Re: Where is pulseaudio started?
- From: "Steven W. Orr" <steveo@xxxxxxxxxxx>
- Date: Thu, 27 Aug 2009 00:16:33 -0400
On 08/26/09 20:45, quoth Marko Vojinovic:
Ok Steven, let me do a google search on "pulseaudio home page", follow the
first link which reads www.pulseaudio.org, click on the "documentation" link,
scroll down to "KDE" and read http://www.pulseaudio.org/wiki/PerfectSetup#KDE
for you here. It says:
KDE 4 uses Phonon as the main audio interface. The Xine backend of Phonon
should eventually use PulseAudio automatically, but at the time of writing the
pulse plugin for Xine is too unreliable, so it's disabled by default. While
waiting for that to get better, Phonon uses Alsa. Therefore, to get Phonon to
use PulseAudio, you have to edit your ~/.asoundrc or /etc/asound.conf.
So when your favorite KDE app tries to play some sound, it talks to Phonon,
which either uses xine backend to talk to pulseaudio directly, or uses alsa.
Now let me scroll back to the top of the page and read
http://www.pulseaudio.org/wiki/PerfectSetup#ALSAApplications for you:
If the PulseAudio plugin for alsalibs is installed all applications with
support for the ALSA API should be able to access a PulseAudio server. You
need version 1.0.12 or newer of the ALSA packages for the PulseAudio plugin to
To activate the driver edit /etc/asound.conf or ~/.asoundrc and add:
Now you you can access the PulseAudio server under the virtual ALSA device
% aplay -Dpulse foo.wav
% amixer -Dpulse
If you want to make the PulseAudio driver the default, use something like this
in the ALSA configuration files:
Now let me take a look at /etc/asound.conf and ~/.asoundrc instead of you, and
find that this is precisely how a default Fedora system is configured.
So how does it work? Open your favorite sound app, and ask it to play some
music. If it is a typical KDE app, it will utilize Phonon, which redirects to
ALSA, where pulseaudio plugin for alsa takes over, checks if the pulseaudio
binary is already running and transfers audio handling to it. If it is not
running, the plugin launches /etc/pulse/default.pa, which is an equivalent of
an userland "init script" for pulseaudio. It launches the actual binary. Look
at the first line:
This is where it actually gets executed. (I hope you are familiar with the
Now, once executed, pulseaudio starts receiving signals to be played from all
apps that try to use it natively, or try to use ALSA or ESD or Phonon or
whatever. All these signals get mixed and sent to ALSA sound driver which
talks to actual hardware to play the sound.
So in a nutshell, whatever your app tries to use as a sound interface, it gets
eventually rerouted to pulseaudio, which gets executed if it is not running
already. If it doesn't get rerouted to pulseaudio, something is broken
(typically the app itself), and you don't get any sound from that app by
default. File a bug against it.
Can pulseaudio be simply shut OFF?
I don't think so, at least not so easily. As you can see above, it is way too
much integrated in the system. There is no single place where it is invoked
and where it could be "shut off". You need to uninstall it altogether and let
every app find it's own way to fallback to alsa.
Unfortunately, I am running KDE-4.2.4 and if there's a way to shut the
little stinker off, I'd be grateful to know how.
AFAICS, KDE is using Xine backend by now, which talks to pulseaudio natively.
I don't think that you can find an option to shut it down and use alsa. But do
take a look at systemsettings -> Multimedia, maybe there you can set
preferences the way you like. Here I talk about the latest KDE 4.3, you should
probably yum update.
I have no idea what it is that pulseaudio is supposed to actually do that
I'm supposed to like about it. I used to have sound. I still have sound.
Let me read the very first sentence from http://www.pulseaudio.org/ for you:
PulseAudio is a sound server for POSIX and Win32 systems. A sound server is
basically a proxy for your sound applications. It allows you to do advanced
operations on your sound data as it passes between your application and your
hardware. Things like transferring the audio to a different machine, changing
the sample format or channel count and mixing several sounds into one are
easily achieved using a sound server.
Then let me click on "About pulseaudio" link and read
http://www.pulseaudio.org/wiki/AboutPulseAudio#Details for you:
PulseAudio is a networked sound server, similar in theory to the Enlightened
Sound Daemon (EsounD). PulseAudio is however much more advanced and has
A sound server can serve many functions:
* Software mixing of multiple audio streams, bypassing any restrictions
the hardware has.
* Network transparency, allowing an application to play back or record
audio on a different machine than the one it is running on.
* Sound API abstraction, alleviating the need for multiple backends in
applications to handle the wide diversity of sound systems out there.
* Generic hardware abstraction, giving the possibility of doing things
like individual volumes per application.
In a nutshell, pulseaudio is for audio what X is for graphics. Imagine every
particular app having to talk directly to radeon, intel or nvidia drivers in
order to display itself on the screen. It is extremely complicated to maintain
such an app. X is an abstraction layer that provides a standardized graphics
interface to each app, and talks to the drivers in the background, "mixing the
signals" of all apps into a set of windows that you can see on the screen.
Pulseaudio does the same thing, for audio. The way I see it, it is a Good
Thing, providing a lot of functionality.
Finally, this is how top reports the cpu usage on my system at the moment:
I am running compiz-fusion/emerald under latest KDE, have a bunch of windows
open on 8 desktops, listening to mp3 in xmms, while downloading some stuff with
ktorrent. Now, if you compare the cpu usage by X and by pulseaudio, I think I
should "turn off" X first, before pulseaudio, if I were to follow your logic.
You never listen to several audio sources simultaneously, right? So you don't
need pulseaudio server, right? I guess you also never look at two windows on
the screen simultaneously, right? So you don't actually need X, right?
I am sorry if this e-mail sounds a bit like venting, but *please* next time
use google and read about things yourself, don't expect from people on the
list to quote things that can be found on the web (and in a rather obvious
Marko, I thank you for your help. I had read the pa material before but I did
not realize that removing it from the system was really not an option. After
reading your reply, I upgraded to kde-4.3.0 and that actually made a huge
difference. Time will tell, but so far, I do not seem to be getting syslog
messages constantly at a rate of about 26 per second. The messages now seem to
be only happening when I do something that causes a sound to be generated, and
it stops after a second or two with a rate of about 13/second. This is a
I *might* not be feeling so grateful if your answer had not coincided with an
upgrade that showed such an improvement ;-) but since it worked out as well as
it did, I say we declare victory and withdraw. There's a beer waiting for you
if you get to the Boston area. :-)>
Time flies like the wind. Fruit flies like a banana. Stranger things have .0.
happened but none stranger than this. Does your driver's license say Organ ..0
Donor?Black holes are where God divided by zero. Listen to me! We are all- 000
individuals! What if this weren't a hypothetical question?
steveo at syslang.net
Description: OpenPGP digital signature
fedora-list mailing list
To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
- Re: Where is pulseaudio started?
- From: Marko Vojinovic
- Re: Where is pulseaudio started?
- Prev by Date: Re: DHCP configuration question
- Next by Date: Re: MythTV vs php
- Previous by thread: Re: Where is pulseaudio started?
- Next by thread: Re: Where is pulseaudio started?