## ffmpeg / libavcodec / resample2.c @ f25ba8b3

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1 | aaaf1635 | Michael Niedermayer | ```
/*
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2 | ```
* audio resampling
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3 | ```
* Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
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4 | ```
*
``` |
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5 | ```
* This library is free software; you can redistribute it and/or
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6 | ```
* modify it under the terms of the GNU Lesser General Public
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7 | ```
* License as published by the Free Software Foundation; either
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8 | ```
* version 2 of the License, or (at your option) any later version.
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9 | ```
*
``` |
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10 | ```
* This library is distributed in the hope that it will be useful,
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11 | ```
* but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 | ```
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 | ```
* Lesser General Public License for more details.
``` |
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14 | ```
*
``` |
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15 | ```
* You should have received a copy of the GNU Lesser General Public
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16 | ```
* License along with this library; if not, write to the Free Software
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17 | ```
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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18 | ```
*
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19 | ```
*/
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20 | |||

21 | ```
/**
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22 | ```
* @file resample2.c
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23 | ```
* audio resampling
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24 | ```
* @author Michael Niedermayer <michaelni@gmx.at>
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25 | ```
*/
``` |
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26 | |||

27 | #include "avcodec.h" |
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28 | #include "common.h" |
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29 | 1ac31760 | Michael Niedermayer | #include "dsputil.h" |

30 | aaaf1635 | Michael Niedermayer | |

31 | #define PHASE_SHIFT 10 |
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32 | #define PHASE_COUNT (1<<PHASE_SHIFT) |
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33 | #define PHASE_MASK (PHASE_COUNT-1) |
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34 | 51a88020 | Michael Niedermayer | #define FILTER_SIZE 16 |

35 | ```
//#define LINEAR 1
``` |
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36 | |||

37 | #if 1 |
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38 | aaaf1635 | Michael Niedermayer | #define FILTER_SHIFT 15 |

39 | |||

40 | 51a88020 | Michael Niedermayer | ```
#define FELEM int16_t
``` |

41 | ```
#define FELEM2 int32_t
``` |
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42 | ```
#define FELEM_MAX INT16_MAX
``` |
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43 | ```
#define FELEM_MIN INT16_MIN
``` |
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44 | ```
#else
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45 | f25ba8b3 | Michael Niedermayer | #define FILTER_SHIFT 22 |

46 | 51a88020 | Michael Niedermayer | |

47 | ```
#define FELEM int32_t
``` |
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48 | ```
#define FELEM2 int64_t
``` |
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49 | ```
#define FELEM_MAX INT32_MAX
``` |
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50 | ```
#define FELEM_MIN INT32_MIN
``` |
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51 | ```
#endif
``` |
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52 | |||

53 | |||

54 | aaaf1635 | Michael Niedermayer | typedef struct AVResampleContext{ |

55 | 51a88020 | Michael Niedermayer | FELEM *filter_bank; |

56 | aaaf1635 | Michael Niedermayer | ```
int filter_length;
``` |

57 | ```
int ideal_dst_incr;
``` |
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58 | ```
int dst_incr;
``` |
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59 | ```
int index;
``` |
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60 | ```
int frac;
``` |
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61 | ```
int src_incr;
``` |
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62 | ```
int compensation_distance;
``` |
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63 | }AVResampleContext; |
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64 | |||

65 | ```
/**
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66 | ```
* 0th order modified bessel function of the first kind.
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67 | ```
*/
``` |
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68 | double bessel(double x){ |
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69 | double v=1; |
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70 | double t=1; |
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71 | ```
int i;
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72 | |||

73 | for(i=1; i<50; i++){ |
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74 | t *= i; |
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75 | ```
v += pow(x*x/4, i)/(t*t);
``` |
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76 | } |
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77 | ```
return v;
``` |
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78 | } |
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79 | |||

80 | ```
/**
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81 | ```
* builds a polyphase filterbank.
``` |
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82 | ```
* @param factor resampling factor
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83 | ```
* @param scale wanted sum of coefficients for each filter
``` |
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84 | ```
* @param type 0->cubic, 1->blackman nuttall windowed sinc, 2->kaiser windowed sinc beta=16
``` |
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85 | ```
*/
``` |
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86 | 51a88020 | Michael Niedermayer | void av_build_filter(FELEM *filter, double factor, int tap_count, int phase_count, int scale, int type){ |

87 | aaaf1635 | Michael Niedermayer | ```
int ph, i, v;
``` |

88 | ```
double x, y, w, tab[tap_count];
``` |
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89 | const int center= (tap_count-1)/2; |
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90 | |||

91 | ```
/* if upsampling, only need to interpolate, no filter */
``` |
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92 | if (factor > 1.0) |
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93 | factor = 1.0; |
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94 | |||

