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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
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"
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#include "get_bits.h" // for ff_reverse
31
#include "put_bits.h"
32
#include "ac3.h"
33
#include "audioconvert.h"
34

    
35
typedef struct AC3EncodeContext {
36
    PutBitContext pb;
37
    int nb_channels;
38
    int nb_all_channels;
39
    int lfe_channel;
40
    const uint8_t *channel_map;
41
    int bit_rate;
42
    unsigned int sample_rate;
43
    unsigned int bitstream_id;
44
    unsigned int frame_size_min; /* minimum frame size in case rounding is necessary */
45
    unsigned int frame_size; /* current frame size in words */
46
    unsigned int bits_written;
47
    unsigned int samples_written;
48
    int sr_shift;
49
    unsigned int frame_size_code;
50
    unsigned int sr_code; /* frequency */
51
    unsigned int channel_mode;
52
    int lfe;
53
    unsigned int bitstream_mode;
54
    short last_samples[AC3_MAX_CHANNELS][256];
55
    unsigned int chbwcod[AC3_MAX_CHANNELS];
56
    int nb_coefs[AC3_MAX_CHANNELS];
57

    
58
    /* bitrate allocation control */
59
    int slow_gain_code, slow_decay_code, fast_decay_code, db_per_bit_code, floor_code;
60
    AC3BitAllocParameters bit_alloc;
61
    int coarse_snr_offset;
62
    int fast_gain_code[AC3_MAX_CHANNELS];
63
    int fine_snr_offset[AC3_MAX_CHANNELS];
64
    /* mantissa encoding */
65
    int mant1_cnt, mant2_cnt, mant4_cnt;
66
} AC3EncodeContext;
67

    
68
static int16_t costab[64];
69
static int16_t sintab[64];
70
static int16_t xcos1[128];
71
static int16_t xsin1[128];
72

    
73
#define MDCT_NBITS 9
74
#define N         (1 << MDCT_NBITS)
75

    
76
/* new exponents are sent if their Norm 1 exceed this number */
77
#define EXP_DIFF_THRESHOLD 1000
78

    
79
static inline int16_t fix15(float a)
80
{
81
    int v;
82
    v = (int)(a * (float)(1 << 15));
83
    if (v < -32767)
84
        v = -32767;
85
    else if (v > 32767)
86
        v = 32767;
87
    return v;
88
}
89

    
90
typedef struct IComplex {
91
    short re,im;
92
} IComplex;
93

    
94
static av_cold void fft_init(int ln)
95
{
96
    int i, n;
97
    float alpha;
98

    
99
    n = 1 << ln;
100

    
101
    for(i=0;i<(n/2);i++) {
102
        alpha = 2 * M_PI * (float)i / (float)n;
103
        costab[i] = fix15(cos(alpha));
104
        sintab[i] = fix15(sin(alpha));
105
    }
106
}
107

    
108
/* butter fly op */
109
#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
110
{\
111
  int ax, ay, bx, by;\
112
  bx=pre1;\
113
  by=pim1;\
114
  ax=qre1;\
115
  ay=qim1;\
116
  pre = (bx + ax) >> 1;\
117
  pim = (by + ay) >> 1;\
118
  qre = (bx - ax) >> 1;\
119
  qim = (by - ay) >> 1;\
120
}
121

    
122
#define CMUL(pre, pim, are, aim, bre, bim) \
123
{\
124
   pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\
125
   pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\
126
}
127

    
128

    
129
/* do a 2^n point complex fft on 2^ln points. */
130
static void fft(IComplex *z, int ln)
131
{
132
    int        j, l, np, np2;
133
    int        nblocks, nloops;
134
    register IComplex *p,*q;
135
    int tmp_re, tmp_im;
136

    
137
    np = 1 << ln;
138

    
139
    /* reverse */
140
    for(j=0;j<np;j++) {
141
        int k = ff_reverse[j] >> (8 - ln);
142
        if (k < j)
143
            FFSWAP(IComplex, z[k], z[j]);
144
    }
145

    
146
    /* pass 0 */
147

    
148
    p=&z[0];
149
    j=(np >> 1);
150
    do {
151
        BF(p[0].re, p[0].im, p[1].re, p[1].im,
152
           p[0].re, p[0].im, p[1].re, p[1].im);
153
        p+=2;
154
    } while (--j != 0);
155

    
156
    /* pass 1 */
157

    
158
    p=&z[0];
159
    j=np >> 2;
160
    do {
161
        BF(p[0].re, p[0].im, p[2].re, p[2].im,
162
           p[0].re, p[0].im, p[2].re, p[2].im);
163
        BF(p[1].re, p[1].im, p[3].re, p[3].im,
164
           p[1].re, p[1].im, p[3].im, -p[3].re);
165
        p+=4;
166
    } while (--j != 0);
167

    
168
    /* pass 2 .. ln-1 */
169

    
170
    nblocks = np >> 3;
171
    nloops = 1 << 2;
172
    np2 = np >> 1;
173
    do {
174
        p = z;
175
        q = z + nloops;
176
        for (j = 0; j < nblocks; ++j) {
177

