Statistics
| Branch: | Revision:

ffmpeg / libavcodec / fft.c @ faca5619

History | View | Annotate | Download (10.1 KB)

1
/*
2
 * FFT/IFFT transforms
3
 * Copyright (c) 2008 Loren Merritt
4
 * Copyright (c) 2002 Fabrice Bellard
5
 * Partly based on libdjbfft by D. J. Bernstein
6
 *
7
 * This file is part of FFmpeg.
8
 *
9
 * FFmpeg is free software; you can redistribute it and/or
10
 * modify it under the terms of the GNU Lesser General Public
11
 * License as published by the Free Software Foundation; either
12
 * version 2.1 of the License, or (at your option) any later version.
13
 *
14
 * FFmpeg is distributed in the hope that it will be useful,
15
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17
 * Lesser General Public License for more details.
18
 *
19
 * You should have received a copy of the GNU Lesser General Public
20
 * License along with FFmpeg; if not, write to the Free Software
21
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22
 */
23

    
24
/**
25
 * @file libavcodec/fft.c
26
 * FFT/IFFT transforms.
27
 */
28

    
29
#include "dsputil.h"
30

    
31
/* cos(2*pi*x/n) for 0<=x<=n/4, followed by its reverse */
32
DECLARE_ALIGNED_16(FFTSample, ff_cos_16[8]);
33
DECLARE_ALIGNED_16(FFTSample, ff_cos_32[16]);
34
DECLARE_ALIGNED_16(FFTSample, ff_cos_64[32]);
35
DECLARE_ALIGNED_16(FFTSample, ff_cos_128[64]);
36
DECLARE_ALIGNED_16(FFTSample, ff_cos_256[128]);
37
DECLARE_ALIGNED_16(FFTSample, ff_cos_512[256]);
38
DECLARE_ALIGNED_16(FFTSample, ff_cos_1024[512]);
39
DECLARE_ALIGNED_16(FFTSample, ff_cos_2048[1024]);
40
DECLARE_ALIGNED_16(FFTSample, ff_cos_4096[2048]);
41
DECLARE_ALIGNED_16(FFTSample, ff_cos_8192[4096]);
42
DECLARE_ALIGNED_16(FFTSample, ff_cos_16384[8192]);
43
DECLARE_ALIGNED_16(FFTSample, ff_cos_32768[16384]);
44
DECLARE_ALIGNED_16(FFTSample, ff_cos_65536[32768]);
45
FFTSample * const ff_cos_tabs[] = {
46
    ff_cos_16, ff_cos_32, ff_cos_64, ff_cos_128, ff_cos_256, ff_cos_512, ff_cos_1024,
47
    ff_cos_2048, ff_cos_4096, ff_cos_8192, ff_cos_16384, ff_cos_32768, ff_cos_65536,
48
};
49

    
50
static int split_radix_permutation(int i, int n, int inverse)
51
{
52
    int m;
53
    if(n <= 2) return i&1;
54
    m = n >> 1;
55
    if(!(i&m))            return split_radix_permutation(i, m, inverse)*2;
56
    m >>= 1;
57
    if(inverse == !(i&m)) return split_radix_permutation(i, m, inverse)*4 + 1;
58
    else                  return split_radix_permutation(i, m, inverse)*4 - 1;
59
}
60

    
61
av_cold int ff_fft_init(FFTContext *s, int nbits, int inverse)
62
{
63
    int i, j, m, n;
64
    float alpha, c1, s1, s2;
65
    int split_radix = 1;
66
    int av_unused has_vectors;
67

    
68
    if (nbits < 2 || nbits > 16)
69
        goto fail;
70
    s->nbits = nbits;
71
    n = 1 << nbits;
72

    
73
    s->tmp_buf = NULL;
74
    s->exptab  = av_malloc((n / 2) * sizeof(FFTComplex));
75
    if (!s->exptab)
76
        goto fail;
77
    s->revtab = av_malloc(n * sizeof(uint16_t));
78
    if (!s->revtab)
79
        goto fail;
80
    s->inverse = inverse;
81

