81b6843e91b00426ec33807b18027141fa9ac6b8
[libav.git] / libavcodec / fft.c
1 /*
2 * FFT/IFFT transforms
3 * Copyright (c) 2002 Fabrice Bellard.
4 *
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
9 *
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
14 *
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
18 */
19
20 /**
21 * @file fft.c
22 * FFT/IFFT transforms.
23 */
24
25 #include "dsputil.h"
26
27 /**
28 * The size of the FFT is 2^nbits. If inverse is TRUE, inverse FFT is
29 * done
30 */
31 int ff_fft_init(FFTContext *s, int nbits, int inverse)
32 {
33 int i, j, m, n;
34 float alpha, c1, s1, s2;
35
36 s->nbits = nbits;
37 n = 1 << nbits;
38
39 s->exptab = av_malloc((n / 2) * sizeof(FFTComplex));
40 if (!s->exptab)
41 goto fail;
42 s->revtab = av_malloc(n * sizeof(uint16_t));
43 if (!s->revtab)
44 goto fail;
45 s->inverse = inverse;
46
47 s2 = inverse ? 1.0 : -1.0;
48
49 for(i=0;i<(n/2);i++) {
50 alpha = 2 * M_PI * (float)i / (float)n;
51 c1 = cos(alpha);
52 s1 = sin(alpha) * s2;
53 s->exptab[i].re = c1;
54 s->exptab[i].im = s1;
55 }
56 s->fft_calc = ff_fft_calc_c;
57 s->exptab1 = NULL;
58
59 /* compute constant table for HAVE_SSE version */
60 #if (defined(HAVE_MMX) && defined(HAVE_BUILTIN_VECTOR)) || defined(HAVE_ALTIVEC)
61 {
62 int has_vectors = 0;
63
64 #if defined(HAVE_MMX)
65 has_vectors = mm_support() & MM_SSE;
66 #endif
67 #if defined(HAVE_ALTIVEC) && !defined(ALTIVEC_USE_REFERENCE_C_CODE)
68 has_vectors = mm_support() & MM_ALTIVEC;
69 #endif
70 if (has_vectors) {
71 int np, nblocks, np2, l;
72 FFTComplex *q;
73
74 np = 1 << nbits;
75 nblocks = np >> 3;
76 np2 = np >> 1;
77 s->exptab1 = av_malloc(np * 2 * sizeof(FFTComplex));
78 if (!s->exptab1)
79 goto fail;
80 q = s->exptab1;
81 do {
82 for(l = 0; l < np2; l += 2 * nblocks) {
83 *q++ = s->exptab[l];
84 *q++ = s->exptab[l + nblocks];
85
86 q->re = -s->exptab[l].im;
87 q->im = s->exptab[l].re;
88 q++;
89 q->re = -s->exptab[l + nblocks].im;
90 q->im = s->exptab[l + nblocks].re;
91 q++;
92 }
93 nblocks = nblocks >> 1;
94 } while (nblocks != 0);
95 av_freep(&s->exptab);
96 #if defined(HAVE_MMX)
97 s->fft_calc = ff_fft_calc_sse;
98 #else
99 s->fft_calc = ff_fft_calc_altivec;
100 #endif
101 }
102 }
103 #endif
104
105 /* compute bit reverse table */
106
107 for(i=0;i<n;i++) {
108 m=0;
109 for(j=0;j<nbits;j++) {
110 m |= ((i >> j) & 1) << (nbits-j-1);
111 }
112 s->revtab[i]=m;
113 }
114 return 0;
115 fail:
116 av_freep(&s->revtab);
117 av_freep(&s->exptab);
118 av_freep(&s->exptab1);
119 return -1;
120 }
121
122 /* butter fly op */
123 #define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
124 {\
125 FFTSample ax, ay, bx, by;\
126 bx=pre1;\
127 by=pim1;\
128 ax=qre1;\
129 ay=qim1;\
130 pre = (bx + ax);\
131 pim = (by + ay);\
132 qre = (bx - ax);\
133 qim = (by - ay);\
134 }
135
136 #define MUL16(a,b) ((a) * (b))
137
138 #define CMUL(pre, pim, are, aim, bre, bim) \
139 {\
140 pre = (MUL16(are, bre) - MUL16(aim, bim));\
141 pim = (MUL16(are, bim) + MUL16(bre, aim));\
142 }
143
144 /**
145 * Do a complex FFT with the parameters defined in ff_fft_init(). The
146 * input data must be permuted before with s->revtab table. No
147 * 1.0/sqrt(n) normalization is done.
