trick.

I was also confused by this bit. If ALSA is part of the kernel, how can it not be installed?

The article doesn't note kernel-ALSA and the old userspace-ALSA libraries that apps use to push audio.

Well, you could compile your kernel without ALSA.

I think it could only make sense for sending sound over the network.

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