    
82
    s2 = inverse ? 1.0 : -1.0;
83

    
84
    s->fft_permute = ff_fft_permute_c;
85
    s->fft_calc    = ff_fft_calc_c;
86
    s->imdct_calc  = ff_imdct_calc_c;
87
    s->imdct_half  = ff_imdct_half_c;
88
    s->exptab1     = NULL;
89

    
90
#if HAVE_MMX && HAVE_YASM
91
    has_vectors = mm_support();
92
    if (has_vectors & FF_MM_SSE && HAVE_SSE) {
93
        /* SSE for P3/P4/K8 */
94
        s->imdct_calc  = ff_imdct_calc_sse;
95
        s->imdct_half  = ff_imdct_half_sse;
96
        s->fft_permute = ff_fft_permute_sse;
97
        s->fft_calc    = ff_fft_calc_sse;
98
    } else if (has_vectors & FF_MM_3DNOWEXT && HAVE_AMD3DNOWEXT) {
99
        /* 3DNowEx for K7 */
100
        s->imdct_calc = ff_imdct_calc_3dn2;
101
        s->imdct_half = ff_imdct_half_3dn2;
102
        s->fft_calc   = ff_fft_calc_3dn2;
103
    } else if (has_vectors & FF_MM_3DNOW && HAVE_AMD3DNOW) {
104
        /* 3DNow! for K6-2/3 */
105
        s->imdct_calc = ff_imdct_calc_3dn;
106
        s->imdct_half = ff_imdct_half_3dn;
107
        s->fft_calc   = ff_fft_calc_3dn;
108
    }
109
#elif HAVE_ALTIVEC
110
    has_vectors = mm_support();
111
    if (has_vectors & FF_MM_ALTIVEC) {
112
        s->fft_calc = ff_fft_calc_altivec;
113
        split_radix = 0;
114
    }
115
#endif
116

    
117
    if (split_radix) {
118
        for(j=4; j<=nbits; j++) {
119
            int m = 1<<j;
120
            double freq = 2*M_PI/m;
121
            FFTSample *tab = ff_cos_tabs[j-4];
122
            for(i=0; i<=m/4; i++)
123
                tab[i] = cos(i*freq);
124
            for(i=1; i<m/4; i++)
125
                tab[m/2-i] = tab[i];
126
        }
127
        for(i=0; i<n; i++)
128
            s->revtab[-split_radix_permutation(i, n, s->inverse) & (n-1)] = i;
129
        s->tmp_buf = av_malloc(n * sizeof(FFTComplex));
130
    } else {
131
        int np, nblocks, np2, l;
132
        FFTComplex *q;
133

    
134
        for(i=0; i<(n/2); i++) {
135
            alpha = 2 * M_PI * (float)i / (float)n;
136
            c1 = cos(alpha);
137
            s1 = sin(alpha) * s2;
138
            s->exptab[i].re = c1;
139
            s->exptab[i].im = s1;
140
        }
141

    
142
        np = 1 << nbits;
143
        nblocks = np >> 3;
144
        np2 = np >> 1;
145
        s->exptab1 = av_malloc(np * 2 * sizeof(FFTComplex));
146
        if (!s->exptab1)
147
            goto fail;
148
        q = s->exptab1;
149
        do {
150
            for(l = 0; l < np2; l += 2 * nblocks) {
151
                *q++ = s->exptab[l];
152
                *q++ = s->exptab[l + nblocks];
153

    
154
                q->re = -s->exptab[l].im;
155
                q->im = s->exptab[l].re;
156
                q++;
157
                q->re = -s->exptab[l + nblocks].im;
158
                q->im = s->exptab[l + nblocks].re;
159
                q++;
160
            }
161
            nblocks = nblocks >> 1;
162
        } while (nblocks != 0);
163
        av_freep(&s->exptab);
164

    
165
        /* compute bit reverse table */
166
        for(i=0;i<n;i++) {
167
            m=0;
168
            for(j=0;j<nbits;j++) {
169
                m |= ((i >> j) & 1) << (nbits-j-1);
170
            }
171
            s->revtab[i]=m;
172
        }
173
    }
174

    
175
    return 0;
176
 fail:
177
    av_freep(&s->revtab);
178
    av_freep(&s->exptab);
179
    av_freep(&s->exptab1);
180
    av_freep(&s->tmp_buf);
181
    return -1;
182
}
183

