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5
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1 /*
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2 * SpanDSP - a series of DSP components for telephony
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3 *
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4 * plc.c
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5 *
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6 * Written by Steve Underwood <steveu@coppice.org>
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7 *
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8 * Copyright (C) 2004 Steve Underwood
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9 *
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10 * All rights reserved.
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11 *
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12 * This program is free software; you can redistribute it and/or modify
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13 * it under the terms of the GNU General Public License version 2, as
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14 * published by the Free Software Foundation.
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15 *
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16 * This program is distributed in the hope that it will be useful,
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17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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19 * GNU General Public License for more details.
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20 *
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21 * You should have received a copy of the GNU General Public License
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22 * along with this program; if not, write to the Free Software
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23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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24 *
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25 * $Id: plc.c,v 1.16 2006/11/19 14:07:24 steveu Exp $
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26 */
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27
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28 /*! \file */
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29
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30 #ifdef HAVE_CONFIG_H
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31 #include <config.h>
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32 #endif
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33
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34 #include <stdio.h>
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35 #include <inttypes.h>
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36 #include <stdlib.h>
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37 #include <string.h>
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38 #if defined(HAVE_TGMATH_H)
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39 #include <tgmath.h>
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40 #endif
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41 #if defined(HAVE_MATH_H)
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42 #include <math.h>
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43 #endif
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44 #include <limits.h>
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45
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46 #include "spandsp/telephony.h"
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47 #include "spandsp/dc_restore.h"
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48 #include "spandsp/plc.h"
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49
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50 /* We do a straight line fade to zero volume in 50ms when we are filling in for missing data. */
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51 #define ATTENUATION_INCREMENT 0.0025f /* Attenuation per sample */
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52
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53 #define ms_to_samples(t) (((t)*SAMPLE_RATE)/1000)
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54
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55 static void save_history(plc_state_t *s, int16_t *buf, int len)
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56 {
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57 if (len >= PLC_HISTORY_LEN)
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58 {
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59 /* Just keep the last part of the new data, starting at the beginning of the buffer */
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60 memcpy(s->history, buf + len - PLC_HISTORY_LEN, sizeof(int16_t)*PLC_HISTORY_LEN);
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61 s->buf_ptr = 0;
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62 return;
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63 }
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64 if (s->buf_ptr + len > PLC_HISTORY_LEN)
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65 {
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66 /* Wraps around - must break into two sections */
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67 memcpy(s->history + s->buf_ptr, buf, sizeof(int16_t)*(PLC_HISTORY_LEN - s->buf_ptr));
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68 len -= (PLC_HISTORY_LEN - s->buf_ptr);
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69 memcpy(s->history, buf + (PLC_HISTORY_LEN - s->buf_ptr), sizeof(int16_t)*len);
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70 s->buf_ptr = len;
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71 return;
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72 }
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73 /* Can use just one section */
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74 memcpy(s->history + s->buf_ptr, buf, sizeof(int16_t)*len);
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75 s->buf_ptr += len;
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76 }
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77 /*- End of function --------------------------------------------------------*/
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78
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79 static __inline__ void normalise_history(plc_state_t *s)
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80 {
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81 int16_t tmp[PLC_HISTORY_LEN];
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82
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83 if (s->buf_ptr == 0)
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84 return;
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85 memcpy(tmp, s->history, sizeof(int16_t)*s->buf_ptr);
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86 memcpy(s->history, s->history + s->buf_ptr, sizeof(int16_t)*(PLC_HISTORY_LEN - s->buf_ptr));
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87 memcpy(s->history + PLC_HISTORY_LEN - s->buf_ptr, tmp, sizeof(int16_t)*s->buf_ptr);
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88 s->buf_ptr = 0;
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89 }
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90 /*- End of function --------------------------------------------------------*/
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91
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92 static __inline__ int amdf_pitch(int min_pitch, int max_pitch, int16_t amp[], int len)
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93 {
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94 int i;
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95 int j;
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96 int acc;
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97 int min_acc;
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98 int pitch;
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99
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100 pitch = min_pitch;
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101 min_acc = INT_MAX;
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102 for (i = max_pitch; i <= min_pitch; i++)
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103 {
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104 acc = 0;
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105 for (j = 0; j < len; j++)
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106 acc += abs(amp[i + j] - amp[j]);
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107 if (acc < min_acc)
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108 {
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109 min_acc = acc;
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110 pitch = i;
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111 }
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112 }
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113 return pitch;
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114 }
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115 /*- End of function --------------------------------------------------------*/
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116
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117 int plc_rx(plc_state_t *s, int16_t amp[], int len)
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118 {
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119 int i;
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120 int pitch_overlap;
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121 float old_step;
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122 float new_step;
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123 float old_weight;
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124 float new_weight;
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125 float gain;
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126
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127 if (s->missing_samples)
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128 {
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129 /* Although we have a real signal, we need to smooth it to fit well
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130 with the synthetic signal we used for the previous block */
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131
