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1
/*
2
 * The simplest AC-3 encoder
3
 * Copyright (c) 2000 Fabrice Bellard
4
 *
5
 * This file is part of FFmpeg.
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 *
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 * 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
 *
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 * 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.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
21

    
22
/**
23
 * @file libavcodec/ac3enc.c
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 * The simplest AC-3 encoder.
25
 */
26
//#define DEBUG
27
//#define DEBUG_BITALLOC
28
#include "libavutil/crc.h"
29
#include "avcodec.h"
30
#include "bitstream.h" // for ff_reverse
31
#include "put_bits.h"
32
#include "ac3.h"
33

    
34
typedef struct AC3EncodeContext {
35
    PutBitContext pb;
36
    int nb_channels;
37
    int nb_all_channels;
38
    int lfe_channel;
39
    int bit_rate;
40
    unsigned int sample_rate;
41
    unsigned int bitstream_id;
42
    unsigned int frame_size_min; /* minimum frame size in case rounding is necessary */
43
    unsigned int frame_size; /* current frame size in words */
44
    unsigned int bits_written;
45
    unsigned int samples_written;
46
    int sr_shift;
47
    unsigned int frame_size_code;
48
    unsigned int sr_code; /* frequency */
49
    unsigned int channel_mode;
50
    int lfe;
51
    unsigned int bitstream_mode;
52
    short last_samples[AC3_MAX_CHANNELS][256];
53
    unsigned int chbwcod[AC3_MAX_CHANNELS];
54
    int nb_coefs[AC3_MAX_CHANNELS];
55

    
56
    /* bitrate allocation control */
57
    int slow_gain_code, slow_decay_code, fast_decay_code, db_per_bit_code, floor_code;
58
    AC3BitAllocParameters bit_alloc;
59
    int coarse_snr_offset;
60
    int fast_gain_code[AC3_MAX_CHANNELS];
61
    int fine_snr_offset[AC3_MAX_CHANNELS];
62
    /* mantissa encoding */
63
    int mant1_cnt, mant2_cnt, mant4_cnt;
64
} AC3EncodeContext;
65

    
66
static int16_t costab[64];
67
static int16_t sintab[64];
68
static int16_t xcos1[128];
69
static int16_t xsin1[128];
70

    
71
#define MDCT_NBITS 9
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#define N         (1 << MDCT_NBITS)
73

    
74
/* new exponents are sent if their Norm 1 exceed this number */
75
#define EXP_DIFF_THRESHOLD 1000
76

    
77
static inline int16_t fix15(float a)
78
{
79
    int v;
80
    v = (int)(a * (float)(1 << 15));
81
    if (v < -32767)
82
        v = -32767;
83
    else if (v > 32767)
84
        v = 32767;
85
    return v;
86
}
87

    
88
typedef struct IComplex {
89
    short re,im;
90
} IComplex;
91

    
92
static av_cold void fft_init(int ln)
93
{
94
    int i, n;
95
    float alpha;
96

    
97
    n = 1 << ln;
98

    
99
    for(i=0;i<(n/2);i++) {
100
        alpha = 2 * M_PI * (float)i / (float)n;
101
        costab[i] = fix15(cos(alpha));
102
        sintab[i] = fix15(sin(alpha));
103
    }
104
}
105

    
106
/* butter fly op */
107
#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
108
{\
109
  int ax, ay, bx, by;\
110
  bx=pre1;\
111
  by=pim1;\
112
  ax=qre1;\
113
  ay=qim1;\
114
  pre = (bx + ax) >> 1;\
115
  pim = (by + ay) >> 1;\
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  qre = (bx - ax) >> 1;\
117
  qim = (by - ay) >> 1;\
118
}
119

    
120
#define CMUL(pre, pim, are, aim, bre, bim) \
121
{\
122
   pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\
123
   pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\
124
}
125

    
126

    
127
/* do a 2^n point complex fft on 2^ln points. */
128
static void fft(IComplex *z, int ln)
129
{
130
    int        j, l, np, np2;
131
    int        nblocks, nloops;
132
    register IComplex *p,*q;
133
    int tmp_re, tmp_im;
134

    
135
    np = 1 << ln;
136

    
137
    /* reverse */
138
    for(j=0;j<np;j++) {
139
        int k = ff_reverse[j] >> (8 - ln);
140
        if (k < j)
141
            FFSWAP(IComplex, z[k], z[j]);
142
    }
143

    
144
    /* pass 0 */
145

    
146
    p=&z[0];
147
    j=(np >> 1);
148
    do {
149
        BF(p[0].re, p[0].im, p[1].re, p[1].im,
150
           p[0].re, p[0].im, p[1].re, p[1].im);
151
        p+=2;
152
    } while (--j != 0);
153

    
154
    /* pass 1 */
155

    
156
    p=&z[0];
157
    j=np >> 2;
158
    do {
159
        BF(p[0].re, p[0].im, p[2].re, p[2].im,
160
           p[0].re, p[0].im, p[2].re, p[2].im);
161
        BF(p[1].re, p[1].im, p[3].re, p[3].im,
162
           p[1].re, p[1].im, p[3].im, -p[3].re);
163
        p+=4;
164
    } while (--j != 0);
165

    
166
    /* pass 2 .. ln-1 */
167

    
168
    nblocks = np >> 3;
169
    nloops = 1 << 2;
170
    np2 = np >> 1;
171
    do {
172
        p = z;
173
        q = z + nloops;
174
        for (j = 0; j < nblocks; ++j) {
175

    
176
            BF(p->re, p->im, q->re, q->im,
177
               p->re, p->im, q->re, q->im);
178

    
179
            p++;
180
            q++;
181
            for(l = nblocks; l < np2; l += nblocks) {
182
                CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
183
                BF(p->re, p->im, q->re, q->im,
184
                   p->re, p->im, tmp_re, tmp_im);
185
                p++;
186
                q++;
187
            }
188
            p += nloops;
189
            q += nloops;
190
        }
191
        nblocks = nblocks >> 1;
192
        nloops = nloops << 1;
193
    } while (nblocks != 0);
194
}
195

