Remove documentation of non-existing function parameters.
[libav.git] / libavcodec / mdct.c
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1/*
2 * MDCT/IMDCT transforms
406792e7 3 * Copyright (c) 2002 Fabrice Bellard
bb6f5690 4 *
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5 * This file is part of FFmpeg.
6 *
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
9 * License as published by the Free Software Foundation; either
b78e7197 10 * version 2.1 of the License, or (at your option) any later version.
bb6f5690 11 *
b78e7197 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
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
b78e7197 18 * License along with FFmpeg; if not, write to the Free Software
5509bffa 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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20 */
21#include "dsputil.h"
22
983e3246 23/**
bad5537e 24 * @file libavcodec/mdct.c
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25 * MDCT/IMDCT transforms.
26 */
27
4eb7a735 28// Generate a Kaiser-Bessel Derived Window.
3ed546fe 29#define BESSEL_I0_ITER 50 // default: 50 iterations of Bessel I0 approximation
5363c43e 30av_cold void ff_kbd_window_init(float *window, float alpha, int n)
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31{
32 int i, j;
33 double sum = 0.0, bessel, tmp;
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34 double local_window[n];
35 double alpha2 = (alpha * M_PI / n) * (alpha * M_PI / n);
4eb7a735 36
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37 for (i = 0; i < n; i++) {
38 tmp = i * (n - i) * alpha2;
4eb7a735 39 bessel = 1.0;
3ed546fe 40 for (j = BESSEL_I0_ITER; j > 0; j--)
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41 bessel = bessel * tmp / (j * j) + 1;
42 sum += bessel;
43 local_window[i] = sum;
44 }
45
46 sum++;
3ed546fe 47 for (i = 0; i < n; i++)
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48 window[i] = sqrt(local_window[i] / sum);
49}
50
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51DECLARE_ALIGNED(16, float, ff_sine_128 [ 128]);
52DECLARE_ALIGNED(16, float, ff_sine_256 [ 256]);
53DECLARE_ALIGNED(16, float, ff_sine_512 [ 512]);
54DECLARE_ALIGNED(16, float, ff_sine_1024[1024]);
55DECLARE_ALIGNED(16, float, ff_sine_2048[2048]);
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56DECLARE_ALIGNED(16, float, ff_sine_4096[4096]);
57float *ff_sine_windows[6] = {
58 ff_sine_128, ff_sine_256, ff_sine_512, ff_sine_1024, ff_sine_2048, ff_sine_4096
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59};
60
9146e4d6 61// Generate a sine window.
5363c43e 62av_cold void ff_sine_window_init(float *window, int n) {
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63 int i;
64 for(i = 0; i < n; i++)
71375e05 65 window[i] = sinf((i + 0.5) * (M_PI / (2.0 * n)));
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66}
67
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68/**
69 * init MDCT or IMDCT computation.
bb6f5690 70 */
5363c43e 71av_cold int ff_mdct_init(MDCTContext *s, int nbits, int inverse)
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72{
73 int n, n4, i;
77f11d8a 74 double alpha;
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75
76 memset(s, 0, sizeof(*s));
77 n = 1 << nbits;
78 s->nbits = nbits;
79 s->n = n;
80 n4 = n >> 2;
d9823692 81 s->tcos = av_malloc(n4 * sizeof(FFTSample));
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82 if (!s->tcos)
83 goto fail;
d9823692 84 s->tsin = av_malloc(n4 * sizeof(FFTSample));
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85 if (!s->tsin)
86 goto fail;
87
88 for(i=0;i<n4;i++) {
89 alpha = 2 * M_PI * (i + 1.0 / 8.0) / n;
90 s->tcos[i] = -cos(alpha);
91 s->tsin[i] = -sin(alpha);
92 }
68951ecf 93 if (ff_fft_init(&s->fft, s->nbits - 2, inverse) < 0)
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94 goto fail;
95 return 0;
96 fail:
97 av_freep(&s->tcos);
98 av_freep(&s->tsin);
99 return -1;
100}
101
102/* complex multiplication: p = a * b */
103#define CMUL(pre, pim, are, aim, bre, bim) \
104{\
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105 FFTSample _are = (are);\
106 FFTSample _aim = (aim);\
107 FFTSample _bre = (bre);\
108 FFTSample _bim = (bim);\
