## ffmpeg / libavcodec / resample2.c @ 7a886063

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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 | b78e7197 | Diego Biurrun | ```
* This file is part of FFmpeg.
``` |

6 | ```
*
``` |
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7 | ```
* FFmpeg is free software; you can redistribute it and/or
``` |
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8 | aaaf1635 | Michael Niedermayer | ```
* modify it under the terms of the GNU Lesser General Public
``` |

9 | ```
* License as published by the Free Software Foundation; either
``` |
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10 | b78e7197 | Diego Biurrun | ```
* version 2.1 of the License, or (at your option) any later version.
``` |

11 | aaaf1635 | Michael Niedermayer | ```
*
``` |

12 | b78e7197 | Diego Biurrun | ```
* FFmpeg is distributed in the hope that it will be useful,
``` |

13 | aaaf1635 | Michael Niedermayer | ```
* but WITHOUT ANY WARRANTY; without even the implied warranty of
``` |

14 | ```
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
``` |
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15 | ```
* Lesser General Public License for more details.
``` |
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16 | ```
*
``` |
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17 | ```
* You should have received a copy of the GNU Lesser General Public
``` |
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18 | b78e7197 | Diego Biurrun | ```
* License along with FFmpeg; if not, write to the Free Software
``` |

19 | 5509bffa | Diego Biurrun | ```
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
``` |

20 | aaaf1635 | Michael Niedermayer | ```
*
``` |

21 | ```
*/
``` |
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22 | 115329f1 | Diego Biurrun | |

23 | aaaf1635 | Michael Niedermayer | ```
/**
``` |

24 | ```
* @file resample2.c
``` |
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25 | ```
* audio resampling
``` |
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26 | ```
* @author Michael Niedermayer <michaelni@gmx.at>
``` |
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27 | ```
*/
``` |
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28 | |||

29 | #include "avcodec.h" |
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30 | #include "common.h" |
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31 | 1ac31760 | Michael Niedermayer | #include "dsputil.h" |

32 | aaaf1635 | Michael Niedermayer | |

33 | 51a88020 | Michael Niedermayer | #if 1 |

34 | aaaf1635 | Michael Niedermayer | #define FILTER_SHIFT 15 |

35 | |||

36 | 51a88020 | Michael Niedermayer | ```
#define FELEM int16_t
``` |

37 | ```
#define FELEM2 int32_t
``` |
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38 | ```
#define FELEM_MAX INT16_MAX
``` |
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39 | ```
#define FELEM_MIN INT16_MIN
``` |
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40 | ```
#else
``` |
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41 | f25ba8b3 | Michael Niedermayer | #define FILTER_SHIFT 22 |

42 | 51a88020 | Michael Niedermayer | |

43 | ```
#define FELEM int32_t
``` |
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44 | ```
#define FELEM2 int64_t
``` |
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45 | ```
#define FELEM_MAX INT32_MAX
``` |
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46 | ```
#define FELEM_MIN INT32_MIN
``` |
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47 | ```
#endif
``` |
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48 | |||

49 | |||

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

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

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

53 | ```
int ideal_dst_incr;
``` |
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54 | ```
int dst_incr;
``` |
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55 | ```
int index;
``` |
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56 | ```
int frac;
``` |
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57 | ```
int src_incr;
``` |
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58 | ```
int compensation_distance;
``` |
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59 | ed861c6b | Michael Niedermayer | ```
int phase_shift;
``` |

60 | ```
int phase_mask;
``` |
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61 | ```
int linear;
``` |
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62 | aaaf1635 | Michael Niedermayer | }AVResampleContext; |

63 | |||

64 | ```
/**
``` |
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65 | ```
* 0th order modified bessel function of the first kind.
``` |
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66 | ```
*/
``` |
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67 | 7b49ce2e | Stefan Huehner | static double bessel(double x){ |

