1 | /* |
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2 | Copyright (C) 2003-2015 Paul Brossier <piem@aubio.org> |
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3 | |
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4 | This file is part of aubio. |
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5 | |
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6 | aubio is free software: you can redistribute it and/or modify |
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7 | it under the terms of the GNU General Public License as published by |
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8 | the Free Software Foundation, either version 3 of the License, or |
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9 | (at your option) any later version. |
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10 | |
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11 | aubio is distributed in the hope that it will be useful, |
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12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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14 | GNU General Public License for more details. |
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15 | |
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16 | You should have received a copy of the GNU General Public License |
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17 | along with aubio. If not, see <http://www.gnu.org/licenses/>. |
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18 | |
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19 | */ |
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20 | |
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21 | #ifndef AUBIO_FILTER_BIQUAD_H |
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22 | #define AUBIO_FILTER_BIQUAD_H |
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23 | |
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24 | /** \file |
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25 | |
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26 | Second order Infinite Impulse Response filter |
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27 | |
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28 | This file implements a normalised biquad filter (second order IIR): |
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29 | |
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30 | \f$ y[n] = b_0 x[n] + b_1 x[n-1] + b_2 x[n-2] - a_1 y[n-1] - a_2 y[n-2] \f$ |
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31 | |
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32 | The filtfilt version runs the filter twice, forward and backward, to |
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33 | compensate the phase shifting of the forward operation. |
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34 | |
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35 | See also <a href="http://en.wikipedia.org/wiki/Digital_biquad_filter">Digital |
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36 | biquad filter</a> on wikipedia. |
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37 | |
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38 | \example temporal/test-biquad.c |
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39 | |
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40 | */ |
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41 | |
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42 | #ifdef __cplusplus |
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43 | extern "C" { |
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44 | #endif |
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45 | |
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46 | /** set coefficients of a biquad filter |
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47 | |
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48 | \param f filter object as returned by new_aubio_filter() |
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49 | \param b0 forward filter coefficient |
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50 | \param b1 forward filter coefficient |
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51 | \param b2 forward filter coefficient |
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52 | \param a1 feedback filter coefficient |
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53 | \param a2 feedback filter coefficient |
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54 | |
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55 | */ |
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56 | uint_t aubio_filter_set_biquad (aubio_filter_t * f, lsmp_t b0, lsmp_t b1, |
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57 | lsmp_t b2, lsmp_t a1, lsmp_t a2); |
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58 | |
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59 | /** create biquad filter with `b0`, `b1`, `b2`, `a1`, `a2` coeffs |
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60 | |
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61 | \param b0 forward filter coefficient |
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62 | \param b1 forward filter coefficient |
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63 | \param b2 forward filter coefficient |
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64 | \param a1 feedback filter coefficient |
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65 | \param a2 feedback filter coefficient |
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66 | |
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67 | */ |
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68 | aubio_filter_t *new_aubio_filter_biquad (lsmp_t b0, lsmp_t b1, lsmp_t b2, |
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69 | lsmp_t a1, lsmp_t a2); |
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70 | |
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71 | #ifdef __cplusplus |
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72 | } |
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73 | #endif |
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74 | |
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75 | #endif /* AUBIO_FILTER_BIQUAD_H */ |
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