spandsp: silence_gen.h Source File

spandsp 0.0.6

silence_gen.h
1/*
2 * SpanDSP - a series of DSP components for telephony
3 *
4 * silence_gen.c - A silence generator, for inserting timed silences.
5 *
6 * Written by Steve Underwood <steveu@coppice.org>
7 *
8 * Copyright (C) 2006 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
26#if !defined(_SPANDSP_SILENCE_GEN_H_)
27#define _SPANDSP_SILENCE_GEN_H_
28
29typedef struct silence_gen_state_s silence_gen_state_t;
30
31#if defined(__cplusplus)
32extern "C"
33{
34#endif
35
36/*! Generate a block of silent audio samples.
37 \brief Generate a block of silent audio samples.
38 \param s The silence generator context.
39 \param amp The audio sample buffer.
40 \param max_len The number of samples to be generated.
41 \return The number of samples actually generated. This will be zero when
42 there is nothing to send.
43*/
44 SPAN_DECLARE_NONSTD(int) silence_gen(silence_gen_state_t *s, int16_t *amp, int max_len);
45
46/*! Set a silence generator context to output continuous silence.
47 \brief Set a silence generator context to output continuous silence.
48 \param s The silence generator context.
49*/
50SPAN_DECLARE(void) silence_gen_always(silence_gen_state_t *s);
51
52/*! Set a silence generator context to output a specified period of silence.
53 \brief Set a silence generator context to output a specified period of silence.
54 \param s The silence generator context.
55 \param silent_samples The number of samples to be generated.
56*/
57SPAN_DECLARE(void) silence_gen_set(silence_gen_state_t *s, int silent_samples);
58
59/*! Alter the period of a silence generator context by a specified amount.
60 \brief Alter the period of a silence generator context by a specified amount.
61 \param s The silence generator context.
62 \param silent_samples The number of samples to change the setting by. A positive number
63 increases the duration. A negative number reduces it. The duration
64 is prevented from going negative.
65*/
66SPAN_DECLARE(void) silence_gen_alter(silence_gen_state_t *s, int silent_samples);
67
68/*! Find how long a silence generator context has to run.
69 \brief Find how long a silence generator context has to run.
70 \param s The silence generator context.
71 \return The number of samples remaining.
72*/
73SPAN_DECLARE(int) silence_gen_remainder(silence_gen_state_t *s);
74
75/*! Find the total silence generated to date by a silence generator context.
76 \brief Find the total silence generated to date.
77 \param s The silence generator context.
78 \return The number of samples generated.
79*/
80SPAN_DECLARE(int) silence_gen_generated(silence_gen_state_t *s);
81
82/*! Change the status reporting function associated with a silence generator context.
83 \brief Change the status reporting function associated with a silence generator context.
84 \param s The silence generator context.
85 \param handler The callback routine used to report status changes.
86 \param user_data An opaque pointer. */
87SPAN_DECLARE(void) silence_gen_status_handler(silence_gen_state_t *s, modem_status_func_t handler, void *user_data);
88
89/*! Initialise a timed silence generator context.
90 \brief Initialise a timed silence generator context.
91 \param s The silence generator context.
92 \param silent_samples The initial number of samples to set the silence to.
93 \return A pointer to the silence generator context.
94*/
95SPAN_DECLARE(silence_gen_state_t *) silence_gen_init(silence_gen_state_t *s, int silent_samples);
96
97SPAN_DECLARE(int) silence_gen_release(silence_gen_state_t *s);
98
99SPAN_DECLARE(int) silence_gen_free(silence_gen_state_t *s);
100
101/* The following dummy routines, to absorb data, don't really have a proper home,
102 so they have been put here. */
103
104/*! A dummy routine to use as a receive callback, when we aren't really
105 trying to process what is received. It just absorbs and ignores the
106 data.
107 \brief Dummy receive callback.
108 \param user_data The context.
109 \param amp The signal.buffer
110 \param len The length of the signal buffer
111 \return 0.
112*/
113 SPAN_DECLARE_NONSTD(int) span_dummy_rx(void *user_data, const int16_t amp[], int len);
114
115/*! A dummy routine to use as a signal modifier callback, when we aren't
116 really trying to process the signal. It just returns without affecting
117 anything.
118 \brief Dummy signal modifier callback.
119 \param user_data The context.
120 \param amp The signal.buffer
121 \param len The length of the signal buffer
122 \return 0.
123*/
124SPAN_DECLARE(int) span_dummy_mod(void *user_data, int16_t amp[], int len);
125
126/*! A dummy routine to use as a receive fillin callback, when we aren't really
127 trying to process what is received. It just absorbs and ignores the
128 request.
129 \brief Dummy receive fillin callback.
130 \param user_data The context.
131 \param len The length of the signal buffer
132 \return 0.
133*/
134 SPAN_DECLARE_NONSTD(int) span_dummy_rx_fillin(void *user_data, int len);
135
136#if defined(__cplusplus)
137}
138#endif
139
140#endif
141/*- End of file ------------------------------------------------------------*/
modem_status_func_t
void(* modem_status_func_t)(void *user_data, int status)
Definition async.h:114
SPAN_DECLARE_NONSTD
SPAN_DECLARE_NONSTD(void) async_rx_put_bit(void *user_data
Accept a bit from a received serial bit stream.
span_dummy_mod
int span_dummy_mod(void *user_data, int16_t amp[], int len)
Dummy signal modifier callback.
Definition silence_gen.c:154
silence_gen_always
void silence_gen_always(silence_gen_state_t *s)
Set a silence generator context to output continuous silence.
Definition silence_gen.c:73
silence_gen_status_handler
void silence_gen_status_handler(silence_gen_state_t *s, modem_status_func_t handler, void *user_data)
Change the status reporting function associated with a silence generator context.
Definition silence_gen.c:111
silence_gen_remainder
int silence_gen_remainder(silence_gen_state_t *s)
Find how long a silence generator context has to run.
Definition silence_gen.c:99
silence_gen_init
silence_gen_state_t * silence_gen_init(silence_gen_state_t *s, int silent_samples)
Initialise a timed silence generator context.
Definition silence_gen.c:118
silence_gen_set
void silence_gen_set(silence_gen_state_t *s, int silent_samples)
Set a silence generator context to output a specified period of silence.
Definition silence_gen.c:79
silence_gen_alter
void silence_gen_alter(silence_gen_state_t *s, int silent_samples)
Alter the period of a silence generator context by a specified amount.
Definition silence_gen.c:86
silence_gen_generated
int silence_gen_generated(silence_gen_state_t *s)
Find the total silence generated to date.
Definition silence_gen.c:105
silence_gen_state_s
Definition private/silence_gen.h:30