2 Copyright (C) 2003-2015 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 functions useful in audio signal processing
25 #ifndef AUBIO_MUSICUTILS_H
26 #define AUBIO_MUSICUTILS_H
34 \param window_type type of the window to create
35 \param size length of the window to create (see fvec_set_window())
38 fvec_t *new_aubio_window (char_t * window_type, uint_t size);
40 /** set elements of a vector to window coefficients
42 \param window exsting ::fvec_t to use
43 \param window_type type of the window to create
45 List of available window types: "rectangle", "hamming", "hanning",
46 "hanningz", "blackman", "blackman_harris", "gaussian", "welch", "parzen",
49 "default" is equivalent to "hanningz".
53 - <a href="http://en.wikipedia.org/wiki/Window_function">Window
54 function</a> on Wikipedia
55 - Amalia de Götzen, Nicolas Bernardini, and Daniel Arfib. Traditional (?)
56 implementations of a phase vocoder: the tricks of the trade. In Proceedings of
57 the International Conference on Digital Audio Effects (DAFx-00), pages 37–44,
58 Uni- versity of Verona, Italy, 2000.
59 (<a href="http://www.cs.princeton.edu/courses/archive/spr09/cos325/Bernardini.pdf">
63 uint_t fvec_set_window (fvec_t * window, char_t * window_type);
65 /** compute the principal argument
67 This function maps the input phase to its corresponding value wrapped in the
68 range \f$ [-\pi, \pi] \f$.
70 \param phase unwrapped phase to map to the unit circle
72 \return equivalent phase wrapped to the unit circle
75 smpl_t aubio_unwrap2pi (smpl_t phase);
77 /** convert frequency bin to midi value */
78 smpl_t aubio_bintomidi (smpl_t bin, smpl_t samplerate, smpl_t fftsize);
80 /** convert midi value to frequency bin */
81 smpl_t aubio_miditobin (smpl_t midi, smpl_t samplerate, smpl_t fftsize);
83 /** convert frequency bin to frequency (Hz) */
84 smpl_t aubio_bintofreq (smpl_t bin, smpl_t samplerate, smpl_t fftsize);
86 /** convert frequency (Hz) to frequency bin */
87 smpl_t aubio_freqtobin (smpl_t freq, smpl_t samplerate, smpl_t fftsize);
89 /** convert frequency (Hz) to mel
91 \param freq input frequency, in Hz
95 Converts a scalar from the frequency domain to the mel scale using Slaney
96 Auditory Toolbox's implementation:
98 If \f$ f < 1000 \f$, \f$ m = 3 f / 200 \f$.
100 If \f$ f >= 1000 \f$, \f$ m = 1000 + 27 \frac{{ln}(f) - ln(1000))}
101 {{ln}(6400) - ln(1000)}
107 aubio_meltohz(), aubio_hztomel_htk().
110 smpl_t aubio_hztomel (smpl_t freq);
112 /** convert mel to frequency (Hz)
116 \return output frequency, in Hz
118 Converts a scalar from the mel scale to the frequency domain using Slaney
119 Auditory Toolbox's implementation:
121 If \f$ f < 1000 \f$, \f$ f = 200 m/3 \f$.
123 If \f$ f \geq 1000 \f$, \f$ f = 1000 + \left(\frac{6400}{1000}\right)
124 ^{\frac{m - 1000}{27}} \f$
129 aubio_hztomel(), aubio_meltohz_htk().
134 Malcolm Slaney, *Auditory Toolbox Version 2, Technical Report #1998-010*
135 https://engineering.purdue.edu/~malcolm/interval/1998-010/
138 smpl_t aubio_meltohz (smpl_t mel);
140 /** convert frequency (Hz) to mel
142 \param freq input frequency, in Hz
146 Converts a scalar from the frequency domain to the mel scale, using the
147 equation defined by O'Shaughnessy, as implemented in the HTK speech
150 \f$ m = 1127 + ln(1 + \frac{f}{700}) \f$
155 aubio_meltohz_htk(), aubio_hztomel().
160 Douglas O'Shaughnessy (1987). *Speech communication: human and machine*.
161 Addison-Wesley. p. 150. ISBN 978-0-201-16520-3.
163 HTK Speech Recognition Toolkit: http://htk.eng.cam.ac.uk/
166 smpl_t aubio_hztomel_htk (smpl_t freq);
168 /** convert mel to frequency (Hz)
172 \return output frequency, in Hz
174 Converts a scalar from the mel scale to the frequency domain, using the
175 equation defined by O'Shaughnessy, as implemented in the HTK speech
178 \f$ f = 700 * {e}^\left(\frac{f}{1127} - 1\right) \f$
183 aubio_hztomel_htk(), aubio_meltohz().
186 smpl_t aubio_meltohz_htk (smpl_t mel);
188 /** convert frequency (Hz) to midi value (0-128) */
189 smpl_t aubio_freqtomidi (smpl_t freq);
191 /** convert midi value (0-128) to frequency (Hz) */
192 smpl_t aubio_miditofreq (smpl_t midi);
194 /** clean up cached memory at the end of program
196 This function should be used at the end of programs to purge all cached
197 memory. So far it is only useful to clean FFTW's cache.
200 void aubio_cleanup (void);
202 /** zero-crossing rate (ZCR)
204 The zero-crossing rate is the number of times a signal changes sign,
205 divided by the length of this signal.
207 \param v vector to compute ZCR from
209 \return zero-crossing rate of v
212 smpl_t aubio_zero_crossing_rate (fvec_t * v);
214 /** compute sound level on a linear scale
216 This gives the average of the square amplitudes.
218 \param v vector to compute level from
223 smpl_t aubio_level_lin (const fvec_t * v);
225 /** compute sound pressure level (SPL) in dB
227 This quantity is often wrongly called 'loudness'.
229 This gives ten times the log10 of the average of the square amplitudes.
231 \param v vector to compute dB SPL from
233 \return level of v in dB SPL
236 smpl_t aubio_db_spl (const fvec_t * v);
238 /** check if buffer level in dB SPL is under a given threshold
240 \param v vector to get level from
241 \param threshold threshold in dB SPL
243 \return 0 if level is under the given threshold, 1 otherwise
246 uint_t aubio_silence_detection (const fvec_t * v, smpl_t threshold);
248 /** get buffer level if level >= threshold, 1. otherwise
250 \param v vector to get level from
251 \param threshold threshold in dB SPL
253 \return level in dB SPL if level >= threshold, 1. otherwise
256 smpl_t aubio_level_detection (const fvec_t * v, smpl_t threshold);
258 /** clamp the values of a vector within the range [-abs(max), abs(max)]
260 \param in vector to clamp
261 \param absmax maximum value over which input vector elements should be clamped
264 void fvec_clamp(fvec_t *in, smpl_t absmax);
270 #endif /* AUBIO_MUSICUTILS_H */