    
196
/* do a 512 point mdct */
197
static void mdct512(int32_t *out, int16_t *in)
198
{
199
    int i, re, im, re1, im1;
200
    int16_t rot[N];
201
    IComplex x[N/4];
202

    
203
    /* shift to simplify computations */
204
    for(i=0;i<N/4;i++)
205
        rot[i] = -in[i + 3*N/4];
206
    for(i=N/4;i<N;i++)
207
        rot[i] = in[i - N/4];
208

    
209
    /* pre rotation */
210
    for(i=0;i<N/4;i++) {
211
        re = ((int)rot[2*i] - (int)rot[N-1-2*i]) >> 1;
212
        im = -((int)rot[N/2+2*i] - (int)rot[N/2-1-2*i]) >> 1;
213
        CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
214
    }
215

    
216
    fft(x, MDCT_NBITS - 2);
217

    
218
    /* post rotation */
219
    for(i=0;i<N/4;i++) {
220
        re = x[i].re;
221
        im = x[i].im;
222
        CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
223
        out[2*i] = im1;
224
        out[N/2-1-2*i] = re1;
225
    }
226
}
227

    
228
/* XXX: use another norm ? */
229
static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)
230
{
231
    int sum, i;
232
    sum = 0;
233
    for(i=0;i<n;i++) {
234
        sum += abs(exp1[i] - exp2[i]);
235
    }
236
    return sum;
237
}
238

    
239
static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
240
                                 uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
241
                                 int ch, int is_lfe)
242
{
243
    int i, j;
244
    int exp_diff;
245

    
246
    /* estimate if the exponent variation & decide if they should be
247
       reused in the next frame */
248
    exp_strategy[0][ch] = EXP_NEW;
249
    for(i=1;i<NB_BLOCKS;i++) {
250
        exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);
251
#ifdef DEBUG
252
        av_log(NULL, AV_LOG_DEBUG, "exp_diff=%d\n", exp_diff);
253
#endif
254
        if (exp_diff > EXP_DIFF_THRESHOLD)
255
            exp_strategy[i][ch] = EXP_NEW;
256
        else
257
            exp_strategy[i][ch] = EXP_REUSE;
258
    }
259
    if (is_lfe)
260
        return;
261

    
262
    /* now select the encoding strategy type : if exponents are often
263
       recoded, we use a coarse encoding */
264
    i = 0;
265
    while (i < NB_BLOCKS) {
266
        j = i + 1;
267
        while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)
268
            j++;
269
        switch(j - i) {
270
        case 1:
271
            exp_strategy[i][ch] = EXP_D45;
272
            break;
273
        case 2:
274
        case 3:
275
            exp_strategy[i][ch] = EXP_D25;
276
            break;
277
        default:
278
            exp_strategy[i][ch] = EXP_D15;
279
            break;
280
        }
281
        i = j;
282
    }
283
}
284

    
285
/* set exp[i] to min(exp[i], exp1[i]) */
286
static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n)
287
{
288
    int i;
289

    
290
    for(i=0;i<n;i++) {
291
        if (exp1[i] < exp[i])
292
            exp[i] = exp1[i];
293
    }
294
}
295

    
296
/* update the exponents so that they are the ones the decoder will
297
   decode. Return the number of bits used to code the exponents */
298
static int encode_exp(uint8_t encoded_exp[N/2],
299
                      uint8_t exp[N/2],
300
                      int nb_exps,
301
                      int exp_strategy)
302
{
303
    int group_size, nb_groups, i, j, k, exp_min;
304
    uint8_t exp1[N/2];
305

    
306
    switch(exp_strategy) {
307
    case EXP_D15:
308
        group_size = 1;
309
        break;
310
    case EXP_D25:
311
        group_size = 2;
312
        break;
313
    default:
314
    case EXP_D45:
315
        group_size = 4;
316
        break;
317
    }
318
    nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
319

    
320
    /* for each group, compute the minimum exponent */
321
    exp1[0] = exp[0]; /* DC exponent is handled separately */
322
    k = 1;
323
    for(i=1;i<=nb_groups;i++) {
324
        exp_min = exp[k];
325
        assert(exp_min >= 0 && exp_min <= 24);
326
        for(j=1;j<group_size;j++) {
327
            if (exp[k+j] < exp_min)
328
                exp_min = exp[k+j];
329
        }
330
        exp1[i] = exp_min;
331
        k += group_size;
332
    }
333

    
334
    /* constraint for DC exponent */
335
    if (exp1[0] > 15)
336
        exp1[0] = 15;
337

    
338
    /* Decrease the delta between each groups to within 2
339
     * so that they can be differentially encoded */
340
    for (i=1;i<=nb_groups;i++)
341
        exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
342
    for (i=nb_groups-1;i>=0;i--)
343
        exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
344

    
345
    /* now we have the exponent values the decoder will see */
346
    encoded_exp[0] = exp1[0];
347
    k = 1;
348
    for(i=1;i<=nb_groups;i++) {
349
        for(j=0;j<group_size;j++) {
350
            encoded_exp[k+j] = exp1[i];
351
        }
352
        k += group_size;
353
    }
354

    
355
#if defined(DEBUG)
356
    av_log(NULL, AV_LOG_DEBUG, "exponents: strategy=%d\n", exp_strategy);
357
    for(i=0;i<=nb_groups * group_size;i++) {
358
        av_log(NULL, AV_LOG_DEBUG, "%d ", encoded_exp[i]);
359
    }
360
    av_log(NULL, AV_LOG_DEBUG, "\n");
361
#endif
362

    
363
    return 4 + (nb_groups / 3) * 7;
364
}
365

    
366
/* return the size in bits taken by the mantissa */
367
static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
368
{
369
    int bits, mant, i;
370

