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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.
6
 *
7
 * FFmpeg is free software; you can redistribute it and/or
8
 * modify it under the terms of the GNU Lesser General Public
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 * 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
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 * 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"
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#include "get_bits.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
    const uint8_t *channel_map;
40
    int bit_rate;
41
    unsigned int sample_rate;
42
    unsigned int bitstream_id;
43
    unsigned int frame_size_min; /* minimum frame size in case rounding is necessary */
44
    unsigned int frame_size; /* current frame size in words */
45
    unsigned int bits_written;
46
    unsigned int samples_written;
47
    int sr_shift;
48
    unsigned int frame_size_code;
49
    unsigned int sr_code; /* frequency */
50
    unsigned int channel_mode;
51
    int lfe;
52
    unsigned int bitstream_mode;
53
    short last_samples[AC3_MAX_CHANNELS][256];
54
    unsigned int chbwcod[AC3_MAX_CHANNELS];
55
    int nb_coefs[AC3_MAX_CHANNELS];
56

    
57
    /* bitrate allocation control */
58
    int slow_gain_code, slow_decay_code, fast_decay_code, db_per_bit_code, floor_code;
59
    AC3BitAllocParameters bit_alloc;
60
    int coarse_snr_offset;
61
    int fast_gain_code[AC3_MAX_CHANNELS];
62
    int fine_snr_offset[AC3_MAX_CHANNELS];
63
    /* mantissa encoding */
64
    int mant1_cnt, mant2_cnt, mant4_cnt;
65
} AC3EncodeContext;
66

    
67
static int16_t costab[64];
68
static int16_t sintab[64];
69
static int16_t xcos1[128];
70
static int16_t xsin1[128];
71

    
72
#define MDCT_NBITS 9
73
#define N         (1 << MDCT_NBITS)
74

    
75
/* new exponents are sent if their Norm 1 exceed this number */
76
#define EXP_DIFF_THRESHOLD 1000
77

    
78
static inline int16_t fix15(float a)
79
{
80
    int v;
81
    v = (int)(a * (float)(1 << 15));
82
    if (v < -32767)
83
        v = -32767;
84
    else if (v > 32767)
85
        v = 32767;
86
    return v;
87
}
88

    
89
typedef struct IComplex {
90
    short re,im;
91
} IComplex;
92

    
93
static av_cold void fft_init(int ln)
94
{
95
    int i, n;
96
    float alpha;
97

    
98
    n = 1 << ln;
99

    
100
    for(i=0;i<(n/2);i++) {
101
        alpha = 2 * M_PI * (float)i / (float)n;
102
        costab[i] = fix15(cos(alpha));
103
        sintab[i] = fix15(sin(alpha));
104
    }
105
}
106

    
107
/* butter fly op */
108
#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
109
{\
110
  int ax, ay, bx, by;\
111
  bx=pre1;\
112
  by=pim1;\
113
  ax=qre1;\
114
  ay=qim1;\
115
  pre = (bx + ax) >> 1;\
116
  pim = (by + ay) >> 1;\
117
  qre = (bx - ax) >> 1;\
118
  qim = (by - ay) >> 1;\
119
}
120

    
121
#define CMUL(pre, pim, are, aim, bre, bim) \
122
{\
123
   pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\
124
   pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\
125
}
126

    
127

    
128
/* do a 2^n point complex fft on 2^ln points. */
129
static void fft(IComplex *z, int ln)
130
{
131
    int        j, l, np, np2;
132
    int        nblocks, nloops;
133
    register IComplex *p,*q;
134
    int tmp_re, tmp_im;
135

    
136
    np = 1 << ln;
137

    
138
    /* reverse */
139
    for(j=0;j<np;j++) {
140
        int k = ff_reverse[j] >> (8 - ln);
141
        if (k < j)
142
            FFSWAP(IComplex, z[k], z[j]);
143
    }
144

    
145
    /* pass 0 */
146

    
147
    p=&z[0];
148
    j=(np >> 1);
149
    do {
150
        BF(p[0].re, p[0].im, p[1].re, p[1].im,
151
           p[0].re, p[0].im, p[1].re, p[1].im);
152
        p+=2;
153
    } while (--j != 0);
154

    
155
    /* pass 1 */
156

    
157
    p=&z[0];
158
    j=np >> 2;
159
    do {
160
        BF(p[0].re, p[0].im, p[2].re, p[2].im,
161
           p[0].re, p[0].im, p[2].re, p[2].im);
162
        BF(p[1].re, p[1].im, p[3].re, p[3].im,
163
           p[1].re, p[1].im, p[3].im, -p[3].re);
164
        p+=4;
165
    } while (--j != 0);
166

    
167
    /* pass 2 .. ln-1 */
168

    
169
    nblocks = np >> 3;
170
    nloops = 1 << 2;
171
    np2 = np >> 1;
172
    do {
173
        p = z;
174
        q = z + nloops;
175
        for (j = 0; j < nblocks; ++j) {
176

    
177
            BF(p->re, p->im, q->re, q->im,
178
               p->re, p->im, q->re, q->im);
179

    
180
            p++;
181
            q++;
182
            for(l = nblocks; l < np2; l += nblocks) {
183
                CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
184
                BF(p->re, p->im, q->re, q->im,
185
                   p->re, p->im, tmp_re, tmp_im);
186
                p++;
187
                q++;
188
            }
189
            p += nloops;
190
            q += nloops;
191
        }
192
        nblocks = nblocks >> 1;
193
        nloops = nloops << 1;
194
    } while (nblocks != 0);
195
}
196

    
197
/* do a 512 point mdct */
198
static void mdct512(int32_t *out, int16_t *in)
199
{
200
    int i, re, im, re1, im1;
201
    int16_t rot[N];
202
    IComplex x[N/4];
203