    
178
            BF(p->re, p->im, q->re, q->im,
179
               p->re, p->im, q->re, q->im);
180

    
181
            p++;
182
            q++;
183
            for(l = nblocks; l < np2; l += nblocks) {
184
                CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
185
                BF(p->re, p->im, q->re, q->im,
186
                   p->re, p->im, tmp_re, tmp_im);
187
                p++;
188
                q++;
189
            }
190
            p += nloops;
191
            q += nloops;
192
        }
193
        nblocks = nblocks >> 1;
194
        nloops = nloops << 1;
195
    } while (nblocks != 0);
196
}
197

    
198
/* do a 512 point mdct */
199
static void mdct512(int32_t *out, int16_t *in)
200
{
201
    int i, re, im, re1, im1;
202
    int16_t rot[N];
203
    IComplex x[N/4];
204

    
205
    /* shift to simplify computations */
206
    for(i=0;i<N/4;i++)
207
        rot[i] = -in[i + 3*N/4];
208
    for(i=N/4;i<N;i++)
209
        rot[i] = in[i - N/4];
210

    
211
    /* pre rotation */
212
    for(i=0;i<N/4;i++) {
213
        re = ((int)rot[2*i] - (int)rot[N-1-2*i]) >> 1;
214
        im = -((int)rot[N/2+2*i] - (int)rot[N/2-1-2*i]) >> 1;
215
        CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
216
    }
217

    
218
    fft(x, MDCT_NBITS - 2);
219

    
220
    /* post rotation */
221
    for(i=0;i<N/4;i++) {
222
        re = x[i].re;
223
        im = x[i].im;
224
        CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
225
        out[2*i] = im1;
226
        out[N/2-1-2*i] = re1;
227
    }
228
}
229

    
230
/* XXX: use another norm ? */
231
static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)
232
{
233
    int sum, i;
234
    sum = 0;
235
    for(i=0;i<n;i++) {
236
        sum += abs(exp1[i] - exp2[i]);
237
    }
238
    return sum;
239
}
240

    
241
static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
242
                                 uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
243
                                 int ch, int is_lfe)
244
{
245
    int i, j;
246
    int exp_diff;
247

    
248
    /* estimate if the exponent variation & decide if they should be
249
       reused in the next frame */
250
    exp_strategy[0][ch] = EXP_NEW;
251
    for(i=1;i<NB_BLOCKS;i++) {
252
        exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);
253
#ifdef DEBUG
254
        av_log(NULL, AV_LOG_DEBUG, "exp_diff=%d\n", exp_diff);
255
#endif
256
        if (exp_diff > EXP_DIFF_THRESHOLD)
257
            exp_strategy[i][ch] = EXP_NEW;
258
        else
259
            exp_strategy[i][ch] = EXP_REUSE;
260
    }
261
    if (is_lfe)
262
        return;
263

    
264
    /* now select the encoding strategy type : if exponents are often
265
       recoded, we use a coarse encoding */
266
    i = 0;
267
    while (i < NB_BLOCKS) {
268
        j = i + 1;
269
        while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)
270
            j++;
271
        switch(j - i) {
272
        case 1:
273
            exp_strategy[i][ch] = EXP_D45;
274
            break;
275
        case 2:
276
        case 3:
277
            exp_strategy[i][ch] = EXP_D25;
278
            break;
279
        default:
280
            exp_strategy[i][ch] = EXP_D15;
281
            break;
282
        }
283
        i = j;
284
    }
285
}
286

    
287
/* set exp[i] to min(exp[i], exp1[i]) */
288
static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n)
289
{
290
    int i;
291

    
292
    for(i=0;i<n;i++) {
293
        if (exp1[i] < exp[i])
294
            exp[i] = exp1[i];
295
    }
296
}
297

    
298
/* update the exponents so that they are the ones the decoder will
299
   decode. Return the number of bits used to code the exponents */
300
static int encode_exp(uint8_t encoded_exp[N/2],
301
                      uint8_t exp[N/2],
302
                      int nb_exps,
303
                      int exp_strategy)
304
{
305
    int group_size, nb_groups, i, j, k, exp_min;
306
    uint8_t exp1[N/2];
307

    
308
    switch(exp_strategy) {
309
    case EXP_D15:
310
        group_size = 1;
311
        break;
312
    case EXP_D25:
313
        group_size = 2;
314
        break;
315
    default:
316
    case EXP_D45:
317
        group_size = 4;
318
        break;
319
    }
320
    nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
321

    
322
    /* for each group, compute the minimum exponent */
323
    exp1[0] = exp[0]; /* DC exponent is handled separately */
324
    k = 1;
325
    for(i=1;i<=nb_groups;i++) {
326
        exp_min = exp[k];
327
        assert(exp_min >= 0 && exp_min <= 24);
328
        for(j=1;j<group_size;j++) {
329
            if (exp[k+j] < exp_min)
330
                exp_min = exp[k+j];
331
        }
332
        exp1[i] = exp_min;
333
        k += group_size;
334
    }
335

