pulseaudio: no sound, Fedora 12, what debugging/diagnostic info is needed to solve this problem?

[Rick Sewill]

On Thu, 2010-03-04 at 12:31 +0000, Marko Vojinovic wrote: 
> On Thursday 04 March 2010 04:32:35 am Rick Sewill wrote:
> > I believe many software programs use alsa.
> > I believe alsa, in turn, uses pulseaudio.
> 
> No. Userland apps talk to pulseaudio, which talks to alsa which talks to 
> hardware. That is a natural flow of audio data (when doing playback). 
> Pulseaudio is built and works on top of alsa.
>  
> > I must add a caveat.  I believe programs can be configured to use alsa.
> 
> If a program is configured to use alsa, the alsa-pulseaudio plugin would catch 
> it trying to talk to alsa and redirect the communication to pulseaudio, which 
> would mimic alsa for that app. After pulseaudio does its processing, it 
> forwards the results to alsa. Only pulseaudio actually talks to the real alsa.
> 
> Of course, you can disable the plugin or pulseaudio and let apps talk directly 
> to alsa, but that would be a broken configuration.
> 
> > I believe some programs can be configured to use pulseaudio, bypassing
> > alsa.  I believe some programs can be configured to bypass pulseaudio,
> > and go straight to the hardware device drivers.
> 
> All programs should be configured to use pulseaudio, if they support it. If 
> not, they should be configured to use alsa, whereby the alsa-pulseaudio-plugin 
> will interfere as above. Hardware device drivers are part of alsa, and no user 
> app should ever talk to hardware directly.
>  
> > pavucontrol
> 
> Also, there are two mixers in the story --- the hardware mixer (for alsa) and 
> the userland mixer (pavucontrol, for pulseaudio). In regular circumstances you 
> never want to mess with the hardware mixer, since it is used by pulseaudio 
> when communicating to alsa. The hardware mixer is not easy to access either, 
> you must specifically ask for it to be displayed, using appropriate switches 
> in, say, "alsamixer" app.
> 
> The only mixer that a user should actually use is pavucontrol. Or kmix or 
> gnome volume control mixer or some other similar thing. They all handle 
> basically the same controls (using different GUIs) and use pulseaudio in the 
> background.
> 
> I hope this clears things up a little.
> 
> HTH, :-)
> Marko
> 
> 

Thank you for your explanation!  I admit my ignorance.

So it's backwards from what I thought.  

Pulseaudio goes to alsa to the hardware?

-Rick