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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/mathematics.h" | |
26 | #include "fft.h" | |
27 | #include "fft-internal.h" | |
28 | ||
29 | /** | |
30 | * @file | |
31 | * MDCT/IMDCT transforms. | |
32 | */ | |
33 | ||
34 | #if FFT_FLOAT | |
35 | # define RSCALE(x) (x) | |
36 | #else | |
37 | #if FFT_FIXED_32 | |
38 | # define RSCALE(x) (((x) + 32) >> 6) | |
39 | #else /* FFT_FIXED_32 */ | |
40 | # define RSCALE(x) ((x) >> 1) | |
41 | #endif /* FFT_FIXED_32 */ | |
42 | #endif | |
43 | ||
44 | /** | |
45 | * init MDCT or IMDCT computation. | |
46 | */ | |
47 | av_cold int ff_mdct_init(FFTContext *s, int nbits, int inverse, double scale) | |
48 | { | |
49 | int n, n4, i; | |
50 | double alpha, theta; | |
51 | int tstep; | |
52 | ||
53 | memset(s, 0, sizeof(*s)); | |
54 | n = 1 << nbits; | |
55 | s->mdct_bits = nbits; | |
56 | s->mdct_size = n; | |
57 | n4 = n >> 2; | |
58 | s->mdct_permutation = FF_MDCT_PERM_NONE; | |
59 | ||
60 | if (ff_fft_init(s, s->mdct_bits - 2, inverse) < 0) | |
61 | goto fail; | |
62 | ||
63 | s->tcos = av_malloc_array(n/2, sizeof(FFTSample)); | |
64 | if (!s->tcos) | |
65 | goto fail; | |
66 | ||
67 | switch (s->mdct_permutation) { | |
68 | case FF_MDCT_PERM_NONE: | |
69 | s->tsin = s->tcos + n4; | |
70 | tstep = 1; | |
71 | break; | |
72 | case FF_MDCT_PERM_INTERLEAVE: | |
73 | s->tsin = s->tcos + 1; | |
74 | tstep = 2; | |
75 | break; | |
76 | default: | |
77 | goto fail; | |
78 | } | |
79 | ||
80 | theta = 1.0 / 8.0 + (scale < 0 ? n4 : 0); | |
81 | scale = sqrt(fabs(scale)); | |
82 | for(i=0;i<n4;i++) { | |
83 | alpha = 2 * M_PI * (i + theta) / n; | |
84 | s->tcos[i*tstep] = FIX15(-cos(alpha) * scale); | |
85 | s->tsin[i*tstep] = FIX15(-sin(alpha) * scale); | |
86 | } | |
87 | return 0; | |
88 | fail: | |
89 | ff_mdct_end(s); | |
90 | return -1; | |
91 | } | |
92 | ||
93 | /** | |
94 | * Compute the middle half of the inverse MDCT of size N = 2^nbits, | |
95 | * thus excluding the parts that can be derived by symmetry | |
96 | * @param output N/2 samples | |
97 | * @param input N/2 samples | |
98 | */ | |
99 | void ff_imdct_half_c(FFTContext *s, FFTSample *output, const FFTSample *input) | |
100 | { | |
101 | int k, n8, n4, n2, n, j; | |
102 | const uint16_t *revtab = s->revtab; | |
103 | const FFTSample *tcos = s->tcos; | |
104 | const FFTSample *tsin = s->tsin; | |
105 | const FFTSample *in1, *in2; | |
106 | FFTComplex *z = (FFTComplex *)output; | |
107 | ||
108 | n = 1 << s->mdct_bits; | |
109 | n2 = n >> 1; | |
110 | n4 = n >> 2; | |
111 | n8 = n >> 3; | |
112 | ||
113 | /* pre rotation */ | |
114 | in1 = input; | |
115 | in2 = input + n2 - 1; | |
116 | for(k = 0; k < n4; k++) { | |
117 | j=revtab[k]; | |
118 | CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]); | |