    
184
void ff_fft_permute_c(FFTContext *s, FFTComplex *z)
185
{
186
    int j, k, np;
187
    FFTComplex tmp;
188
    const uint16_t *revtab = s->revtab;
189
    np = 1 << s->nbits;
190

    
191
    if (s->tmp_buf) {
192
        /* TODO: handle split-radix permute in a more optimal way, probably in-place */
193
        for(j=0;j<np;j++) s->tmp_buf[revtab[j]] = z[j];
194
        memcpy(z, s->tmp_buf, np * sizeof(FFTComplex));
195
        return;
196
    }
197

    
198
    /* reverse */
199
    for(j=0;j<np;j++) {
200
        k = revtab[j];
201
        if (k < j) {
202
            tmp = z[k];
203
            z[k] = z[j];
204
            z[j] = tmp;
205
        }
206
    }
207
}
208

    
209
av_cold void ff_fft_end(FFTContext *s)
210
{
211
    av_freep(&s->revtab);
212
    av_freep(&s->exptab);
213
    av_freep(&s->exptab1);
214
    av_freep(&s->tmp_buf);
215
}
216

    
217
#define sqrthalf (float)M_SQRT1_2
218

    
219
#define BF(x,y,a,b) {\
220
    x = a - b;\
221
    y = a + b;\
222
}
223

    
224
#define BUTTERFLIES(a0,a1,a2,a3) {\
225
    BF(t3, t5, t5, t1);\
226
    BF(a2.re, a0.re, a0.re, t5);\
227
    BF(a3.im, a1.im, a1.im, t3);\
228
    BF(t4, t6, t2, t6);\
229
    BF(a3.re, a1.re, a1.re, t4);\
230
    BF(a2.im, a0.im, a0.im, t6);\
231
}
232

    
233
// force loading all the inputs before storing any.
234
// this is slightly slower for small data, but avoids store->load aliasing
235
// for addresses separated by large powers of 2.
236
#define BUTTERFLIES_BIG(a0,a1,a2,a3) {\
237
    FFTSample r0=a0.re, i0=a0.im, r1=a1.re, i1=a1.im;\
238
    BF(t3, t5, t5, t1);\
239
    BF(a2.re, a0.re, r0, t5);\
240
    BF(a3.im, a1.im, i1, t3);\
241
    BF(t4, t6, t2, t6);\
242
    BF(a3.re, a1.re, r1, t4);\
243
    BF(a2.im, a0.im, i0, t6);\
244
}
245

    
246
#define TRANSFORM(a0,a1,a2,a3,wre,wim) {\
247
    t1 = a2.re * wre + a2.im * wim;\
248
    t2 = a2.im * wre - a2.re * wim;\
249
    t5 = a3.re * wre - a3.im * wim;\
250
    t6 = a3.im * wre + a3.re * wim;\
251
    BUTTERFLIES(a0,a1,a2,a3)\
252
}
253

    
254
#define TRANSFORM_ZERO(a0,a1,a2,a3) {\
255
    t1 = a2.re;\
256
    t2 = a2.im;\
257
    t5 = a3.re;\
258
    t6 = a3.im;\
259
    BUTTERFLIES(a0,a1,a2,a3)\
260
}
261

    
262
/* z[0...8n-1], w[1...2n-1] */
263
#define PASS(name)\
264
static void name(FFTComplex *z, const FFTSample *wre, unsigned int n)\
265
{\
266
    FFTSample t1, t2, t3, t4, t5, t6;\
267
    int o1 = 2*n;\
268
    int o2 = 4*n;\
269
    int o3 = 6*n;\
270
    const FFTSample *wim = wre+o1;\
271
    n--;\
272
\
273
    TRANSFORM_ZERO(z[0],z[o1],z[o2],z[o3]);\
274
    TRANSFORM(z[1],z[o1+1],z[o2+1],z[o3+1],wre[1],wim[-1]);\
275
    do {\
276
        z += 2;\
277
        wre += 2;\
278
        wim -= 2;\
279
        TRANSFORM(z[0],z[o1],z[o2],z[o3],wre[0],wim[0]);\
280
        TRANSFORM(z[1],z[o1+1],z[o2+1],z[o3+1],wre[1],wim[-1]);\
281
    } while(--n);\
282
}
283

