2 Copyright (C) 2003-2009 Paul Brossier <piem@aubio.org>
4 This file is part of aubio.
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.
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.
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/>.
22 * various math functions
36 - <a href="http://en.wikipedia.org/wiki/Window_function">Window
37 function</a> on Wikipedia
38 - Amalia de Götzen, Nicolas Bernardini, and Daniel Arfib. Traditional (?)
39 implementations of a phase vocoder: the tricks of the trade. In Proceedings of
40 the International Conference on Digital Audio Effects (DAFx-00), pages 37–44,
41 Uni- versity of Verona, Italy, 2000.
42 (<a href="http://profs.sci.univr.it/%7Edafx/Final-Papers/ps/Bernardini.ps.gz">
46 fvec_t *new_aubio_window (char_t * window_type, uint_t size);
48 /** compute the principal argument
50 This function maps the input phase to its corresponding value wrapped in the
51 range \f$ [-\pi, \pi] \f$.
53 \param phase unwrapped phase to map to the unit circle
55 \return equivalent phase wrapped to the unit circle
58 smpl_t aubio_unwrap2pi (smpl_t phase);
60 /** compute the mean of a vector
62 \param s vector to compute norm from
67 smpl_t fvec_mean (fvec_t * s);
69 /** find the max of a vector
71 \param s vector to get the max from
73 \return the value of the minimum of v
76 smpl_t fvec_max (fvec_t * s);
78 /** find the min of a vector
80 \param s vector to get the min from
82 \return the value of the maximum of v
85 smpl_t fvec_min (fvec_t * s);
87 /** find the index of the min of a vector
89 \param s vector to get the index from
91 \return the index of the minimum element of v
94 uint_t fvec_min_elem (fvec_t * s);
96 /** find the index of the max of a vector
98 \param s vector to get the index from
100 \return the index of the maximum element of v
103 uint_t fvec_max_elem (fvec_t * s);
105 /** swap the left and right halves of a vector
107 This function swaps the left part of the signal with the right part of the
110 \f$ a[0], a[1], ..., a[\frac{N}{2}], a[\frac{N}{2}+1], ..., a[N-1], a[N] \f$
114 \f$ a[\frac{N}{2}+1], ..., a[N-1], a[N], a[0], a[1], ..., a[\frac{N}{2}] \f$
116 This operation, known as 'fftshift' in the Matlab Signal Processing Toolbox,
117 can be used before computing the FFT to simplify the phase relationship of the
118 resulting spectrum. See Amalia de Götzen's paper referred to above.
121 void fvec_shift (fvec_t * v);
123 /** compute the sum of all elements of a vector
125 \param v vector to compute the sum of
130 smpl_t fvec_sum (fvec_t * v);
132 /** compute the energy of a vector
134 This function compute the sum of the squared elements of a vector.
136 \param v vector to get the energy from
138 \return the energy of v
141 smpl_t fvec_local_energy (fvec_t * v);
143 /** compute the High Frequency Content of a vector
145 The High Frequency Content is defined as \f$ \sum_0^{N-1} (k+1) v[k] \f$.
147 \param v vector to get the energy from
152 smpl_t fvec_local_hfc (fvec_t * v);
154 /** computes the p-norm of a vector
156 Computes the p-norm of a vector for \f$ p = \alpha \f$
158 \f$ L^p = ||x||_p = (|x_1|^p + |x_2|^p + ... + |x_n|^p ) ^ \frac{1}{p} \f$
160 If p = 1, the result is the Manhattan distance.
162 If p = 2, the result is the Euclidean distance.
164 As p tends towards large values, \f$ L^p \f$ tends towards the maximum of the
169 - <a href="http://en.wikipedia.org/wiki/Lp_space">\f$L^p\f$ space</a> on
172 \param v vector to compute norm from
173 \param p order of the computed norm
175 \return the p-norm of v
178 smpl_t fvec_alpha_norm (fvec_t * v, smpl_t p);
180 /** alpha normalisation
182 This function divides all elements of a vector by the p-norm as computed by
185 \param v vector to compute norm from
186 \param p order of the computed norm
189 void fvec_alpha_normalise (fvec_t * v, smpl_t p);
191 /** add a constant to each elements of a vector
193 \param v vector to add constant to
194 \param c constant to add to v
197 void fvec_add (fvec_t * v, smpl_t c);
199 /** remove the minimum value of the vector to each elements
201 \param v vector to remove minimum from
204 void fvec_min_removal (fvec_t * v);
206 /** compute moving median theshold of a vector
208 This function computes the moving median threshold value of at the given
209 position of a vector, taking the median amongs post elements before and up to
210 pre elements after pos.
