This is a visualization based on on the monoscope output plugin from
alsaplayer.

The monoscope convolution matching code was written by Ralph Loader.

The monoscope.c and monoscope.h files are under the BSD license (without advertising clause). 

This implementation is taken from alsaplayer version 0.99.54, at
http://www.alsaplayer.org/

Note: only one instance of this plugin may be created at a time: it has a
lot of static data.  This should be fixed (and it shouldn't be hard to do
so, either).