    
371
    bits = 0;
372
    for(i=0;i<nb_coefs;i++) {
373
        mant = m[i];
374
        switch(mant) {
375
        case 0:
376
            /* nothing */
377
            break;
378
        case 1:
379
            /* 3 mantissa in 5 bits */
380
            if (s->mant1_cnt == 0)
381
                bits += 5;
382
            if (++s->mant1_cnt == 3)
383
                s->mant1_cnt = 0;
384
            break;
385
        case 2:
386
            /* 3 mantissa in 7 bits */
387
            if (s->mant2_cnt == 0)
388
                bits += 7;
389
            if (++s->mant2_cnt == 3)
390
                s->mant2_cnt = 0;
391
            break;
392
        case 3:
393
            bits += 3;
394
            break;
395
        case 4:
396
            /* 2 mantissa in 7 bits */
397
            if (s->mant4_cnt == 0)
398
                bits += 7;
399
            if (++s->mant4_cnt == 2)
400
                s->mant4_cnt = 0;
401
            break;
402
        case 14:
403
            bits += 14;
404
            break;
405
        case 15:
406
            bits += 16;
407
            break;
408
        default:
409
            bits += mant - 1;
410
            break;
411
        }
412
    }
413
    return bits;
414
}
415

    
416

    
417
static void bit_alloc_masking(AC3EncodeContext *s,
418
                              uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
419
                              uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
420
                              int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
421
                              int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50])
422
{
423
    int blk, ch;
424
    int16_t band_psd[NB_BLOCKS][AC3_MAX_CHANNELS][50];
425

    
426
    for(blk=0; blk<NB_BLOCKS; blk++) {
427
        for(ch=0;ch<s->nb_all_channels;ch++) {
428
            if(exp_strategy[blk][ch] == EXP_REUSE) {
429
                memcpy(psd[blk][ch], psd[blk-1][ch], (N/2)*sizeof(int16_t));
430
                memcpy(mask[blk][ch], mask[blk-1][ch], 50*sizeof(int16_t));
431
            } else {
432
                ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,
433
                                          s->nb_coefs[ch],
434
                                          psd[blk][ch], band_psd[blk][ch]);
435
                ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, band_psd[blk][ch],
436
                                           0, s->nb_coefs[ch],
437
                                           ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
438
                                           ch == s->lfe_channel,
439
                                           DBA_NONE, 0, NULL, NULL, NULL,
440
                                           mask[blk][ch]);
441
            }
442
        }
443
    }
444
}
445

    
446
static int bit_alloc(AC3EncodeContext *s,
447
                     int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50],
448
                     int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
449
                     uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
450
                     int frame_bits, int coarse_snr_offset, int fine_snr_offset)
451
{
452
    int i, ch;
453
    int snr_offset;
454

    
455
    snr_offset = (((coarse_snr_offset - 15) << 4) + fine_snr_offset) << 2;
456

    
457
    /* compute size */
458
    for(i=0;i<NB_BLOCKS;i++) {
459
        s->mant1_cnt = 0;
460
        s->mant2_cnt = 0;
461
        s->mant4_cnt = 0;
462
        for(ch=0;ch<s->nb_all_channels;ch++) {
463
            ff_ac3_bit_alloc_calc_bap(mask[i][ch], psd[i][ch], 0,
464
                                      s->nb_coefs[ch], snr_offset,
465
                                      s->bit_alloc.floor, ff_ac3_bap_tab,
466
                                      bap[i][ch]);
467
            frame_bits += compute_mantissa_size(s, bap[i][ch],
468
                                                 s->nb_coefs[ch]);
469
        }
470
    }
471
#if 0
472
    printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",
473
           coarse_snr_offset, fine_snr_offset, frame_bits,
474
           16 * s->frame_size - ((frame_bits + 7) & ~7));
475
#endif
476
    return 16 * s->frame_size - frame_bits;
477
}
478

    
479
#define SNR_INC1 4
480

    
481
static int compute_bit_allocation(AC3EncodeContext *s,
482
                                  uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
483
                                  uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
484
                                  uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
485
                                  int frame_bits)
486
{
487
    int i, ch;
488
    int coarse_snr_offset, fine_snr_offset;
489
    uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
490
    int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
491
    int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50];
492
    static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
493

    
494
    /* init default parameters */
495
    s->slow_decay_code = 2;
496
    s->fast_decay_code = 1;
497
    s->slow_gain_code = 1;
498
    s->db_per_bit_code = 2;
499
    s->floor_code = 4;
500
    for(ch=0;ch<s->nb_all_channels;ch++)
501
        s->fast_gain_code[ch] = 4;
502

    
503
    /* compute real values */
504
    s->bit_alloc.sr_code = s->sr_code;
505
    s->bit_alloc.sr_shift = s->sr_shift;
506
    s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->sr_shift;
507
    s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->sr_shift;
508
    s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
509
    s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
510
    s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
511

    
512
    /* header size */
513
    frame_bits += 65;
514
    // if (s->channel_mode == 2)
515
    //    frame_bits += 2;
516
    frame_bits += frame_bits_inc[s->channel_mode];
517

    
518
    /* audio blocks */
519
    for(i=0;i<NB_BLOCKS;i++) {
520
        frame_bits += s->nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
521
        if (s->channel_mode == AC3_CHMODE_STEREO) {
522
            frame_bits++; /* rematstr */
523
            if(i==0) frame_bits += 4;
524
        }
525
        frame_bits += 2 * s->nb_channels; /* chexpstr[2] * c */
526
        if (s->lfe)
527
            frame_bits++; /* lfeexpstr */
528
        for(ch=0;ch<s->nb_channels;ch++) {
529
            if (exp_strategy[i][ch] != EXP_REUSE)
530
                frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
531
        }
532
        frame_bits++; /* baie */
533
        frame_bits++; /* snr */
534
        frame_bits += 2; /* delta / skip */
535
    }
536
    frame_bits++; /* cplinu for block 0 */
537
    /* bit alloc info */
538
    /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
539
    /* csnroffset[6] */
540
    /* (fsnoffset[4] + fgaincod[4]) * c */
541
    frame_bits += 2*4 + 3 + 6 + s->nb_all_channels * (4 + 3);
542

