[SailfishDevel] Setting up PulseAudio via CLI and system wide equalizer

[Mikael Erkkilä]

Hello everyone,

in TJC there has been a great interest in getting a system wide 
equalizer. Even some dream from diverting certain audio inputs to 
different sinks. Basically PulseAudio should be able do to all these 
tasks...

see here for the TJC discussions:
https://together.jolla.com/question/27201/request-system-wide-equalizer/
https://together.jolla.com/question/82958/audio-control-in-sailfish-setting-volume-via-cmd-line/?answer=88072#post-id-88072

So now to the requests from TJC. Basically they are asking for something 
similar like pavucontrol on Linux Desktop Distros. This is a GUI which 
handles PulseAudio and can f.e. send your VLC Video input to your HDMI 
while your Skype is diverted to bluetooth. There is also an equalizer in 
pulseaudio but which is pretty hiden at least for non-Ubuntu distros :) 
There is also another one from via ALSA called Alsaequal which can f.e. 
be found in Ubuntu/Debian repositories...

I am basically playing around with PulseAudio. It is not my aim to write 
a functioning program with GUI front-end. I know there are several 
amazing developers out there which are better suited for that. But I 
would like to make some first steps and maybe show how one basically can 
do these things via command line input on Sailfish...

What I managed to do so far:

  * after installing alsa-utils via pkcon I was able to change the
    master volume/balance via cmd line like 'amixer sset Master 80%,80%'
  * I saw that there were also other sinks available but I didn't look
    further because I don't know all of these...but I am sure that if I
    would just use another sink then I could set it via 'amixer sset
    [Bluetooth,...] 80%,80%
  * Diverting inputs to different sinks should be feasible via pacmd
    move-sink-input|move-source-output index sink-index|sink-name (see
    man pulse-cli-syntax in linux)

Main Problem: By using this approach you totally rule over the current 
volume setting protocol. So as I stated in TJC, you can mute your phone 
and you will not get it back again with your volume buttons... It was 
noted that correct volume handling is done via the dbus-socket, so 
should I rather stick to that even if I have no idea about it or try my 
luck with over-riding it via amixer and pacmd :) Can anyone give me some 
additional info on audio handling in Sailfish?

What are your thoughts on that?

Cheers Mika




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