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/>.
23 Various math functions
25 \example test-mathutils.c
26 \example test-mathutils-window.c
34 #include "musicutils.h"
40 /** compute the mean of a vector
42 \param s vector to compute mean from
43 \return the mean of `v`
46 smpl_t fvec_mean (fvec_t * s);
48 /** find the max of a vector
50 \param s vector to get the max from
52 \return the value of the minimum of v
55 smpl_t fvec_max (fvec_t * s);
57 /** find the min of a vector
59 \param s vector to get the min from
61 \return the value of the maximum of v
64 smpl_t fvec_min (fvec_t * s);
66 /** find the index of the min of a vector
68 \param s vector to get the index from
70 \return the index of the minimum element of v
73 uint_t fvec_min_elem (fvec_t * s);
75 /** find the index of the max of a vector
77 \param s vector to get the index from
79 \return the index of the maximum element of v
82 uint_t fvec_max_elem (fvec_t * s);
84 /** swap the left and right halves of a vector
86 This function swaps the left part of the signal with the right part of the
89 \f$ a[0], a[1], ..., a[\frac{N}{2}], a[\frac{N}{2}+1], ..., a[N-1], a[N] \f$
93 \f$ a[\frac{N}{2}+1], ..., a[N-1], a[N], a[0], a[1], ..., a[\frac{N}{2}] \f$
95 This operation, known as 'fftshift' in the Matlab Signal Processing Toolbox,
96 can be used before computing the FFT to simplify the phase relationship of the
97 resulting spectrum. See Amalia de Götzen's paper referred to above.
100 void fvec_shift (fvec_t * v);
102 /** compute the sum of all elements of a vector
104 \param v vector to compute the sum of
109 smpl_t fvec_sum (fvec_t * v);
111 /** compute the energy of a vector
113 This function compute the sum of the squared elements of a vector, normalised
116 \param v vector to get the energy from
118 \return the energy of v
121 smpl_t fvec_local_energy (fvec_t * v);
123 /** compute the High Frequency Content of a vector
125 The High Frequency Content is defined as \f$ \sum_0^{N-1} (k+1) v[k] \f$.
127 \param v vector to get the energy from
132 smpl_t fvec_local_hfc (fvec_t * v);
134 /** computes the p-norm of a vector
136 Computes the p-norm of a vector for \f$ p = \alpha \f$
138 \f$ L^p = ||x||_p = (|x_1|^p + |x_2|^p + ... + |x_n|^p ) ^ \frac{1}{p} \f$
140 If p = 1, the result is the Manhattan distance.
142 If p = 2, the result is the Euclidean distance.
144 As p tends towards large values, \f$ L^p \f$ tends towards the maximum of the
149 - <a href="http://en.wikipedia.org/wiki/Lp_space">\f$L^p\f$ space</a> on
152 \param v vector to compute norm from
153 \param p order of the computed norm
155 \return the p-norm of v
158 smpl_t fvec_alpha_norm (fvec_t * v, smpl_t p);
160 /** alpha normalisation
162 This function divides all elements of a vector by the p-norm as computed by
165 \param v vector to compute norm from
166 \param p order of the computed norm
169 void fvec_alpha_normalise (fvec_t * v, smpl_t p);
171 /** add a constant to each elements of a vector
173 \param v vector to add constant to
174 \param c constant to add to v
177 void fvec_add (fvec_t * v, smpl_t c);
179 /** remove the minimum value of the vector to each elements
181 \param v vector to remove minimum from
184 void fvec_min_removal (fvec_t * v);
186 /** compute moving median threshold of a vector
188 This function computes the moving median threshold value of at the given
189 position of a vector, taking the median among post elements before and up to
190 pre elements after pos.
192 \param v input vector
193 \param tmp temporary vector of length post+1+pre
194 \param post length of causal part to take before pos
195 \param pre length of anti-causal part to take after pos
196 \param pos index to compute threshold for
198 \return moving median threshold value
201 smpl_t fvec_moving_thres (fvec_t * v, fvec_t * tmp, uint_t post, uint_t pre,
204 /** apply adaptive threshold to a vector
206 For each points at position p of an input vector, this function remove the
207 moving median threshold computed at p.
209 \param v input vector
210 \param tmp temporary vector of length post+1+pre
211 \param post length of causal part to take before pos
212 \param pre length of anti-causal part to take after pos
215 void fvec_adapt_thres (fvec_t * v, fvec_t * tmp, uint_t post, uint_t pre);
217 /** returns the median of a vector
219 The QuickSelect routine is based on the algorithm described in "Numerical
220 recipes in C", Second Edition, Cambridge University Press, 1992, Section 8.5,
223 This implementation of the QuickSelect routine is based on Nicolas
224 Devillard's implementation, available at http://ndevilla.free.fr/median/median/
225 and in the Public Domain.
227 \param v vector to get median from
229 \return the median of v
232 smpl_t fvec_median (fvec_t * v);
234 /** finds exact peak index by quadratic interpolation
236 See [Quadratic Interpolation of Spectral
237 Peaks](https://ccrma.stanford.edu/~jos/sasp/Quadratic_Peak_Interpolation.html),
238 by Julius O. Smith III
240 \f$ p_{frac} = \frac{1}{2} \frac {x[p-1] - x[p+1]} {x[p-1] - 2 x[p] + x[p+1]} \in [ -.5, .5] \f$
242 \param x vector to get the interpolated peak position from
243 \param p index of the peak in vector `x`
244 \return \f$ p + p_{frac} \f$ exact peak position of interpolated maximum or minimum
247 smpl_t fvec_quadratic_peak_pos (fvec_t * x, uint_t p);
249 /** Quadratic interpolation using Lagrange polynomial.
251 Inspired from ``Comparison of interpolation algorithms in real-time sound
252 processing'', Vladimir Arnost,
254 \param s0,s1,s2 are 3 consecutive samples of a curve
255 \param pf is the floating point index [0;2]
257 \return \f$ s0 + (pf/2.)*((pf-3.)*s0-2.*(pf-2.)*s1+(pf-1.)*s2); \f$
260 smpl_t aubio_quadfrac (smpl_t s0, smpl_t s1, smpl_t s2, smpl_t pf);
262 /** return 1 if v[p] is a peak and positive, 0 otherwise
264 This function returns 1 if a peak is found at index p in the vector v. The
265 peak is defined as follows:
271 \param v input vector
272 \param p position of supposed for peak
274 \return 1 if a peak is found, 0 otherwise
277 uint_t fvec_peakpick (fvec_t * v, uint_t p);
279 /** return 1 if a is a power of 2, 0 otherwise */
280 uint_t aubio_is_power_of_two(uint_t a);
282 /** return the next power of power of 2 greater than a */
283 uint_t aubio_next_power_of_two(uint_t a);
285 /** compute normalised autocorrelation function
287 \param input vector to compute autocorrelation from
288 \param output vector to store autocorrelation function to
291 void aubio_autocorr (fvec_t * input, fvec_t * output);