    
543
    /* auxdatae, crcrsv */
544
    frame_bits += 2;
545

    
546
    /* CRC */
547
    frame_bits += 16;
548

    
549
    /* calculate psd and masking curve before doing bit allocation */
550
    bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask);
551

    
552
    /* now the big work begins : do the bit allocation. Modify the snr
553
       offset until we can pack everything in the requested frame size */
554

    
555
    coarse_snr_offset = s->coarse_snr_offset;
556
    while (coarse_snr_offset >= 0 &&
557
           bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0)
558
        coarse_snr_offset -= SNR_INC1;
559
    if (coarse_snr_offset < 0) {
560
        av_log(NULL, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
561
        return -1;
562
    }
563
    while ((coarse_snr_offset + SNR_INC1) <= 63 &&
564
           bit_alloc(s, mask, psd, bap1, frame_bits,
565
                     coarse_snr_offset + SNR_INC1, 0) >= 0) {
566
        coarse_snr_offset += SNR_INC1;
567
        memcpy(bap, bap1, sizeof(bap1));
568
    }
569
    while ((coarse_snr_offset + 1) <= 63 &&
570
           bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) {
571
        coarse_snr_offset++;
572
        memcpy(bap, bap1, sizeof(bap1));
573
    }
574

    
575
    fine_snr_offset = 0;
576
    while ((fine_snr_offset + SNR_INC1) <= 15 &&
577
           bit_alloc(s, mask, psd, bap1, frame_bits,
578
                     coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {
579
        fine_snr_offset += SNR_INC1;
580
        memcpy(bap, bap1, sizeof(bap1));
581
    }
582
    while ((fine_snr_offset + 1) <= 15 &&
583
           bit_alloc(s, mask, psd, bap1, frame_bits,
584
                     coarse_snr_offset, fine_snr_offset + 1) >= 0) {
585
        fine_snr_offset++;
586
        memcpy(bap, bap1, sizeof(bap1));
587
    }
588

    
589
    s->coarse_snr_offset = coarse_snr_offset;
590
    for(ch=0;ch<s->nb_all_channels;ch++)
591
        s->fine_snr_offset[ch] = fine_snr_offset;
592
#if defined(DEBUG_BITALLOC)
593
    {
594
        int j;
595

    
596
        for(i=0;i<6;i++) {
597
            for(ch=0;ch<s->nb_all_channels;ch++) {
598
                printf("Block #%d Ch%d:\n", i, ch);
599
                printf("bap=");
600
                for(j=0;j<s->nb_coefs[ch];j++) {
601
                    printf("%d ",bap[i][ch][j]);
602
                }
603
                printf("\n");
604
            }
605
        }
606
    }
607
#endif
608
    return 0;
609
}
610

    
611
static av_cold int AC3_encode_init(AVCodecContext *avctx)
612
{
613
    int freq = avctx->sample_rate;
614
    int bitrate = avctx->bit_rate;
615
    int channels = avctx->channels;
616
    AC3EncodeContext *s = avctx->priv_data;
617
    int i, j, ch;
618
    float alpha;
619
    int bw_code;
620
    static const uint8_t channel_mode_defs[6] = {
621
        0x01, /* C */
622
        0x02, /* L R */
623
        0x03, /* L C R */
624
        0x06, /* L R SL SR */
625
        0x07, /* L C R SL SR */
626
        0x07, /* L C R SL SR (+LFE) */
627
    };
628

    
629
    avctx->frame_size = AC3_FRAME_SIZE;
630

    
631
    ac3_common_init();
632

    
633
    /* number of channels */
634
    if (channels < 1 || channels > 6)
635
        return -1;
636
    s->channel_mode = channel_mode_defs[channels - 1];
637
    s->lfe = (channels == 6) ? 1 : 0;
638
    s->nb_all_channels = channels;
639
    s->nb_channels = channels > 5 ? 5 : channels;
640
    s->lfe_channel = s->lfe ? 5 : -1;
641

    
642
    /* frequency */
643
    for(i=0;i<3;i++) {
644
        for(j=0;j<3;j++)
645
            if ((ff_ac3_sample_rate_tab[j] >> i) == freq)
646
                goto found;
647
    }
648
    return -1;
649
 found:
650
    s->sample_rate = freq;
651
    s->sr_shift = i;
652
    s->sr_code = j;
653
    s->bitstream_id = 8 + s->sr_shift;
654
    s->bitstream_mode = 0; /* complete main audio service */
655

    
656
    /* bitrate & frame size */
657
    for(i=0;i<19;i++) {
658
        if ((ff_ac3_bitrate_tab[i] >> s->sr_shift)*1000 == bitrate)
659
            break;
660
    }
661
    if (i == 19)
662
        return -1;
663
    s->bit_rate = bitrate;
664
    s->frame_size_code = i << 1;
665
    s->frame_size_min = ff_ac3_frame_size_tab[s->frame_size_code][s->sr_code];
666
    s->bits_written = 0;
667
    s->samples_written = 0;
668
    s->frame_size = s->frame_size_min;
669

    
670
    /* bit allocation init */
671
    if(avctx->cutoff) {
672
        /* calculate bandwidth based on user-specified cutoff frequency */
673
        int cutoff = av_clip(avctx->cutoff, 1, s->sample_rate >> 1);
674
        int fbw_coeffs = cutoff * 512 / s->sample_rate;
675
        bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
676
    } else {
677
        /* use default bandwidth setting */
678
        /* XXX: should compute the bandwidth according to the frame
679
           size, so that we avoid annoying high frequency artifacts */
680
        bw_code = 50;
681
    }
682
    for(ch=0;ch<s->nb_channels;ch++) {
683
        /* bandwidth for each channel */
684
        s->chbwcod[ch] = bw_code;
685
        s->nb_coefs[ch] = bw_code * 3 + 73;
686
    }
687
    if (s->lfe) {
688
        s->nb_coefs[s->lfe_channel] = 7; /* fixed */
689
    }
690
    /* initial snr offset */
691
    s->coarse_snr_offset = 40;
692

