[pulseaudio-discuss] New to pulseaudio mixer logic, can you explain this effect to me?

Andrea andrea at z80.it
Tue Apr 30 17:46:13 PDT 2013

I recently upgraded from an old KDE3.5+arts installation to a full upgraded
debian wheezy with kde4.8+phonon4.6+pulseaudio2.0+alsa

upon installation i added pavucontrol1.0 and amarok2.6 to my desktop using the 
standard repositories (i use wheezy base + contrib + nonfree).

the first time i started my installation i unmuted the alsa output via 
alsamixer (obviously).

now i am trying to reach a confortable use case that i was used to with 
kde 3.5.

In short i want to keep amarok playing from my collection at a soft volume 
level *and* hearing the system notifications (example, the email arrived) at a 
noticeable level *over* the music.

with pavucontrol, I am setting the output volume in the "output devices" tab 
to a confortable high level, say a -2 db. this the maximum output i am 
allowing in this particular moment. this is my *master* level i want to adjust 
based on environment condition (if  at the phone i lower this, if i'm alone i 
upper this)

then in the playback section I set the "system sounds" stream at a confortably 
high level, say -4db, to get a noticeable notification, if i may.

and then i set the libvlc audio stream that is opened by amarok at a much 
lover level, say -12db, to get a reasonable background music level (this is 
the control that moves using both the pavucontrol and the volume control of 
amarok interface.

Now, i am writing this because i get an effect that is unplanned and i am 
searchin both an explanation for this and the method i need to implement to 
get che results i want, that are

1. get a single control to use to adapt to environment conditions (i'm on the 
phone, ecc.)

2. get a place to setup the relative levels of the sound sources.

the effect i am getting is that *every* time i receive an email, i am notified 
by the kde system notifier with a sound, and this sound is played, obviously, 
at the level i set up with the system sounds control. 

what is *very* annoying is that while playing the sound, it seems that the 
master level is going up then down, so while i hear the notify i hear also the 
background music at a higher level for some deciseconds before and after the 
notification sounds,

The overall results is as i go up with the master volume and then down.

i read the document on the mixer logic, and i can see this mechanics based on 
a technical standpoint (it's more accurate to leave all volume sources to 0 db 
to get the max digital dynamic range and use only the master at the analog 
output to set the out level.) *BUT* this is good only from a single-source 

When i have the pulseaudio system mixing multiple sources, i cannot let the 
inner volume control (the control at the source) touch the outer control (the 
analog output in this case) because this will touch the level of another 
stream and this is no desired.

how can i configure the control logic to return to an approach more like an 
analog mixer?

thank you all.

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