WHAT YOU WILL FIND HERE

A C++ library with Python bindings "Loudia" It is used to build audio applications.

Loudia is specially targeted for researchers. The algorithms are not necessarily tuned for performance but rather for:

• Ease of use

• Flexibility and clarity of the algorithms

• Variety of algorithms

The following algorithms are implemented:

• Window

• Unwrap

• Fast Fourier Transform (FFT/IFFT) (wrapper around libfftw [http://www.fftw.org/])

• Discrete Cosine Transform (DCT)

• Filters (based on Scipy [http://www.scipy.org] implementation):

  • LowPass
  • HighPass
  • BandPass
  • BandStop

  in the following types:

  • Chebyshev I
  • Chebyshev II
  • Bessel
  • Butterworth

• Correlation / Autocorrelation

  • Direct calculation
  • FFT based calculation

• Resampling (wrapper around libsamplerate [http://www.mega-nerd.com/SRC/])

• Onset Detection Functions:

  • High Frequency Content (HFC)
  • Flux
  • Phase Deviation
  • Complex Domain
  • Modified Kullback-Liebler
  • Peak Center of Gravity

• Pitch Estimation:

  • Autocorrelation Function based (ACF)
  • Inverse Problem based

• Spectral Bands

  • Mel bands

• MFCC

• LPC

• Sinusoidal Modelling:

  • Peak Detection
  • Peak Interpolation
  • Peak Tracking

• Spectral Whitening

• Spectral Noise Suppression

• Non-negative Matrix Factorization (NMF)

• Other experimental and/or unfinished algorithm implementations

  • Spectral Reassignment
  • Adaptative Optimized Kernel (AOK) (modification of AOK 4.1 [http://www.macunix.net/aok.html])
  • Peak Synthesis
  • Incremental Non-negative Matrix Factorization (INMF)
  • LPC residual

Numerous examples which can also be used for testing in some cases can be found in python/ Some of the examples require an audio WAVE filename as input argument.

DEPENDENCIES

The C++ library Libaudio requires:

• libsamplerate-dev >=0.1.3
• libfftw3-dev >=3.1.2
• gcc
• python >=2.5

The Python bindings Libaudio require:

• swig
• numpy-dev
• python-dev

Libaudio uses a template library called Eigen (http://eigen.tuxfamily.org).

In C++ all algorithms use Eigen::Matrix types as inputs and outputs.

In the Python bindings use Numpy arrays as inputs and outputs.

BUILD/INSTALL LOUDIA

To build and install Loudia run: ./waf configure --prefix=/some/install/dir ./waf build sudo ./waf install

To uninstall it run: sudo ./waf uninstall

Several options allow different building modes.

To build without Python bindings run: ./waf configure --no-python-bindings ./waf build --no-python-bindings

To build the documentation run: ./waf configure --doc ./waf build --doc

To build in debug mode run: ./waf configure --debug ./waf build --debug

These options can be combined.

QUICK HOWTO

From Python you may create algorithm, change its parameters and call the process method:

import numpy import pylab import loudia

We create a 120 samples frame

of a sine at 440 Hz

with a samplerate of 8000 Hz

data_frame = numpy.array(numpy.sin(2numpy.pi440.0*numpy.arange( 0.0, 120/8000.0, 1/8000.0)))

fft = loudia.FFT() fft.setFftSize( 256 )

result = fft.process( data_frame )

Note that the results of the FFT algorithm

are stacked in rows (we only plot the first)

pylab.subplot(211) pylab.plot( abs( result[0,:] ) )

When setting several parameters we might

not want the algorithm to reconfigure itself

method after each parameter setting,

and we will call the setup() manually

fft.setFftSize( 1024, False ) fft.setZeroPhase( True, False ) fft.setup()

result = fft.process( data_frame )

Note that the results of the FFT algorithm

are stacked in rows (we only plot the first)

pylab.subplot(212) pylab.plot( abs( result[0,:] ) )

pylab.show()

LIMITATIONS

A few assumptions are used when using the library:

• Loudia has no algorithm for loading audio frames

• All algorithms take Eigen::Matrix types as inputs and outputs in the process() methods

• Loudia does NOT have a streaming mode. All algorithms mantain a state which can be reset using reset(). And the process() methods may act on preallocated matrices. Therefore with the use of Eigen::Map, Loudia can be used inside streaming libraries that expose the buffers.

Loudia (C) 2008, 2009 Ricard Marxer