spandsp 0.0.6
|
00001 /* 00002 * SpanDSP - a series of DSP components for telephony 00003 * 00004 * silence_gen.c - A silence generator, for inserting timed silences. 00005 * 00006 * Written by Steve Underwood <steveu@coppice.org> 00007 * 00008 * Copyright (C) 2006 Steve Underwood 00009 * 00010 * All rights reserved. 00011 * 00012 * This program is free software; you can redistribute it and/or modify 00013 * it under the terms of the GNU Lesser General Public License version 2.1, 00014 * as published by the Free Software Foundation. 00015 * 00016 * This program is distributed in the hope that it will be useful, 00017 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00018 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00019 * GNU Lesser General Public License for more details. 00020 * 00021 * You should have received a copy of the GNU Lesser General Public 00022 * License along with this program; if not, write to the Free Software 00023 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 00024 * 00025 * $Id: silence_gen.h,v 1.19 2009/09/04 14:38:47 steveu Exp $ 00026 */ 00027 00028 #if !defined(_SPANDSP_SILENCE_GEN_H_) 00029 #define _SPANDSP_SILENCE_GEN_H_ 00030 00031 typedef struct silence_gen_state_s silence_gen_state_t; 00032 00033 #if defined(__cplusplus) 00034 extern "C" 00035 { 00036 #endif 00037 00038 /*! Generate a block of silent audio samples. 00039 \brief Generate a block of silent audio samples. 00040 \param s The silence generator context. 00041 \param amp The audio sample buffer. 00042 \param max_len The number of samples to be generated. 00043 \return The number of samples actually generated. This will be zero when 00044 there is nothing to send. 00045 */ 00046 SPAN_DECLARE_NONSTD(int) silence_gen(silence_gen_state_t *s, int16_t *amp, int max_len); 00047 00048 /*! Set a silence generator context to output continuous silence. 00049 \brief Set a silence generator context to output continuous silence. 00050 \param s The silence generator context. 00051 */ 00052 SPAN_DECLARE(void) silence_gen_always(silence_gen_state_t *s); 00053 00054 /*! Set a silence generator context to output a specified period of silence. 00055 \brief Set a silence generator context to output a specified period of silence. 00056 \param s The silence generator context. 00057 \param silent_samples The number of samples to be generated. 00058 */ 00059 SPAN_DECLARE(void) silence_gen_set(silence_gen_state_t *s, int silent_samples); 00060 00061 /*! Alter the period of a silence generator context by a specified amount. 00062 \brief Alter the period of a silence generator context by a specified amount. 00063 \param s The silence generator context. 00064 \param silent_samples The number of samples to change the setting by. A positive number 00065 increases the duration. A negative number reduces it. The duration 00066 is prevented from going negative. 00067 */ 00068 SPAN_DECLARE(void) silence_gen_alter(silence_gen_state_t *s, int silent_samples); 00069 00070 /*! Find how long a silence generator context has to run. 00071 \brief Find how long a silence generator context has to run. 00072 \param s The silence generator context. 00073 \return The number of samples remaining. 00074 */ 00075 SPAN_DECLARE(int) silence_gen_remainder(silence_gen_state_t *s); 00076 00077 /*! Find the total silence generated to date by a silence generator context. 00078 \brief Find the total silence generated to date. 00079 \param s The silence generator context. 00080 \return The number of samples generated. 00081 */ 00082 SPAN_DECLARE(int) silence_gen_generated(silence_gen_state_t *s); 00083 00084 /*! Change the status reporting function associated with a silence generator context. 00085 \brief Change the status reporting function associated with a silence generator context. 00086 \param s The silence generator context. 00087 \param handler The callback routine used to report status changes. 00088 \param user_data An opaque pointer. */ 00089 SPAN_DECLARE(void) silence_gen_status_handler(silence_gen_state_t *s, modem_tx_status_func_t handler, void *user_data); 00090 00091 /*! Initialise a timed silence generator context. 00092 \brief Initialise a timed silence generator context. 00093 \param s The silence generator context. 00094 \param silent_samples The initial number of samples to set the silence to. 00095 \return A pointer to the silence generator context. 00096 */ 00097 SPAN_DECLARE(silence_gen_state_t *) silence_gen_init(silence_gen_state_t *s, int silent_samples); 00098 00099 SPAN_DECLARE(int) silence_gen_release(silence_gen_state_t *s); 00100 00101 SPAN_DECLARE(int) silence_gen_free(silence_gen_state_t *s); 00102 00103 /* The following dummy routines, to absorb data, don't really have a proper home, 00104 so they have been put here. */ 00105 00106 /*! A dummy routine to use as a receive callback, when we aren't really 00107 trying to process what is received. It just absorbs and ignores the 00108 data. 00109 \brief Dummy receive callback. 00110 \param user_data The context. 00111 \param amp The signal.buffer 00112 \param len The length of the signal buffer 00113 \return 0. 00114 */ 00115 SPAN_DECLARE_NONSTD(int) span_dummy_rx(void *user_data, const int16_t amp[], int len); 00116 00117 /*! A dummy routine to use as a signal modifier callback, when we aren't 00118 really trying to process the signal. It just returns without affecting 00119 anything. 00120 \brief Dummy signal modifier callback. 00121 \param user_data The context. 00122 \param amp The signal.buffer 00123 \param len The length of the signal buffer 00124 \return 0. 00125 */ 00126 SPAN_DECLARE(int) span_dummy_mod(void *user_data, int16_t amp[], int len); 00127 00128 /*! A dummy routine to use as a receive fillin callback, when we aren't really 00129 trying to process what is received. It just absorbs and ignores the 00130 request. 00131 \brief Dummy receive fillin callback. 00132 \param user_data The context. 00133 \param len The length of the signal buffer 00134 \return 0. 00135 */ 00136 SPAN_DECLARE_NONSTD(int) span_dummy_rx_fillin(void *user_data, int len); 00137 00138 #if defined(__cplusplus) 00139 } 00140 #endif 00141 00142 #endif 00143 /*- End of file ------------------------------------------------------------*/