    
204
    /* shift to simplify computations */
205
    for(i=0;i<N/4;i++)
206
        rot[i] = -in[i + 3*N/4];
207
    for(i=N/4;i<N;i++)
208
        rot[i] = in[i - N/4];
209

    
210
    /* pre rotation */
211
    for(i=0;i<N/4;i++) {
212
        re = ((int)rot[2*i] - (int)rot[N-1-2*i]) >> 1;
213
        im = -((int)rot[N/2+2*i] - (int)rot[N/2-1-2*i]) >> 1;
214
        CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
215
    }
216

    
217
    fft(x, MDCT_NBITS - 2);
218

    
219
    /* post rotation */
220
    for(i=0;i<N/4;i++) {
221
        re = x[i].re;
222
        im = x[i].im;
223
        CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
224
        out[2*i] = im1;
225
        out[N/2-1-2*i] = re1;
226
    }
227
}
228

    
229
/* XXX: use another norm ? */
230
static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)
231
{
232
    int sum, i;
233
    sum = 0;
234
    for(i=0;i<n;i++) {
235
        sum += abs(exp1[i] - exp2[i]);
236
    }
237
    return sum;
238
}
239

    
240
static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
241
                                 uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
242
                                 int ch, int is_lfe)
243
{
244
    int i, j;
245
    int exp_diff;
246

    
247
    /* estimate if the exponent variation & decide if they should be
248
       reused in the next frame */
249
    exp_strategy[0][ch] = EXP_NEW;
250
    for(i=1;i<NB_BLOCKS;i++) {
251
        exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);
252
#ifdef DEBUG
253
        av_log(NULL, AV_LOG_DEBUG, "exp_diff=%d\n", exp_diff);
254
#endif
255
        if (exp_diff > EXP_DIFF_THRESHOLD)
256
            exp_strategy[i][ch] = EXP_NEW;
257
        else
258
            exp_strategy[i][ch] = EXP_REUSE;
259
    }
260
    if (is_lfe)
261
        return;
262

    
263
    /* now select the encoding strategy type : if exponents are often
264
       recoded, we use a coarse encoding */
265
    i = 0;
266
    while (i < NB_BLOCKS) {
267
        j = i + 1;
268
        while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)
269
            j++;
270
        switch(j - i) {
271
        case 1:
272
            exp_strategy[i][ch] = EXP_D45;
273
            break;
274
        case 2:
275
        case 3:
276
            exp_strategy[i][ch] = EXP_D25;
277
            break;
278
        default:
279
            exp_strategy[i][ch] = EXP_D15;
280
            break;
281
        }
282
        i = j;
283
    }
284
}
285

    
286
/* set exp[i] to min(exp[i], exp1[i]) */
287
static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n)
288
{
289
    int i;
290

    
291
    for(i=0;i<n;i++) {
292
        if (exp1[i] < exp[i])
293
            exp[i] = exp1[i];
294
    }
295
}
296

    
297
/* update the exponents so that they are the ones the decoder will
298
   decode. Return the number of bits used to code the exponents */
299
static int encode_exp(uint8_t encoded_exp[N/2],
300
                      uint8_t exp[N/2],
301
                      int nb_exps,
302
                      int exp_strategy)
303
{
304
    int group_size, nb_groups, i, j, k, exp_min;
305
    uint8_t exp1[N/2];
306

    
307
    switch(exp_strategy) {
308
    case EXP_D15:
309
        group_size = 1;
310
        break;
311
    case EXP_D25:
312
        group_size = 2;
313
        break;
314
    default:
315
    case EXP_D45:
316
        group_size = 4;
317
        break;
318
    }
319
    nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
320

    
321
    /* for each group, compute the minimum exponent */
322
    exp1[0] = exp[0]; /* DC exponent is handled separately */
323
    k = 1;
324
    for(i=1;i<=nb_groups;i++) {
325
        exp_min = exp[k];
326
        assert(exp_min >= 0 && exp_min <= 24);
327
        for(j=1;j<group_size;j++) {
328
            if (exp[k+j] < exp_min)
329
                exp_min = exp[k+j];
330
        }
331
        exp1[i] = exp_min;
332
        k += group_size;
333
    }
334

    
335
    /* constraint for DC exponent */
336
    if (exp1[0] > 15)
337
        exp1[0] = 15;
338

    
339
    /* Decrease the delta between each groups to within 2
340
     * so that they can be differentially encoded */
341
    for (i=1;i<=nb_groups;i++)
342
        exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
343
    for (i=nb_groups-1;i>=0;i--)
344
        exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
345

    
346
    /* now we have the exponent values the decoder will see */
347
    encoded_exp[0] = exp1[0];
348
    k = 1;
349
    for(i=1;i<=nb_groups;i++) {
350
        for(j=0;j<group_size;j++) {
351
            encoded_exp[k+j] = exp1[i];
352
        }
353
        k += group_size;
354
    }
355

    
356
#if defined(DEBUG)
357
    av_log(NULL, AV_LOG_DEBUG, "exponents: strategy=%d\n", exp_strategy);
358
    for(i=0;i<=nb_groups * group_size;i++) {
359
        av_log(NULL, AV_LOG_DEBUG, "%d ", encoded_exp[i]);
360
    }
361
    av_log(NULL, AV_LOG_DEBUG, "\n");
362
#endif
363

    
364
    return 4 + (nb_groups / 3) * 7;
365
}
366

    
367
/* return the size in bits taken by the mantissa */
368
static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
369
{
370
    int bits, mant, i;
371