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132 /* The start of the real data is overlapped with the next 1/4 cycle
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133 of the synthetic data. */
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134 pitch_overlap = s->pitch >> 2;
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135 if (pitch_overlap > len)
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136 pitch_overlap = len;
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137 gain = 1.0f - s->missing_samples*ATTENUATION_INCREMENT;
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138 if (gain < 0.0f)
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139 gain = 0.0f;
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140 new_step = 1.0f/pitch_overlap;
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141 old_step = new_step*gain;
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142 new_weight = new_step;
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143 old_weight = (1.0f - new_step)*gain;
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144 for (i = 0; i < pitch_overlap; i++)
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145 {
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146 amp[i] = fsaturate(old_weight*s->pitchbuf[s->pitch_offset] + new_weight*amp[i]);
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147 if (++s->pitch_offset >= s->pitch)
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148 s->pitch_offset = 0;
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149 new_weight += new_step;
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150 old_weight -= old_step;
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151 if (old_weight < 0.0f)
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152 old_weight = 0.0f;
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153 }
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154 s->missing_samples = 0;
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155 }
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156 save_history(s, amp, len);
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157 return len;
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158 }
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159 /*- End of function --------------------------------------------------------*/
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160
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161 int plc_fillin(plc_state_t *s, int16_t amp[], int len)
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162 {
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163 int i;
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164 int pitch_overlap;
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165 float old_step;
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166 float new_step;
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167 float old_weight;
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168 float new_weight;
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169 float gain;
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170 int16_t *orig_amp;
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171 int orig_len;
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172
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173 orig_amp = amp;
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174 orig_len = len;
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175 if (s->missing_samples == 0)
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176 {
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177 /* As the gap in real speech starts we need to assess the last known pitch,
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178 and prepare the synthetic data we will use for fill-in */
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179 normalise_history(s);
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180 s->pitch = amdf_pitch(PLC_PITCH_MIN, PLC_PITCH_MAX, s->history + PLC_HISTORY_LEN - CORRELATION_SPAN - PLC_PITCH_MIN, CORRELATION_SPAN);
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181 /* We overlap a 1/4 wavelength */
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182 pitch_overlap = s->pitch >> 2;
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183 /* Cook up a single cycle of pitch, using a single of the real signal with 1/4
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184 cycle OLA'ed to make the ends join up nicely */
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185 /* The first 3/4 of the cycle is a simple copy */
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186 for (i = 0; i < s->pitch - pitch_overlap; i++)
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187 s->pitchbuf[i] = s->history[PLC_HISTORY_LEN - s->pitch + i];
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188 /* The last 1/4 of the cycle is overlapped with the end of the previous cycle */
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189 new_step = 1.0f/pitch_overlap;
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190 new_weight = new_step;
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191 for ( ; i < s->pitch; i++)
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192 {
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193 s->pitchbuf[i] = s->history[PLC_HISTORY_LEN - s->pitch + i]*(1.0f - new_weight) + s->history[PLC_HISTORY_LEN - 2*s->pitch + i]*new_weight;
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194 new_weight += new_step;
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195 }
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196 /* We should now be ready to fill in the gap with repeated, decaying cycles
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197 of what is in pitchbuf */
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198
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199 gain = 1.0f;
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200 /* We need to OLA the first 1/4 wavelength of the synthetic data, to smooth
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201 it into the previous real data. To avoid the need to introduce a delay
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202 in the stream, reverse the last 1/4 wavelength, and OLA with that. */
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203 new_step = 1.0f/pitch_overlap;
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204 old_step = new_step;
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205 new_weight = new_step;
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206 old_weight = 1.0f - new_step;
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207 for (i = 0; i < pitch_overlap; i++)
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208 {
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209 amp[i] = fsaturate(old_weight*s->history[PLC_HISTORY_LEN - 1 - i] + new_weight*s->pitchbuf[i]);
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210 new_weight += new_step;
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211 old_weight -= old_step;
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212 if (old_weight < 0.0f)
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213 old_weight = 0.0f;
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214 }
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215 s->pitch_offset = i;
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216 }
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217 else
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218 {
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219 gain = 1.0f - s->missing_samples*ATTENUATION_INCREMENT;
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220 i = 0;
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221 }
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222 for ( ; gain > 0.0f && i < len; i++)
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223 {
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224 amp[i] = (int16_t) (s->pitchbuf[s->pitch_offset]*gain);
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225 gain -= ATTENUATION_INCREMENT;
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226 if (++s->pitch_offset >= s->pitch)
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227 s->pitch_offset = 0;
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228 }
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229 for ( ; i < len; i++)
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230 amp[i] = 0;
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231 s->missing_samples += orig_len;
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232 save_history(s, amp, len);
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233 return len;
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234 }
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235 /*- End of function --------------------------------------------------------*/
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236
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237 plc_state_t *plc_init(plc_state_t *s)
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238 {
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239 if (s == NULL)
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240 {
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241 if ((s = (plc_state_t *) malloc(sizeof(*s))) == NULL)
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242 return NULL;
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243 }
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244 memset(s, 0, sizeof(*s));
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245 return s;
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246 }
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247 /*- End of function --------------------------------------------------------*/
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248
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249 int plc_release(plc_state_t *s)
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250 {
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251 free(s);
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252 return 0;
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253 }
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254 /*- End of function --------------------------------------------------------*/
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255 /*- End of file ------------------------------------------------------------*/
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