95 | for(ph=0;ph<phase_count;ph++) { |
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96 | double norm = 0; |
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97 | double e= 0; |
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98 | for(i=0;i<tap_count;i++) { |
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99 | x = M_PI * ((double)(i - center) - (double)ph / phase_count) * factor; |
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100 | if (x == 0) y = 1.0; |
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101 | ```
else y = sin(x) / x;
``` |
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102 | ```
switch(type){
``` |
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103 | case 0:{ |
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104 | const float d= -0.5; //first order derivative = -0.5 |
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105 | x = fabs(((double)(i - center) - (double)ph / phase_count) * factor); |
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106 | if(x<1.0) y= 1 - 3*x*x + 2*x*x*x + d*( -x*x + x*x*x); |
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107 | else y= d*(-4 + 8*x - 5*x*x + x*x*x); |
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108 | ```
break;}
``` |
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109 | case 1: |
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110 | w = 2.0*x / (factor*tap_count) + M_PI; |
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111 | y *= 0.3635819 - 0.4891775 * cos(w) + 0.1365995 * cos(2*w) - 0.0106411 * cos(3*w); |
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112 | ```
break;
``` |
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113 | case 2: |
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114 | w = 2.0*x / (factor*tap_count*M_PI); |
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115 | 08f7073a | Michael Niedermayer | y *= bessel(16*sqrt(FFMAX(1-w*w, 0))); |

116 | aaaf1635 | Michael Niedermayer | ```
break;
``` |

117 | } |
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118 | |||

119 | tab[i] = y; |
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120 | norm += y; |
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121 | } |
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122 | |||

123 | ```
/* normalize so that an uniform color remains the same */
``` |
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124 | for(i=0;i<tap_count;i++) { |
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125 | 51a88020 | Michael Niedermayer | v = clip(lrintf(tab[i] * scale / norm + e), FELEM_MIN, FELEM_MAX); |

126 | aaaf1635 | Michael Niedermayer | filter[ph * tap_count + i] = v; |

127 | e += tab[i] * scale / norm - v; |
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128 | } |
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129 | } |
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130 | } |
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131 | |||

132 | ```
/**
``` |
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133 | ```
* initalizes a audio resampler.
``` |
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134 | ```
* note, if either rate is not a integer then simply scale both rates up so they are
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135 | ```
*/
``` |
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136 | AVResampleContext *av_resample_init(int out_rate, int in_rate){ |
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137 | ```
AVResampleContext *c= av_mallocz(sizeof(AVResampleContext));
``` |
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138 | double factor= FFMIN(out_rate / (double)in_rate, 1.0); |
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139 | |||

140 | memset(c, 0, sizeof(AVResampleContext)); |
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141 | |||

142 | 51a88020 | Michael Niedermayer | c->filter_length= ceil(FILTER_SIZE/factor); |

143 | c->filter_bank= av_mallocz(c->filter_length*(PHASE_COUNT+1)*sizeof(FELEM)); |
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144 | aaaf1635 | Michael Niedermayer | av_build_filter(c->filter_bank, factor, c->filter_length, PHASE_COUNT, 1<<FILTER_SHIFT, 1); |

145 | 51a88020 | Michael Niedermayer | memcpy(&c->filter_bank[c->filter_length*PHASE_COUNT+1], c->filter_bank, (c->filter_length-1)*sizeof(FELEM)); |

146 | 2ac615da | Michael Niedermayer | ```
c->filter_bank[c->filter_length*PHASE_COUNT]= c->filter_bank[c->filter_length - 1];
``` |

147 | aaaf1635 | Michael Niedermayer | |

148 | c->src_incr= out_rate; |
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149 | c->ideal_dst_incr= c->dst_incr= in_rate * PHASE_COUNT; |
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150 | c->index= -PHASE_COUNT*((c->filter_length-1)/2); |
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151 | |||

152 | ```
return c;
``` |
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153 | } |
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154 | |||

155 | ```
void av_resample_close(AVResampleContext *c){
``` |
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156 | av_freep(&c->filter_bank); |
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157 | av_freep(&c); |
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158 | } |
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159 | |||

160 | void av_resample_compensate(AVResampleContext *c, int sample_delta, int compensation_distance){ |
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161 | 08f7073a | Michael Niedermayer | ```
// sample_delta += (c->ideal_dst_incr - c->dst_incr)*(int64_t)c->compensation_distance / c->ideal_dst_incr;
``` |

162 | aaaf1635 | Michael Niedermayer | c->compensation_distance= compensation_distance; |

163 | 08f7073a | Michael Niedermayer | c->dst_incr = c->ideal_dst_incr - c->ideal_dst_incr * (int64_t)sample_delta / compensation_distance; |

164 | aaaf1635 | Michael Niedermayer | } |

165 | |||

166 | ```
/**
``` |
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167 | ```
* resamples.
``` |
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168 | ```
* @param src an array of unconsumed samples
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169 | ```
* @param consumed the number of samples of src which have been consumed are returned here
``` |
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170 | ```
* @param src_size the number of unconsumed samples available
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171 | ```
* @param dst_size the amount of space in samples available in dst
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172 | ```
* @param update_ctx if this is 0 then the context wont be modified, that way several channels can be resampled with the same context
``` |
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173 | ```
* @return the number of samples written in dst or -1 if an error occured
``` |
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174 | ```
*/
``` |
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175 | int av_resample(AVResampleContext *c, short *dst, short *src, int *consumed, int src_size, int dst_size, int update_ctx){ |
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176 | ```
int dst_index, i;
``` |
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177 | ```
int index= c->index;
``` |
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178 | ```
int frac= c->frac;
``` |
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179 | ```
int dst_incr_frac= c->dst_incr % c->src_incr;
``` |
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180 | ```
int dst_incr= c->dst_incr / c->src_incr;
``` |
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181 | 80e85288 | Michael Niedermayer | ```
int compensation_distance= c->compensation_distance;
``` |

