00001 /* 00002 * SpanDSP - a series of DSP components for telephony 00003 * 00004 * tone_generate.h - General telephony tone generation. 00005 * 00006 * Written by Steve Underwood <steveu@coppice.org> 00007 * 00008 * Copyright (C) 2001 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 General Public License version 2, as 00014 * 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 General Public License for more details. 00020 * 00021 * You should have received a copy of the GNU General Public License 00022 * along with this program; if not, write to the Free Software 00023 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 00024 * 00025 * $Id: tone_generate.h,v 1.29 2007/04/08 08:16:18 steveu Exp $ 00026 */ 00027 00028 /*! \file */ 00029 00030 #if !defined(_SPANDSP_TONE_GENERATE_H_) 00031 #define _SPANDSP_TONE_GENERATE_H_ 00032 00033 /*! \page tone_generation_page Tone generation 00034 \section tone_generation_page_sec_1 What does it do? 00035 The tone generation module provides for the generation of cadenced tones, 00036 suitable for a wide range of telephony applications. 00037 00038 \section tone_generation_page_sec_2 How does it work? 00039 Oscillators are a problem. They oscillate due to instability, and yet we need 00040 them to behave in a stable manner. A look around the web will reveal many papers 00041 on this subject. Many describe rather complex solutions to the problem. However, 00042 we are only concerned with telephony applications. It is possible to generate 00043 the tones we need with a very simple efficient scheme. It is also practical to 00044 use an exhaustive test to prove the oscillator is stable under all the 00045 conditions in which we will use it. 00046 */ 00047 00048 /*! 00049 Cadenced dual tone generator descriptor. 00050 */ 00051 typedef struct 00052 { 00053 int32_t phase_rate[2]; 00054 float gain[2]; 00055 int modulate; 00056 00057 int duration[4]; 00058 00059 int repeat; 00060 } tone_gen_descriptor_t; 00061 00062 /*! 00063 Cadenced dual tone generator state descriptor. This defines the state of 00064 a single working instance of a generator. 00065 */ 00066 typedef struct 00067 { 00068 int32_t phase_rate[2]; 00069 float gain[2]; 00070 int modulate; 00071 00072 uint32_t phase[2]; 00073 00074 int duration[4]; 00075 00076 int repeat; 00077 00078 int current_section; 00079 int current_position; 00080 } tone_gen_state_t; 00081 00082 #if defined(__cplusplus) 00083 extern "C" 00084 { 00085 #endif 00086 00087 /*! Create a tone generator descriptor 00088 \brief Create a tone generator descriptor 00089 \param s The descriptor 00090 \param f1 The first frequency, in Hz 00091 \param l1 The level of the first frequency, in dBm0 00092 \param f2 0 for no second frequency, a positive number for the second frequency, 00093 in Hz, or a negative number for an AM modulation frequency, in Hz 00094 \param l2 The level of the second frequency, in dBm0, or the percentage modulation depth 00095 for an AM modulated tone. 00096 \param d1 x 00097 \param d2 x 00098 \param d3 x 00099 \param d4 x 00100 \param repeat x */ 00101 void make_tone_gen_descriptor(tone_gen_descriptor_t *s, 00102 int f1, 00103 int l1, 00104 int f2, 00105 int l2, 00106 int d1, 00107 int d2, 00108 int d3, 00109 int d4, 00110 int repeat); 00111 00112 void tone_gen_init(tone_gen_state_t *s, tone_gen_descriptor_t *t); 00113 00114 int tone_gen(tone_gen_state_t *s, int16_t amp[], int max_samples); 00115 00116 #if defined(__cplusplus) 00117 } 00118 #endif 00119 00120 #endif 00121 /*- End of file ------------------------------------------------------------*/