    
336
    /* constraint for DC exponent */
337
    if (exp1[0] > 15)
338
        exp1[0] = 15;
339

    
340
    /* Decrease the delta between each groups to within 2
341
     * so that they can be differentially encoded */
342
    for (i=1;i<=nb_groups;i++)
343
        exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
344
    for (i=nb_groups-1;i>=0;i--)
345
        exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
346

    
347
    /* now we have the exponent values the decoder will see */
348
    encoded_exp[0] = exp1[0];
349
    k = 1;
350
    for(i=1;i<=nb_groups;i++) {
351
        for(j=0;j<group_size;j++) {
352
            encoded_exp[k+j] = exp1[i];
353
        }
354
        k += group_size;
355
    }
356

    
357
#if defined(DEBUG)
358
    av_log(NULL, AV_LOG_DEBUG, "exponents: strategy=%d\n", exp_strategy);
359
    for(i=0;i<=nb_groups * group_size;i++) {
360
        av_log(NULL, AV_LOG_DEBUG, "%d ", encoded_exp[i]);
361
    }
362
    av_log(NULL, AV_LOG_DEBUG, "\n");
363
#endif
364

    
365
    return 4 + (nb_groups / 3) * 7;
366
}
367

    
368
/* return the size in bits taken by the mantissa */
369
static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
370
{
371
    int bits, mant, i;
372

    
373
    bits = 0;
374
    for(i=0;i<nb_coefs;i++) {
375
        mant = m[i];
376
        switch(mant) {
377
        case 0:
378
            /* nothing */
379
            break;
380
        case 1:
381
            /* 3 mantissa in 5 bits */
382
            if (s->mant1_cnt == 0)
383
                bits += 5;
384
            if (++s->mant1_cnt == 3)
385
                s->mant1_cnt = 0;
386
            break;
387
        case 2:
388
            /* 3 mantissa in 7 bits */
389
            if (s->mant2_cnt == 0)
390
                bits += 7;
391
            if (++s->mant2_cnt == 3)
392
                s->mant2_cnt = 0;
393
            break;
394
        case 3:
395
            bits += 3;
396
            break;
397
        case 4:
398
            /* 2 mantissa in 7 bits */
399
            if (s->mant4_cnt == 0)
400
                bits += 7;
401
            if (++s->mant4_cnt == 2)
402
                s->mant4_cnt = 0;
403
            break;
404
        case 14:
405
            bits += 14;
406
            break;
407
        case 15:
408
            bits += 16;
409
            break;
410
        default:
411
            bits += mant - 1;
412
            break;
413
        }
414
    }
415
    return bits;
416
}
417

    
418

    
419
static void bit_alloc_masking(AC3EncodeContext *s,
420
                              uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
421
                              uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
422
                              int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
423
                              int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50])
424
{
425
    int blk, ch;
426
    int16_t band_psd[NB_BLOCKS][AC3_MAX_CHANNELS][50];
427

    
428
    for(blk=0; blk<NB_BLOCKS; blk++) {
429
        for(ch=0;ch<s->nb_all_channels;ch++) {
430
            if(exp_strategy[blk][ch] == EXP_REUSE) {
431
                memcpy(psd[blk][ch], psd[blk-1][ch], (N/2)*sizeof(int16_t));
432
                memcpy(mask[blk][ch], mask[blk-1][ch], 50*sizeof(int16_t));
433
            } else {
434
                ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,
435
                                          s->nb_coefs[ch],
436
                                          psd[blk][ch], band_psd[blk][ch]);
437
                ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, band_psd[blk][ch],
438
                                           0, s->nb_coefs[ch],
439
                                           ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
440
                                           ch == s->lfe_channel,
441
                                           DBA_NONE, 0, NULL, NULL, NULL,
442
                                           mask[blk][ch]);
443
            }
444
        }
445
    }
446
}
447

    
448
static int bit_alloc(AC3EncodeContext *s,
449
                     int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50],
450
                     int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
451
                     uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
452
                     int frame_bits, int coarse_snr_offset, int fine_snr_offset)
453
{
454
    int i, ch;
455
    int snr_offset;
456

    
457
    snr_offset = (((coarse_snr_offset - 15) << 4) + fine_snr_offset) << 2;
458

    
459
    /* compute size */
460
    for(i=0;i<NB_BLOCKS;i++) {
461
        s->mant1_cnt = 0;
462
        s->mant2_cnt = 0;
463
        s->mant4_cnt = 0;
464
        for(ch=0;ch<s->nb_all_channels;ch++) {
465
            ff_ac3_bit_alloc_calc_bap(mask[i][ch], psd[i][ch], 0,
466
                                      s->nb_coefs[ch], snr_offset,
467
                                      s->bit_alloc.floor, ff_ac3_bap_tab,
468
                                      bap[i][ch]);
469
            frame_bits += compute_mantissa_size(s, bap[i][ch],
470
                                                 s->nb_coefs[ch]);
471
        }
472
    }
473
#if 0
474
    printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",
475
           coarse_snr_offset, fine_snr_offset, frame_bits,
476
           16 * s->frame_size - ((frame_bits + 7) & ~7));
477
#endif
478
    return 16 * s->frame_size - frame_bits;
479
}
480

