1 | /* |
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2 | Copyright (C) 2003 Paul Brossier |
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3 | |
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4 | This program is free software; you can redistribute it and/or modify |
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5 | it under the terms of the GNU General Public License as published by |
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6 | the Free Software Foundation; either version 2 of the License, or |
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7 | (at your option) any later version. |
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8 | |
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9 | This program is distributed in the hope that it will be useful, |
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10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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12 | GNU General Public License for more details. |
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13 | |
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14 | You should have received a copy of the GNU General Public License |
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15 | along with this program; if not, write to the Free Software |
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16 | Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
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17 | |
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18 | */ |
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19 | |
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20 | #ifndef BIQUAD_H |
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21 | #define BIQUAD_H |
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22 | |
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23 | /** \file |
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24 | |
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25 | Second order Infinite Impulse Response filter |
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26 | |
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27 | This file implements a normalised biquad filter (second order IIR): |
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28 | |
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29 | \f$ y[n] = b_1 x[n] + b_2 x[n-1] + b_3 x[n-2] - a_2 y[n-1] - a_3 y[n-2] \f$ |
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30 | |
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31 | The filtfilt version runs the filter twice, forward and backward, to |
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32 | compensate the phase shifting of the forward operation. |
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33 | |
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34 | */ |
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35 | |
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36 | #ifdef __cplusplus |
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37 | extern "C" { |
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38 | #endif |
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39 | |
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40 | /** biquad filter object */ |
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41 | typedef struct _aubio_biquad_t aubio_biquad_t; |
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42 | |
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43 | /** filter input vector |
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44 | |
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45 | \param b biquad object as returned by new_aubio_biquad |
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46 | \param in input vector to filter |
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47 | |
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48 | */ |
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49 | void aubio_biquad_do(aubio_biquad_t * b, fvec_t * in); |
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50 | /** filter input vector forward and backward |
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51 | |
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52 | \param b biquad object as returned by new_aubio_biquad |
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53 | \param in input vector to filter |
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54 | \param tmp memory space to use for computation |
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55 | |
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56 | */ |
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57 | void aubio_biquad_do_filtfilt(aubio_biquad_t * b, fvec_t * in, fvec_t * tmp); |
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58 | /** create new biquad filter |
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59 | |
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60 | \param b1 forward filter coefficient |
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61 | \param b2 forward filter coefficient |
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62 | \param b3 forward filter coefficient |
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63 | \param a2 feedback filter coefficient |
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64 | \param a3 feedback filter coefficient |
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65 | |
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66 | */ |
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67 | aubio_biquad_t * new_aubio_biquad(lsmp_t b1, lsmp_t b2, lsmp_t b3, lsmp_t a2, lsmp_t a3); |
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68 | |
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69 | /** delete biquad filter |
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70 | |
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71 | \param b biquad object to delete |
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72 | |
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73 | */ |
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74 | void del_aubio_biquad(aubio_biquad_t * b); |
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75 | |
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76 | #ifdef __cplusplus |
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77 | } |
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78 | #endif |
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79 | |
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80 | #endif /*BIQUAD_H*/ |
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