aubio: spectral/specdesc.h Source File

aubio 0.4.8

specdesc.h
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1 /*
2 Copyright (C) 2003-2013 Paul Brossier <piem@aubio.org>
3
4 This file is part of aubio.
5
6 aubio is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
10
11 aubio is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with aubio. If not, see <http://www.gnu.org/licenses/>.
18
19 */
20
21 /** \file
22
23 Spectral description functions
24
25 All of the following spectral description functions take as arguments the FFT
26 of a windowed signal (as created with aubio_pvoc). They output one smpl_t per
27 buffer (stored in a vector of size [1]).
28
29 \section specdesc Spectral description functions
30
31 A list of the spectral description methods currently available follows.
32
33 \subsection onsetdesc Onset detection functions
34
35 These functions are designed to raise at notes attacks in music signals.
36
37 \b \p energy : Energy based onset detection function
38
39 This function calculates the local energy of the input spectral frame.
40
41 \b \p hfc : High Frequency Content onset detection function
42
43 This method computes the High Frequency Content (HFC) of the input spectral
44 frame. The resulting function is efficient at detecting percussive onsets.
45
46 Paul Masri. Computer modeling of Sound for Transformation and Synthesis of
47 Musical Signal. PhD dissertation, University of Bristol, UK, 1996.
48
49 \b \p complex : Complex Domain Method onset detection function
50
51 Christopher Duxbury, Mike E. Davies, and Mark B. Sandler. Complex domain
52 onset detection for musical signals. In Proceedings of the Digital Audio
53 Effects Conference, DAFx-03, pages 90-93, London, UK, 2003.
54
55 \b \p phase : Phase Based Method onset detection function
56
57 Juan-Pablo Bello, Mike P. Davies, and Mark B. Sandler. Phase-based note onset
58 detection for music signals. In Proceedings of the IEEE International
59 Conference on Acoustics Speech and Signal Processing, pages 441444,
60 Hong-Kong, 2003.
61
62 \b \p wphase : Weighted Phase Deviation onset detection function
63
64 S. Dixon. Onset detection revisited. In Proceedings of the 9th International
65 Conference on Digital Audio Ef- fects (DAFx) , pages 133–137, 2006.
66
67 http://www.eecs.qmul.ac.uk/~simond/pub/2006/dafx.pdf
68
69 \b \p specdiff : Spectral difference method onset detection function
70
71 Jonhatan Foote and Shingo Uchihashi. The beat spectrum: a new approach to
72 rhythm analysis. In IEEE International Conference on Multimedia and Expo
73 (ICME 2001), pages 881884, Tokyo, Japan, August 2001.
74
75 \b \p kl : Kullback-Liebler onset detection function
76
77 Stephen Hainsworth and Malcom Macleod. Onset detection in music audio
78 signals. In Proceedings of the International Computer Music Conference
79 (ICMC), Singapore, 2003.
80
81 \b \p mkl : Modified Kullback-Liebler onset detection function
82
83 Paul Brossier, ``Automatic annotation of musical audio for interactive
84 systems'', Chapter 2, Temporal segmentation, PhD thesis, Centre for Digital
85 music, Queen Mary University of London, London, UK, 2006.
86
87 \b \p specflux : Spectral Flux
88
89 Simon Dixon, Onset Detection Revisited, in ``Proceedings of the 9th
90 International Conference on Digital Audio Effects'' (DAFx-06), Montreal,
91 Canada, 2006.
92
93 \subsection shapedesc Spectral shape descriptors
94
95 The following descriptors are described in:
96
97 Geoffroy Peeters, <i>A large set of audio features for sound description
98 (similarity and classification) in the CUIDADO project</i>, CUIDADO I.S.T.
99 Project Report 2004 (<a
100 href="http://www.ircam.fr/anasyn/peeters/ARTICLES/Peeters_2003_cuidadoaudiofeatures.pdf">pdf</a>)
101
102 \b \p centroid : Spectral centroid
103
104 The spectral centroid represents the barycenter of the spectrum.
105
106 \e Note: This function returns the result in bin. To get the spectral
107 centroid in Hz, aubio_bintofreq() should be used.
