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5
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1 /*
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2 * SpanDSP - a series of DSP components for telephony
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3 *
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4 * tone_detect.h - General telephony tone detection, and specific
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5 * detection of Bell MF, and MFC/R2.
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6 *
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7 * Written by Steve Underwood <steveu@coppice.org>
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8 *
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9 * Copyright (C) 2001, 2005 Steve Underwood
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10 *
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11 * All rights reserved.
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12 *
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13 * This program is free software; you can redistribute it and/or modify
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14 * it under the terms of the GNU General Public License version 2, as
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15 * published by the Free Software Foundation.
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16 *
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17 * This program is distributed in the hope that it will be useful,
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18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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20 * GNU General Public License for more details.
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21 *
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22 * You should have received a copy of the GNU General Public License
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23 * along with this program; if not, write to the Free Software
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24 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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25 *
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26 * $Id: tone_detect.h,v 1.27 2006/10/24 13:45:28 steveu Exp $
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27 */
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28
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29 #if !defined(_TONE_DETECT_H_)
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30 #define _TONE_DETECT_H_
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31
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32 /*!
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33 Floating point Goertzel filter descriptor.
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34 */
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35 typedef struct
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36 {
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37 float fac;
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38 int samples;
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39 } goertzel_descriptor_t;
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40
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41 /*!
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42 Floating point Goertzel filter state descriptor.
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43 */
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44 typedef struct
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45 {
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46 float v2;
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47 float v3;
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48 float fac;
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49 int samples;
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50 int current_sample;
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51 } goertzel_state_t;
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52
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53 #ifdef __cplusplus
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54 extern "C" {
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55 #endif
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56
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57 /*! \brief Create a descriptor for use with either a Goertzel transform */
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58 void make_goertzel_descriptor(goertzel_descriptor_t *t,
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59 float freq,
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60 int samples);
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61
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62 /*! \brief Initialise the state of a Goertzel transform.
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63 \param s The Goertzel context. If NULL, a context is allocated with malloc.
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64 \param t The Goertzel descriptor.
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65 \return A pointer to the Goertzel state. */
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66 goertzel_state_t *goertzel_init(goertzel_state_t *s,
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67 goertzel_descriptor_t *t);
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68
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69 /*! \brief Reset the state of a Goertzel transform.
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70 \param s The Goertzel context.
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71 \param t The Goertzel descriptor.
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72 \return A pointer to the Goertzel state. */
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73 void goertzel_reset(goertzel_state_t *s);
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74
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75 /*! \brief Update the state of a Goertzel transform.
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76 \param s The Goertzel context
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77 \param amp The samples to be transformed
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78 \param samples The number of samples
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79 \return The number of samples unprocessed */
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80 int goertzel_update(goertzel_state_t *s,
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81 const int16_t amp[],
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82 int samples);
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83
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84 /*! \brief Evaluate the final result of a Goertzel transform.
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85 \param s The Goertzel context
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86 \return The result of the transform. */
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87 float goertzel_result(goertzel_state_t *s);
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88
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89 /*! \brief Update the state of a Goertzel transform.
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90 \param s The Goertzel context
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91 \param amp The sample to be transformed. */
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92 static __inline__ void goertzel_sample(goertzel_state_t *s, int16_t amp)
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93 {
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94 float v1;
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95
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96 v1 = s->v2;
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97 s->v2 = s->v3;
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98 s->v3 = s->fac*s->v2 - v1 + amp;
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99 s->current_sample++;
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100 }
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101 /*- End of function --------------------------------------------------------*/
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102
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103 #ifdef __cplusplus
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104 }
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105 #endif
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106
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107 #endif
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108 /*- End of file ------------------------------------------------------------*/
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