182 | aaaf1635 | Michael Niedermayer | |

183 | for(dst_index=0; dst_index < dst_size; dst_index++){ |
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184 | 51a88020 | Michael Niedermayer | FELEM *filter= c->filter_bank + c->filter_length*(index & PHASE_MASK); |

185 | aaaf1635 | Michael Niedermayer | ```
int sample_index= index >> PHASE_SHIFT;
``` |

186 | 51a88020 | Michael Niedermayer | ```
FELEM2 val=0;
``` |

187 | 80e85288 | Michael Niedermayer | |

188 | aaaf1635 | Michael Niedermayer | if(sample_index < 0){ |

189 | for(i=0; i<c->filter_length; i++) |
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190 | b9d2085b | Michael Niedermayer | val += src[ABS(sample_index + i) % src_size] * filter[i]; |

191 | aaaf1635 | Michael Niedermayer | }else if(sample_index + c->filter_length > src_size){ |

192 | ```
break;
``` |
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193 | ```
}else{
``` |
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194 | 51a88020 | Michael Niedermayer | ```
#ifdef LINEAR
``` |

195 | aaaf1635 | Michael Niedermayer | ```
int64_t v=0;
``` |

196 | f25ba8b3 | Michael Niedermayer | int sub_phase= (frac<<8) / c->src_incr; |

197 | aaaf1635 | Michael Niedermayer | for(i=0; i<c->filter_length; i++){ |

198 | f25ba8b3 | Michael Niedermayer | ```
int64_t coeff= filter[i]*(256 - sub_phase) + filter[i + c->filter_length]*sub_phase;
``` |

199 | aaaf1635 | Michael Niedermayer | v += src[sample_index + i] * coeff; |

200 | } |
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201 | f25ba8b3 | Michael Niedermayer | ```
val= v>>8;
``` |

202 | aaaf1635 | Michael Niedermayer | ```
#else
``` |

203 | for(i=0; i<c->filter_length; i++){ |
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204 | 51a88020 | Michael Niedermayer | val += src[sample_index + i] * (FELEM2)filter[i]; |

205 | aaaf1635 | Michael Niedermayer | } |

206 | ```
#endif
``` |
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207 | } |
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208 | |||

209 | val = (val + (1<<(FILTER_SHIFT-1)))>>FILTER_SHIFT; |
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210 | dst[dst_index] = (unsigned)(val + 32768) > 65535 ? (val>>31) ^ 32767 : val; |
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211 | |||

212 | frac += dst_incr_frac; |
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213 | index += dst_incr; |
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214 | ```
if(frac >= c->src_incr){
``` |
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215 | frac -= c->src_incr; |
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216 | index++; |
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217 | } |
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218 | 80e85288 | Michael Niedermayer | |

219 | if(dst_index + 1 == compensation_distance){ |
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220 | ```
compensation_distance= 0;
``` |
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221 | dst_incr_frac= c->ideal_dst_incr % c->src_incr; |
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222 | dst_incr= c->ideal_dst_incr / c->src_incr; |
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223 | } |
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224 | aaaf1635 | Michael Niedermayer | } |

225 | b9d2085b | Michael Niedermayer | ```
*consumed= FFMAX(index, 0) >> PHASE_SHIFT;
``` |

226 | ```
index= FFMIN(index, 0);
``` |
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227 | |||

228 | 80e85288 | Michael Niedermayer | ```
if(compensation_distance){
``` |

229 | compensation_distance -= dst_index; |
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230 | ```
assert(compensation_distance > 0);
``` |
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231 | } |
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232 | aaaf1635 | Michael Niedermayer | ```
if(update_ctx){
``` |

233 | c->frac= frac; |
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234 | b9d2085b | Michael Niedermayer | c->index= index; |

235 | 80e85288 | Michael Niedermayer | c->dst_incr= dst_incr_frac + c->src_incr*dst_incr; |

236 | c->compensation_distance= compensation_distance; |
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237 | aaaf1635 | Michael Niedermayer | } |

238 | 08f7073a | Michael Niedermayer | ```
#if 0
``` |

239 | ```
if(update_ctx && !c->compensation_distance){
``` |
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240 | ```
#undef rand
``` |
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241 | ```
av_resample_compensate(c, rand() % (8000*2) - 8000, 8000*2);
``` |
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242 | ```
av_log(NULL, AV_LOG_DEBUG, "%d %d %d\n", c->dst_incr, c->ideal_dst_incr, c->compensation_distance);
``` |
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243 | ```
}
``` |
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244 | ```
#endif
``` |
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245 | |||

246 | aaaf1635 | Michael Niedermayer | ```
return dst_index;
``` |

247 | } |