--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spandsp-0.0.6pre17/src/spandsp/tone_generate.h	Fri Jun 25 15:50:58 2010 +0200
@@ -0,0 +1,104 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * tone_generate.h - General telephony tone generation.
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *
+ * Copyright (C) 2001 Steve Underwood
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License version 2.1,
+ * 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * $Id: tone_generate.h,v 1.39 2009/06/02 16:03:56 steveu Exp $
+ */
+
+/*! \file */
+
+#if !defined(_SPANDSP_TONE_GENERATE_H_)
+#define _SPANDSP_TONE_GENERATE_H_
+
+/*! \page tone_generation_page Tone generation
+\section tone_generation_page_sec_1 What does it do?
+The tone generation module provides for the generation of cadenced tones,
+suitable for a wide range of telephony applications. 
+
+\section tone_generation_page_sec_2 How does it work?
+Oscillators are a problem. They oscillate due to instability, and yet we need
+them to behave in a stable manner. A look around the web will reveal many papers
+on this subject. Many describe rather complex solutions to the problem. However,
+we are only concerned with telephony applications. It is possible to generate
+the tones we need with a very simple efficient scheme. It is also practical to
+use an exhaustive test to prove the oscillator is stable under all the
+conditions in which we will use it. 
+*/
+
+typedef struct tone_gen_tone_descriptor_s tone_gen_tone_descriptor_t;
+
+/*!
+    Cadenced multi-tone generator descriptor.
+*/
+typedef struct tone_gen_descriptor_s tone_gen_descriptor_t;
+
+/*!
+    Cadenced multi-tone generator state descriptor. This defines the state of
+    a single working instance of a generator.
+*/
+typedef struct tone_gen_state_s tone_gen_state_t;
+
+#if defined(__cplusplus)
+extern "C"
+{
+#endif
+
+/*! Create a tone generator descriptor
+    \brief Create a tone generator descriptor
+    \param s The descriptor
+    \param f1 The first frequency, in Hz
+    \param l1 The level of the first frequency, in dBm0
+    \param f2 0 for no second frequency, a positive number for the second frequency,
+           in Hz, or a negative number for an AM modulation frequency, in Hz
+    \param l2 The level of the second frequency, in dBm0, or the percentage modulation depth
+           for an AM modulated tone.
+    \param d1 x
+    \param d2 x
+    \param d3 x
+    \param d4 x
+    \param repeat x */
+SPAN_DECLARE(void) make_tone_gen_descriptor(tone_gen_descriptor_t *s,
+                                            int f1,
+                                            int l1,
+                                            int f2,
+                                            int l2,
+                                            int d1,
+                                            int d2,
+                                            int d3,
+                                            int d4,
+                                            int repeat);
+
+SPAN_DECLARE_NONSTD(int) tone_gen(tone_gen_state_t *s, int16_t amp[], int max_samples);
+
+SPAN_DECLARE(tone_gen_state_t *) tone_gen_init(tone_gen_state_t *s, tone_gen_descriptor_t *t);
+
+SPAN_DECLARE(int) tone_gen_release(tone_gen_state_t *s);
+
+SPAN_DECLARE(int) tone_gen_free(tone_gen_state_t *s);
+
+#if defined(__cplusplus)
+}
+#endif
+
+#endif
+/*- End of file ------------------------------------------------------------*/