    
284
PASS(pass)
285
#undef BUTTERFLIES
286
#define BUTTERFLIES BUTTERFLIES_BIG
287
PASS(pass_big)
288

    
289
#define DECL_FFT(n,n2,n4)\
290
static void fft##n(FFTComplex *z)\
291
{\
292
    fft##n2(z);\
293
    fft##n4(z+n4*2);\
294
    fft##n4(z+n4*3);\
295
    pass(z,ff_cos_##n,n4/2);\
296
}
297

    
298
static void fft4(FFTComplex *z)
299
{
300
    FFTSample t1, t2, t3, t4, t5, t6, t7, t8;
301

    
302
    BF(t3, t1, z[0].re, z[1].re);
303
    BF(t8, t6, z[3].re, z[2].re);
304
    BF(z[2].re, z[0].re, t1, t6);
305
    BF(t4, t2, z[0].im, z[1].im);
306
    BF(t7, t5, z[2].im, z[3].im);
307
    BF(z[3].im, z[1].im, t4, t8);
308
    BF(z[3].re, z[1].re, t3, t7);
309
    BF(z[2].im, z[0].im, t2, t5);
310
}
311

    
312
static void fft8(FFTComplex *z)
313
{
314
    FFTSample t1, t2, t3, t4, t5, t6, t7, t8;
315

    
316
    fft4(z);
317

    
318
    BF(t1, z[5].re, z[4].re, -z[5].re);
319
    BF(t2, z[5].im, z[4].im, -z[5].im);
320
    BF(t3, z[7].re, z[6].re, -z[7].re);
321
    BF(t4, z[7].im, z[6].im, -z[7].im);
322
    BF(t8, t1, t3, t1);
323
    BF(t7, t2, t2, t4);
324
    BF(z[4].re, z[0].re, z[0].re, t1);
325
    BF(z[4].im, z[0].im, z[0].im, t2);
326
    BF(z[6].re, z[2].re, z[2].re, t7);
327
    BF(z[6].im, z[2].im, z[2].im, t8);
328

    
329
    TRANSFORM(z[1],z[3],z[5],z[7],sqrthalf,sqrthalf);
330
}
331

    
332
#if !CONFIG_SMALL
333
static void fft16(FFTComplex *z)
334
{
335
    FFTSample t1, t2, t3, t4, t5, t6;
336

    
337
    fft8(z);
338
    fft4(z+8);
339
    fft4(z+12);
340

    
341
    TRANSFORM_ZERO(z[0],z[4],z[8],z[12]);
342
    TRANSFORM(z[2],z[6],z[10],z[14],sqrthalf,sqrthalf);
343
    TRANSFORM(z[1],z[5],z[9],z[13],ff_cos_16[1],ff_cos_16[3]);
344
    TRANSFORM(z[3],z[7],z[11],z[15],ff_cos_16[3],ff_cos_16[1]);
345
}
346
#else
347
DECL_FFT(16,8,4)
348
#endif
349
DECL_FFT(32,16,8)
350
DECL_FFT(64,32,16)
351
DECL_FFT(128,64,32)
352
DECL_FFT(256,128,64)
353
DECL_FFT(512,256,128)
354
#if !CONFIG_SMALL
355
#define pass pass_big
356
#endif
357
DECL_FFT(1024,512,256)
358
DECL_FFT(2048,1024,512)
359
DECL_FFT(4096,2048,1024)
360
DECL_FFT(8192,4096,2048)
361
DECL_FFT(16384,8192,4096)
362
DECL_FFT(32768,16384,8192)
363
DECL_FFT(65536,32768,16384)
364

    
365
static void (*fft_dispatch[])(FFTComplex*) = {
366
    fft4, fft8, fft16, fft32, fft64, fft128, fft256, fft512, fft1024,
367
    fft2048, fft4096, fft8192, fft16384, fft32768, fft65536,
368
};
369

    
370
void ff_fft_calc_c(FFTContext *s, FFTComplex *z)
371
{
372
    fft_dispatch[s->nbits-2](z);
373
}
374