How do you use both Pulse Audio and Alsa?

Question

Can someone explain the relationship between the different sound components and if they all need to be installed in order to get sound?

For example, I have one called "Playback: ... (PulseAudio Mixer)" and another called "Intel ICH5 Alsa Mixer" which both seem to affect my sound. Can I uninstall one of them and still have working audio?

Answer 1

There are four layers in this abridged explanation of the audio stack.

1. The hardware.
2. ALSA.
3. Pulseaudio
4. Applications.

ALSA has all the hardware support. It's great at talking to a whole load of different stuff but it's relatively rubbish at talking to more than one application or providing network-aware features like Pulseaudio.

In this sort of stack, PulseAudio is the only thing that interfaces with the main ALSA devices so if you want to make a sound, you either have to kick PulseAudio off, or interface with it.

PulseAudio can accept connections from clients that only speak ALSA (it pretends to be an ALSA device) for legacy reasons which allows things like Wine, Skype, et al to work (most of the time).

---

Theoretically you could remove PulseAudio. In practice this would probably completely knacker your system if you're using more than one application that wants to make a noise at once. Our media centre box here only uses ALSA for this reason (plus I need raw HD over HDMI access that old PulseAudio used to interfere with - it might not now).

I would suggest you keep both. You need ALSA and PulseAudio, for all its alleged sins, does a pretty good job these days.

Answer 2

There is a similar question in Super User site, and a Good answer. You can check that. However I am copying most useful info here. All credit goes to original answerer.

ALSA is the kernel level sound mixer, it manages your sound card directly. ALSA is a crap (seriously) and it can handle a few (sometimes just one) channel. PulseAudio is a software mixer, on top of the userland (like you'd run an app). When it runs, it uses Alsa's channel and manages EVERY mixing stuff, devices, network devices, everything by itself. (It's like one more unneeded layer) Actually you can run only ALSA, but you might get mixing problems and Ubuntu comes with PA support/PA dependence. (Some apps are hard coded to use PulseAudio, with custom patches and so on.) (PulseAudio also consumes much more CPU than OSS or ALSA.)