/* * SpanDSP - a series of DSP components for telephony * * silence_gen.c - A silence generator, for inserting timed silences. * * Written by Steve Underwood <steveu@coppice.org> * * Copyright (C) 2006 Steve Underwood * * All rights reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2, 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 General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * * $Id: silence_gen.h,v 1.7 2007/04/08 08:16:18 steveu Exp $ */#if !defined(_SPANDSP_SILENCE_GEN_H_)#define _SPANDSP_SILENCE_GEN_H_typedef struct{    int remaining_samples;    int total_samples;} silence_gen_state_t;#if defined(__cplusplus)extern "C"{#endif/*! Generate a block of silent audio samples.    \brief Generate a block of silent audio samples.    \param s The silence generator context.    \param amp The audio sample buffer.    \param max_len The number of samples to be generated.    \return The number of samples actually generated. This will be zero when            there is nothing to send.*/int silence_gen(silence_gen_state_t *s, int16_t *amp, int max_len);/*! Set a silence generator context to output continuous silence.    \brief Set a silence generator context to output continuous silence.    \param s The silence generator context.*/void silence_gen_always(silence_gen_state_t *s);/*! Set a silence generator context to output a specified period of silence.    \brief Set a silence generator context to output a specified period of silence.    \param s The silence generator context.    \param silent_samples The number of samples to be generated.*/void silence_gen_set(silence_gen_state_t *s, int silent_samples);/*! Alter the period of a silence generator context by a specified amount.    \brief Alter the period of a silence generator context by a specified amount.    \param s The silence generator context.    \param silent_samples The number of samples to change the setting by. A positive number                          increases the duration. A negative number reduces it. The duration                          is prevented from going negative.*/void silence_gen_alter(silence_gen_state_t *s, int silent_samples);/*! Find how long a silence generator context has to run.    \brief Find how long a silence generator context has to run.    \param s The silence generator context.    \return The number of samples remaining.*/int silence_gen_remainder(silence_gen_state_t *s);/*! Find the total silence generated to date by a silence generator context.    \brief Find the total silence generated to date.    \param s The silence generator context.    \return The number of samples generated.*/int silence_gen_generated(silence_gen_state_t *s);/*! Initialise a timed silence generator context.    \brief Initialise a timed silence generator context.    \param s The silence generator context.    \param the initial number of samples to set the silence to.    \return A pointer to the silence generator context.*/silence_gen_state_t *silence_gen_init(silence_gen_state_t *s, int silent_samples);#if defined(__cplusplus)}#endif#endif/*- End of file ------------------------------------------------------------*/