[pulseaudio-discuss] LADSPA Per Channel\Audio Woes

Tanu Kaskinen tanuk at iki.fi
Thu Oct 13 13:02:05 UTC 2016

On Thu, 2016-10-13 at 01:25 -0400, Dylan Taft wrote:
> Whoops, sorry.  It is late, the proof of concept .alsarc is here
> https://ubuntuforums.org/showthread.php?t=2339802
> On Thu, Oct 13, 2016 at 1:24 AM, Dylan Taft <dylanetaft at gmail.com> wrote:
> > I need to use a LADSPA per channel to correct an issue with audio
> > output on an 2011 iMAC 27.  By default, audio is very overdriven and
> > sounds very poor.  The iMac has 4 speakers.  I think I figured out
> > what is going on - there is no hardware bandpass filtering, so bass
> > tones and mid tones sent to the high register speakers are overdriving
> > it and probably damaging it.  OSX must do upmixing and low + highpass
> > filtering in software.
> > 
> > 
> > I have a proof of concept Alsa config file
> > http://askubuntu.com/questions/43950/how-can-i-apply-a-ladspa-plugin-to-a-pulseaudio-stream
> > 
> > How would I either get a PulseAudio sink set up to point at my custom
> > ALSA PCM, or, how would I apply a LADSPA plugin, with different
> > parameters for each channel, to a PulseAudio sink?
> > 
> > Sorry, I am stuck, appreciate any help.  Thanks.

You can put

    load-module module-alsa-sink device=upmix20

to /etc/pulse/default.pa. That will conflict with the automatically
loaded modules, however. Before you make the change, you can use
pavucontrol or pactl to choose the "off" profile for the sound card.
That will prevent the automatically loaded modules from trying to
access the device.


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