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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_generate.h - General telephony tone generation, and specific
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5 * generation of Bell MF, MFC/R2 and network supervisory tones.
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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 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_generate.h,v 1.24 2006/11/24 12:34:55 steveu Exp $
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27 */
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28
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29 /*! \file */
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30
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31 #if !defined(_TONE_GENERATE_H_)
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32 #define _TONE_GENERATE_H_
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33
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34 /*! \page tone_generation_page Tone generation
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35 \section tone_generation_page_sec_1 What does it do?
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36 The tone generation module provides for the generation of cadenced tones,
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37 suitable for a wide range of telephony applications.
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38
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39 \section tone_generation_page_sec_2 How does it work?
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40 Oscillators are a problem. They oscillate due to instability, and yet we need
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41 them to behave in a stable manner. A look around the web will reveal many papers
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42 on this subject. Many describe rather complex solutions to the problem. However,
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43 we are only concerned with telephony applications. It is possible to generate
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44 the tones we need with a very simple efficient scheme. It is also practical to
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45 use an exhaustive test to prove the oscillator is stable under all the
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46 conditions in which we will use it.
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47 */
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48
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49 /*!
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50 Cadenced dual tone generator descriptor.
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51 */
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52 typedef struct
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53 {
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54 int32_t phase_rate[2];
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55 float gain[2];
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56 int modulate;
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57
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58 int duration[4];
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59
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60 int repeat;
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61 } tone_gen_descriptor_t;
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62
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63 /*!
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64 Cadenced dual tone generator state descriptor. This defines the state of
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65 a single working instance of a generator.
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66 */
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67 typedef struct
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68 {
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69 int32_t phase_rate[2];
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70 float gain[2];
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71 int modulate;
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72
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73 uint32_t phase[2];
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74
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75 int duration[4];
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76
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77 int repeat;
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78
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79 int current_section;
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80 int current_position;
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81 } tone_gen_state_t;
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82
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83 typedef struct
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84 {
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85 /*! First freq */
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86 int f1;
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87 /*! Second freq. 0 for none. Negative for an AM modulation tone. */
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88 int f2;
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89 /*! Level of the first freq (dBm0) */
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90 int8_t level1;
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91 /*! Level of the second freq (dBm0), or % modulation for AM */
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92 int8_t level2;
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93 /*! Tone on time (ms) */
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94 uint16_t on_time1;
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95 /*! Minimum post tone silence (ms) */
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96 uint16_t off_time1;
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97 /*! Tone on time (ms) */
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98 uint16_t on_time2;
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99 /*! Minimum post tone silence (ms) */
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100 uint16_t off_time2;
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101 /*! TRUE if cyclic tone, FALSE for one shot. */
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102 int8_t repeat;
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103 } cadenced_tone_t;
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104
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105 #ifdef __cplusplus
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106 extern "C" {
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107 #endif
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108
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109 void make_tone_descriptor(tone_gen_descriptor_t *desc, cadenced_tone_t *tone);
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110
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111 /*! Create a tone generator descriptor
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112 \brief Create a tone generator descriptor
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113 \param s The descriptor
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114 \param f1 The first frequency, in Hz
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115 \param l1 The level of the first frequency, in dBm0
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116 \param f2 0 for no second frequency, a positive number for the second frequency,
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117 in Hz, or a negative number for an AM modulation frequency, in Hz
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118 \param l2 The level of the second frequency, in dBm0, or the percentage modulation depth
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119 for an AM modulated tone.
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120 \param d1 x
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121 \param d2 x
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122 \param d3 x
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123 \param d4 x
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124 \param repeat x */
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125 void make_tone_gen_descriptor(tone_gen_descriptor_t *s,
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126 int f1,
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127 int l1,
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128 int f2,
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129 int l2,
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130 int d1,
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131 int d2,
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132 int d3,
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133 int d4,
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134 int repeat);
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135
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136 void tone_gen_init(tone_gen_state_t *s, tone_gen_descriptor_t *t);
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137
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138 int tone_gen(tone_gen_state_t *s, int16_t amp[], int max_samples);
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139
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140 #ifdef __cplusplus
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141 }
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142 #endif
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143
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144 #endif
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145 /*- End of file ------------------------------------------------------------*/
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