    
372
    bits = 0;
373
    for(i=0;i<nb_coefs;i++) {
374
        mant = m[i];
375
        switch(mant) {
376
        case 0:
377
            /* nothing */
378
            break;
379
        case 1:
380
            /* 3 mantissa in 5 bits */
381
            if (s->mant1_cnt == 0)
382
                bits += 5;
383
            if (++s->mant1_cnt == 3)
384
                s->mant1_cnt = 0;
385
            break;
386
        case 2:
387
            /* 3 mantissa in 7 bits */
388
            if (s->mant2_cnt == 0)
389
                bits += 7;
390
            if (++s->mant2_cnt == 3)
391
                s->mant2_cnt = 0;
392
            break;
393
        case 3:
394
            bits += 3;
395
            break;
396
        case 4:
397
            /* 2 mantissa in 7 bits */
398
            if (s->mant4_cnt == 0)
399
                bits += 7;
400
            if (++s->mant4_cnt == 2)
401
                s->mant4_cnt = 0;
402
            break;
403
        case 14:
404
            bits += 14;
405
            break;
406
        case 15:
407
            bits += 16;
408
            break;
409
        default:
410
            bits += mant - 1;
411
            break;
412
        }
413
    }
414
    return bits;
415
}
416

    
417

    
418
static void bit_alloc_masking(AC3EncodeContext *s,
419
                              uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
420
                              uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
421
                              int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
422
                              int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50])
423
{
424
    int blk, ch;
425
    int16_t band_psd[NB_BLOCKS][AC3_MAX_CHANNELS][50];
426

    
427
    for(blk=0; blk<NB_BLOCKS; blk++) {
428
        for(ch=0;ch<s->nb_all_channels;ch++) {
429
            if(exp_strategy[blk][ch] == EXP_REUSE) {
430
                memcpy(psd[blk][ch], psd[blk-1][ch], (N/2)*sizeof(int16_t));
431
                memcpy(mask[blk][ch], mask[blk-1][ch], 50*sizeof(int16_t));
432
            } else {
433
                ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,
434
                                          s->nb_coefs[ch],
435
                                          psd[blk][ch], band_psd[blk][ch]);
436
                ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, band_psd[blk][ch],
437
                                           0, s->nb_coefs[ch],
438
                                           ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
439
                                           ch == s->lfe_channel,
440
                                           DBA_NONE, 0, NULL, NULL, NULL,
441
                                           mask[blk][ch]);
442
            }
443
        }
444
    }
445
}
446

    
447
static int bit_alloc(AC3EncodeContext *s,
448
                     int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50],
449
                     int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
450
                     uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
451
                     int frame_bits, int coarse_snr_offset, int fine_snr_offset)
452
{
453
    int i, ch;
454
    int snr_offset;
455

    
456
    snr_offset = (((coarse_snr_offset - 15) << 4) + fine_snr_offset) << 2;
457

    
458
    /* compute size */
459
    for(i=0;i<NB_BLOCKS;i++) {
460
        s->mant1_cnt = 0;
461
        s->mant2_cnt = 0;
462
        s->mant4_cnt = 0;
463
        for(ch=0;ch<s->nb_all_channels;ch++) {
464
            ff_ac3_bit_alloc_calc_bap(mask[i][ch], psd[i][ch], 0,
465
                                      s->nb_coefs[ch], snr_offset,
466
                                      s->bit_alloc.floor, ff_ac3_bap_tab,
467
                                      bap[i][ch]);
468
            frame_bits += compute_mantissa_size(s, bap[i][ch],
469
                                                 s->nb_coefs[ch]);
470
        }
471
    }
472
#if 0
473
    printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",
474
           coarse_snr_offset, fine_snr_offset, frame_bits,
475
           16 * s->frame_size - ((frame_bits + 7) & ~7));
476
#endif
477
    return 16 * s->frame_size - frame_bits;
478
}
479

    
480
#define SNR_INC1 4
481

    
482
static int compute_bit_allocation(AC3EncodeContext *s,
483
                                  uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
484
                                  uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
485
                                  uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
486
                                  int frame_bits)
487
{
488
    int i, ch;
489
    int coarse_snr_offset, fine_snr_offset;
490
    uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
491
    int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
492
    int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50];
493
    static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
494

    
495
    /* init default parameters */
496
    s->slow_decay_code = 2;
497
    s->fast_decay_code = 1;
498
    s->slow_gain_code = 1;
499
    s->db_per_bit_code = 2;
500
    s->floor_code = 4;
501
    for(ch=0;ch<s->nb_all_channels;ch++)
502
        s->fast_gain_code[ch] = 4;
503

    
504
    /* compute real values */
505
    s->bit_alloc.sr_code = s->sr_code;
506
    s->bit_alloc.sr_shift = s->sr_shift;
507
    s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->sr_shift;
508
    s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->sr_shift;
509
    s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
510
    s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
511
    s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
512

    
513
    /* header size */
514
    frame_bits += 65;
515
    // if (s->channel_mode == 2)
516
    //    frame_bits += 2;
517
    frame_bits += frame_bits_inc[s->channel_mode];
518

    
519
    /* audio blocks */
520
    for(i=0;i<NB_BLOCKS;i++) {
521
        frame_bits += s->nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
522
        if (s->channel_mode == AC3_CHMODE_STEREO) {
523
            frame_bits++; /* rematstr */
524
            if(i==0) frame_bits += 4;
525
        }
526
        frame_bits += 2 * s->nb_channels; /* chexpstr[2] * c */
527
        if (s->lfe)
528
            frame_bits++; /* lfeexpstr */
529
        for(ch=0;ch<s->nb_channels;ch++) {
530
            if (exp_strategy[i][ch] != EXP_REUSE)
531
                frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
532
        }
533
        frame_bits++; /* baie */
534
        frame_bits++; /* snr */
535
        frame_bits += 2; /* delta / skip */
536
    }
537
    frame_bits++; /* cplinu for block 0 */
538
    /* bit alloc info */
539
    /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
540
    /* csnroffset[6] */
541
    /* (fsnoffset[4] + fgaincod[4]) * c */
542
    frame_bits += 2*4 + 3 + 6 + s->nb_all_channels * (4 + 3);
543