119 | in1 += 2; | |
120 | in2 -= 2; | |
121 | } | |
122 | s->fft_calc(s, z); | |
123 | ||
124 | /* post rotation + reordering */ | |
125 | for(k = 0; k < n8; k++) { | |
126 | FFTSample r0, i0, r1, i1; | |
127 | CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]); | |
128 | CMUL(r1, i0, z[n8+k ].im, z[n8+k ].re, tsin[n8+k ], tcos[n8+k ]); | |
129 | z[n8-k-1].re = r0; | |
130 | z[n8-k-1].im = i0; | |
131 | z[n8+k ].re = r1; | |
132 | z[n8+k ].im = i1; | |
133 | } | |
134 | } | |
135 | ||
136 | /** | |
137 | * Compute inverse MDCT of size N = 2^nbits | |
138 | * @param output N samples | |
139 | * @param input N/2 samples | |
140 | */ | |
141 | void ff_imdct_calc_c(FFTContext *s, FFTSample *output, const FFTSample *input) | |
142 | { | |
143 | int k; | |
144 | int n = 1 << s->mdct_bits; | |
145 | int n2 = n >> 1; | |
146 | int n4 = n >> 2; | |
147 | ||
148 | ff_imdct_half_c(s, output+n4, input); | |
149 | ||
150 | for(k = 0; k < n4; k++) { | |
151 | output[k] = -output[n2-k-1]; | |
152 | output[n-k-1] = output[n2+k]; | |
153 | } | |
154 | } | |
155 | ||
156 | /** | |
157 | * Compute MDCT of size N = 2^nbits | |
158 | * @param input N samples | |
159 | * @param out N/2 samples | |
160 | */ | |
161 | void ff_mdct_calc_c(FFTContext *s, FFTSample *out, const FFTSample *input) | |
162 | { | |
163 | int i, j, n, n8, n4, n2, n3; | |
164 | FFTDouble re, im; | |
165 | const uint16_t *revtab = s->revtab; | |
166 | const FFTSample *tcos = s->tcos; | |
167 | const FFTSample *tsin = s->tsin; | |
168 | FFTComplex *x = (FFTComplex *)out; | |
169 | ||
170 | n = 1 << s->mdct_bits; | |
171 | n2 = n >> 1; | |
172 | n4 = n >> 2; | |
173 | n8 = n >> 3; | |
174 | n3 = 3 * n4; | |
175 | ||
176 | /* pre rotation */ | |
177 | for(i=0;i<n8;i++) { | |
178 | re = RSCALE(-input[2*i+n3] - input[n3-1-2*i]); | |
179 | im = RSCALE(-input[n4+2*i] + input[n4-1-2*i]); | |
180 | j = revtab[i]; | |
181 | CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]); | |
182 | ||
183 | re = RSCALE( input[2*i] - input[n2-1-2*i]); | |
184 | im = RSCALE(-input[n2+2*i] - input[ n-1-2*i]); | |
185 | j = revtab[n8 + i]; | |
186 | CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]); | |
187 | } | |
188 | ||
189 | s->fft_calc(s, x); | |
190 | ||
191 | /* post rotation */ | |
192 | for(i=0;i<n8;i++) { | |
193 | FFTSample r0, i0, r1, i1; | |
194 | CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]); | |
195 | CMUL(i0, r1, x[n8+i ].re, x[n8+i ].im, -tsin[n8+i ], -tcos[n8+i ]); | |
196 | x[n8-i-1].re = r0; | |
197 | x[n8-i-1].im = i0; | |
198 | x[n8+i ].re = r1; | |
199 | x[n8+i ].im = i1; | |
200 | } | |
201 | } | |
202 | ||
203 | av_cold void ff_mdct_end(FFTContext *s) | |
204 | { | |
205 | av_freep(&s->tcos); | |
206 | ff_fft_end(s); | |
207 | } |