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 General Public License version 2, as
00014  * 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 General Public License for more details.
00020  *
00021  * You should have received a copy of the GNU General Public License
00022  * 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 1.12 2007/04/10 16:12:20 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     int shift;
00053 
00054     int32_t reading;
00055 } power_meter_t;
00056 
00057 #ifdef __cplusplus
00058 extern "C"
00059 {
00060 #endif
00061 
00062 /*! Initialise a power meter context.
00063     \brief Initialise a power meter context.
00064     \param s The power meter context.
00065     \param shift The shift to be used by the IIR filter.
00066     \return The power meter context. */
00067 power_meter_t *power_meter_init(power_meter_t *s, int shift);
00068 
00069 /*! Change the damping factor of a power meter context.
00070     \brief Change the damping factor of a power meter context.
00071     \param s The power meter context.
00072     \param shift The new shift to be used by the IIR filter.
00073     \return The power meter context. */
00074 power_meter_t *power_meter_damping(power_meter_t *s, int shift);
00075 
00076 /*! Update a power meter.
00077     \brief Update a power meter.
00078     \param s The power meter context.
00079     \param amp The amplitude of the new audio sample.
00080     \return The current power meter reading. */
00081 int32_t power_meter_update(power_meter_t *s, int16_t amp);
00082 
00083 /*! Get the current power meter reading.
00084     \brief Get the current power meter reading.
00085     \param s The power meter context.
00086     \return The current power meter reading. */
00087 int32_t power_meter_current(power_meter_t *s);
00088 
00089 /*! Get the current power meter reading, in dBm0.
00090     \brief Get the current power meter reading, in dBm0.
00091     \param s The power meter context.
00092     \return The current power meter reading, in dBm0. */
00093 float power_meter_current_dbm0(power_meter_t *s);
00094 
00095 /*! Get the current power meter reading, in dBOv.
00096     \brief Get the current power meter reading, in dBOv.
00097     \param s The power meter context.
00098     \return The current power meter reading, in dBOv. */
00099 float power_meter_current_dbov(power_meter_t *s);
00100 
00101 /*! Get the power meter reading which represents a specified power level in dBm0.
00102     \brief Get the current power meter reading, in dBm0.
00103     \param level A power level, in dB0m.
00104     \return The equivalent power meter reading. */
00105 int32_t power_meter_level_dbm0(float level);
00106 
00107 /*! Get the power meter reading which represents a specified power level in dBOv.
00108     \brief Get the current power meter reading, in dBOv.
00109     \param level A power level, in dBOv.
00110     \return The equivalent power meter reading. */
00111 int32_t power_meter_level_dbov(float level);
00112 
00113 #ifdef __cplusplus
00114 }
00115 #endif
00116 
00117 #endif
00118 /*- End of file ------------------------------------------------------------*/

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