    
693
    /* mdct init */
694
    fft_init(MDCT_NBITS - 2);
695
    for(i=0;i<N/4;i++) {
696
        alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
697
        xcos1[i] = fix15(-cos(alpha));
698
        xsin1[i] = fix15(-sin(alpha));
699
    }
700

    
701
    avctx->coded_frame= avcodec_alloc_frame();
702
    avctx->coded_frame->key_frame= 1;
703

    
704
    return 0;
705
}
706

    
707
/* output the AC-3 frame header */
708
static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
709
{
710
    init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
711

    
712
    put_bits(&s->pb, 16, 0x0b77); /* frame header */
713
    put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
714
    put_bits(&s->pb, 2, s->sr_code);
715
    put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min));
716
    put_bits(&s->pb, 5, s->bitstream_id);
717
    put_bits(&s->pb, 3, s->bitstream_mode);
718
    put_bits(&s->pb, 3, s->channel_mode);
719
    if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
720
        put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
721
    if (s->channel_mode & 0x04)
722
        put_bits(&s->pb, 2, 1); /* XXX -6 dB */
723
    if (s->channel_mode == AC3_CHMODE_STEREO)
724
        put_bits(&s->pb, 2, 0); /* surround not indicated */
725
    put_bits(&s->pb, 1, s->lfe); /* LFE */
726
    put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
727
    put_bits(&s->pb, 1, 0); /* no compression control word */
728
    put_bits(&s->pb, 1, 0); /* no lang code */
729
    put_bits(&s->pb, 1, 0); /* no audio production info */
730
    put_bits(&s->pb, 1, 0); /* no copyright */
731
    put_bits(&s->pb, 1, 1); /* original bitstream */
732
    put_bits(&s->pb, 1, 0); /* no time code 1 */
733
    put_bits(&s->pb, 1, 0); /* no time code 2 */
734
    put_bits(&s->pb, 1, 0); /* no additional bit stream info */
735
}
736

    
737
/* symetric quantization on 'levels' levels */
738
static inline int sym_quant(int c, int e, int levels)
739
{
740
    int v;
741

    
742
    if (c >= 0) {
743
        v = (levels * (c << e)) >> 24;
744
        v = (v + 1) >> 1;
745
        v = (levels >> 1) + v;
746
    } else {
747
        v = (levels * ((-c) << e)) >> 24;
748
        v = (v + 1) >> 1;
749
        v = (levels >> 1) - v;
750
    }
751
    assert (v >= 0 && v < levels);
752
    return v;
753
}
754

    
755
/* asymetric quantization on 2^qbits levels */
756
static inline int asym_quant(int c, int e, int qbits)
757
{
758
    int lshift, m, v;
759

    
760
    lshift = e + qbits - 24;
761
    if (lshift >= 0)
762
        v = c << lshift;
763
    else
764
        v = c >> (-lshift);
765
    /* rounding */
766
    v = (v + 1) >> 1;
767
    m = (1 << (qbits-1));
768
    if (v >= m)
769
        v = m - 1;
770
    assert(v >= -m);
771
    return v & ((1 << qbits)-1);
772
}
773

    
774
/* Output one audio block. There are NB_BLOCKS audio blocks in one AC-3
775
   frame */
776
static void output_audio_block(AC3EncodeContext *s,
777
                               uint8_t exp_strategy[AC3_MAX_CHANNELS],
778
                               uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],
779
                               uint8_t bap[AC3_MAX_CHANNELS][N/2],
780
                               int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],
781
                               int8_t global_exp[AC3_MAX_CHANNELS],
782
                               int block_num)
783
{
784
    int ch, nb_groups, group_size, i, baie, rbnd;
785
    uint8_t *p;
786
    uint16_t qmant[AC3_MAX_CHANNELS][N/2];
787
    int exp0, exp1;
788
    int mant1_cnt, mant2_cnt, mant4_cnt;
789
    uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
790
    int delta0, delta1, delta2;
791

    
792
    for(ch=0;ch<s->nb_channels;ch++)
793
        put_bits(&s->pb, 1, 0); /* 512 point MDCT */
794
    for(ch=0;ch<s->nb_channels;ch++)
795
        put_bits(&s->pb, 1, 1); /* no dither */
796
    put_bits(&s->pb, 1, 0); /* no dynamic range */
797
    if (block_num == 0) {
798
        /* for block 0, even if no coupling, we must say it. This is a
799
           waste of bit :-) */
800
        put_bits(&s->pb, 1, 1); /* coupling strategy present */
801
        put_bits(&s->pb, 1, 0); /* no coupling strategy */
802
    } else {
803
        put_bits(&s->pb, 1, 0); /* no new coupling strategy */
804
    }
805

    
806
    if (s->channel_mode == AC3_CHMODE_STEREO)
807
      {
808
        if(block_num==0)
809
          {
810
            /* first block must define rematrixing (rematstr)  */
811
            put_bits(&s->pb, 1, 1);
812

    
813
            /* dummy rematrixing rematflg(1:4)=0 */
814
            for (rbnd=0;rbnd<4;rbnd++)
815
              put_bits(&s->pb, 1, 0);
816
          }
817
        else
818
          {
819
            /* no matrixing (but should be used in the future) */
820
            put_bits(&s->pb, 1, 0);
821
          }
822
      }
823

    
824
#if defined(DEBUG)
825
    {
826
      static int count = 0;
827
      av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++);
828
    }
829
#endif
830
    /* exponent strategy */
831
    for(ch=0;ch<s->nb_channels;ch++) {
832
        put_bits(&s->pb, 2, exp_strategy[ch]);
833
    }
834