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109 (pre) = _are * _bre - _aim * _bim;\
110 (pim) = _are * _bim + _aim * _bre;\
111}
112
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113/**
114 * Compute the middle half of the inverse MDCT of size N = 2^nbits,
115 * thus excluding the parts that can be derived by symmetry
116 * @param output N/2 samples
117 * @param input N/2 samples
118 */
d46ac5bf 119void ff_imdct_half_c(MDCTContext *s, FFTSample *output, const FFTSample *input)
bb6f5690 120{
46803f4f 121 int k, n8, n4, n2, n, j;
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122 const uint16_t *revtab = s->fft.revtab;
123 const FFTSample *tcos = s->tcos;
124 const FFTSample *tsin = s->tsin;
125 const FFTSample *in1, *in2;
46803f4f 126 FFTComplex *z = (FFTComplex *)output;
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127
128 n = 1 << s->nbits;
129 n2 = n >> 1;
130 n4 = n >> 2;
46803f4f 131 n8 = n >> 3;
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132
133 /* pre rotation */
134 in1 = input;
135 in2 = input + n2 - 1;
136 for(k = 0; k < n4; k++) {
137 j=revtab[k];
138 CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]);
139 in1 += 2;
140 in2 -= 2;
141 }
68951ecf 142 ff_fft_calc(&s->fft, z);
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143
144 /* post rotation + reordering */
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145 output += n4;
146 for(k = 0; k < n8; k++) {
147 FFTSample r0, i0, r1, i1;
148 CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]);
149 CMUL(r1, i0, z[n8+k ].im, z[n8+k ].re, tsin[n8+k ], tcos[n8+k ]);
150 z[n8-k-1].re = r0;
151 z[n8-k-1].im = i0;
152 z[n8+k ].re = r1;
153 z[n8+k ].im = i1;
bb6f5690 154 }
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155}
156
157/**
158 * Compute inverse MDCT of size N = 2^nbits
159 * @param output N samples
160 * @param input N/2 samples
b9fa3208 161 */
d46ac5bf 162void ff_imdct_calc_c(MDCTContext *s, FFTSample *output, const FFTSample *input)
b9fa3208 163{
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164 int k;
165 int n = 1 << s->nbits;
166 int n2 = n >> 1;
167 int n4 = n >> 2;
bb6f5690 168
d46ac5bf 169 ff_imdct_half_c(s, output+n4, input);
bb6f5690 170
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171 for(k = 0; k < n4; k++) {
172 output[k] = -output[n2-k-1];
173 output[n-k-1] = output[n2+k];
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174 }
175}
176
177/**
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178 * Compute MDCT of size N = 2^nbits
179 * @param input N samples
180 * @param out N/2 samples
bb6f5690 181 */
0a570e82 182void ff_mdct_calc(MDCTContext *s, FFTSample *out, const FFTSample *input)
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183{
184 int i, j, n, n8, n4, n2, n3;
0a570e82 185 FFTSample re, im;
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186 const uint16_t *revtab = s->fft.revtab;
187 const FFTSample *tcos = s->tcos;
188 const FFTSample *tsin = s->tsin;
46803f4f 189 FFTComplex *x = (FFTComplex *)out;
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190
191 n = 1 << s->nbits;
192 n2 = n >> 1;
193 n4 = n >> 2;
194 n8 = n >> 3;
195 n3 = 3 * n4;
196
197 /* pre rotation */
198 for(i=0;i<n8;i++) {
199 re = -input[2*i+3*n4] - input[n3-1-2*i];
200 im = -input[n4+2*i] + input[n4-1-2*i];
201 j = revtab[i];
202 CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);
203
204 re = input[2*i] - input[n2-1-2*i];
205 im = -(input[n2+2*i] + input[n-1-2*i]);
206 j = revtab[n8 + i];
207 CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
208 }
209
68951ecf 210 ff_fft_calc(&s->fft, x);
115329f1 211
bb6f5690 212 /* post rotation */
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213 for(i=0;i<n8;i++) {
214 FFTSample r0, i0, r1, i1;
215 CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]);
216 CMUL(i0, r1, x[n8+i ].re, x[n8+i ].im, -tsin[n8+i ], -tcos[n8+i ]);
217 x[n8-i-1].re = r0;
218 x[n8-i-1].im = i0;
219 x[n8+i ].re = r1;
220 x[n8+i ].im = i1;
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221 }
222}
223
5363c43e 224av_cold void ff_mdct_end(MDCTContext *s)
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225{
226 av_freep(&s->tcos);
227 av_freep(&s->tsin);
68951ecf 228 ff_fft_end(&s->fft);
bb6f5690 229}