--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spandsp-0.0.3/spandsp-0.0.3/src/power_meter.c	Fri Jun 25 16:00:21 2010 +0200
@@ -0,0 +1,114 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * power_meter.c
+ *
+ * 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.c,v 1.18 2006/11/19 14:07:25 steveu Exp $
+ */
+
+/*! \file */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <inttypes.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <string.h>
+#include <float.h>
+#if defined(HAVE_TGMATH_H)
+#include <tgmath.h>
+#endif
+#if defined(HAVE_MATH_H)
+#include <math.h>
+#endif
+#include <assert.h>
+
+#include "spandsp/telephony.h"
+#include "spandsp/power_meter.h"
+
+power_meter_t *power_meter_init(power_meter_t *s, int shift)
+{
+    if (s == NULL)
+        return NULL;
+    s->shift = shift;
+    s->reading = 0;
+    return s;
+}
+/*- End of function --------------------------------------------------------*/
+
+power_meter_t *power_meter_damping(power_meter_t *s, int shift)
+{
+    s->shift = shift;
+    return s;
+}
+/*- End of function --------------------------------------------------------*/
+
+int32_t power_meter_update(power_meter_t *s, int16_t amp)
+{
+    s->reading += ((amp*amp - s->reading) >> s->shift);
+    return s->reading;
+}
+/*- End of function --------------------------------------------------------*/
+
+int32_t power_meter_level_dbm0(float level)
+{
+    float l;
+
+    level -= DBM0_MAX_POWER;
+    if (level > 0.0)
+        level = 0.0;
+    l = powf(10.0f, level/10.0f)*(32767.0f*32767.0f);
+    return (int32_t) l;
+}
+/*- End of function --------------------------------------------------------*/
+
+int32_t power_meter_level_dbov(float level)
+{
+    float l;
+
+    if (level > 0.0)
+        level = 0.0;
+    l = powf(10.0f, level/10.0f)*(32767.0f*32767.0f);
+    return (int32_t) l;
+}
+/*- End of function --------------------------------------------------------*/
+
+float power_meter_dbm0(power_meter_t *s)
+{
+    if (s->reading <= 0)
+        return FLT_MIN;
+    /* This is based on A-law, but u-law is only 0.03dB different, so don't worry. */
+    return log10f((float) s->reading/(32767.0f*32767.0f))*10.0f + DBM0_MAX_POWER;
+}
+/*- End of function --------------------------------------------------------*/
+
+float power_meter_dbov(power_meter_t *s)
+{
+    if (s->reading <= 0)
+        return FLT_MIN;
+    return log10f((float) s->reading/(32767.0f*32767.0f))*10.0f;
+}
+/*- End of function --------------------------------------------------------*/
+/*- End of file ------------------------------------------------------------*/