[pulseaudio-discuss] selective sound amplification by frequency @ PulseAudio.

[Tanu Kaskinen]

On Wed, Jan 09, 2008 at 09:15:33AM +0100, Adam Sulmicki wrote:
> Folks,
> 
> I have followed the suggestions given by Tanu Kaskinen, sadly I'm having
> problems. With new settings the program crashes with memory protection
> violation. Despite repeated attempts, I am unable to produce a meaningful bt
> under gdb. Furthermore, pulseaudio does not seem to run for me under
> valgrind.
> 
> THEREFORE, the question is: Can anyone else duplicate the problem?

Yes. Sorry, it was my fault to give a bit bad example. That
was because I didn't remember that the particular plugin (or
any plugin with control out ports) doesn't work with
pulseaudio 0.9.7. It's fixed in 0.9.8.

So you'll need newer pulseaudio or some other equalizer
plugin. Or just apply this patch to 0.9.7 sources:

http://www.pulseaudio.org/changeset/1952

(Raw patch file is at
http://www.pulseaudio.org/changeset/1952?format=diff&new=1952)

I don't know which alternative would be the easiest.

I don't know how many equalizer ladspa plugins there exists.
I have tried the "Triple band parametric with shelves"
equalizer, which is also in swh-plugins, and that does work
in 0.9.7. I would guess that "Single band parametric" works
too, since it is probably the same thing but simpler.

This is how you would load them:

    load-module module-ladspa-sink sink_name=ladspa_out channels=2 master=alsa_output.pci_1274_5000_alsa_playback_0 plugin=triple_para_1204 label=triplePara control=X,X,X,X,X,X,X,X,X,X,X,X,X,X,X

    load-module module-ladspa-sink sink_name=ladspa_out channels=2 master=alsa_output.pci_1274_5000_alsa_playback_0 plugin=single_para_1203 label=singlePara control=X,X,X

The single parametric version might be enough for your
needs. It amplifies just one frequency (and the ones around
it), which in this case would be 6000 Hz. The three control
parameters have the following names:

Gain (dB)
Frequency (Hz)
Bandwidth (octaves)

So gain would be something between 40 and 50, frequency 6000
and bandwidth about one octave or sligthly less (the
parameters are explained at
http://plugin.org.uk/ladspa-swh/docs/ladspa-swh.html#tth_sEc2.97).

> PS : any idea what program this picture is from?
> http://www.linux-user.de/ausgabe/2003/11/026-muse/07_equalizer.png
> It is in german so I can't quite figure out, but it does mention "multiband
> equalization". The whole article is here :
> http://www.linux-user.de/ausgabe/2003/11/026-muse/ .

The article seems to be about MusE
(http://muse-sequencer.org/) and the picture is the
program's equalizer (which seems to use the mbeq ladspa
plugin internally).

-- 
Tanu Kaskinen