    
544
    /* auxdatae, crcrsv */
545
    frame_bits += 2;
546

    
547
    /* CRC */
548
    frame_bits += 16;
549

    
550
    /* calculate psd and masking curve before doing bit allocation */
551
    bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask);
552

    
553
    /* now the big work begins : do the bit allocation. Modify the snr
554
       offset until we can pack everything in the requested frame size */
555

    
556
    coarse_snr_offset = s->coarse_snr_offset;
557
    while (coarse_snr_offset >= 0 &&
558
           bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0)
559
        coarse_snr_offset -= SNR_INC1;
560
    if (coarse_snr_offset < 0) {
561
        av_log(NULL, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
562
        return -1;
563
    }
564
    while ((coarse_snr_offset + SNR_INC1) <= 63 &&
565
           bit_alloc(s, mask, psd, bap1, frame_bits,
566
                     coarse_snr_offset + SNR_INC1, 0) >= 0) {
567
        coarse_snr_offset += SNR_INC1;
568
        memcpy(bap, bap1, sizeof(bap1));
569
    }
570
    while ((coarse_snr_offset + 1) <= 63 &&
571
           bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) {
572
        coarse_snr_offset++;
573
        memcpy(bap, bap1, sizeof(bap1));
574
    }
575

    
576
    fine_snr_offset = 0;
577
    while ((fine_snr_offset + SNR_INC1) <= 15 &&
578
           bit_alloc(s, mask, psd, bap1, frame_bits,
579
                     coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {
580
        fine_snr_offset += SNR_INC1;
581
        memcpy(bap, bap1, sizeof(bap1));
582
    }
583
    while ((fine_snr_offset + 1) <= 15 &&
584
           bit_alloc(s, mask, psd, bap1, frame_bits,
585
                     coarse_snr_offset, fine_snr_offset + 1) >= 0) {
586
        fine_snr_offset++;
587
        memcpy(bap, bap1, sizeof(bap1));
588
    }
589

    
590
    s->coarse_snr_offset = coarse_snr_offset;
591
    for(ch=0;ch<s->nb_all_channels;ch++)
592
        s->fine_snr_offset[ch] = fine_snr_offset;
593
#if defined(DEBUG_BITALLOC)
594
    {
595
        int j;
596

    
597
        for(i=0;i<6;i++) {
598
            for(ch=0;ch<s->nb_all_channels;ch++) {
599
                printf("Block #%d Ch%d:\n", i, ch);
600
                printf("bap=");
601
                for(j=0;j<s->nb_coefs[ch];j++) {
602
                    printf("%d ",bap[i][ch][j]);
603
                }
604
                printf("\n");
605
            }
606
        }
607
    }
608
#endif
609
    return 0;
610
}
611

    
612
static av_cold int AC3_encode_init(AVCodecContext *avctx)
613
{
614
    int freq = avctx->sample_rate;
615
    int bitrate = avctx->bit_rate;
616
    int channels = avctx->channels;
617
    AC3EncodeContext *s = avctx->priv_data;
618
    int i, j, ch;
619
    float alpha;
620
    int bw_code;
621
    static const uint8_t channel_mode_defs[6] = {
622
        0x01, /* C */
623
        0x02, /* L R */
624
        0x03, /* L C R */
625
        0x06, /* L R SL SR */
626
        0x07, /* L C R SL SR */
627
        0x07, /* L C R SL SR (+LFE) */
628
    };
629

    
630
    avctx->frame_size = AC3_FRAME_SIZE;
631

    
632
    ac3_common_init();
633

    
634
    /* number of channels */
635
    if (channels < 1 || channels > 6)
636
        return -1;
637
    s->channel_mode = channel_mode_defs[channels - 1];
638
    s->lfe = (channels == 6) ? 1 : 0;
639
    s->nb_all_channels = channels;
640
    s->nb_channels = channels > 5 ? 5 : channels;
641
    s->lfe_channel = s->lfe ? 5 : -1;
642
    s->channel_map = ff_ac3_enc_channel_map[s->channel_mode][s->lfe];
643

    
644
    /* frequency */
645
    for(i=0;i<3;i++) {
646
        for(j=0;j<3;j++)
647
            if ((ff_ac3_sample_rate_tab[j] >> i) == freq)
648
                goto found;
649
    }
650
    return -1;
651
 found:
652
    s->sample_rate = freq;
653
    s->sr_shift = i;
654
    s->sr_code = j;
655
    s->bitstream_id = 8 + s->sr_shift;
656
    s->bitstream_mode = 0; /* complete main audio service */
657

    
658
    /* bitrate & frame size */
659
    for(i=0;i<19;i++) {
660
        if ((ff_ac3_bitrate_tab[i] >> s->sr_shift)*1000 == bitrate)
661
            break;
662
    }
663
    if (i == 19)
664
        return -1;
665
    s->bit_rate = bitrate;
666
    s->frame_size_code = i << 1;
667
    s->frame_size_min = ff_ac3_frame_size_tab[s->frame_size_code][s->sr_code];
668
    s->bits_written = 0;
669
    s->samples_written = 0;
670
    s->frame_size = s->frame_size_min;
671

    
672
    /* bit allocation init */
673
    if(avctx->cutoff) {
674
        /* calculate bandwidth based on user-specified cutoff frequency */
675
        int cutoff = av_clip(avctx->cutoff, 1, s->sample_rate >> 1);
676
        int fbw_coeffs = cutoff * 512 / s->sample_rate;
677
        bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
678
    } else {
679
        /* use default bandwidth setting */
680
        /* XXX: should compute the bandwidth according to the frame
681
           size, so that we avoid annoying high frequency artifacts */
682
        bw_code = 50;
683
    }
684
    for(ch=0;ch<s->nb_channels;ch++) {
685
        /* bandwidth for each channel */
686
        s->chbwcod[ch] = bw_code;
687
        s->nb_coefs[ch] = bw_code * 3 + 73;
688
    }
689
    if (s->lfe) {
690
        s->nb_coefs[s->lfe_channel] = 7; /* fixed */
691
    }
692
    /* initial snr offset */
693
    s->coarse_snr_offset = 40;
694