    
481
#define SNR_INC1 4
482

    
483
static int compute_bit_allocation(AC3EncodeContext *s,
484
                                  uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
485
                                  uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
486
                                  uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
487
                                  int frame_bits)
488
{
489
    int i, ch;
490
    int coarse_snr_offset, fine_snr_offset;
491
    uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
492
    int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
493
    int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50];
494
    static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
495

    
496
    /* init default parameters */
497
    s->slow_decay_code = 2;
498
    s->fast_decay_code = 1;
499
    s->slow_gain_code = 1;
500
    s->db_per_bit_code = 2;
501
    s->floor_code = 4;
502
    for(ch=0;ch<s->nb_all_channels;ch++)
503
        s->fast_gain_code[ch] = 4;
504

    
505
    /* compute real values */
506
    s->bit_alloc.sr_code = s->sr_code;
507
    s->bit_alloc.sr_shift = s->sr_shift;
508
    s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->sr_shift;
509
    s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->sr_shift;
510
    s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
511
    s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
512
    s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
513

    
514
    /* header size */
515
    frame_bits += 65;
516
    // if (s->channel_mode == 2)
517
    //    frame_bits += 2;
518
    frame_bits += frame_bits_inc[s->channel_mode];
519

    
520
    /* audio blocks */
521
    for(i=0;i<NB_BLOCKS;i++) {
522
        frame_bits += s->nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
523
        if (s->channel_mode == AC3_CHMODE_STEREO) {
524
            frame_bits++; /* rematstr */
525
            if(i==0) frame_bits += 4;
526
        }
527
        frame_bits += 2 * s->nb_channels; /* chexpstr[2] * c */
528
        if (s->lfe)
529
            frame_bits++; /* lfeexpstr */
530
        for(ch=0;ch<s->nb_channels;ch++) {
531
            if (exp_strategy[i][ch] != EXP_REUSE)
532
                frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
533
        }
534
        frame_bits++; /* baie */
535
        frame_bits++; /* snr */
536
        frame_bits += 2; /* delta / skip */
537
    }
538
    frame_bits++; /* cplinu for block 0 */
539
    /* bit alloc info */
540
    /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
541
    /* csnroffset[6] */
542
    /* (fsnoffset[4] + fgaincod[4]) * c */
543
    frame_bits += 2*4 + 3 + 6 + s->nb_all_channels * (4 + 3);
544

    
545
    /* auxdatae, crcrsv */
546
    frame_bits += 2;
547

    
548
    /* CRC */
549
    frame_bits += 16;
550

    
551
    /* calculate psd and masking curve before doing bit allocation */
552
    bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask);
553

    
554
    /* now the big work begins : do the bit allocation. Modify the snr
555
       offset until we can pack everything in the requested frame size */
556

    
557
    coarse_snr_offset = s->coarse_snr_offset;
558
    while (coarse_snr_offset >= 0 &&
559
           bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0)
560
        coarse_snr_offset -= SNR_INC1;
561
    if (coarse_snr_offset < 0) {
562
        av_log(NULL, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
563
        return -1;
564
    }
565
    while ((coarse_snr_offset + SNR_INC1) <= 63 &&
566
           bit_alloc(s, mask, psd, bap1, frame_bits,
567
                     coarse_snr_offset + SNR_INC1, 0) >= 0) {
568
        coarse_snr_offset += SNR_INC1;
569
        memcpy(bap, bap1, sizeof(bap1));
570
    }
571
    while ((coarse_snr_offset + 1) <= 63 &&
572
           bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) {
573
        coarse_snr_offset++;
574
        memcpy(bap, bap1, sizeof(bap1));
575
    }
576

    
577
    fine_snr_offset = 0;
578
    while ((fine_snr_offset + SNR_INC1) <= 15 &&
579
           bit_alloc(s, mask, psd, bap1, frame_bits,
580
                     coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {
581
        fine_snr_offset += SNR_INC1;
582
        memcpy(bap, bap1, sizeof(bap1));
583
    }
584
    while ((fine_snr_offset + 1) <= 15 &&
585
           bit_alloc(s, mask, psd, bap1, frame_bits,
586
                     coarse_snr_offset, fine_snr_offset + 1) >= 0) {
587
        fine_snr_offset++;
588
        memcpy(bap, bap1, sizeof(bap1));
589
    }
590

    
591
    s->coarse_snr_offset = coarse_snr_offset;
592
    for(ch=0;ch<s->nb_all_channels;ch++)
593
        s->fine_snr_offset[ch] = fine_snr_offset;
594
#if defined(DEBUG_BITALLOC)
595
    {
596
        int j;
597

    
598
        for(i=0;i<6;i++) {
599
            for(ch=0;ch<s->nb_all_channels;ch++) {
600
                printf("Block #%d Ch%d:\n", i, ch);
601
                printf("bap=");
602
                for(j=0;j<s->nb_coefs[ch];j++) {
603
                    printf("%d ",bap[i][ch][j]);
604
                }
605
                printf("\n");
606
            }
607
        }
608
    }
609
#endif
610
    return 0;
611
}
612