148 */
149 void ff_fft_calc_c(FFTContext *s, FFTComplex *z)
150 {
151 int ln = s->nbits;
152 int j, np, np2;
153 int nblocks, nloops;
154 register FFTComplex *p, *q;
155 FFTComplex *exptab = s->exptab;
156 int l;
157 FFTSample tmp_re, tmp_im;
158
159 np = 1 << ln;
160
161 /* pass 0 */
162
163 p=&z[0];
164 j=(np >> 1);
165 do {
166 BF(p[0].re, p[0].im, p[1].re, p[1].im,
167 p[0].re, p[0].im, p[1].re, p[1].im);
168 p+=2;
169 } while (--j != 0);
170
171 /* pass 1 */
172
173
174 p=&z[0];
175 j=np >> 2;
176 if (s->inverse) {
177 do {
178 BF(p[0].re, p[0].im, p[2].re, p[2].im,
179 p[0].re, p[0].im, p[2].re, p[2].im);
180 BF(p[1].re, p[1].im, p[3].re, p[3].im,
181 p[1].re, p[1].im, -p[3].im, p[3].re);
182 p+=4;
183 } while (--j != 0);
184 } else {
185 do {
186 BF(p[0].re, p[0].im, p[2].re, p[2].im,
187 p[0].re, p[0].im, p[2].re, p[2].im);
188 BF(p[1].re, p[1].im, p[3].re, p[3].im,
189 p[1].re, p[1].im, p[3].im, -p[3].re);
190 p+=4;
191 } while (--j != 0);
192 }
193 /* pass 2 .. ln-1 */
194
195 nblocks = np >> 3;
196 nloops = 1 << 2;
197 np2 = np >> 1;
198 do {
199 p = z;
200 q = z + nloops;
201 for (j = 0; j < nblocks; ++j) {
202 BF(p->re, p->im, q->re, q->im,
203 p->re, p->im, q->re, q->im);
204
205 p++;
206 q++;
207 for(l = nblocks; l < np2; l += nblocks) {
208 CMUL(tmp_re, tmp_im, exptab[l].re, exptab[l].im, q->re, q->im);
209 BF(p->re, p->im, q->re, q->im,
210 p->re, p->im, tmp_re, tmp_im);
211 p++;
212 q++;
213 }
214
215 p += nloops;
216 q += nloops;
217 }
218 nblocks = nblocks >> 1;
219 nloops = nloops << 1;
220 } while (nblocks != 0);
221 }
222
223 /**
224 * Do the permutation needed BEFORE calling ff_fft_calc()
225 */
226 void ff_fft_permute(FFTContext *s, FFTComplex *z)
227 {
228 int j, k, np;
229 FFTComplex tmp;
230 const uint16_t *revtab = s->revtab;
231
232 /* reverse */
233 np = 1 << s->nbits;
234 for(j=0;j<np;j++) {
235 k = revtab[j];
236 if (k < j) {
237 tmp = z[k];
238 z[k] = z[j];
239 z[j] = tmp;
240 }
241 }
242 }
243
244 void ff_fft_end(FFTContext *s)
245 {
246 av_freep(&s->revtab);
247 av_freep(&s->exptab);
248 av_freep(&s->exptab1);
249 }
250