    
695
    /* mdct init */
696
    fft_init(MDCT_NBITS - 2);
697
    for(i=0;i<N/4;i++) {
698
        alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
699
        xcos1[i] = fix15(-cos(alpha));
700
        xsin1[i] = fix15(-sin(alpha));
701
    }
702

    
703
    avctx->coded_frame= avcodec_alloc_frame();
704
    avctx->coded_frame->key_frame= 1;
705

    
706
    return 0;
707
}
708

    
709
/* output the AC-3 frame header */
710
static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
711
{
712
    init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
713

    
714
    put_bits(&s->pb, 16, 0x0b77); /* frame header */
715
    put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
716
    put_bits(&s->pb, 2, s->sr_code);
717
    put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min));
718
    put_bits(&s->pb, 5, s->bitstream_id);
719
    put_bits(&s->pb, 3, s->bitstream_mode);
720
    put_bits(&s->pb, 3, s->channel_mode);
721
    if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
722
        put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
723
    if (s->channel_mode & 0x04)
724
        put_bits(&s->pb, 2, 1); /* XXX -6 dB */
725
    if (s->channel_mode == AC3_CHMODE_STEREO)
726
        put_bits(&s->pb, 2, 0); /* surround not indicated */
727
    put_bits(&s->pb, 1, s->lfe); /* LFE */
728
    put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
729
    put_bits(&s->pb, 1, 0); /* no compression control word */
730
    put_bits(&s->pb, 1, 0); /* no lang code */
731
    put_bits(&s->pb, 1, 0); /* no audio production info */
732
    put_bits(&s->pb, 1, 0); /* no copyright */
733
    put_bits(&s->pb, 1, 1); /* original bitstream */
734
    put_bits(&s->pb, 1, 0); /* no time code 1 */
735
    put_bits(&s->pb, 1, 0); /* no time code 2 */
736
    put_bits(&s->pb, 1, 0); /* no additional bit stream info */
737
}
738

    
739
/* symetric quantization on 'levels' levels */
740
static inline int sym_quant(int c, int e, int levels)
741
{
742
    int v;
743

    
744
    if (c >= 0) {
745
        v = (levels * (c << e)) >> 24;
746
        v = (v + 1) >> 1;
747
        v = (levels >> 1) + v;
748
    } else {
749
        v = (levels * ((-c) << e)) >> 24;
750
        v = (v + 1) >> 1;
751
        v = (levels >> 1) - v;
752
    }
753
    assert (v >= 0 && v < levels);
754
    return v;
755
}
756

    
757
/* asymetric quantization on 2^qbits levels */
758
static inline int asym_quant(int c, int e, int qbits)
759
{
760
    int lshift, m, v;
761

    
762
    lshift = e + qbits - 24;
763
    if (lshift >= 0)
764
        v = c << lshift;
765
    else
766
        v = c >> (-lshift);
767
    /* rounding */
768
    v = (v + 1) >> 1;
769
    m = (1 << (qbits-1));
770
    if (v >= m)
771
        v = m - 1;
772
    assert(v >= -m);
773
    return v & ((1 << qbits)-1);
774
}
775

    
776
/* Output one audio block. There are NB_BLOCKS audio blocks in one AC-3
777
   frame */
778
static void output_audio_block(AC3EncodeContext *s,
779
                               uint8_t exp_strategy[AC3_MAX_CHANNELS],
780
                               uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],
781
                               uint8_t bap[AC3_MAX_CHANNELS][N/2],
782
                               int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],
783
                               int8_t global_exp[AC3_MAX_CHANNELS],
784
                               int block_num)
785
{
786
    int ch, nb_groups, group_size, i, baie, rbnd;
787
    uint8_t *p;
788
    uint16_t qmant[AC3_MAX_CHANNELS][N/2];
789
    int exp0, exp1;
790
    int mant1_cnt, mant2_cnt, mant4_cnt;
791
    uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
792
    int delta0, delta1, delta2;
793

    
794
    for(ch=0;ch<s->nb_channels;ch++)
795
        put_bits(&s->pb, 1, 0); /* 512 point MDCT */
796
    for(ch=0;ch<s->nb_channels;ch++)
797
        put_bits(&s->pb, 1, 1); /* no dither */
798
    put_bits(&s->pb, 1, 0); /* no dynamic range */
799
    if (block_num == 0) {
800
        /* for block 0, even if no coupling, we must say it. This is a
801
           waste of bit :-) */
802
        put_bits(&s->pb, 1, 1); /* coupling strategy present */
803
        put_bits(&s->pb, 1, 0); /* no coupling strategy */
804
    } else {
805
        put_bits(&s->pb, 1, 0); /* no new coupling strategy */
806
    }
807

    
808
    if (s->channel_mode == AC3_CHMODE_STEREO)
809
      {
810
        if(block_num==0)
811
          {
812
            /* first block must define rematrixing (rematstr)  */
813
            put_bits(&s->pb, 1, 1);
814

    
815
            /* dummy rematrixing rematflg(1:4)=0 */
816
            for (rbnd=0;rbnd<4;rbnd++)
817
              put_bits(&s->pb, 1, 0);
818
          }
819
        else
820
          {
821
            /* no matrixing (but should be used in the future) */
822
            put_bits(&s->pb, 1, 0);
823
          }
824
      }
825

    
826
#if defined(DEBUG)
827
    {
828
      static int count = 0;
829
      av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++);
830
    }
831
#endif
832
    /* exponent strategy */
833
    for(ch=0;ch<s->nb_channels;ch++) {
834
        put_bits(&s->pb, 2, exp_strategy[ch]);
835
    }
836

    
837
    if (s->lfe) {
838
        put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
839
    }
840