    
613
static av_cold int set_channel_info(AC3EncodeContext *s, int channels,
614
                                    int64_t *channel_layout)
615
{
616
    int ch_layout;
617

    
618
    if (channels < 1 || channels > AC3_MAX_CHANNELS)
619
        return -1;
620
    if ((uint64_t)*channel_layout > 0x7FF)
621
        return -1;
622
    ch_layout = *channel_layout;
623
    if (!ch_layout)
624
        ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);
625
    if (avcodec_channel_layout_num_channels(ch_layout) != channels)
626
        return -1;
627

    
628
    s->lfe = !!(ch_layout & CH_LOW_FREQUENCY);
629
    s->nb_all_channels = channels;
630
    s->nb_channels = channels - s->lfe;
631
    s->lfe_channel = s->lfe ? s->nb_channels : -1;
632
    if (s->lfe)
633
        ch_layout -= CH_LOW_FREQUENCY;
634

    
635
    switch (ch_layout) {
636
    case CH_LAYOUT_MONO:           s->channel_mode = AC3_CHMODE_MONO;   break;
637
    case CH_LAYOUT_STEREO:         s->channel_mode = AC3_CHMODE_STEREO; break;
638
    case CH_LAYOUT_SURROUND:       s->channel_mode = AC3_CHMODE_3F;     break;
639
    case CH_LAYOUT_2_1:            s->channel_mode = AC3_CHMODE_2F1R;   break;
640
    case CH_LAYOUT_4POINT0:        s->channel_mode = AC3_CHMODE_3F1R;   break;
641
    case CH_LAYOUT_QUAD:
642
    case CH_LAYOUT_2_2:            s->channel_mode = AC3_CHMODE_2F2R;   break;
643
    case CH_LAYOUT_5POINT0:
644
    case CH_LAYOUT_5POINT0_BACK:   s->channel_mode = AC3_CHMODE_3F2R;   break;
645
    default:
646
        return -1;
647
    }
648

    
649
    s->channel_map = ff_ac3_enc_channel_map[s->channel_mode][s->lfe];
650
    *channel_layout = ch_layout;
651
    if (s->lfe)
652
        *channel_layout |= CH_LOW_FREQUENCY;
653

    
654
    return 0;
655
}
656

    
657
static av_cold int AC3_encode_init(AVCodecContext *avctx)
658
{
659
    int freq = avctx->sample_rate;
660
    int bitrate = avctx->bit_rate;
661
    AC3EncodeContext *s = avctx->priv_data;
662
    int i, j, ch;
663
    float alpha;
664
    int bw_code;
665

    
666
    avctx->frame_size = AC3_FRAME_SIZE;
667

    
668
    ac3_common_init();
669

    
670
    if (!avctx->channel_layout) {
671
        av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
672
                                      "encoder will guess the layout, but it "
673
                                      "might be incorrect.\n");
674
    }
675
    if (set_channel_info(s, avctx->channels, &avctx->channel_layout)) {
676
        av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");
677
        return -1;
678
    }
679

    
680
    /* frequency */
681
    for(i=0;i<3;i++) {
682
        for(j=0;j<3;j++)
683
            if ((ff_ac3_sample_rate_tab[j] >> i) == freq)
684
                goto found;
685
    }
686
    return -1;
687
 found:
688
    s->sample_rate = freq;
689
    s->sr_shift = i;
690
    s->sr_code = j;
691
    s->bitstream_id = 8 + s->sr_shift;
692
    s->bitstream_mode = 0; /* complete main audio service */
693

    
694
    /* bitrate & frame size */
695
    for(i=0;i<19;i++) {
696
        if ((ff_ac3_bitrate_tab[i] >> s->sr_shift)*1000 == bitrate)
697
            break;
698
    }
699
    if (i == 19)
700
        return -1;
701
    s->bit_rate = bitrate;
702
    s->frame_size_code = i << 1;
703
    s->frame_size_min = ff_ac3_frame_size_tab[s->frame_size_code][s->sr_code];
704
    s->bits_written = 0;
705
    s->samples_written = 0;
706
    s->frame_size = s->frame_size_min;
707

    
708
    /* bit allocation init */
709
    if(avctx->cutoff) {
710
        /* calculate bandwidth based on user-specified cutoff frequency */
711
        int cutoff = av_clip(avctx->cutoff, 1, s->sample_rate >> 1);
712
        int fbw_coeffs = cutoff * 512 / s->sample_rate;
713
        bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
714
    } else {
715
        /* use default bandwidth setting */
716
        /* XXX: should compute the bandwidth according to the frame
717
           size, so that we avoid annoying high frequency artifacts */
718
        bw_code = 50;
719
    }
720
    for(ch=0;ch<s->nb_channels;ch++) {
721
        /* bandwidth for each channel */
722
        s->chbwcod[ch] = bw_code;
723
        s->nb_coefs[ch] = bw_code * 3 + 73;
724
    }
725
    if (s->lfe) {
726
        s->nb_coefs[s->lfe_channel] = 7; /* fixed */
727
    }
728
    /* initial snr offset */
729
    s->coarse_snr_offset = 40;
730