68 | aaaf1635 | Michael Niedermayer | double v=1; |

69 | double t=1; |
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70 | ```
int i;
``` |
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71 | 115329f1 | Diego Biurrun | |

72 | aaaf1635 | Michael Niedermayer | for(i=1; i<50; i++){ |

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

79 | ```
/**
``` |
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80 | ```
* builds a polyphase filterbank.
``` |
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81 | ```
* @param factor resampling factor
``` |
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82 | ```
* @param scale wanted sum of coefficients for each filter
``` |
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83 | ```
* @param type 0->cubic, 1->blackman nuttall windowed sinc, 2->kaiser windowed sinc beta=16
``` |
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84 | ```
*/
``` |
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85 | 51a88020 | Michael Niedermayer | void av_build_filter(FELEM *filter, double factor, int tap_count, int phase_count, int scale, int type){ |

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

87 | ```
double x, y, w, tab[tap_count];
``` |
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88 | const int center= (tap_count-1)/2; |
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89 | |||

90 | ```
/* if upsampling, only need to interpolate, no filter */
``` |
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91 | if (factor > 1.0) |
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92 | factor = 1.0; |
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93 | |||

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

115 | aaaf1635 | Michael Niedermayer | ```
break;
``` |

116 | } |
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117 | |||

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

122 | ```
/* normalize so that an uniform color remains the same */
``` |
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123 | for(i=0;i<tap_count;i++) { |
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124 | 51a88020 | Michael Niedermayer | v = clip(lrintf(tab[i] * scale / norm + e), FELEM_MIN, FELEM_MAX); |

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

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

131 | ```
/**
``` |
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132 | ```
* initalizes a audio resampler.
``` |
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133 | ```
* note, if either rate is not a integer then simply scale both rates up so they are
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134 | ```
*/
``` |
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135 | 6e225de2 | Michael Niedermayer | AVResampleContext *av_resample_init(int out_rate, int in_rate, int filter_size, int phase_shift, int linear, double cutoff){ |

136 | aaaf1635 | Michael Niedermayer | ```
AVResampleContext *c= av_mallocz(sizeof(AVResampleContext));
``` |

137 | 6e225de2 | Michael Niedermayer | double factor= FFMIN(out_rate * cutoff / in_rate, 1.0); |

138 | ed861c6b | Michael Niedermayer | int phase_count= 1<<phase_shift; |

139 | 115329f1 | Diego Biurrun | |

140 | ed861c6b | Michael Niedermayer | c->phase_shift= phase_shift; |

141 | ```
c->phase_mask= phase_count-1;
``` |
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142 | c->linear= linear; |
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143 | aaaf1635 | Michael Niedermayer | |

144 | f0ff20a1 | Wolfram Gloger | c->filter_length= FFMAX((int)ceil(filter_size/factor), 1); |

145 | ed861c6b | Michael Niedermayer | c->filter_bank= av_mallocz(c->filter_length*(phase_count+1)*sizeof(FELEM)); |

146 | av_build_filter(c->filter_bank, factor, c->filter_length, phase_count, 1<<FILTER_SHIFT, 1); |
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147 | memcpy(&c->filter_bank[c->filter_length*phase_count+1], c->filter_bank, (c->filter_length-1)*sizeof(FELEM)); |
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148 | ```
c->filter_bank[c->filter_length*phase_count]= c->filter_bank[c->filter_length - 1];
``` |
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149 | aaaf1635 | Michael Niedermayer | |

150 | c->src_incr= out_rate; |
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151 | ed861c6b | Michael Niedermayer | c->ideal_dst_incr= c->dst_incr= in_rate * phase_count; |

152 | c->index= -phase_count*((c->filter_length-1)/2); |
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153 | aaaf1635 | Michael Niedermayer | |

154 | ```
return c;
``` |
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155 | } |
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156 | |||

157 | ```
void av_resample_close(AVResampleContext *c){
``` |
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158 | av_freep(&c->filter_bank); |
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159 | av_freep(&c); |
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160 | } |
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161 | |||

162 | 788d7a8c | Michael Niedermayer | ```
/**
``` |

