LibXtract is a simple, portable, lightweight library of audio feature extraction functions. The purpose of the library is to provide a relatively exhaustive set of feature extraction primatives that are designed to be 'cascaded' to create a extraction hierarchies.

For example, 'variance', 'average deviation', 'skewness' and 'kurtosis', all require the 'mean' of the input vector to be precomputed. However, rather than compute the 'mean' 'inside' each function, it is expected that the 'mean' will be passed in as an argument. This means that if the user wishes to use all of these features, the mean is calculated only once, and then passed to any functions that require it.

This philosophy of 'cascading' features is followed throughout the library, for example with features that operate on the magnitude spectrum of a signal vector (e.g. 'irregularity'), the magnitude spectrum is not calculated 'inside' the respective function, instead, a pointer to the first element in an array containing the magnitude spectrum is passed in as an argument.

Hopefully this not only makes the library more efficient when computing large numbers of features, but also makes it more flexible because extraction functions can be combined arbitrarily (one can take the irregularility of the Mel Frequency Cepstral Coefficients for example).

A complete list of features can be found by viewing the header files, or reading the doxygen documentation, available with this package.

The latest source code release for LibXtract can be downloaded from https://github.com/jamiebullock/LibXtract/downloads.

To compile LibXtract from the source code release, the following optional software is also needed:

fftw3 (compiled with floating-point support)

To build the PD external, the PD header 'm_pd.h' is required, this can be found in the Pure Data source code release.

If you are compiling LibXtract from a GIT clone, the autotools build system is required. This includes:

automake >= 1.11
autoconf >= 2.68
libtool >= 2.4

If you are installing from a GIT clone, first run:

sh autogen.sh

If autogen.sh was successful, or you downloaded the source release, type:

./configure --enable-pd_example --enable-fft
make
sudo make install

There following configure flags are optional:

--enable-pd_example (to build the PD example)
--enable-fft (to enable functions that require fftw3)
--enable-simpletest (to build the simpletest example)

If you wish to build a Universal binary on OS X, you may need to do something like this:

CFLAGS="-isysroot /Developer/SDKs/MacOSX10.4u.sdk -Wl,-syslibroot,/Developer/SDKs/MacOSX10.4u.sdk -arch i386 -arch ppc" \./configure --isable-dependency-tracking --your-options

Type:

cd examples/MSP
make
sudo make install

To build for a specific architecture:

make intel
or
make ppc

To build the python bindings, add to your configure flags:

--enable-swig --with-python

This requres additional dependencies to be resolved:

swig >= 1.3
python (with development files) >= 2.5

It might work with earlier versions of Python, but this has not been tested.

If you do not have the 'standard' version of Python on OS X, you might need to tell the configure script where the python library is e.g.:

./configure --your-flags LDFLAGS="-L/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/config/"

To find your Python library type:

locate libpython

NOTE: The python module will get installed under the main install prefix, so if your install prefix is set to /usr/local, then the python module will get installed to /usr/local/lib/python2.5/site-packages/libxtract/xtract. You may need to add this to your PYTHONPATH environment variable. For example in ~/.bash_profile add: export PYTHONPATH=/usr/local/lib/python2.7/site-packages

To build the java bindings, add to your configure flags:

--enable-swig --with-java

This requres additional dependencies to be resolved:

swig >= 1.3
java (with development files) >= 2.0

It might work with other versions of Java, but this has not been tested.

On OS X, you will probably need to set your CLASSPATH environment variable before running ./configure

export CLASSPATH=/System/Library/Frameworks/JavaVM.framework/Classes/classes.jar

On OS X, you also probably need to tell the configure script where to find your Java (JNI) headers.

./configure --flags  CFLAGS="-I/System/Library/Frameworks/JavaVM.framework/Headers"

To find out where your headers are:

locate jni.h

## Disclaimer

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.