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Rev | Author | Line No. | Line |
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4349 | Serge | 1 | /* |
2 | * MDCT/IMDCT transforms |
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3 | * Copyright (c) 2002 Fabrice Bellard |
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4 | * |
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5 | * This file is part of FFmpeg. |
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6 | * |
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7 | * FFmpeg is free software; you can redistribute it and/or |
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8 | * modify it under the terms of the GNU Lesser General Public |
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9 | * License as published by the Free Software Foundation; either |
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10 | * version 2.1 of the License, or (at your option) any later version. |
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11 | * |
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12 | * FFmpeg is distributed in the hope that it will be useful, |
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13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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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 | * License along with FFmpeg; if not, write to the Free Software |
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19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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20 | */ |
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21 | |||
22 | #include |
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23 | #include |
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24 | #include "libavutil/common.h" |
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25 | #include "libavutil/mathematics.h" |
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26 | #include "fft.h" |
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27 | #include "fft-internal.h" |
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28 | |||
29 | /** |
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30 | * @file |
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31 | * MDCT/IMDCT transforms. |
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32 | */ |
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33 | |||
34 | #if CONFIG_FFT_FLOAT |
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35 | # define RSCALE(x) (x) |
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36 | #else |
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37 | #if CONFIG_FFT_FIXED_32 |
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38 | # define RSCALE(x) (((x) + 32) >> 6) |
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39 | #else /* CONFIG_FFT_FIXED_32 */ |
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40 | # define RSCALE(x) ((x) >> 1) |
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41 | #endif /* CONFIG_FFT_FIXED_32 */ |
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42 | #endif |
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43 | |||
44 | /** |
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45 | * init MDCT or IMDCT computation. |
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46 | */ |
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47 | av_cold int ff_mdct_init(FFTContext *s, int nbits, int inverse, double scale) |
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48 | { |
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49 | int n, n4, i; |
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50 | double alpha, theta; |
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51 | int tstep; |
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52 | |||
53 | memset(s, 0, sizeof(*s)); |
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54 | n = 1 << nbits; |
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55 | s->mdct_bits = nbits; |
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56 | s->mdct_size = n; |
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57 | n4 = n >> 2; |
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58 | s->mdct_permutation = FF_MDCT_PERM_NONE; |
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59 | |||
60 | if (ff_fft_init(s, s->mdct_bits - 2, inverse) < 0) |
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61 | goto fail; |
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62 | |||
63 | s->tcos = av_malloc(n/2 * sizeof(FFTSample)); |
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64 | if (!s->tcos) |
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65 | goto fail; |
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66 | |||
67 | switch (s->mdct_permutation) { |
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68 | case FF_MDCT_PERM_NONE: |
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69 | s->tsin = s->tcos + n4; |
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70 | tstep = 1; |
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71 | break; |
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72 | case FF_MDCT_PERM_INTERLEAVE: |
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73 | s->tsin = s->tcos + 1; |
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74 | tstep = 2; |
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75 | break; |
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76 | default: |
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77 | goto fail; |
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78 | } |
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79 | |||
80 | theta = 1.0 / 8.0 + (scale < 0 ? n4 : 0); |
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81 | scale = sqrt(fabs(scale)); |
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82 | for(i=0;i |
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83 | alpha = 2 * M_PI * (i + theta) / n; |
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84 | s->tcos[i*tstep] = FIX15(-cos(alpha) * scale); |
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85 | s->tsin[i*tstep] = FIX15(-sin(alpha) * scale); |
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86 | } |
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87 | return 0; |
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88 | fail: |
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89 | ff_mdct_end(s); |
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90 | return -1; |
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91 | } |
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92 | |||
93 | /** |
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94 | * Compute the middle half of the inverse MDCT of size N = 2^nbits, |
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95 | * thus excluding the parts that can be derived by symmetry |
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96 | * @param output N/2 samples |
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97 | * @param input N/2 samples |
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98 | */ |
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99 | void ff_imdct_half_c(FFTContext *s, FFTSample *output, const FFTSample *input) |
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100 | { |
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101 | int k, n8, n4, n2, n, j; |
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102 | const uint16_t *revtab = s->revtab; |
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103 | const FFTSample *tcos = s->tcos; |
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104 | const FFTSample *tsin = s->tsin; |