163 | ```
* Compensates samplerate/timestamp drift. The compensation is done by changing
``` |
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164 | ```
* the resampler parameters, so no audible clicks or similar distortions ocur
``` |
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165 | ```
* @param compensation_distance distance in output samples over which the compensation should be performed
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166 | ```
* @param sample_delta number of output samples which should be output less
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167 | ```
*
``` |
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168 | ```
* example: av_resample_compensate(c, 10, 500)
``` |
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169 | ```
* here instead of 510 samples only 500 samples would be output
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170 | ```
*
``` |
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171 | 115329f1 | Diego Biurrun | ```
* note, due to rounding the actual compensation might be slightly different,
``` |

172 | 788d7a8c | Michael Niedermayer | ```
* especially if the compensation_distance is large and the in_rate used during init is small
``` |

173 | ```
*/
``` |
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174 | aaaf1635 | Michael Niedermayer | void av_resample_compensate(AVResampleContext *c, int sample_delta, int compensation_distance){ |

175 | 08f7073a | Michael Niedermayer | ```
// sample_delta += (c->ideal_dst_incr - c->dst_incr)*(int64_t)c->compensation_distance / c->ideal_dst_incr;
``` |

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

177 | 08f7073a | Michael Niedermayer | c->dst_incr = c->ideal_dst_incr - c->ideal_dst_incr * (int64_t)sample_delta / compensation_distance; |

178 | aaaf1635 | Michael Niedermayer | } |

179 | |||

180 | ```
/**
``` |
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181 | ```
* resamples.
``` |
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182 | ```
* @param src an array of unconsumed samples
``` |
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183 | ```
* @param consumed the number of samples of src which have been consumed are returned here
``` |
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184 | ```
* @param src_size the number of unconsumed samples available
``` |
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185 | ```
* @param dst_size the amount of space in samples available in dst
``` |
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186 | ```
* @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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187 | ```
* @return the number of samples written in dst or -1 if an error occured
``` |
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188 | ```
*/
``` |
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189 | int av_resample(AVResampleContext *c, short *dst, short *src, int *consumed, int src_size, int dst_size, int update_ctx){ |
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190 | ```
int dst_index, i;
``` |
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191 | ```
int index= c->index;
``` |
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192 | ```
int frac= c->frac;
``` |
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193 | ```
int dst_incr_frac= c->dst_incr % c->src_incr;
``` |
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194 | ```
int dst_incr= c->dst_incr / c->src_incr;
``` |
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195 | 80e85288 | Michael Niedermayer | ```
int compensation_distance= c->compensation_distance;
``` |

196 | 53f0090d | Michael Niedermayer | |

197 | 6cb5dcb3 | Michael Niedermayer | if(compensation_distance == 0 && c->filter_length == 1 && c->phase_shift==0){ |

198 | 53f0090d | Michael Niedermayer | ```
int64_t index2= ((int64_t)index)<<32;
``` |

199 | int64_t incr= (1LL<<32) * c->dst_incr / c->src_incr; |
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200 | ```
dst_size= FFMIN(dst_size, (src_size-1-index) * (int64_t)c->src_incr / c->dst_incr);
``` |
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201 | 115329f1 | Diego Biurrun | |

202 | 6cb5dcb3 | Michael Niedermayer | for(dst_index=0; dst_index < dst_size; dst_index++){ |

203 | 53f0090d | Michael Niedermayer | ```
dst[dst_index] = src[index2>>32];
``` |

204 | index2 += incr; |
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205 | 6cb5dcb3 | Michael Niedermayer | } |

