aubio
0.4.9
spectral
specdesc.h
Go to the documentation of this file.
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/*
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Copyright (C) 2003-2013 Paul Brossier <piem@aubio.org>
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This file is part of aubio.
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aubio is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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aubio is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with aubio. If not, see <http://www.gnu.org/licenses/>.
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*/
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/** \file
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Spectral description functions
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All of the following spectral description functions take as arguments the FFT
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of a windowed signal (as created with aubio_pvoc). They output one smpl_t per
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buffer (stored in a vector of size [1]).
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\section specdesc Spectral description functions
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A list of the spectral description methods currently available follows.
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\subsection onsetdesc Onset detection functions
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These functions are designed to raise at notes attacks in music signals.
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\b \p energy : Energy based onset detection function
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This function calculates the local energy of the input spectral frame.
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\b \p hfc : High Frequency Content onset detection function
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This method computes the High Frequency Content (HFC) of the input spectral
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frame. The resulting function is efficient at detecting percussive onsets.
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Paul Masri. Computer modeling of Sound for Transformation and Synthesis of
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Musical Signal. PhD dissertation, University of Bristol, UK, 1996.
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\b \p complex : Complex Domain Method onset detection function
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Christopher Duxbury, Mike E. Davies, and Mark B. Sandler. Complex domain
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onset detection for musical signals. In Proceedings of the Digital Audio
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Effects Conference, DAFx-03, pages 90-93, London, UK, 2003.
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\b \p phase : Phase Based Method onset detection function
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Juan-Pablo Bello, Mike P. Davies, and Mark B. Sandler. Phase-based note onset
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detection for music signals. In Proceedings of the IEEE International
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Conference on Acoustics Speech and Signal Processing, pages 441444,
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Hong-Kong, 2003.
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\b \p wphase : Weighted Phase Deviation onset detection function
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S. Dixon. Onset detection revisited. In Proceedings of the 9th International
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Conference on Digital Audio Ef- fects (DAFx) , pages 133–137, 2006.
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http://www.eecs.qmul.ac.uk/~simond/pub/2006/dafx.pdf
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\b \p specdiff : Spectral difference method onset detection function
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Jonhatan Foote and Shingo Uchihashi. The beat spectrum: a new approach to
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rhythm analysis. In IEEE International Conference on Multimedia and Expo
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(ICME 2001), pages 881884, Tokyo, Japan, August 2001.
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\b \p kl : Kullback-Liebler onset detection function
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Stephen Hainsworth and Malcom Macleod. Onset detection in music audio
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signals. In Proceedings of the International Computer Music Conference
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(ICMC), Singapore, 2003.
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\b \p mkl : Modified Kullback-Liebler onset detection function
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Paul Brossier, ``Automatic annotation of musical audio for interactive
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systems'', Chapter 2, Temporal segmentation, PhD thesis, Centre for Digital
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music, Queen Mary University of London, London, UK, 2006.
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\b \p specflux : Spectral Flux
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Simon Dixon, Onset Detection Revisited, in ``Proceedings of the 9th
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International Conference on Digital Audio Effects'' (DAFx-06), Montreal,
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Canada, 2006.
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\subsection shapedesc Spectral shape descriptors
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The following descriptors are described in:
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Geoffroy Peeters, <i>A large set of audio features for sound description
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(similarity and classification) in the CUIDADO project</i>, CUIDADO I.S.T.
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Project Report 2004 (<a
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href="http://www.ircam.fr/anasyn/peeters/ARTICLES/Peeters_2003_cuidadoaudiofeatures.pdf">pdf</a>)
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\b \p centroid : Spectral centroid
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The spectral centroid represents the barycenter of the spectrum.
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\e Note: This function returns the result in bin. To get the spectral
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centroid in Hz, aubio_bintofreq() should be used.
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\b \p spread : Spectral spread
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The spectral spread is the variance of the spectral distribution around its
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centroid.
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See also <a href="http://en.wikipedia.org/wiki/Standard_deviation">Standard
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deviation</a> on Wikipedia.
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\b \p skewness : Spectral skewness
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Similarly, the skewness is computed from the third order moment of the
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spectrum. A negative skewness indicates more energy on the lower part of the
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spectrum. A positive skewness indicates more energy on the high frequency of
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the spectrum.
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See also <a href="http://en.wikipedia.org/wiki/Skewness">Skewness</a> on
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Wikipedia.
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\b \p kurtosis : Spectral kurtosis
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The kurtosis is a measure of the flatness of the spectrum, computed from the
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fourth order moment.
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See also <a href="http://en.wikipedia.org/wiki/Kurtosis">Kurtosis</a> on
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Wikipedia.
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\b \p slope : Spectral slope
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The spectral slope represents decreasing rate of the spectral amplitude,
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computed using a linear regression.
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\b \p decrease : Spectral decrease
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The spectral decrease is another representation of the decreasing rate,
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based on perceptual criteria.
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\b \p rolloff : Spectral roll-off
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This function returns the bin number below which 95% of the spectrum energy
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is found.
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\example spectral/test-specdesc.c
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*/
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#ifndef AUBIO_SPECDESC_H
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#define AUBIO_SPECDESC_H
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#ifdef __cplusplus
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extern
"C"
{
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#endif
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/** spectral description structure */
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typedef
struct
_aubio_specdesc_t
aubio_specdesc_t
;
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/** execute spectral description function on a spectral frame
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Generic function to compute spectral description.
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\param o spectral description object as returned by new_aubio_specdesc()
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\param fftgrain input signal spectrum as computed by aubio_pvoc_do
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\param desc output vector (one sample long, to send to the peak picking)
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*/
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void
aubio_specdesc_do
(
aubio_specdesc_t
* o,
const
cvec_t
* fftgrain,
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fvec_t
* desc);
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/** creation of a spectral description object
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\param method spectral description method
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\param buf_size length of the input spectrum frame
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The parameter \p method is a string that can be any of:
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- onset novelty functions: `complex`, `energy`, `hfc`, `kl`, `mkl`,
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`phase`, `specdiff`, `specflux`, `wphase`,
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- spectral descriptors: `centroid`, `decrease`, `kurtosis`, `rolloff`,
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`skewness`, `slope`, `spread`.
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*/
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aubio_specdesc_t
*
new_aubio_specdesc
(
const
char_t
* method,
uint_t
buf_size);
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/** deletion of a spectral descriptor
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\param o spectral descriptor object as returned by new_aubio_specdesc()
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*/
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void
del_aubio_specdesc
(
aubio_specdesc_t
* o);
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#ifdef __cplusplus
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}
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#endif
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#endif
/* AUBIO_SPECDESC_H */
aubio_specdesc_do
void aubio_specdesc_do(aubio_specdesc_t *o, const cvec_t *fftgrain, fvec_t *desc)
execute spectral description function on a spectral frame
char_t
char char_t
character
Definition:
types.h:64
aubio_specdesc_t
struct _aubio_specdesc_t aubio_specdesc_t
spectral description structure
Definition:
specdesc.h:163
del_aubio_specdesc
void del_aubio_specdesc(aubio_specdesc_t *o)
deletion of a spectral descriptor
new_aubio_specdesc
aubio_specdesc_t * new_aubio_specdesc(const char_t *method, uint_t buf_size)
creation of a spectral description object
fvec_t
Buffer for real data.
Definition:
fvec.h:67
cvec_t
Vector of real-valued phase and spectrum data.
Definition:
cvec.h:63
uint_t
unsigned int uint_t
unsigned integer
Definition:
types.h:60
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