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

Jan Alexander Steffens jan.steffens at gmail.com
Tue Apr 30 18:28:15 PDT 2013

On Wed, May 1, 2013 at 2:46 AM, Andrea <andrea at z80.it> wrote:
> 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
> perspective.
> 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.
>  Andrea

Usually it works well, i.e. there are no noticeable volume changes in
background streams.

If it doesn't, uncomment and disable flat-volumes in /etc/pulse/daemon.conf.

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