--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spandsp-0.0.3/spandsp-0.0.3/src/spandsp/power_meter.h	Fri Jun 25 16:00:21 2010 +0200
@@ -0,0 +1,111 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * power_meter.h
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *
+ * Copyright (C) 2003 Steve Underwood
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * $Id: power_meter.h,v 1.8 2006/10/24 13:45:28 steveu Exp $
+ */
+
+#if !defined(_POWER_METER_H_)
+#define _POWER_METER_H_
+
+/*! \page power_meter_page Power metering
+
+\section power_meter_page_sec_1 What does it do?
+The power metering module implements a simple IIR type running power meter. The damping
+factor of the IIR is selectable when the meter instance is created.
+
+Note that the definition of dBOv is quite vague in most places - is it peak since wave,
+peak square wave, etc.? This code is based on the well defined wording in RFC3389:
+
+"For example, in the case of a u-law system, the reference would be a square wave with
+values +/-8031, and this square wave represents 0dBov.  This translates into 6.18dBm0".
+
+\section power_meter_page_sec_2 How does it work?
+*/
+
+/*!
+    Power meter descriptor. This defines the working state for a
+    single instance of a power measurement device.
+*/
+typedef struct
+{
+    int shift;
+
+    int32_t reading;
+} power_meter_t;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*! Initialise a power meter context.
+    \brief Initialise a power meter context.
+    \param s The power meter context.
+    \param shift The shift to be used by the IIR filter.
+    \return The power meter context. */
+power_meter_t *power_meter_init(power_meter_t *s, int shift);
+
+/*! Change the damping factor of a power meter context.
+    \brief Change the damping factor of a power meter context.
+    \param s The power meter context.
+    \param shift The new shift to be used by the IIR filter.
+    \return The power meter context. */
+power_meter_t *power_meter_damping(power_meter_t *s, int shift);
+
+/*! Update a power meter.
+    \brief Update a power meter.
+    \param s The power meter context.
+    \param amp The amplitude of the new audio sample.
+    \return The current power meter reading. */
+int32_t power_meter_update(power_meter_t *s, int16_t amp);
+
+/*! Get the current power meter reading, in dBm0.
+    \brief Get the current power meter reading, in dBm0.
+    \param s The power meter context.
+    \return The current power meter reading, in dBm0. */
+float power_meter_dbm0(power_meter_t *s);
+
+/*! Get the current power meter reading, in dBOv.
+    \brief Get the current power meter reading, in dBOv.
+    \param s The power meter context.
+    \return The current power meter reading, in dBOv. */
+float power_meter_dbov(power_meter_t *s);
+
+/*! Get the power meter reading which represents a specified power level in dBm0.
+    \brief Get the current power meter reading, in dBm0.
+    \param level A power level, in dB0m.
+    \return The equivalent power meter reading. */
+int32_t power_meter_level_dbm0(float level);
+
+/*! Get the power meter reading which represents a specified power level in dBOv.
+    \brief Get the current power meter reading, in dBOv.
+    \param level A power level, in dBOv.
+    \return The equivalent power meter reading. */
+int32_t power_meter_level_dbov(float level);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+/*- End of file ------------------------------------------------------------*/