    
731
    /* mdct init */
732
    fft_init(MDCT_NBITS - 2);
733
    for(i=0;i<N/4;i++) {
734
        alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
735
        xcos1[i] = fix15(-cos(alpha));
736
        xsin1[i] = fix15(-sin(alpha));
737
    }
738

    
739
    avctx->coded_frame= avcodec_alloc_frame();
740
    avctx->coded_frame->key_frame= 1;
741

    
742
    return 0;
743
}
744

    
745
/* output the AC-3 frame header */
746
static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
747
{
748
    init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
749

    
750
    put_bits(&s->pb, 16, 0x0b77); /* frame header */
751
    put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
752
    put_bits(&s->pb, 2, s->sr_code);
753
    put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min));
754
    put_bits(&s->pb, 5, s->bitstream_id);
755
    put_bits(&s->pb, 3, s->bitstream_mode);
756
    put_bits(&s->pb, 3, s->channel_mode);
757
    if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
758
        put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
759
    if (s->channel_mode & 0x04)
760
        put_bits(&s->pb, 2, 1); /* XXX -6 dB */
761
    if (s->channel_mode == AC3_CHMODE_STEREO)
762
        put_bits(&s->pb, 2, 0); /* surround not indicated */
763
    put_bits(&s->pb, 1, s->lfe); /* LFE */
764
    put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
765
    put_bits(&s->pb, 1, 0); /* no compression control word */
766
    put_bits(&s->pb, 1, 0); /* no lang code */
767
    put_bits(&s->pb, 1, 0); /* no audio production info */
768
    put_bits(&s->pb, 1, 0); /* no copyright */
769
    put_bits(&s->pb, 1, 1); /* original bitstream */
770
    put_bits(&s->pb, 1, 0); /* no time code 1 */
771
    put_bits(&s->pb, 1, 0); /* no time code 2 */
772
    put_bits(&s->pb, 1, 0); /* no additional bit stream info */
773
}
774

    
775
/* symetric quantization on 'levels' levels */
776
static inline int sym_quant(int c, int e, int levels)
777
{
778
    int v;
779

    
780
    if (c >= 0) {
781
        v = (levels * (c << e)) >> 24;
782
        v = (v + 1) >> 1;
783
        v = (levels >> 1) + v;
784
    } else {
785
        v = (levels * ((-c) << e)) >> 24;
786
        v = (v + 1) >> 1;
787
        v = (levels >> 1) - v;
788
    }
789
    assert (v >= 0 && v < levels);
790
    return v;
791
}
792

    
793
/* asymetric quantization on 2^qbits levels */
794
static inline int asym_quant(int c, int e, int qbits)
795
{
796
    int lshift, m, v;
797

    
798
    lshift = e + qbits - 24;
799
    if (lshift >= 0)
800
        v = c << lshift;
801
    else
802
        v = c >> (-lshift);
803
    /* rounding */
804
    v = (v + 1) >> 1;
805
    m = (1 << (qbits-1));
806
    if (v >= m)
807
        v = m - 1;
808
    assert(v >= -m);
809
    return v & ((1 << qbits)-1);
810
}
811

    
812
/* Output one audio block. There are NB_BLOCKS audio blocks in one AC-3
813
   frame */
814
static void output_audio_block(AC3EncodeContext *s,
815
                               uint8_t exp_strategy[AC3_MAX_CHANNELS],
816
                               uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],
817
                               uint8_t bap[AC3_MAX_CHANNELS][N/2],
818
                               int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],
819
                               int8_t global_exp[AC3_MAX_CHANNELS],
820
                               int block_num)
821
{
822
    int ch, nb_groups, group_size, i, baie, rbnd;
823
    uint8_t *p;
824
    uint16_t qmant[AC3_MAX_CHANNELS][N/2];
825
    int exp0, exp1;
826
    int mant1_cnt, mant2_cnt, mant4_cnt;
827
    uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
828
    int delta0, delta1, delta2;
829

    
830
    for(ch=0;ch<s->nb_channels;ch++)
831
        put_bits(&s->pb, 1, 0); /* 512 point MDCT */
832
    for(ch=0;ch<s->nb_channels;ch++)
833
        put_bits(&s->pb, 1, 1); /* no dither */
834
    put_bits(&s->pb, 1, 0); /* no dynamic range */
835
    if (block_num == 0) {
836
        /* for block 0, even if no coupling, we must say it. This is a
837
           waste of bit :-) */
838
        put_bits(&s->pb, 1, 1); /* coupling strategy present */
839
        put_bits(&s->pb, 1, 0); /* no coupling strategy */
840
    } else {
841
        put_bits(&s->pb, 1, 0); /* no new coupling strategy */
842
    }
843

    
844
    if (s->channel_mode == AC3_CHMODE_STEREO)
845
      {
846
        if(block_num==0)
847
          {
848
            /* first block must define rematrixing (rematstr)  */
849
            put_bits(&s->pb, 1, 1);
850