    
841
    for(ch=0;ch<s->nb_channels;ch++) {
842
        if (exp_strategy[ch] != EXP_REUSE)
843
            put_bits(&s->pb, 6, s->chbwcod[ch]);
844
    }
845

    
846
    /* exponents */
847
    for (ch = 0; ch < s->nb_all_channels; ch++) {
848
        switch(exp_strategy[ch]) {
849
        case EXP_REUSE:
850
            continue;
851
        case EXP_D15:
852
            group_size = 1;
853
            break;
854
        case EXP_D25:
855
            group_size = 2;
856
            break;
857
        default:
858
        case EXP_D45:
859
            group_size = 4;
860
            break;
861
        }
862
        nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
863
        p = encoded_exp[ch];
864

    
865
        /* first exponent */
866
        exp1 = *p++;
867
        put_bits(&s->pb, 4, exp1);
868

    
869
        /* next ones are delta encoded */
870
        for(i=0;i<nb_groups;i++) {
871
            /* merge three delta in one code */
872
            exp0 = exp1;
873
            exp1 = p[0];
874
            p += group_size;
875
            delta0 = exp1 - exp0 + 2;
876

    
877
            exp0 = exp1;
878
            exp1 = p[0];
879
            p += group_size;
880
            delta1 = exp1 - exp0 + 2;
881

    
882
            exp0 = exp1;
883
            exp1 = p[0];
884
            p += group_size;
885
            delta2 = exp1 - exp0 + 2;
886

    
887
            put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
888
        }
889

    
890
        if (ch != s->lfe_channel)
891
            put_bits(&s->pb, 2, 0); /* no gain range info */
892
    }
893

    
894
    /* bit allocation info */
895
    baie = (block_num == 0);
896
    put_bits(&s->pb, 1, baie);
897
    if (baie) {
898
        put_bits(&s->pb, 2, s->slow_decay_code);
899
        put_bits(&s->pb, 2, s->fast_decay_code);
900
        put_bits(&s->pb, 2, s->slow_gain_code);
901
        put_bits(&s->pb, 2, s->db_per_bit_code);
902
        put_bits(&s->pb, 3, s->floor_code);
903
    }
904

    
905
    /* snr offset */
906
    put_bits(&s->pb, 1, baie); /* always present with bai */
907
    if (baie) {
908
        put_bits(&s->pb, 6, s->coarse_snr_offset);
909
        for(ch=0;ch<s->nb_all_channels;ch++) {
910
            put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
911
            put_bits(&s->pb, 3, s->fast_gain_code[ch]);
912
        }
913
    }
914

    
915
    put_bits(&s->pb, 1, 0); /* no delta bit allocation */
916
    put_bits(&s->pb, 1, 0); /* no data to skip */
917

    
918
    /* mantissa encoding : we use two passes to handle the grouping. A
919
       one pass method may be faster, but it would necessitate to
920
       modify the output stream. */
921

    
922
    /* first pass: quantize */
923
    mant1_cnt = mant2_cnt = mant4_cnt = 0;
924
    qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
925

    
926
    for (ch = 0; ch < s->nb_all_channels; ch++) {
927
        int b, c, e, v;
928

    
929
        for(i=0;i<s->nb_coefs[ch];i++) {
930
            c = mdct_coefs[ch][i];
931
            e = encoded_exp[ch][i] - global_exp[ch];
932
            b = bap[ch][i];
933
            switch(b) {
934
            case 0:
935
                v = 0;
936
                break;
937
            case 1:
938
                v = sym_quant(c, e, 3);
939
                switch(mant1_cnt) {
940
                case 0:
941
                    qmant1_ptr = &qmant[ch][i];
942
                    v = 9 * v;
943
                    mant1_cnt = 1;
944
                    break;
945
                case 1:
946
                    *qmant1_ptr += 3 * v;
947
                    mant1_cnt = 2;
948
                    v = 128;
949
                    break;
950
                default:
951
                    *qmant1_ptr += v;
952
                    mant1_cnt = 0;
953
                    v = 128;
954
                    break;
955
                }
956
                break;
957
            case 2:
958
                v = sym_quant(c, e, 5);
959
                switch(mant2_cnt) {
960
                case 0:
961
                    qmant2_ptr = &qmant[ch][i];
962
                    v = 25 * v;
963
                    mant2_cnt = 1;
964
                    break;
965
                case 1:
966
                    *qmant2_ptr += 5 * v;
967
                    mant2_cnt = 2;
968
                    v = 128;
969
                    break;
970
                default:
971
                    *qmant2_ptr += v;
972
                    mant2_cnt = 0;
973
                    v = 128;
974
                    break;
975
                }
976
                break;
977
            case 3:
978
                v = sym_quant(c, e, 7);
979
                break;
980
            case 4:
981
                v = sym_quant(c, e, 11);
982
                switch(mant4_cnt) {
983
                case 0:
984
                    qmant4_ptr = &qmant[ch][i];
985
                    v = 11 * v;
986
                    mant4_cnt = 1;
987
                    break;
988
                default:
989
                    *qmant4_ptr += v;
990
                    mant4_cnt = 0;
991
                    v = 128;
992
                    break;
993
                }
994
                break;
995
            case 5:
996
                v = sym_quant(c, e, 15);
997
                break;
998
            case 14:
999
                v = asym_quant(c, e, 14);
1000
                break;
1001
            case 15:
1002
                v = asym_quant(c, e, 16);
1003
                break;
1004
            default:
1005
                v = asym_quant(c, e, b - 1);
1006
                break;
1007
            }
1008
            qmant[ch][i] = v;
1009
        }
1010
    }
1011

    
1012
    /* second pass : output the values */
1013
    for (ch = 0; ch < s->nb_all_channels; ch++) {
1014
        int b, q;
1015

