aulevel: calculate audio levels in dBov

7 files changed, 162 insertions, 0 deletions

diff --git a/include/baresip.h b/include/baresip.h
index f00b5c9..5087296 100644
--- a/include/baresip.h
+++ b/include/baresip.h
@@ -65,6 +65,18 @@ const char *account_stun_host(const struct account *acc);
 
 
 /*
+ * Audio-level
+ */
+
+
+#define AULEVEL_MIN  (-96.0)
+#define AULEVEL_MAX    (0.0)
+
+
+double aulevel_calc_dbov(const int16_t *sampv, size_t sampc);
+
+
+/*
  * Call
  */
 
diff --git a/src/aulevel.c b/src/aulevel.c
new file mode 100644
index 0000000..bc9a27a
--- /dev/null
+++ b/src/aulevel.c
@@ -0,0 +1,85 @@
+/**
+ * @file src/aulevel.c  Audio level
+ *
+ * Copyright (C) 2017 Creytiv.com
+ */
+
+#include <math.h>
+#include <re.h>
+#include <baresip.h>
+#include "core.h"
+
+
+/**
+ * Generic routine to calculate RMS (Root-Mean-Square) from
+ * a set of signed 16-bit values
+ *
+ * \verbatim
+
+	     .---------------
+	     |   N-1
+	     |  ----.
+	     |  \
+	     |   \        2
+	     |    |   s[n]
+	     |   /
+	     |  /
+	 _   |  ----'
+	  \  |   n=0
+	   \ |  ------------
+	    \|       N
+
+   \endverbatim
+ *
+ * @param data Array of signed 16-bit values
+ * @param len  Number of values
+ *
+ * @return RMS value from 0 to 32768
+ */
+static double calc_rms(const int16_t *data, size_t len)
+{
+	double sum = 0;
+	size_t i;
+
+	if (!data || !len)
+		return .0;
+
+	for (i = 0; i < len; i++) {
+		const double sample = data[i];
+
+		sum += sample * sample;
+	}
+
+	return sqrt(sum / (double)len);
+}
+
+
+/**
+ * Calculate the audio level in dBov from a set of audio samples.
+ * dBov is the level, in decibels, relative to the overload point
+ * of the system
+ *
+ * @param sampv Audio samples
+ * @param sampc Number of audio samples
+ *
+ * @return Audio level expressed in dBov
+ */
+double aulevel_calc_dbov(const int16_t *sampv, size_t sampc)
+{
+	static const double peak = 32767.0;
+	double rms, dbov;
+
+	if (!sampv || !sampc)
+		return AULEVEL_MIN;
+
+	rms = calc_rms(sampv, sampc) / peak;
+
+	dbov = 20 * log10(rms);
+
+	if (dbov < AULEVEL_MIN)
+		dbov = AULEVEL_MIN;
+	else if (dbov > AULEVEL_MAX)
+		dbov = AULEVEL_MAX;
+
+	return dbov;
+}
diff --git a/src/srcs.mk b/src/srcs.mk
index c538600..cdb2a26 100644
--- a/src/srcs.mk
+++ b/src/srcs.mk
@@ -8,6 +8,7 @@ SRCS	+= account.c
 SRCS	+= aucodec.c
 SRCS	+= audio.c
 SRCS	+= aufilt.c
+SRCS	+= aulevel.c
 SRCS	+= auplay.c
 SRCS	+= ausrc.c
 SRCS	+= baresip.c
diff --git a/test/aulevel.c b/test/aulevel.c
new file mode 100644
index 0000000..6d083f6
--- /dev/null
+++ b/test/aulevel.c
@@ -0,0 +1,61 @@
+/**
+ * @file test/aulevel.c  Baresip selftest -- audio levels
+ *
+ * Copyright (C) 2010 - 2017 Creytiv.com
+ */
+
+#include <re.h>
+#include <baresip.h>
+#include "test.h"
+
+
+#define DEBUG_MODULE "aulevel"
+#define DEBUG_LEVEL 5
+#include <re_dbg.h>
+
+
+#define PREC .6
+
+
+int test_aulevel(void)
+{
+	static const struct {
+		int16_t sampv[2];
+		double level;
+	} testv[] = {
+
+		{  {    0,     -0},    -96.0  },
+		{  {    0,      1},    -93.0  },
+		{  {    1,     -1},    -90.0  },
+		{  {    2,     -2},    -84.0  },
+		{  {    4,     -4},    -78.0  },
+		{  {    8,     -8},    -72.0  },
+		{  {   16,    -16},    -66.0  },
+		{  {   32,    -32},    -60.0  },
+		{  {   64,    -64},    -54.0  },
+		{  {  128,   -128},    -48.0  },
+		{  {  256,   -256},    -42.0  },
+		{  {  512,   -512},    -36.0  },
+		{  { 1024,  -1024},    -30.0  },
+		{  { 2048,  -2048},    -24.0  },
+		{  { 4096,  -4096},    -18.0  },
+		{  { 8192,  -8192},    -12.0  },
+		{  {16384, -16384},     -6.0  },
+		{  {32767, -32768},      0.0  },
+	};
+	size_t i;
+	int err = 0;
+
+	for (i=0; i<ARRAY_SIZE(testv); i++) {
+
+		double level;
+
+		level = aulevel_calc_dbov(testv[i].sampv,
+					  ARRAY_SIZE(testv[i].sampv));
+
+		ASSERT_DOUBLE_EQ(testv[i].level, level, PREC);
+	}
+
+ out:
+	return err;
+}
diff --git a/test/main.c b/test/main.c
index 125f1ec..f443dcb 100644
--- a/test/main.c
+++ b/test/main.c
@@ -23,6 +23,7 @@ struct test {
 
 static const struct test tests[] = {
 	TEST(test_account),
+	TEST(test_aulevel),
 	TEST(test_call_af_mismatch),
 	TEST(test_call_answer),
 	TEST(test_call_answer_hangup_a),
diff --git a/test/srcs.mk b/test/srcs.mk
index 3c481ac..b3a2637 100644
--- a/test/srcs.mk
+++ b/test/srcs.mk
@@ -9,6 +9,7 @@
 # Test-cases:
 #
 TEST_SRCS	+= account.c
+TEST_SRCS	+= aulevel.c
 TEST_SRCS	+= call.c
 TEST_SRCS	+= cmd.c
 TEST_SRCS	+= contact.c
diff --git a/test/test.h b/test/test.h
index 3a19ec1..a68d61d 100644
--- a/test/test.h
+++ b/test/test.h
@@ -178,6 +178,7 @@ int mock_vidisp_register(struct vidisp **vidispp);
 /* test cases */
 
 int test_account(void);
+int test_aulevel(void);
 int test_cmd(void);
 int test_cmd_long(void);
 int test_contact(void);