[pulseaudio-discuss] Questions about sinks and sink inputs

[Pali Rohár]

On Tuesday 24 November 2015 06:13:51 Tanu Kaskinen wrote:
> On Sun, 2015-11-22 at 23:33 +1000, Jonathan Wilson wrote:
> > I am trying to understand how sinks and sink inputs work.
> > The code I am trying to figure out creates the following sinks:
> > master_sink (external sink obtained from ALSA sink module via pa_namereq_get)
> > raw_sink (created with the flat_volume_sink parameter of the 
> > pa_sink_new_data structure set to master_sink)
> > voip_sink (created with the flat_volume_sink parameter of the 
> > pa_sink_new_data structure set to raw_sink)
> > 
> > And the following sink inputs:
> > aep_sink_input (created with the sink parameter of the 
> > pa_sink_input_new_data structure set to raw_sink and the origin_sink 
> > parameter of the pa_sink_input_new_data structure set to voip_sink)
> > hw_sink_input (created with the sink parameter of the 
> > pa_sink_input_new_data structure set to master_sink and the origin_sink 
> > parameter of the pa_sink_input_new_data structure set to raw_sink)
> > cs_call_sink_input (created with the sink parameter of the 
> > pa_sink_input_new_data structure set to voip_sink and the origin_sink 
> > parameter of the pa_sink_input_new_data structure set to 0)
> > 
> > I then have some other code that feeds audio into the voip_sink sink
> > Can someone tell me the pathway in which audio will go from the app through 
> > to being fed into master_sink (and from there into the hardware)?
> > Which sinks and sink inputs will it pass through and in which order?
> > 
> > What about if audio passes into the raw_sink sink, what path will it take 
> > through the code in that case?
> 
> I guess this is Maemo or MeeGo, or possibly Sailfish?

Yes, this is for Maemo system.

> I have worked on those systems in the past, and this sounds very
> familiar (and certainly not something that is in upstream). Could you
> send /etc/pulse/system.pa?
> 
> > And where should I be looking (e.g. specific callback functions on the 
> > sinks or sink inputs) for anything that might be doing any kind of 
> > processing on the audio?
> 
> Are you looking for a way to do your own processing, or are you just
> trying to understand what processing your device does and how?

We are trying to understand how that Maemo pulseaudio code is working...

-- 
Pali Rohár
pali.rohar at gmail.com