    
851
            /* dummy rematrixing rematflg(1:4)=0 */
852
            for (rbnd=0;rbnd<4;rbnd++)
853
              put_bits(&s->pb, 1, 0);
854
          }
855
        else
856
          {
857
            /* no matrixing (but should be used in the future) */
858
            put_bits(&s->pb, 1, 0);
859
          }
860
      }
861

    
862
#if defined(DEBUG)
863
    {
864
      static int count = 0;
865
      av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++);
866
    }
867
#endif
868
    /* exponent strategy */
869
    for(ch=0;ch<s->nb_channels;ch++) {
870
        put_bits(&s->pb, 2, exp_strategy[ch]);
871
    }
872

    
873
    if (s->lfe) {
874
        put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
875
    }
876

    
877
    for(ch=0;ch<s->nb_channels;ch++) {
878
        if (exp_strategy[ch] != EXP_REUSE)
879
            put_bits(&s->pb, 6, s->chbwcod[ch]);
880
    }
881

    
882
    /* exponents */
883
    for (ch = 0; ch < s->nb_all_channels; ch++) {
884
        switch(exp_strategy[ch]) {
885
        case EXP_REUSE:
886
            continue;
887
        case EXP_D15:
888
            group_size = 1;
889
            break;
890
        case EXP_D25:
891
            group_size = 2;
892
            break;
893
        default:
894
        case EXP_D45:
895
            group_size = 4;
896
            break;
897
        }
898
        nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
899
        p = encoded_exp[ch];
900

    
901
        /* first exponent */
902
        exp1 = *p++;
903
        put_bits(&s->pb, 4, exp1);
904

    
905
        /* next ones are delta encoded */
906
        for(i=0;i<nb_groups;i++) {
907
            /* merge three delta in one code */
908
            exp0 = exp1;
909
            exp1 = p[0];
910
            p += group_size;
911
            delta0 = exp1 - exp0 + 2;
912

    
913
            exp0 = exp1;
914
            exp1 = p[0];
915
            p += group_size;
916
            delta1 = exp1 - exp0 + 2;
917

    
918
            exp0 = exp1;
919
            exp1 = p[0];
920
            p += group_size;
921
            delta2 = exp1 - exp0 + 2;
922

    
923
            put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
924
        }
925

    
926
        if (ch != s->lfe_channel)
927
            put_bits(&s->pb, 2, 0); /* no gain range info */
928
    }
929

    
930
    /* bit allocation info */
931
    baie = (block_num == 0);
932
    put_bits(&s->pb, 1, baie);
933
    if (baie) {
934
        put_bits(&s->pb, 2, s->slow_decay_code);
935
        put_bits(&s->pb, 2, s->fast_decay_code);
936
        put_bits(&s->pb, 2, s->slow_gain_code);
937
        put_bits(&s->pb, 2, s->db_per_bit_code);
938
        put_bits(&s->pb, 3, s->floor_code);
939
    }
940

    
941
    /* snr offset */
942
    put_bits(&s->pb, 1, baie); /* always present with bai */
943
    if (baie) {
944
        put_bits(&s->pb, 6, s->coarse_snr_offset);
945
        for(ch=0;ch<s->nb_all_channels;ch++) {
946
            put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
947
            put_bits(&s->pb, 3, s->fast_gain_code[ch]);
948
        }
949
    }
950

    
951
    put_bits(&s->pb, 1, 0); /* no delta bit allocation */
952
    put_bits(&s->pb, 1, 0); /* no data to skip */
953

    
954
    /* mantissa encoding : we use two passes to handle the grouping. A
955
       one pass method may be faster, but it would necessitate to
956
       modify the output stream. */
957

    
958
    /* first pass: quantize */
959
    mant1_cnt = mant2_cnt = mant4_cnt = 0;
960
    qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
961

    
962
    for (ch = 0; ch < s->nb_all_channels; ch++) {
963
        int b, c, e, v;
964