206 | 53f0090d | Michael Niedermayer | frac += dst_index * dst_incr_frac; |

207 | index += dst_index * dst_incr; |
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208 | index += frac / c->src_incr; |
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209 | frac %= c->src_incr; |
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210 | 6cb5dcb3 | Michael Niedermayer | ```
}else{
``` |

211 | aaaf1635 | Michael Niedermayer | for(dst_index=0; dst_index < dst_size; dst_index++){ |

212 | ed861c6b | Michael Niedermayer | FELEM *filter= c->filter_bank + c->filter_length*(index & c->phase_mask); |

213 | ```
int sample_index= index >> c->phase_shift;
``` |
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214 | 51a88020 | Michael Niedermayer | ```
FELEM2 val=0;
``` |

215 | 115329f1 | Diego Biurrun | |

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

217 | for(i=0; i<c->filter_length; i++) |
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218 | c26abfa5 | Diego Biurrun | val += src[FFABS(sample_index + i) % src_size] * filter[i]; |

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

220 | ```
break;
``` |
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221 | ed861c6b | Michael Niedermayer | }else if(c->linear){ |

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

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

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

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

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

227 | } |
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228 | f25ba8b3 | Michael Niedermayer | ```
val= v>>8;
``` |

229 | ed861c6b | Michael Niedermayer | ```
}else{
``` |

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

231 | 51a88020 | Michael Niedermayer | val += src[sample_index + i] * (FELEM2)filter[i]; |

232 | aaaf1635 | Michael Niedermayer | } |

233 | } |
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234 | |||

235 | val = (val + (1<<(FILTER_SHIFT-1)))>>FILTER_SHIFT; |
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236 | dst[dst_index] = (unsigned)(val + 32768) > 65535 ? (val>>31) ^ 32767 : val; |
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237 | |||

238 | frac += dst_incr_frac; |
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239 | index += dst_incr; |
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240 | ```
if(frac >= c->src_incr){
``` |
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241 | frac -= c->src_incr; |
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242 | index++; |
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243 | } |
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244 | 80e85288 | Michael Niedermayer | |

245 | if(dst_index + 1 == compensation_distance){ |
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246 | ```
compensation_distance= 0;
``` |
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247 | dst_incr_frac= c->ideal_dst_incr % c->src_incr; |
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248 | dst_incr= c->ideal_dst_incr / c->src_incr; |
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249 | } |
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250 | aaaf1635 | Michael Niedermayer | } |

251 | 6cb5dcb3 | Michael Niedermayer | } |

252 | ed861c6b | Michael Niedermayer | ```
*consumed= FFMAX(index, 0) >> c->phase_shift;
``` |

253 | 4e255822 | Michael Niedermayer | if(index>=0) index &= c->phase_mask; |

254 | b9d2085b | Michael Niedermayer | |

255 | 80e85288 | Michael Niedermayer | ```
if(compensation_distance){
``` |

256 | compensation_distance -= dst_index; |
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257 | ```
assert(compensation_distance > 0);
``` |
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258 | } |
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259 | aaaf1635 | Michael Niedermayer | ```
if(update_ctx){
``` |

260 | c->frac= frac; |
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261 | b9d2085b | Michael Niedermayer | c->index= index; |

262 | 80e85288 | Michael Niedermayer | c->dst_incr= dst_incr_frac + c->src_incr*dst_incr; |

263 | c->compensation_distance= compensation_distance; |
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264 | aaaf1635 | Michael Niedermayer | } |

265 | 115329f1 | Diego Biurrun | ```
#if 0
``` |

266 | 08f7073a | Michael Niedermayer | ```
if(update_ctx && !c->compensation_distance){
``` |

267 | ```
#undef rand
``` |
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268 | ```
av_resample_compensate(c, rand() % (8000*2) - 8000, 8000*2);
``` |
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269 | ```
av_log(NULL, AV_LOG_DEBUG, "%d %d %d\n", c->dst_incr, c->ideal_dst_incr, c->compensation_distance);
``` |
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270 | ```
}
``` |
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271 | ```
#endif
``` |
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272 | 115329f1 | Diego Biurrun | |

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

274 | } |