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105 | const FFTSample *in1, *in2; |
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106 | FFTComplex *z = (FFTComplex *)output; |
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107 | |||
108 | n = 1 << s->mdct_bits; |
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109 | n2 = n >> 1; |
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110 | n4 = n >> 2; |
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111 | n8 = n >> 3; |
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112 | |||
113 | /* pre rotation */ |
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114 | in1 = input; |
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115 | in2 = input + n2 - 1; |
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116 | for(k = 0; k < n4; k++) { |
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117 | j=revtab[k]; |
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118 | CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]); |
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119 | in1 += 2; |
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120 | in2 -= 2; |
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121 | } |
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122 | s->fft_calc(s, z); |
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123 | |||
124 | /* post rotation + reordering */ |
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125 | for(k = 0; k < n8; k++) { |
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126 | FFTSample r0, i0, r1, i1; |
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127 | CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]); |
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128 | CMUL(r1, i0, z[n8+k ].im, z[n8+k ].re, tsin[n8+k ], tcos[n8+k ]); |
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129 | z[n8-k-1].re = r0; |
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130 | z[n8-k-1].im = i0; |
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131 | z[n8+k ].re = r1; |
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132 | z[n8+k ].im = i1; |
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133 | } |
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134 | } |
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135 | |||
136 | /** |
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137 | * Compute inverse MDCT of size N = 2^nbits |
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138 | * @param output N samples |
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139 | * @param input N/2 samples |
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140 | */ |
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141 | void ff_imdct_calc_c(FFTContext *s, FFTSample *output, const FFTSample *input) |
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142 | { |
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143 | int k; |
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144 | int n = 1 << s->mdct_bits; |
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145 | int n2 = n >> 1; |
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146 | int n4 = n >> 2; |
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147 | |||
148 | ff_imdct_half_c(s, output+n4, input); |
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149 | |||
150 | for(k = 0; k < n4; k++) { |
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151 | output[k] = -output[n2-k-1]; |
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152 | output[n-k-1] = output[n2+k]; |
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153 | } |
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154 | } |
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155 | |||
156 | /** |
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157 | * Compute MDCT of size N = 2^nbits |
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158 | * @param input N samples |
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159 | * @param out N/2 samples |
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160 | */ |
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161 | void ff_mdct_calc_c(FFTContext *s, FFTSample *out, const FFTSample *input) |
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162 | { |
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163 | int i, j, n, n8, n4, n2, n3; |
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164 | FFTDouble re, im; |
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165 | const uint16_t *revtab = s->revtab; |
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166 | const FFTSample *tcos = s->tcos; |
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167 | const FFTSample *tsin = s->tsin; |
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168 | FFTComplex *x = (FFTComplex *)out; |
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169 | |||
170 | n = 1 << s->mdct_bits; |
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171 | n2 = n >> 1; |
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172 | n4 = n >> 2; |
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173 | n8 = n >> 3; |
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174 | n3 = 3 * n4; |
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175 | |||
176 | /* pre rotation */ |
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177 | for(i=0;i |
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178 | re = RSCALE(-input[2*i+n3] - input[n3-1-2*i]); |
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179 | im = RSCALE(-input[n4+2*i] + input[n4-1-2*i]); |
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180 | j = revtab[i]; |
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181 | CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]); |
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182 | |||
183 | re = RSCALE( input[2*i] - input[n2-1-2*i]); |
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184 | im = RSCALE(-input[n2+2*i] - input[ n-1-2*i]); |
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185 | j = revtab[n8 + i]; |
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186 | CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]); |
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187 | } |
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188 | |||
189 | s->fft_calc(s, x); |
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190 | |||
191 | /* post rotation */ |
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192 | for(i=0;i |
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193 | FFTSample r0, i0, r1, i1; |
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194 | CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]); |
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195 | CMUL(i0, r1, x[n8+i ].re, x[n8+i ].im, -tsin[n8+i ], -tcos[n8+i ]); |
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196 | x[n8-i-1].re = r0; |
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197 | x[n8-i-1].im = i0; |
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198 | x[n8+i ].re = r1; |
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199 | x[n8+i ].im = i1; |
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200 | } |
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201 | } |
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202 | |||
203 | av_cold void ff_mdct_end(FFTContext *s) |
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204 | { |
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205 | av_freep(&s->tcos); |
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206 | ff_fft_end(s); |
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207 | }><>>><>>>><>>>><> |