    
835
    if (s->lfe) {
836
        put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
837
    }
838

    
839
    for(ch=0;ch<s->nb_channels;ch++) {
840
        if (exp_strategy[ch] != EXP_REUSE)
841
            put_bits(&s->pb, 6, s->chbwcod[ch]);
842
    }
843

    
844
    /* exponents */
845
    for (ch = 0; ch < s->nb_all_channels; ch++) {
846
        switch(exp_strategy[ch]) {
847
        case EXP_REUSE:
848
            continue;
849
        case EXP_D15:
850
            group_size = 1;
851
            break;
852
        case EXP_D25:
853
            group_size = 2;
854
            break;
855
        default:
856
        case EXP_D45:
857
            group_size = 4;
858
            break;
859
        }
860
        nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
861
        p = encoded_exp[ch];
862

    
863
        /* first exponent */
864
        exp1 = *p++;
865
        put_bits(&s->pb, 4, exp1);
866

    
867
        /* next ones are delta encoded */
868
        for(i=0;i<nb_groups;i++) {
869
            /* merge three delta in one code */
870
            exp0 = exp1;
871
            exp1 = p[0];
872
            p += group_size;
873
            delta0 = exp1 - exp0 + 2;
874

    
875
            exp0 = exp1;
876
            exp1 = p[0];
877
            p += group_size;
878
            delta1 = exp1 - exp0 + 2;
879

    
880
            exp0 = exp1;
881
            exp1 = p[0];
882
            p += group_size;
883
            delta2 = exp1 - exp0 + 2;
884

    
885
            put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
886
        }
887

    
888
        if (ch != s->lfe_channel)
889
            put_bits(&s->pb, 2, 0); /* no gain range info */
890
    }
891

    
892
    /* bit allocation info */
893
    baie = (block_num == 0);
894
    put_bits(&s->pb, 1, baie);
895
    if (baie) {
896
        put_bits(&s->pb, 2, s->slow_decay_code);
897
        put_bits(&s->pb, 2, s->fast_decay_code);
898
        put_bits(&s->pb, 2, s->slow_gain_code);
899
        put_bits(&s->pb, 2, s->db_per_bit_code);
900
        put_bits(&s->pb, 3, s->floor_code);
901
    }
902

    
903
    /* snr offset */
904
    put_bits(&s->pb, 1, baie); /* always present with bai */
905
    if (baie) {
906
        put_bits(&s->pb, 6, s->coarse_snr_offset);
907
        for(ch=0;ch<s->nb_all_channels;ch++) {
908
            put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
909
            put_bits(&s->pb, 3, s->fast_gain_code[ch]);
910
        }
911
    }
912

    
913
    put_bits(&s->pb, 1, 0); /* no delta bit allocation */
914
    put_bits(&s->pb, 1, 0); /* no data to skip */
915

    
916
    /* mantissa encoding : we use two passes to handle the grouping. A
917
       one pass method may be faster, but it would necessitate to
918
       modify the output stream. */
919

    
920
    /* first pass: quantize */
921
    mant1_cnt = mant2_cnt = mant4_cnt = 0;
922
    qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
923

    
924
    for (ch = 0; ch < s->nb_all_channels; ch++) {
925
        int b, c, e, v;
926

    
927
        for(i=0;i<s->nb_coefs[ch];i++) {
928
            c = mdct_coefs[ch][i];
929
            e = encoded_exp[ch][i] - global_exp[ch];
930
            b = bap[ch][i];
931
            switch(b) {
932
            case 0:
933
                v = 0;
934
                break;
935
            case 1:
936
                v = sym_quant(c, e, 3);
937
                switch(mant1_cnt) {
938
                case 0:
939
                    qmant1_ptr = &qmant[ch][i];
940
                    v = 9 * v;
941
                    mant1_cnt = 1;
942
                    break;
943
                case 1:
944
                    *qmant1_ptr += 3 * v;
945
                    mant1_cnt = 2;
946
                    v = 128;
947
                    break;
948
                default:
949
                    *qmant1_ptr += v;
950
                    mant1_cnt = 0;
951
                    v = 128;
952
                    break;
953
                }
954
                break;
955
            case 2:
956
                v = sym_quant(c, e, 5);
957
                switch(mant2_cnt) {
958
                case 0:
959
                    qmant2_ptr = &qmant[ch][i];
960
                    v = 25 * v;
961
                    mant2_cnt = 1;
962
                    break;
963
                case 1:
964
                    *qmant2_ptr += 5 * v;
965
                    mant2_cnt = 2;
966
                    v = 128;
967
                    break;
968
                default:
969
                    *qmant2_ptr += v;
970
                    mant2_cnt = 0;
971
                    v = 128;
972
                    break;
973
                }
974
                break;
975
            case 3:
976
                v = sym_quant(c, e, 7);
977
                break;
978
            case 4:
979
                v = sym_quant(c, e, 11);
980
                switch(mant4_cnt) {
981
                case 0:
982
                    qmant4_ptr = &qmant[ch][i];
983
                    v = 11 * v;
984
                    mant4_cnt = 1;
985
                    break;
986
                default:
987
                    *qmant4_ptr += v;
988
                    mant4_cnt = 0;
989
                    v = 128;
990
                    break;
991
                }
992
                break;
993
            case 5:
994
                v = sym_quant(c, e, 15);
995
                break;
996
            case 14:
997
                v = asym_quant(c, e, 14);
998
                break;
999
            case 15:
1000
                v = asym_quant(c, e, 16);
1001
                break;
1002
            default:
1003
                v = asym_quant(c, e, b - 1);
1004
                break;
1005
            }
1006
            qmant[ch][i] = v;
1007
        }
1008
    }
1009

    
1010
    /* second pass : output the values */
1011
    for (ch = 0; ch < s->nb_all_channels; ch++) {
1012
        int b, q;
1013

