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Bug#609441: Pulseaudio

On Saturday, 2011-01-15, Debian wrote:
> Hi,
> Am 15.01.2011 19:53, schrieb Kevin Krammer:
> > Which other sound server are you referring to? JACK?
> First i would say ALSA.
> But your question shows me that i have not understand the sound concept
> at all.
> There are to many components now working on/for the sound.
> Where can i get an overview?
> My hope is that i can solve the problem, if i can get a chance to
> understand it.

I don't think there is an up to date flow graphic somewhere that is intended 
to be understood by non audio developers.
Basically a multimedia component decodes data, e.g. from an MP3 file and 
writes samples to an output. Which can be the audio device provided by ALSA or 
a mixer daemon such as PulseAudio (which in turn will then output to the 

Some devices/drivers allow to be used multiple times, some allow only one 
application writing to them so a mixing component (e.g. PulseAudio) is needed 
in between.

> > Some postings seem to indicate a general ALSA setup problem, i.e. one
> > users says ALSA's aplay won't work either.
> In my case i can say that ALSA is basically working on every PC.
> And the sound was working perfect with KDE 3.5 with ALSA.
> Why it is not working in KDE 4 any more?

Very strange, no idea though.
My system has also been upgraded through the years (KDE3->KDE4 a long time ago 
though) and I don't remember adjusting anything.

> >> But up to now the configuration and interaction of phonon with ALSA is a
> >> mystery.
> > 
> > Phonon (the programming interface) does not interact with ALSA at all.
> > Depending in which Phonon backend is being used, this backends multimedia
> > framework is interacting with ALSA (or a sound server).
> This i have not understand.
> Phonon is an KDE-API for sound - correct?


> Why i have only sound problems with applications where i can't chosse
> ALSA as audio output?

What I am seeing in Systemsettings is my audio device (HDA Intel) and when I 
hover over the entry it says it will try two ALSA devices and then two OSS 
I am pretty sure it succeeds with one of the ALSA devices, but I wouldn't know 
how to check.

> And i get no sound with Virtualbox even i choose ALSA or something else.

Hmm, that sounds like something is blocking the device, virtualbox should be 
totally independent.
Can you use aplay mutiple times in parallel?

> > While I am on Debian SID there is most likely not much difference right
> > now due to the freeze. I have the Xine backend configured and I am not
> > aware of any Xine or ALSA related setup I would have had to make.
> When i read XINE i am thinking just for video.
> But it is also a Player. Like VLC or Kaffeine?

Xine is also a video player, yes. And its multimedia library is used by one of 
Phonon's backends.

> > But maybe Xine did when I installed it in its role as a mediaplayer.
> There must be a reasonable way how applications give the sound data to
> the hardware.
> Up to KDE 4 i thought all this is done by ALSA.
> But now it don't know what the way is?

There could be some backend (in my case Xine) specific configuration that is 
actually doing the output selection, but my guess would be that the Phonon 
Xine backend is doing that.

> > Well, the actual output is handled by the multimedia framework used to
> > implement the chosen Phonon backend (Xine, mplayer, GStreamer, etc).
> How can a Multimedia Player be an backend?

Not the player application itself, the multimedia library/framework it is 

> I have multiple player installed.
> What player is used by kaffeine and flash?

My guess would be that Kaffeine is using the selected Phonon backend through 
Phonon, but I could of course be wrong.
Flash is using its own decoding framework as far as I know.

> And is ALSA a player also?

No, though the package comes with a simple player called aplay.

> > Maybe you can check if the player application of the framework your
> > Phonon backend is using is capable of output.
> On the PC mit onboard sound the phonon output is "PNP Audio Device (USB
> Audio)"
> What will this say to me?

That' the audio device Phonon tells the backend to use, an USB device it 
Check the second tab which backend you are using and see if the player 
application of that framework works, e.g. if you have the Xine backend, check 
the Xine player.


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