[linux-audio-user] Re: Problems with notch filtering

Tom Szilagyi tszilagyi at users.sourceforge.net
Sun Sep 4 16:20:37 EDT 2005

On Sun, 4 Sep 2005 14:30:10 -0500, Reuben Martin <reuben.m at gmail.com>

> I need to be able to pipe stereo audio through a notch filter so that
> I can adjust it while listening and analyzing the effects it is
> having. Unfortunately I cannot find a way to do this. Here's why:
> - The only LADSPA notch filter I can find is "Mag's notch filter"
> (notch_iir_1894.so)

I don't know how 'sharp' you need the notch to be, but maybe you can
try the TAP EQ/BW with a small bandwidth setting. Just a random idea.

> -Jack Rack works great with this plugin, except when I change the
> number of stages in the interface, the change is only applied to one
> channel. (the other controls are applied to both channels)
> -AlsaModularSynth immediately segfaults when trying to load this
> particular plugin
> -Ardour will not work with this either. The controls don't do what
> they are supposed and al I can accomplish with it is some sort of
> wacky low pass filter. (how this is accomplished with a notch filter
> plugin is beyond me...)
> So... What else is there? these are the only programs I know of that I
> can pipe audio through very easily. (please don't suggest Pd, I've
> never gotten it to compile correctly) Anybody else have similar
> problems with this plugin?

I tried the plugin in Aqualung, which is a music player program
supporting LADSPA plugins (http://aqualung.sf.net). It seemed to be
working alright. If you decide to try it, get the latest source from
http://aqualung.sf.net/aqualung-cvs.tar.gz and issue an 'sh autogen.sh'
before the usual ./configure, make, make install stuff. If you are able
to compile Ardour, the needed libs are almost certainly present on your

As this is just a music player, you can't pipe audio through it (since
there is no input), but you can export the audio to a track and play
that. I'm not suggesting that this is an acceptable end solution, but
maybe worth trying out to determine whether there is a problem with
the notch plugin or the other hosts instead.


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