    
1014
        for(i=0;i<s->nb_coefs[ch];i++) {
1015
            q = qmant[ch][i];
1016
            b = bap[ch][i];
1017
            switch(b) {
1018
            case 0:
1019
                break;
1020
            case 1:
1021
                if (q != 128)
1022
                    put_bits(&s->pb, 5, q);
1023
                break;
1024
            case 2:
1025
                if (q != 128)
1026
                    put_bits(&s->pb, 7, q);
1027
                break;
1028
            case 3:
1029
                put_bits(&s->pb, 3, q);
1030
                break;
1031
            case 4:
1032
                if (q != 128)
1033
                    put_bits(&s->pb, 7, q);
1034
                break;
1035
            case 14:
1036
                put_bits(&s->pb, 14, q);
1037
                break;
1038
            case 15:
1039
                put_bits(&s->pb, 16, q);
1040
                break;
1041
            default:
1042
                put_bits(&s->pb, b - 1, q);
1043
                break;
1044
            }
1045
        }
1046
    }
1047
}
1048

    
1049
#define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1050

    
1051
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1052
{
1053
    unsigned int c;
1054

    
1055
    c = 0;
1056
    while (a) {
1057
        if (a & 1)
1058
            c ^= b;
1059
        a = a >> 1;
1060
        b = b << 1;
1061
        if (b & (1 << 16))
1062
            b ^= poly;
1063
    }
1064
    return c;
1065
}
1066

    
1067
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1068
{
1069
    unsigned int r;
1070
    r = 1;
1071
    while (n) {
1072
        if (n & 1)
1073
            r = mul_poly(r, a, poly);
1074
        a = mul_poly(a, a, poly);
1075
        n >>= 1;
1076
    }
1077
    return r;
1078
}
1079

    
1080

    
1081
/* compute log2(max(abs(tab[]))) */
1082
static int log2_tab(int16_t *tab, int n)
1083
{
1084
    int i, v;
1085

    
1086
    v = 0;
1087
    for(i=0;i<n;i++) {
1088
        v |= abs(tab[i]);
1089
    }
1090
    return av_log2(v);
1091
}
1092

    
1093
static void lshift_tab(int16_t *tab, int n, int lshift)
1094
{
1095
    int i;
1096

    
1097
    if (lshift > 0) {
1098
        for(i=0;i<n;i++) {
1099
            tab[i] <<= lshift;
1100
        }
1101
    } else if (lshift < 0) {
1102
        lshift = -lshift;
1103
        for(i=0;i<n;i++) {
1104
            tab[i] >>= lshift;
1105
        }
1106
    }
1107
}
1108

    
1109
/* fill the end of the frame and compute the two crcs */
1110
static int output_frame_end(AC3EncodeContext *s)
1111
{
1112
    int frame_size, frame_size_58, n, crc1, crc2, crc_inv;
1113
    uint8_t *frame;
1114

    
1115
    frame_size = s->frame_size; /* frame size in words */
1116
    /* align to 8 bits */
1117
    flush_put_bits(&s->pb);
1118
    /* add zero bytes to reach the frame size */
1119
    frame = s->pb.buf;
1120
    n = 2 * s->frame_size - (pbBufPtr(&s->pb) - frame) - 2;
1121
    assert(n >= 0);
1122
    if(n>0)
1123
      memset(pbBufPtr(&s->pb), 0, n);
1124

    
1125
    /* Now we must compute both crcs : this is not so easy for crc1
1126
       because it is at the beginning of the data... */
1127
    frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
1128
    crc1 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
1129
                           frame + 4, 2 * frame_size_58 - 4));
1130
    /* XXX: could precompute crc_inv */
1131
    crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
1132
    crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
1133
    AV_WB16(frame+2,crc1);
1134

    
1135
    crc2 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
1136
                           frame + 2 * frame_size_58,
1137
                           (frame_size - frame_size_58) * 2 - 2));
1138
    AV_WB16(frame+2*frame_size-2,crc2);
1139

    
1140
    //    printf("n=%d frame_size=%d\n", n, frame_size);
1141
    return frame_size * 2;
1142
}
1143

    
1144
static int AC3_encode_frame(AVCodecContext *avctx,
1145
                            unsigned char *frame, int buf_size, void *data)
1146
{
1147
    AC3EncodeContext *s = avctx->priv_data;
1148
    int16_t *samples = data;
1149
    int i, j, k, v, ch;
1150
    int16_t input_samples[N];
1151
    int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1152
    uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1153
    uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
1154
    uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1155
    uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1156
    int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
1157
    int frame_bits;
1158

    
1159
    frame_bits = 0;
1160
    for(ch=0;ch<s->nb_all_channels;ch++) {
1161
        /* fixed mdct to the six sub blocks & exponent computation */
1162
        for(i=0;i<NB_BLOCKS;i++) {
1163
            int16_t *sptr;
1164
            int sinc;
1165

    
1166
            /* compute input samples */
1167
            memcpy(input_samples, s->last_samples[ch], N/2 * sizeof(int16_t));
1168
            sinc = s->nb_all_channels;
1169
            sptr = samples + (sinc * (N/2) * i) + ch;
1170
            for(j=0;j<N/2;j++) {
1171
                v = *sptr;
1172
                input_samples[j + N/2] = v;
1173
                s->last_samples[ch][j] = v;
1174
                sptr += sinc;
1175
            }
1176

    
1177
            /* apply the MDCT window */
1178
            for(j=0;j<N/2;j++) {
1179
                input_samples[j] = MUL16(input_samples[j],
1180
                                         ff_ac3_window[j]) >> 15;
1181
                input_samples[N-j-1] = MUL16(input_samples[N-j-1],
1182
                                             ff_ac3_window[j]) >> 15;
1183
            }
1184

    
1185
            /* Normalize the samples to use the maximum available
1186
               precision */
1187
            v = 14 - log2_tab(input_samples, N);
1188
            if (v < 0)
1189
                v = 0;
1190
            exp_samples[i][ch] = v - 9;
1191
            lshift_tab(input_samples, N, v);
1192

