--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spandsp-0.0.3/spandsp-0.0.3/src/dds.c	Fri Jun 25 16:00:21 2010 +0200
@@ -0,0 +1,280 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * dds.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: dds.c,v 1.17 2006/11/19 14:07:24 steveu Exp $
+ */
+
+/*! \file */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <inttypes.h>
+#if defined(HAVE_TGMATH_H)
+#include <tgmath.h>
+#endif
+#if defined(HAVE_MATH_H)
+#include <math.h>
+#endif
+
+#include "spandsp/telephony.h"
+#include "spandsp/dds.h"
+
+#if !defined(M_PI)
+# define M_PI           3.14159265358979323846  /* pi */
+#endif
+
+/* In a A-law or u-law channel, and 128 step sine table is adequate to keep the spectral
+   mess due to the DDS at a similar level to the spectral mess due to the A-law or u-law
+   compression. */
+#define SLENK       7
+#define DDS_STEPS   (1 << SLENK)
+#define DDS_SHIFT   (32 - 2 - SLENK)
+
+/* This is a simple set of direct digital synthesis (DDS) functions to generate sine
+   waves. This version uses a 128 entry sin/cos table to cover one quadrant. */
+
+static const int16_t sine_table[DDS_STEPS] =
+{
+       201,
+       603,
+      1005,
+      1407,
+      1809,
+      2210,
+      2611,
+      3012,
+      3412,
+      3812,
+      4211,
+      4609,
+      5007,
+      5404,
+      5800,
+      6195,
+      6590,
+      6983,
+      7376,
+      7767,
+      8157,
+      8546,
+      8933,
+      9319,
+      9704,
+     10088,
+     10469,
+     10850,
+     11228,
+     11605,
+     11980,
+     12354,
+     12725,
+     13095,
+     13463,
+     13828,
+     14192,
+     14553,
+     14912,
+     15269,
+     15624,
+     15976,
+     16326,
+     16673,
+     17018,
+     17361,
+     17700,
+     18037,
+     18372,
+     18703,
+     19032,
+     19358,
+     19681,
+     20001,
+     20318,
+     20632,
+     20943,
+     21251,
+     21555,
+     21856,
+     22154,
+     22449,
+     22740,
+     23028,
+     23312,
+     23593,
+     23870,
+     24144,
+     24414,
+     24680,
+     24943,
+     25202,
+     25457,
+     25708,
+     25956,
+     26199,
+     26439,
+     26674,
+     26906,
+     27133,
+     27357,
+     27576,
+     27791,
+     28002,
+     28209,
+     28411,
+     28610,
+     28803,
+     28993,
+     29178,
+     29359,
+     29535,
+     29707,
+     29875,
+     30038,
+     30196,
+     30350,
+     30499,
+     30644,
+     30784,
+     30920,
+     31050,
+     31177,
+     31298,
+     31415,
+     31527,
+     31634,
+     31737,
+     31834,
+     31927,
+     32015,
+     32099,
+     32177,
+     32251,
+     32319,
+     32383,
+     32442,
+     32496,
+     32546,
+     32590,
+     32629,
+     32664,
+     32693,
+     32718,
+     32738,
+     32753,
+     32762,
+     32767,
+};
+
+int32_t dds_phase_rate(float frequency)
+{
+    return (int32_t) (frequency*65536.0f*65536.0f/SAMPLE_RATE);
+}
+/*- End of function --------------------------------------------------------*/
+
+float dds_frequency(int32_t phase_rate)
+{
+    return (float) phase_rate*(float) SAMPLE_RATE/(65536.0f*65536.0f);
+}
+/*- End of function --------------------------------------------------------*/
+
+int dds_scaling_dbm0(float level)
+{
+    return (int) (powf(10.0f, (level - DBM0_MAX_POWER)/20.0f)*(32767.0f*1.414214f));
+}
+/*- End of function --------------------------------------------------------*/
+
+int dds_scaling_dbov(float level)
+{
+    return (int) (powf(10.0f, (level + 3.02f)/20.0f)*(32767.0f*1.414214f));
+}
+/*- End of function --------------------------------------------------------*/
+
+int16_t dds_lookup(uint32_t phase)
+{
+    uint32_t step;
+    uint32_t fred;
+    int16_t amp;
+
+    phase >>= DDS_SHIFT;
+    step = phase & (DDS_STEPS - 1);
+    fred = step;
+    if ((phase & DDS_STEPS))
+        step = (DDS_STEPS - 1) - step;
+    amp = sine_table[step];
+    if ((phase & (2*DDS_STEPS)))
+    	amp = -amp;
+    return amp;
+}
+/*- End of function --------------------------------------------------------*/
+
+int16_t dds_offset(uint32_t phase_acc, int32_t phase_offset)
+{
+    return dds_lookup(phase_acc + phase_offset);
+}
+/*- End of function --------------------------------------------------------*/
+
+int16_t dds(uint32_t *phase_acc, int32_t phase_rate)
+{
+    int16_t amp;
+
+    amp = dds_lookup(*phase_acc);
+    *phase_acc += phase_rate;
+    return amp;
+}
+/*- End of function --------------------------------------------------------*/
+
+int16_t dds_mod(uint32_t *phase_acc, int32_t phase_rate, int scale, int32_t phase)
+{
+    int16_t amp;
+
+    amp = (int16_t) ((dds_lookup(*phase_acc + phase)*scale) >> 15);
+    *phase_acc += phase_rate;
+    return amp;
+}
+/*- End of function --------------------------------------------------------*/
+
+icomplex_t dds_complex(uint32_t *phase_acc, int32_t phase_rate)
+{
+    icomplex_t amp;
+
+    amp.re = dds_lookup(*phase_acc + (1 << 30));
+    amp.im = dds_lookup(*phase_acc);
+    *phase_acc += phase_rate;
+    return amp;
+}
+/*- End of function --------------------------------------------------------*/
+
+icomplex_t dds_complex_mod(uint32_t *phase_acc, int32_t phase_rate, int scale, int32_t phase)
+{
+    icomplex_t amp;
+
+    amp.re = (dds_lookup(*phase_acc + phase + (1 << 30))*scale) >> 15;
+    amp.im = (dds_lookup(*phase_acc + phase)*scale) >> 15;
+    *phase_acc += phase_rate;
+    return amp;
+}
+/*- End of function --------------------------------------------------------*/
+/*- End of file ------------------------------------------------------------*/