[pulseaudio-discuss] how to map equalizer to arbitrary device

[Daniel Sonck]

On Friday, February 14, 2014 09:15:53 PM Malte Gell wrote:
> Am 12.02.2014 19:19, schrieb Alexander E. Patrakov:
> > 12.02.2014 22:52, Malte Gell wrote:
> >> I would like to use the EQ with my bluetooth headphone, so how do I map
> >> the EQ to the bluetooth device? I would like to have a output device
> >> named like "FFT based equlizer on Philips SHB9100", how do I get it?
> > 
> > 1. As you have obviously followed some instruction to get to the stage
> > where it actually creates a sink, please find the instruction again. It
> > says either "pacmd load-module module-ladspa-sink lots-of-magic" or "add
> > the equivalent load-module directive to default.pa".
> 
> Yes, there is a line in ~/.pulse/default.pa:
> 
> load-module module-ladspa-sink sink_name=ladspa_output.mbeq_1197.mbeq
> master=alsa_output.pci-0000_00_1b.0.analog-stereo plugin=mbeq_1197
> label=mbeq
> control=-16.0,-16.0,6.5,6.5,6.0,5.5,4.5,1.0,1.0,1.0,-8.0,-10.0,-16.0,-16.0,-
> 20.4
> 
> I could change the value for master to my bluetooth sink
> bluez_sink.00_23_78_AB_09_A6 but is there no load-module option that
> allows to map a module to two sinks at the same time?
> 
> Thanks
> Malte
Well you can, but it takes some more configuration. Before doing this, think 
about the problem this faces:

You have two different audio devices that work with different buffers, different 
timers and probably different audio requirements. This will create a problem 
for pulseaudio related to synchronization. One sound card might ask for audio 
a little faster each time so you might notice some delays or roughness... This 
is the reason that it doesn't support multiple sinks... But if you don't mind 
that, then:

Basically you would want a dummy sink for all your audio, you can choose to 
add the equalizer to the dummy sink, connect the monitor of the dummy sink to 
the two outputs and you're done. You can also add individual equalizers to 
each output and connect the dummy sink monitor to the two equalizers. It's a 
matter of what you actually want to achieve with the equalizers.

Now, for the basic splitting (you can decide where you want to add the 
equalizer(s) to):

You make a null sink for all your audio:
load-module module-null-sink sink_name=AudioOut

And use the loopback module to connect the monitor of the null to the different 
soundcards:
load-module module-loopback source=AudioOut.monitor sink=<audiocard_1>
load-module module-loopback source=AudioOut.monitor sink=<audiocard_2>

Daniel Sonck