108
109 \b \p spread : Spectral spread
110
111 The spectral spread is the variance of the spectral distribution around its
112 centroid.
113
114 See also <a href="http://en.wikipedia.org/wiki/Standard_deviation">Standard
115 deviation</a> on Wikipedia.
116
117 \b \p skewness : Spectral skewness
118
119 Similarly, the skewness is computed from the third order moment of the
120 spectrum. A negative skewness indicates more energy on the lower part of the
121 spectrum. A positive skewness indicates more energy on the high frequency of
122 the spectrum.
123
124 See also <a href="http://en.wikipedia.org/wiki/Skewness">Skewness</a> on
125 Wikipedia.
126
127 \b \p kurtosis : Spectral kurtosis
128
129 The kurtosis is a measure of the flatness of the spectrum, computed from the
130 fourth order moment.
131
132 See also <a href="http://en.wikipedia.org/wiki/Kurtosis">Kurtosis</a> on
133 Wikipedia.
134
135 \b \p slope : Spectral slope
136
137 The spectral slope represents decreasing rate of the spectral amplitude,
138 computed using a linear regression.
139
140 \b \p decrease : Spectral decrease
141
142 The spectral decrease is another representation of the decreasing rate,
143 based on perceptual criteria.
144
145 \b \p rolloff : Spectral roll-off
146
147 This function returns the bin number below which 95% of the spectrum energy
148 is found.
149
150 \example spectral/test-specdesc.c
151
152 */
153
154
155 #ifndef AUBIO_SPECDESC_H
156 #define AUBIO_SPECDESC_H
157
158 #ifdef __cplusplus
159 extern "C" {
160 #endif
161
162 /** spectral description structure */
163 typedef struct _aubio_specdesc_t aubio_specdesc_t;
164
165 /** execute spectral description function on a spectral frame
166
167 Generic function to compute spectral description.
168
169 \param o spectral description object as returned by new_aubio_specdesc()
170 \param fftgrain input signal spectrum as computed by aubio_pvoc_do
171 \param desc output vector (one sample long, to send to the peak picking)
172
173 */
174 void aubio_specdesc_do (aubio_specdesc_t * o, const cvec_t * fftgrain,
175 fvec_t * desc);
176
177 /** creation of a spectral description object
178
179 \param method spectral description method
180 \param buf_size length of the input spectrum frame
181
182 The parameter \p method is a string that can be any of:
183
184 - onset novelty functions: `complex`, `energy`, `hfc`, `kl`, `mkl`,
185 `phase`, `specdiff`, `specflux`, `wphase`,
186
187 - spectral descriptors: `centroid`, `decrease`, `kurtosis`, `rolloff`,
188 `skewness`, `slope`, `spread`.
189
190 */
191 aubio_specdesc_t *new_aubio_specdesc (const char_t * method, uint_t buf_size);
192
193 /** deletion of a spectral descriptor
194
195 \param o spectral descriptor object as returned by new_aubio_specdesc()
196
197 */
198 void del_aubio_specdesc (aubio_specdesc_t * o);
199
200 #ifdef __cplusplus
201 }
202 #endif
203
204 #endif /* AUBIO_SPECDESC_H */
del_aubio_specdesc
void del_aubio_specdesc(aubio_specdesc_t *o)
deletion of a spectral descriptor
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
aubio_specdesc_t
struct _aubio_specdesc_t aubio_specdesc_t
spectral description structure
Definition: specdesc.h:163
fvec_t
Buffer for real data.
Definition: fvec.h:67
new_aubio_specdesc
aubio_specdesc_t * new_aubio_specdesc(const char_t *method, uint_t buf_size)
creation of a spectral description object
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
char_t
char char_t
character
Definition: types.h:64