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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 * power_meter.h
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5 *
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6 * Written by Steve Underwood <steveu@coppice.org>
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7 *
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8 * Copyright (C) 2003 Steve Underwood
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9 *
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10 * All rights reserved.
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11 *
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12 * This program is free software; you can redistribute it and/or modify
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13 * it under the terms of the GNU General Public License version 2, as
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14 * published by the Free Software Foundation.
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15 *
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16 * This program is distributed in the hope that it will be useful,
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17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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19 * GNU General Public License for more details.
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20 *
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21 * You should have received a copy of the GNU General Public License
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22 * along with this program; if not, write to the Free Software
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23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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24 *
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25 * $Id: power_meter.h,v 1.8 2006/10/24 13:45:28 steveu Exp $
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26 */
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27
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28 #if !defined(_POWER_METER_H_)
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29 #define _POWER_METER_H_
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30
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31 /*! \page power_meter_page Power metering
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32
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33 \section power_meter_page_sec_1 What does it do?
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34 The power metering module implements a simple IIR type running power meter. The damping
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35 factor of the IIR is selectable when the meter instance is created.
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36
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37 Note that the definition of dBOv is quite vague in most places - is it peak since wave,
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38 peak square wave, etc.? This code is based on the well defined wording in RFC3389:
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39
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40 "For example, in the case of a u-law system, the reference would be a square wave with
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41 values +/-8031, and this square wave represents 0dBov. This translates into 6.18dBm0".
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42
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43 \section power_meter_page_sec_2 How does it work?
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44 */
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45
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46 /*!
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47 Power meter descriptor. This defines the working state for a
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48 single instance of a power measurement device.
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49 */
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50 typedef struct
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51 {
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52 int shift;
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53
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54 int32_t reading;
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55 } power_meter_t;
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56
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57 #ifdef __cplusplus
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58 extern "C" {
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59 #endif
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60
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61 /*! Initialise a power meter context.
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62 \brief Initialise a power meter context.
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63 \param s The power meter context.
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64 \param shift The shift to be used by the IIR filter.
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65 \return The power meter context. */
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66 power_meter_t *power_meter_init(power_meter_t *s, int shift);
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67
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68 /*! Change the damping factor of a power meter context.
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69 \brief Change the damping factor of a power meter context.
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70 \param s The power meter context.
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71 \param shift The new shift to be used by the IIR filter.
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72 \return The power meter context. */
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73 power_meter_t *power_meter_damping(power_meter_t *s, int shift);
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74
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75 /*! Update a power meter.
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76 \brief Update a power meter.
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77 \param s The power meter context.
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78 \param amp The amplitude of the new audio sample.
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79 \return The current power meter reading. */
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80 int32_t power_meter_update(power_meter_t *s, int16_t amp);
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81
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82 /*! Get the current power meter reading, in dBm0.
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83 \brief Get the current power meter reading, in dBm0.
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84 \param s The power meter context.
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85 \return The current power meter reading, in dBm0. */
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86 float power_meter_dbm0(power_meter_t *s);
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87
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88 /*! Get the current power meter reading, in dBOv.
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89 \brief Get the current power meter reading, in dBOv.
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90 \param s The power meter context.
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91 \return The current power meter reading, in dBOv. */
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92 float power_meter_dbov(power_meter_t *s);
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93
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94 /*! Get the power meter reading which represents a specified power level in dBm0.
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95 \brief Get the current power meter reading, in dBm0.
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96 \param level A power level, in dB0m.
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97 \return The equivalent power meter reading. */
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98 int32_t power_meter_level_dbm0(float level);
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99
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100 /*! Get the power meter reading which represents a specified power level in dBOv.
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101 \brief Get the current power meter reading, in dBOv.
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102 \param level A power level, in dBOv.
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103 \return The equivalent power meter reading. */
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104 int32_t power_meter_level_dbov(float level);
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105
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106 #ifdef __cplusplus
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107 }
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108 #endif
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109
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110 #endif
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111 /*- End of file ------------------------------------------------------------*/
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