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comparison spandsp-0.0.6pre17/src/spandsp/tone_generate.h @ 4:26cd8f1ef0b1

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import spandsp-0.0.6pre17
author Peter Meerwald <pmeerw@cosy.sbg.ac.at>
date Fri, 25 Jun 2010 15:50:58 +0200
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3:c6c5a16ce2f2 4:26cd8f1ef0b1
1 /*
2 * SpanDSP - a series of DSP components for telephony
3 *
4 * tone_generate.h - General telephony tone generation.
5 *
6 * Written by Steve Underwood <steveu@coppice.org>
7 *
8 * Copyright (C) 2001 Steve Underwood
9 *
10 * All rights reserved.
11 *
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU Lesser General Public License version 2.1,
14 * as published by the Free Software Foundation.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU Lesser General Public License for more details.
20 *
21 * You should have received a copy of the GNU Lesser General Public
22 * License along with this program; if not, write to the Free Software
23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 *
25 * $Id: tone_generate.h,v 1.39 2009/06/02 16:03:56 steveu Exp $
26 */
27
28 /*! \file */
29
30 #if !defined(_SPANDSP_TONE_GENERATE_H_)
31 #define _SPANDSP_TONE_GENERATE_H_
32
33 /*! \page tone_generation_page Tone generation
34 \section tone_generation_page_sec_1 What does it do?
35 The tone generation module provides for the generation of cadenced tones,
36 suitable for a wide range of telephony applications.
37
38 \section tone_generation_page_sec_2 How does it work?
39 Oscillators are a problem. They oscillate due to instability, and yet we need
40 them to behave in a stable manner. A look around the web will reveal many papers
41 on this subject. Many describe rather complex solutions to the problem. However,
42 we are only concerned with telephony applications. It is possible to generate
43 the tones we need with a very simple efficient scheme. It is also practical to
44 use an exhaustive test to prove the oscillator is stable under all the
45 conditions in which we will use it.
46 */
47
48 typedef struct tone_gen_tone_descriptor_s tone_gen_tone_descriptor_t;
49
50 /*!
51 Cadenced multi-tone generator descriptor.
52 */
53 typedef struct tone_gen_descriptor_s tone_gen_descriptor_t;
54
55 /*!
56 Cadenced multi-tone generator state descriptor. This defines the state of
57 a single working instance of a generator.
58 */
59 typedef struct tone_gen_state_s tone_gen_state_t;
60
61 #if defined(__cplusplus)
62 extern "C"
63 {
64 #endif
65
66 /*! Create a tone generator descriptor
67 \brief Create a tone generator descriptor
68 \param s The descriptor
69 \param f1 The first frequency, in Hz
70 \param l1 The level of the first frequency, in dBm0
71 \param f2 0 for no second frequency, a positive number for the second frequency,
72 in Hz, or a negative number for an AM modulation frequency, in Hz
73 \param l2 The level of the second frequency, in dBm0, or the percentage modulation depth
74 for an AM modulated tone.
75 \param d1 x
76 \param d2 x
77 \param d3 x
78 \param d4 x
79 \param repeat x */
80 SPAN_DECLARE(void) make_tone_gen_descriptor(tone_gen_descriptor_t *s,
81 int f1,
82 int l1,
83 int f2,
84 int l2,
85 int d1,
86 int d2,
87 int d3,
88 int d4,
89 int repeat);
90
91 SPAN_DECLARE_NONSTD(int) tone_gen(tone_gen_state_t *s, int16_t amp[], int max_samples);
92
93 SPAN_DECLARE(tone_gen_state_t *) tone_gen_init(tone_gen_state_t *s, tone_gen_descriptor_t *t);
94
95 SPAN_DECLARE(int) tone_gen_release(tone_gen_state_t *s);
96
97 SPAN_DECLARE(int) tone_gen_free(tone_gen_state_t *s);
98
99 #if defined(__cplusplus)
100 }
101 #endif
102
103 #endif
104 /*- End of file ------------------------------------------------------------*/

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