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path: root/libavcodec/mdct_template.c (plain)
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1/*
2 * MDCT/IMDCT transforms
3 * Copyright (c) 2002 Fabrice Bellard
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
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
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22#include <stdlib.h>
23#include <string.h>
24#include "libavutil/common.h"
25#include "libavutil/libm.h"
26#include "libavutil/mathematics.h"
27#include "fft.h"
28#include "fft-internal.h"
29
30/**
31 * @file
32 * MDCT/IMDCT transforms.
33 */
34
35#if FFT_FLOAT
36# define RSCALE(x) (x)
37#else
38#if FFT_FIXED_32
39# define RSCALE(x) (((x) + 32) >> 6)
40#else /* FFT_FIXED_32 */
41# define RSCALE(x) ((x) >> 1)
42#endif /* FFT_FIXED_32 */
43#endif
44
45/**
46 * init MDCT or IMDCT computation.
47 */
48av_cold int ff_mdct_init(FFTContext *s, int nbits, int inverse, double scale)
49{
50 int n, n4, i;
51 double alpha, theta;
52 int tstep;
53
54 memset(s, 0, sizeof(*s));
55 n = 1 << nbits;
56 s->mdct_bits = nbits;
57 s->mdct_size = n;
58 n4 = n >> 2;
59 s->mdct_permutation = FF_MDCT_PERM_NONE;
60
61 if (ff_fft_init(s, s->mdct_bits - 2, inverse) < 0)
62 goto fail;
63
64 s->tcos = av_malloc_array(n/2, sizeof(FFTSample));
65 if (!s->tcos)
66 goto fail;
67
68 switch (s->mdct_permutation) {
69 case FF_MDCT_PERM_NONE:
70 s->tsin = s->tcos + n4;
71 tstep = 1;
72 break;
73 case FF_MDCT_PERM_INTERLEAVE:
74 s->tsin = s->tcos + 1;
75 tstep = 2;
76 break;
77 default:
78 goto fail;
79 }
80
81 theta = 1.0 / 8.0 + (scale < 0 ? n4 : 0);
82 scale = sqrt(fabs(scale));
83 for(i=0;i<n4;i++) {
84 alpha = 2 * M_PI * (i + theta) / n;
85#if FFT_FIXED_32
86 s->tcos[i*tstep] = lrint(-cos(alpha) * 2147483648.0);
87 s->tsin[i*tstep] = lrint(-sin(alpha) * 2147483648.0);
88#else
89 s->tcos[i*tstep] = FIX15(-cos(alpha) * scale);
90 s->tsin[i*tstep] = FIX15(-sin(alpha) * scale);
91#endif
92 }
93 return 0;
94 fail:
95 ff_mdct_end(s);
96 return -1;
97}
98
99/**
100 * Compute the middle half of the inverse MDCT of size N = 2^nbits,
101 * thus excluding the parts that can be derived by symmetry
102 * @param output N/2 samples
103 * @param input N/2 samples
104 */
105void ff_imdct_half_c(FFTContext *s, FFTSample *output, const FFTSample *input)
106{
107 int k, n8, n4, n2, n, j;
108 const uint16_t *revtab = s->revtab;
109 const FFTSample *tcos = s->tcos;
110 const FFTSample *tsin = s->tsin;
111 const FFTSample *in1, *in2;
112 FFTComplex *z = (FFTComplex *)output;
113
114 n = 1 << s->mdct_bits;
115 n2 = n >> 1;
116 n4 = n >> 2;
117 n8 = n >> 3;
118
119 /* pre rotation */
120 in1 = input;
121 in2 = input + n2 - 1;
122 for(k = 0; k < n4; k++) {
123 j=revtab[k];
124 CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]);
125 in1 += 2;
126 in2 -= 2;
127 }
128 s->fft_calc(s, z);
129
130 /* post rotation + reordering */
131 for(k = 0; k < n8; k++) {
132 FFTSample r0, i0, r1, i1;
133 CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]);
134 CMUL(r1, i0, z[n8+k ].im, z[n8+k ].re, tsin[n8+k ], tcos[n8+k ]);
135 z[n8-k-1].re = r0;
136 z[n8-k-1].im = i0;
137 z[n8+k ].re = r1;
138 z[n8+k ].im = i1;
139 }
140}
141
142/**
143 * Compute inverse MDCT of size N = 2^nbits
144 * @param output N samples
145 * @param input N/2 samples
146 */
147void ff_imdct_calc_c(FFTContext *s, FFTSample *output, const FFTSample *input)
148{
149 int k;
150 int n = 1 << s->mdct_bits;
151 int n2 = n >> 1;
152 int n4 = n >> 2;
153
154 ff_imdct_half_c(s, output+n4, input);
155
156 for(k = 0; k < n4; k++) {
157 output[k] = -output[n2-k-1];
158 output[n-k-1] = output[n2+k];
159 }
160}
161
162/**
163 * Compute MDCT of size N = 2^nbits
164 * @param input N samples
165 * @param out N/2 samples
166 */
167void ff_mdct_calc_c(FFTContext *s, FFTSample *out, const FFTSample *input)
168{
169 int i, j, n, n8, n4, n2, n3;
170 FFTDouble re, im;
171 const uint16_t *revtab = s->revtab;
172 const FFTSample *tcos = s->tcos;
173 const FFTSample *tsin = s->tsin;
174 FFTComplex *x = (FFTComplex *)out;
175
176 n = 1 << s->mdct_bits;
177 n2 = n >> 1;
178 n4 = n >> 2;
179 n8 = n >> 3;
180 n3 = 3 * n4;
181
182 /* pre rotation */
183 for(i=0;i<n8;i++) {
184 re = RSCALE(-input[2*i+n3] - input[n3-1-2*i]);
185 im = RSCALE(-input[n4+2*i] + input[n4-1-2*i]);
186 j = revtab[i];
187 CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);
188
189 re = RSCALE( input[2*i] - input[n2-1-2*i]);
190 im = RSCALE(-input[n2+2*i] - input[ n-1-2*i]);
191 j = revtab[n8 + i];
192 CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
193 }
194
195 s->fft_calc(s, x);
196
197 /* post rotation */
198 for(i=0;i<n8;i++) {
199 FFTSample r0, i0, r1, i1;
200 CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]);
201 CMUL(i0, r1, x[n8+i ].re, x[n8+i ].im, -tsin[n8+i ], -tcos[n8+i ]);
202 x[n8-i-1].re = r0;
203 x[n8-i-1].im = i0;
204 x[n8+i ].re = r1;
205 x[n8+i ].im = i1;
206 }
207}
208
209av_cold void ff_mdct_end(FFTContext *s)
210{
211 av_freep(&s->tcos);
212 ff_fft_end(s);
213}
214
generated by cgit at 2024-05-17 13:00:44 (GMT)