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/>.
26 Create a C-weighting filter
28 This file creates a C-weighting digital filter, which reduces low and high
29 frequencies and enhance the middle ones to reflect the ability of the human
32 The implementation is based on the following standard:
34 - IEC/CD 1672: Electroacoustics-Sound Level Meters, IEC, Geneva, Nov. 1996,
35 for A- and C-weighting filters.
39 - <a href="http://en.wikipedia.org/wiki/A-weighting">A-Weighting on
41 - <a href="http://en.wikipedia.org/wiki/Weighting_filter">Weighting filter on
43 - <a href="http://www.mathworks.com/matlabcentral/fileexchange/69">Christophe
44 Couvreur's 'octave' toolbox</a>
46 The coefficients in this file have been computed using Christophe Couvreur's
47 scripts in octave 3.0 (debian package 1:3.0.5-6+b2 with octave-signal
48 1.0.9-1+b1 on i386), with <pre> [b, a] = cdsign(1/Fs) </pre> for various
49 sampling frequencies (8000, 11025, 16000, 22050, 24000, 32000, 44100, 48000,
50 88200, 96000, and 192000 Hz).
52 The sampling frequency should normally be higher than 20kHz, but most common
53 file sampling rates have been included for completeness.
61 /** create new C-design filter
63 \param samplerate sampling frequency of the signal to filter. Should be one of
64 8000, 11025, 16000, 22050, 24000, 32000, 44100, 48000, 88200, 96000, and
66 \param channels number of channels to allocate
68 \return a new filter object
71 aubio_filter_t * new_aubio_filter_c_weighting (uint_t samplerate, uint_t channels);
73 /** set feedback and feedforward coefficients of a C-weighting filter
75 \param f filter object to get coefficients from
78 uint_t aubio_filter_set_c_weighting (aubio_filter_t *f);
84 #endif /* _CDESIGN_H */