power_meter.h

00001 /*
00002  * SpanDSP - a series of DSP components for telephony
00003  *
00004  * power_meter.h
00005  *
00006  * Written by Steve Underwood <steveu@coppice.org>
00007  *
00008  * Copyright (C) 2003 Steve Underwood
00009  *
00010  * All rights reserved.
00011  *
00012  * This program is free software; you can redistribute it and/or modify
00013  * it under the terms of the GNU Lesser General Public License version 2.1,
00014  * as published by the Free Software Foundation.
00015  *
00016  * This program is distributed in the hope that it will be useful,
00017  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00018  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00019  * GNU Lesser General Public License for more details.
00020  *
00021  * You should have received a copy of the GNU Lesser General Public
00022  * License along with this program; if not, write to the Free Software
00023  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
00024  *
00025  * $Id: power_meter.h,v 1.19 2009/05/19 14:15:09 steveu Exp $
00026  */
00027 
00028 #if !defined(_POWER_METER_H_)
00029 #define _POWER_METER_H_
00030 
00031 /*! \page power_meter_page Power metering
00032 
00033 \section power_meter_page_sec_1 What does it do?
00034 The power metering module implements a simple IIR type running power meter. The damping
00035 factor of the IIR is selectable when the meter instance is created.
00036 
00037 Note that the definition of dBOv is quite vague in most places - is it peak since wave,
00038 peak square wave, etc.? This code is based on the well defined wording in RFC3389:
00039 
00040 "For example, in the case of a u-law system, the reference would be a square wave with
00041 values +/-8031, and this square wave represents 0dBov.  This translates into 6.18dBm0".
00042 
00043 \section power_meter_page_sec_2 How does it work?
00044 */
00045 
00046 /*!
00047     Power meter descriptor. This defines the working state for a
00048     single instance of a power measurement device.
00049 */
00050 typedef struct
00051 {
00052     /*! The shift factor, which controls the damping of the power meter. */
00053     int shift;
00054 
00055     /*! The current power reading. */
00056     int32_t reading;
00057 } power_meter_t;
00058 
00059 typedef struct
00060 {
00061     power_meter_t short_term;
00062     power_meter_t medium_term;
00063     int signal_present;
00064     int32_t surge;
00065     int32_t sag;
00066     int32_t min;
00067 } power_surge_detector_state_t;
00068 
00069 #if defined(__cplusplus)
00070 extern "C"
00071 {
00072 #endif
00073 
00074 /*! Initialise a power meter context.
00075     \brief Initialise a power meter context.
00076     \param s The power meter context.
00077     \param shift The shift to be used by the IIR filter.
00078     \return The power meter context. */
00079 SPAN_DECLARE(power_meter_t *) power_meter_init(power_meter_t *s, int shift);
00080 
00081 SPAN_DECLARE(int) power_meter_release(power_meter_t *s);
00082 
00083 SPAN_DECLARE(int) power_meter_free(power_meter_t *s);
00084 
00085 /*! Change the damping factor of a power meter context.
00086     \brief Change the damping factor of a power meter context.
00087     \param s The power meter context.
00088     \param shift The new shift to be used by the IIR filter.
00089     \return The power meter context. */
00090 SPAN_DECLARE(power_meter_t *) power_meter_damping(power_meter_t *s, int shift);
00091 
00092 /*! Update a power meter.
00093     \brief Update a power meter.
00094     \param s The power meter context.
00095     \param amp The amplitude of the new audio sample.
00096     \return The current power meter reading. */
00097 SPAN_DECLARE(int32_t) power_meter_update(power_meter_t *s, int16_t amp);
00098 
00099 /*! Get the current power meter reading.
00100     \brief Get the current power meter reading.
00101     \param s The power meter context.
00102     \return The current power meter reading. */
00103 SPAN_DECLARE(int32_t) power_meter_current(power_meter_t *s);
00104 
00105 /*! Get the current power meter reading, in dBm0.
00106     \brief Get the current power meter reading, in dBm0.
00107     \param s The power meter context.
00108     \return The current power meter reading, in dBm0. */
00109 SPAN_DECLARE(float) power_meter_current_dbm0(power_meter_t *s);
00110 
00111 /*! Get the current power meter reading, in dBOv.
00112     \brief Get the current power meter reading, in dBOv.
00113     \param s The power meter context.
00114     \return The current power meter reading, in dBOv. */
00115 SPAN_DECLARE(float) power_meter_current_dbov(power_meter_t *s);
00116 
00117 /*! Get the power meter reading which represents a specified power level in dBm0.
00118     \brief Get the current power meter reading, in dBm0.
00119     \param level A power level, in dB0m.
00120     \return The equivalent power meter reading. */
00121 SPAN_DECLARE(int32_t) power_meter_level_dbm0(float level);
00122 
00123 /*! Get the power meter reading which represents a specified power level in dBOv.
00124     \brief Get the current power meter reading, in dBOv.
00125     \param level A power level, in dBOv.
00126     \return The equivalent power meter reading. */
00127 SPAN_DECLARE(int32_t) power_meter_level_dbov(float level);
00128 
00129 SPAN_DECLARE(int32_t) power_surge_detector(power_surge_detector_state_t *s, int16_t amp);
00130 
00131 /*! Get the current surge detector short term meter reading, in dBm0.
00132     \brief Get the current surge detector meter reading, in dBm0.
00133     \param s The power surge detector context.
00134     \return The current power surge detector power reading, in dBm0. */
00135 SPAN_DECLARE(float) power_surge_detector_current_dbm0(power_surge_detector_state_t *s);
00136 
00137 /*! Get the current surge detector short term meter reading, in dBOv.
00138     \brief Get the current surge detector meter reading, in dBOv.
00139     \param s The power surge detector context.
00140     \return The current power surge detector power reading, in dBOv. */
00141 SPAN_DECLARE(float) power_surge_detector_current_dbov(power_surge_detector_state_t *s);
00142 
00143 SPAN_DECLARE(power_surge_detector_state_t *) power_surge_detector_init(power_surge_detector_state_t *s, float min, float surge);
00144 
00145 SPAN_DECLARE(int) power_surge_detector_release(power_surge_detector_state_t *s);
00146 
00147 SPAN_DECLARE(int) power_surge_detector_free(power_surge_detector_state_t *s);
00148 
00149 #if defined(__cplusplus)
00150 }
00151 #endif
00152 
00153 #endif
00154 /*- End of file ------------------------------------------------------------*/

Generated on Mon Jan 3 02:31:15 2011 for spandsp by  doxygen 1.4.7