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 1.17 2009/04/12 03:29:58 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(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 #if defined(__cplusplus) 00129 } 00130 #endif 00131 00132 #endif 00133 /*- End of file ------------------------------------------------------------*/