    
1016
        for(i=0;i<s->nb_coefs[ch];i++) {
1017
            q = qmant[ch][i];
1018
            b = bap[ch][i];
1019
            switch(b) {
1020
            case 0:
1021
                break;
1022
            case 1:
1023
                if (q != 128)
1024
                    put_bits(&s->pb, 5, q);
1025
                break;
1026
            case 2:
1027
                if (q != 128)
1028
                    put_bits(&s->pb, 7, q);
1029
                break;
1030
            case 3:
1031
                put_bits(&s->pb, 3, q);
1032
                break;
1033
            case 4:
1034
                if (q != 128)
1035
                    put_bits(&s->pb, 7, q);
1036
                break;
1037
            case 14:
1038
                put_bits(&s->pb, 14, q);
1039
                break;
1040
            case 15:
1041
                put_bits(&s->pb, 16, q);
1042
                break;
1043
            default:
1044
                put_bits(&s->pb, b - 1, q);
1045
                break;
1046
            }
1047
        }
1048
    }
1049
}
1050

    
1051
#define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1052

    
1053
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1054
{
1055
    unsigned int c;
1056

    
1057
    c = 0;
1058
    while (a) {
1059
        if (a & 1)
1060
            c ^= b;
1061
        a = a >> 1;
1062
        b = b << 1;
1063
        if (b & (1 << 16))
1064
            b ^= poly;
1065
    }
1066
    return c;
1067
}
1068

    
1069
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1070
{
1071
    unsigned int r;
1072
    r = 1;
1073
    while (n) {
1074
        if (n & 1)
1075
            r = mul_poly(r, a, poly);
1076
        a = mul_poly(a, a, poly);
1077
        n >>= 1;
1078
    }
1079
    return r;
1080
}
1081

    
1082

    
1083
/* compute log2(max(abs(tab[]))) */
1084
static int log2_tab(int16_t *tab, int n)
1085
{
1086
    int i, v;
1087

    
1088
    v = 0;
1089
    for(i=0;i<n;i++) {
1090
        v |= abs(tab[i]);
1091
    }
1092
    return av_log2(v);
1093
}
1094

    
1095
static void lshift_tab(int16_t *tab, int n, int lshift)
1096
{
1097
    int i;
1098

    
1099
    if (lshift > 0) {
1100
        for(i=0;i<n;i++) {
1101
            tab[i] <<= lshift;
1102
        }
1103
    } else if (lshift < 0) {
1104
        lshift = -lshift;
1105
        for(i=0;i<n;i++) {
1106
            tab[i] >>= lshift;
1107
        }
1108
    }
1109
}
1110

    
1111
/* fill the end of the frame and compute the two crcs */
1112
static int output_frame_end(AC3EncodeContext *s)
1113
{
1114
    int frame_size, frame_size_58, n, crc1, crc2, crc_inv;
1115
    uint8_t *frame;
1116

    
1117
    frame_size = s->frame_size; /* frame size in words */
1118
    /* align to 8 bits */
1119
    flush_put_bits(&s->pb);
1120
    /* add zero bytes to reach the frame size */
1121
    frame = s->pb.buf;
1122
    n = 2 * s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
1123
    assert(n >= 0);
1124
    if(n>0)
1125
      memset(put_bits_ptr(&s->pb), 0, n);
1126

    
1127
    /* Now we must compute both crcs : this is not so easy for crc1
1128
       because it is at the beginning of the data... */
1129
    frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
1130
    crc1 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
1131
                           frame + 4, 2 * frame_size_58 - 4));
1132
    /* XXX: could precompute crc_inv */
1133
    crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
1134
    crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
1135
    AV_WB16(frame+2,crc1);
1136

    
1137
    crc2 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
1138
                           frame + 2 * frame_size_58,
1139
                           (frame_size - frame_size_58) * 2 - 2));
1140
    AV_WB16(frame+2*frame_size-2,crc2);
1141

    
1142
    //    printf("n=%d frame_size=%d\n", n, frame_size);
1143
    return frame_size * 2;
1144
}
1145

    
1146
static int AC3_encode_frame(AVCodecContext *avctx,
1147
                            unsigned char *frame, int buf_size, void *data)
1148
{
1149
    AC3EncodeContext *s = avctx->priv_data;
1150
    int16_t *samples = data;
1151
    int i, j, k, v, ch;
1152
    int16_t input_samples[N];
1153
    int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1154
    uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1155
    uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
1156
    uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1157
    uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1158
    int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
1159
    int frame_bits;
1160

    
1161
    frame_bits = 0;
1162
    for(ch=0;ch<s->nb_all_channels;ch++) {
1163
        int ich = s->channel_map[ch];
1164
        /* fixed mdct to the six sub blocks & exponent computation */
1165
        for(i=0;i<NB_BLOCKS;i++) {
1166
            int16_t *sptr;
1167
            int sinc;
1168

    
1169
            /* compute input samples */
1170
            memcpy(input_samples, s->last_samples[ich], N/2 * sizeof(int16_t));
1171
            sinc = s->nb_all_channels;
1172
            sptr = samples + (sinc * (N/2) * i) + ich;
1173
            for(j=0;j<N/2;j++) {
1174
                v = *sptr;
1175
                input_samples[j + N/2] = v;
1176
                s->last_samples[ich][j] = v;
1177
                sptr += sinc;
1178
            }
1179

    
1180
            /* apply the MDCT window */
1181
            for(j=0;j<N/2;j++) {
1182
                input_samples[j] = MUL16(input_samples[j],
1183
                                         ff_ac3_window[j]) >> 15;
1184
                input_samples[N-j-1] = MUL16(input_samples[N-j-1],
1185
                                             ff_ac3_window[j]) >> 15;
1186
            }
1187

    
1188
            /* Normalize the samples to use the maximum available
1189
               precision */
1190
            v = 14 - log2_tab(input_samples, N);
1191
            if (v < 0)
1192
                v = 0;
1193
            exp_samples[i][ch] = v - 9;
1194
            lshift_tab(input_samples, N, v);
1195