212 \param v input vector
213 \param tmp temporary vector of length post+1+pre
214 \param post length of causal part to take before pos
215 \param pre length of anti-causal part to take after pos
216 \param pos index to compute threshold for
218 \return moving median threshold value
221 smpl_t fvec_moving_thres (fvec_t * v, fvec_t * tmp, uint_t post, uint_t pre,
224 /** apply adaptive threshold to a vector
226 For each points at position p of an input vector, this function remove the
227 moving median threshold computed at p.
229 \param v input vector
230 \param tmp temporary vector of length post+1+pre
231 \param post length of causal part to take before pos
232 \param pre length of anti-causal part to take after pos
235 void fvec_adapt_thres (fvec_t * v, fvec_t * tmp, uint_t post, uint_t pre);
237 /** returns the median of a vector
239 The QuickSelect routine is based on the algorithm described in "Numerical
240 recipes in C", Second Edition, Cambridge University Press, 1992, Section 8.5,
243 This implementation of the QuickSelect routine is based on Nicolas
244 Devillard's implementation, available at http://ndevilla.free.fr/median/median/
245 and in the Public Domain.
247 \param v vector to get median from
249 \return the median of v
252 smpl_t fvec_median (fvec_t * v);
254 /** finds exact peak index by quadratic interpolation*/
255 smpl_t fvec_quadint (fvec_t * x, uint_t pos, uint_t span);
257 /** Quadratic interpolation using Lagrange polynomial.
259 Inspired from ``Comparison of interpolation algorithms in real-time sound
260 processing'', Vladimir Arnost,
262 \param s0,s1,s2 are 3 consecutive samples of a curve
263 \param pf is the floating point index [0;2]
265 \return s0 + (pf/2.)*((pf-3.)*s0-2.*(pf-2.)*s1+(pf-1.)*s2);
268 smpl_t aubio_quadfrac (smpl_t s0, smpl_t s1, smpl_t s2, smpl_t pf);
270 /** return 1 if v[p] is a peak and positive, 0 otherwise
272 This function returns 1 if a peak is found at index p in the vector v. The
273 peak is defined as follows:
279 \param v input vector
280 \param p position of supposed for peak
282 \return 1 if a peak is found, 0 otherwise
285 uint_t fvec_peakpick (fvec_t * v, uint_t p);
287 /** convert frequency bin to midi value */
288 smpl_t aubio_bintomidi (smpl_t bin, smpl_t samplerate, smpl_t fftsize);
290 /** convert midi value to frequency bin */
291 smpl_t aubio_miditobin (smpl_t midi, smpl_t samplerate, smpl_t fftsize);
293 /** convert frequency bin to frequency (Hz) */
294 smpl_t aubio_bintofreq (smpl_t bin, smpl_t samplerate, smpl_t fftsize);
296 /** convert frequency (Hz) to frequency bin */
297 smpl_t aubio_freqtobin (smpl_t freq, smpl_t samplerate, smpl_t fftsize);
299 /** convert frequency (Hz) to midi value (0-128) */
300 smpl_t aubio_freqtomidi (smpl_t freq);
302 /** convert midi value (0-128) to frequency (Hz) */
303 smpl_t aubio_miditofreq (smpl_t midi);
305 /** return 1 if a is a power of 2, 0 otherwise */
306 uint_t aubio_is_power_of_two(uint_t a);
308 /** return the next power of power of 2 greater than a */
309 uint_t aubio_next_power_of_two(uint_t a);
311 /** compute sound pressure level (SPL) in dB
313 This quantity is often wrongly called 'loudness'.
315 \param v vector to compute dB SPL from
317 \return level of v in dB SPL
320 smpl_t aubio_db_spl (fvec_t * v);
322 /** check if buffer level in dB SPL is under a given threshold
324 \param v vector to get level from
325 \param threshold threshold in dB SPL
327 \return 0 if level is under the given threshold, 1 otherwise
330 uint_t aubio_silence_detection (fvec_t * v, smpl_t threshold);
332 /** get buffer level if level >= threshold, 1. otherwise
334 \param v vector to get level from
335 \param threshold threshold in dB SPL
337 \return level in dB SPL if level >= threshold, 1. otherwise
340 smpl_t aubio_level_detection (fvec_t * v, smpl_t threshold);
342 /** compute normalised autocorrelation function
344 \param input vector to compute autocorrelation from
345 \param output vector to store autocorrelation function to
348 void aubio_autocorr (fvec_t * input, fvec_t * output);
350 /** zero-crossing rate (ZCR)
352 The zero-crossing rate is the number of times a signal changes sign,
353 divided by the length of this signal.
355 \param v vector to compute ZCR from
357 \return zero-crossing rate of v
360 smpl_t aubio_zero_crossing_rate (fvec_t * v);
362 /** clean up cached memory at the end of program
364 This function should be used at the end of programs to purge all cached
365 memory. So far it is only useful to clean FFTW's cache.
368 void aubio_cleanup (void);