    
1193
            /* do the MDCT */
1194
            mdct512(mdct_coef[i][ch], input_samples);
1195

    
1196
            /* compute "exponents". We take into account the
1197
               normalization there */
1198
            for(j=0;j<N/2;j++) {
1199
                int e;
1200
                v = abs(mdct_coef[i][ch][j]);
1201
                if (v == 0)
1202
                    e = 24;
1203
                else {
1204
                    e = 23 - av_log2(v) + exp_samples[i][ch];
1205
                    if (e >= 24) {
1206
                        e = 24;
1207
                        mdct_coef[i][ch][j] = 0;
1208
                    }
1209
                }
1210
                exp[i][ch][j] = e;
1211
            }
1212
        }
1213

    
1214
        compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);
1215

    
1216
        /* compute the exponents as the decoder will see them. The
1217
           EXP_REUSE case must be handled carefully : we select the
1218
           min of the exponents */
1219
        i = 0;
1220
        while (i < NB_BLOCKS) {
1221
            j = i + 1;
1222
            while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
1223
                exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
1224
                j++;
1225
            }
1226
            frame_bits += encode_exp(encoded_exp[i][ch],
1227
                                     exp[i][ch], s->nb_coefs[ch],
1228
                                     exp_strategy[i][ch]);
1229
            /* copy encoded exponents for reuse case */
1230
            for(k=i+1;k<j;k++) {
1231
                memcpy(encoded_exp[k][ch], encoded_exp[i][ch],
1232
                       s->nb_coefs[ch] * sizeof(uint8_t));
1233
            }
1234
            i = j;
1235
        }
1236
    }
1237

    
1238
    /* adjust for fractional frame sizes */
1239
    while(s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
1240
        s->bits_written -= s->bit_rate;
1241
        s->samples_written -= s->sample_rate;
1242
    }
1243
    s->frame_size = s->frame_size_min + (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
1244
    s->bits_written += s->frame_size * 16;
1245
    s->samples_written += AC3_FRAME_SIZE;
1246

    
1247
    compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
1248
    /* everything is known... let's output the frame */
1249
    output_frame_header(s, frame);
1250

    
1251
    for(i=0;i<NB_BLOCKS;i++) {
1252
        output_audio_block(s, exp_strategy[i], encoded_exp[i],
1253
                           bap[i], mdct_coef[i], exp_samples[i], i);
1254
    }
1255
    return output_frame_end(s);
1256
}
1257

    
1258
static av_cold int AC3_encode_close(AVCodecContext *avctx)
1259
{
1260
    av_freep(&avctx->coded_frame);
1261
    return 0;
1262
}
1263

    
1264
#if 0
1265
/*************************************************************************/
1266
/* TEST */
1267

1268
#undef random
1269
#define FN (N/4)
1270

1271
void fft_test(void)
1272
{
1273
    IComplex in[FN], in1[FN];
1274
    int k, n, i;
1275
    float sum_re, sum_im, a;
1276

1277
    /* FFT test */
1278

1279
    for(i=0;i<FN;i++) {
1280
        in[i].re = random() % 65535 - 32767;
1281
        in[i].im = random() % 65535 - 32767;
1282
        in1[i] = in[i];
1283
    }
1284
    fft(in, 7);
1285

1286
    /* do it by hand */
1287
    for(k=0;k<FN;k++) {
1288
        sum_re = 0;
1289
        sum_im = 0;
1290
        for(n=0;n<FN;n++) {
1291
            a = -2 * M_PI * (n * k) / FN;
1292
            sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
1293
            sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
1294
        }
1295
        printf("%3d: %6d,%6d %6.0f,%6.0f\n",
1296
               k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
1297
    }
1298
}
1299

1300
void mdct_test(void)
1301
{
1302
    int16_t input[N];
1303
    int32_t output[N/2];
1304
    float input1[N];
1305
    float output1[N/2];
1306
    float s, a, err, e, emax;
1307
    int i, k, n;
1308

1309
    for(i=0;i<N;i++) {
1310
        input[i] = (random() % 65535 - 32767) * 9 / 10;
1311
        input1[i] = input[i];
1312
    }
1313

1314
    mdct512(output, input);
1315

1316
    /* do it by hand */
1317
    for(k=0;k<N/2;k++) {
1318
        s = 0;
1319
        for(n=0;n<N;n++) {
1320
            a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));
1321
            s += input1[n] * cos(a);
1322
        }
1323
        output1[k] = -2 * s / N;
1324
    }
1325

1326
    err = 0;
1327
    emax = 0;
1328
    for(i=0;i<N/2;i++) {
1329
        printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);
1330
        e = output[i] - output1[i];
1331
        if (e > emax)
1332
            emax = e;
1333
        err += e * e;
1334
    }
1335
    printf("err2=%f emax=%f\n", err / (N/2), emax);
1336
}
1337

1338
void test_ac3(void)
1339
{
1340
    AC3EncodeContext ctx;
1341
    unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];
1342
    short samples[AC3_FRAME_SIZE];
1343
    int ret, i;
1344

1345
    AC3_encode_init(&ctx, 44100, 64000, 1);
1346

1347
    fft_test();
1348
    mdct_test();
1349

1350
    for(i=0;i<AC3_FRAME_SIZE;i++)
1351
        samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);
1352
    ret = AC3_encode_frame(&ctx, frame, samples);
1353
    printf("ret=%d\n", ret);
1354
}
1355
#endif
1356

    
1357
AVCodec ac3_encoder = {
1358
    "ac3",
1359
    CODEC_TYPE_AUDIO,
1360
    CODEC_ID_AC3,
1361
    sizeof(AC3EncodeContext),
1362
    AC3_encode_init,
1363
    AC3_encode_frame,
1364
    AC3_encode_close,
1365
    NULL,
1366
    .sample_fmts = (enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
1367
    .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
1368
};