    
1196
            /* do the MDCT */
1197
            mdct512(mdct_coef[i][ch], input_samples);
1198

    
1199
            /* compute "exponents". We take into account the
1200
               normalization there */
1201
            for(j=0;j<N/2;j++) {
1202
                int e;
1203
                v = abs(mdct_coef[i][ch][j]);
1204
                if (v == 0)
1205
                    e = 24;
1206
                else {
1207
                    e = 23 - av_log2(v) + exp_samples[i][ch];
1208
                    if (e >= 24) {
1209
                        e = 24;
1210
                        mdct_coef[i][ch][j] = 0;
1211
                    }
1212
                }
1213
                exp[i][ch][j] = e;
1214
            }
1215
        }
1216

    
1217
        compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);
1218

    
1219
        /* compute the exponents as the decoder will see them. The
1220
           EXP_REUSE case must be handled carefully : we select the
1221
           min of the exponents */
1222
        i = 0;
1223
        while (i < NB_BLOCKS) {
1224
            j = i + 1;
1225
            while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
1226
                exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
1227
                j++;
1228
            }
1229
            frame_bits += encode_exp(encoded_exp[i][ch],
1230
                                     exp[i][ch], s->nb_coefs[ch],
1231
                                     exp_strategy[i][ch]);
1232
            /* copy encoded exponents for reuse case */
1233
            for(k=i+1;k<j;k++) {
1234
                memcpy(encoded_exp[k][ch], encoded_exp[i][ch],
1235
                       s->nb_coefs[ch] * sizeof(uint8_t));
1236
            }
1237
            i = j;
1238
        }
1239
    }
1240

    
1241
    /* adjust for fractional frame sizes */
1242
    while(s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
1243
        s->bits_written -= s->bit_rate;
1244
        s->samples_written -= s->sample_rate;
1245
    }
1246
    s->frame_size = s->frame_size_min + (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
1247
    s->bits_written += s->frame_size * 16;
1248
    s->samples_written += AC3_FRAME_SIZE;
1249

    
1250
    compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
1251
    /* everything is known... let's output the frame */
1252
    output_frame_header(s, frame);
1253

    
1254
    for(i=0;i<NB_BLOCKS;i++) {
1255
        output_audio_block(s, exp_strategy[i], encoded_exp[i],
1256
                           bap[i], mdct_coef[i], exp_samples[i], i);
1257
    }
1258
    return output_frame_end(s);
1259
}
1260

    
1261
static av_cold int AC3_encode_close(AVCodecContext *avctx)
1262
{
1263
    av_freep(&avctx->coded_frame);
1264
    return 0;
1265
}
1266

    
1267
#if 0
1268
/*************************************************************************/
1269
/* TEST */
1270

1271
#undef random
1272
#define FN (N/4)
1273

1274
void fft_test(void)
1275
{
1276
    IComplex in[FN], in1[FN];
1277
    int k, n, i;
1278
    float sum_re, sum_im, a;
1279

1280
    /* FFT test */
1281

1282
    for(i=0;i<FN;i++) {
1283
        in[i].re = random() % 65535 - 32767;
1284
        in[i].im = random() % 65535 - 32767;
1285
        in1[i] = in[i];
1286
    }
1287
    fft(in, 7);
1288

1289
    /* do it by hand */
1290
    for(k=0;k<FN;k++) {
1291
        sum_re = 0;
1292
        sum_im = 0;
1293
        for(n=0;n<FN;n++) {
1294
            a = -2 * M_PI * (n * k) / FN;
1295
            sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
1296
            sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
1297
        }
1298
        printf("%3d: %6d,%6d %6.0f,%6.0f\n",
1299
               k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
1300
    }
1301
}
1302

1303
void mdct_test(void)
1304
{
1305
    int16_t input[N];
1306
    int32_t output[N/2];
1307
    float input1[N];
1308
    float output1[N/2];
1309
    float s, a, err, e, emax;
1310
    int i, k, n;
1311

1312
    for(i=0;i<N;i++) {
1313
        input[i] = (random() % 65535 - 32767) * 9 / 10;
1314
        input1[i] = input[i];
1315
    }
1316

1317
    mdct512(output, input);
1318

1319
    /* do it by hand */
1320
    for(k=0;k<N/2;k++) {
1321
        s = 0;
1322
        for(n=0;n<N;n++) {
1323
            a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));
1324
            s += input1[n] * cos(a);
1325
        }
1326
        output1[k] = -2 * s / N;
1327
    }
1328

1329
    err = 0;
1330
    emax = 0;
1331
    for(i=0;i<N/2;i++) {
1332
        printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);
1333
        e = output[i] - output1[i];
1334
        if (e > emax)
1335
            emax = e;
1336
        err += e * e;
1337
    }
1338
    printf("err2=%f emax=%f\n", err / (N/2), emax);
1339
}
1340

1341
void test_ac3(void)
1342
{
1343
    AC3EncodeContext ctx;
1344
    unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];
1345
    short samples[AC3_FRAME_SIZE];
1346
    int ret, i;
1347

1348
    AC3_encode_init(&ctx, 44100, 64000, 1);
1349

1350
    fft_test();
1351
    mdct_test();
1352

1353
    for(i=0;i<AC3_FRAME_SIZE;i++)
1354
        samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);
1355
    ret = AC3_encode_frame(&ctx, frame, samples);
1356
    printf("ret=%d\n", ret);
1357
}
1358
#endif
1359

    
1360
AVCodec ac3_encoder = {
1361
    "ac3",
1362
    CODEC_TYPE_AUDIO,
1363
    CODEC_ID_AC3,
1364
    sizeof(AC3EncodeContext),
1365
    AC3_encode_init,
1366
    AC3_encode_frame,
1367
    AC3_encode_close,
1368
    NULL,
1369
    .sample_fmts = (enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
1370
    .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
1371
};