    
965
        for(i=0;i<s->nb_coefs[ch];i++) {
966
            c = mdct_coefs[ch][i];
967
            e = encoded_exp[ch][i] - global_exp[ch];
968
            b = bap[ch][i];
969
            switch(b) {
970
            case 0:
971
                v = 0;
972
                break;
973
            case 1:
974
                v = sym_quant(c, e, 3);
975
                switch(mant1_cnt) {
976
                case 0:
977
                    qmant1_ptr = &qmant[ch][i];
978
                    v = 9 * v;
979
                    mant1_cnt = 1;
980
                    break;
981
                case 1:
982
                    *qmant1_ptr += 3 * v;
983
                    mant1_cnt = 2;
984
                    v = 128;
985
                    break;
986
                default:
987
                    *qmant1_ptr += v;
988
                    mant1_cnt = 0;
989
                    v = 128;
990
                    break;
991
                }
992
                break;
993
            case 2:
994
                v = sym_quant(c, e, 5);
995
                switch(mant2_cnt) {
996
                case 0:
997
                    qmant2_ptr = &qmant[ch][i];
998
                    v = 25 * v;
999
                    mant2_cnt = 1;
1000
                    break;
1001
                case 1:
1002
                    *qmant2_ptr += 5 * v;
1003
                    mant2_cnt = 2;
1004
                    v = 128;
1005
                    break;
1006
                default:
1007
                    *qmant2_ptr += v;
1008
                    mant2_cnt = 0;
1009
                    v = 128;
1010
                    break;
1011
                }
1012
                break;
1013
            case 3:
1014
                v = sym_quant(c, e, 7);
1015
                break;
1016
            case 4:
1017
                v = sym_quant(c, e, 11);
1018
                switch(mant4_cnt) {
1019
                case 0:
1020
                    qmant4_ptr = &qmant[ch][i];
1021
                    v = 11 * v;
1022
                    mant4_cnt = 1;
1023
                    break;
1024
                default:
1025
                    *qmant4_ptr += v;
1026
                    mant4_cnt = 0;
1027
                    v = 128;
1028
                    break;
1029
                }
1030
                break;
1031
            case 5:
1032
                v = sym_quant(c, e, 15);
1033
                break;
1034
            case 14:
1035
                v = asym_quant(c, e, 14);
1036
                break;
1037
            case 15:
1038
                v = asym_quant(c, e, 16);
1039
                break;
1040
            default:
1041
                v = asym_quant(c, e, b - 1);
1042
                break;
1043
            }
1044
            qmant[ch][i] = v;
1045
        }
1046
    }
1047

    
1048
    /* second pass : output the values */
1049
    for (ch = 0; ch < s->nb_all_channels; ch++) {
1050
        int b, q;
1051

    
1052
        for(i=0;i<s->nb_coefs[ch];i++) {
1053
            q = qmant[ch][i];
1054
            b = bap[ch][i];
1055
            switch(b) {
1056
            case 0:
1057
                break;
1058
            case 1:
1059
                if (q != 128)
1060
                    put_bits(&s->pb, 5, q);
1061
                break;
1062
            case 2:
1063
                if (q != 128)
1064
                    put_bits(&s->pb, 7, q);
1065
                break;
1066
            case 3:
1067
                put_bits(&s->pb, 3, q);
1068
                break;
1069
            case 4:
1070
                if (q != 128)
1071
                    put_bits(&s->pb, 7, q);
1072
                break;
1073
            case 14:
1074
                put_bits(&s->pb, 14, q);
1075
                break;
1076
            case 15:
1077
                put_bits(&s->pb, 16, q);
1078
                break;
1079
            default:
1080
                put_bits(&s->pb, b - 1, q);
1081
                break;
1082
            }
1083
        }
1084
    }
1085
}
1086

    
1087
#define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1088

    
1089
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1090
{
1091
    unsigned int c;
1092

    
1093
    c = 0;
1094
    while (a) {
1095
        if (a & 1)
1096
            c ^= b;
1097
        a = a >> 1;
1098
        b = b << 1;
1099
        if (b & (1 << 16))
1100
            b ^= poly;
1101
    }
1102
    return c;
1103
}
1104

    
1105
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1106
{
1107
    unsigned int r;
1108
    r = 1;
1109
    while (n) {
1110
        if (n & 1)
1111
            r = mul_poly(r, a, poly);
1112
        a = mul_poly(a, a, poly);
1113
        n >>= 1;
1114
    }
1115
    return r;
1116
}
1117

    
1118

    
1119
/* compute log2(max(abs(tab[]))) */
1120
static int log2_tab(int16_t *tab, int n)
1121
{
1122
    int i, v;
1123

    
1124
    v = 0;
1125
    for(i=0;i<n;i++) {
1126
        v |= abs(tab[i]);
1127
    }
1128
    return av_log2(v);
1129
}
1130

    
1131
static void lshift_tab(int16_t *tab, int n, int lshift)
1132
{
1133
    int i;
1134

    
1135
    if (lshift > 0) {
1136
        for(i=0;i<n;i++) {
1137
            tab[i] <<= lshift;
1138
        }
1139
    } else if (lshift < 0) {
1140
        lshift = -lshift;
1141
        for(i=0;i<n;i++) {
1142
            tab[i] >>= lshift;
1143
        }
1144
    }
1145
}
1146

    
1147
/* fill the end of the frame and compute the two crcs */
1148
static int output_frame_end(AC3EncodeContext *s)
1149
{
1150
    int frame_size, frame_size_58, n, crc1, crc2, crc_inv;
1151
    uint8_t *frame;
1152

    
1153
    frame_size = s->frame_size; /* frame size in words */
1154
    /* align to 8 bits */
1155
    flush_put_bits(&s->pb);
1156
    /* add zero bytes to reach the frame size */
1157
    frame = s->pb.buf;
1158
    n = 2 * s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
1159
    assert(n >= 0);
1160
    if(n>0)
1161
      memset(put_bits_ptr(&s->pb), 0, n);
1162

    
1163
    /* Now we must compute both crcs : this is not so easy for crc1
1164
       because it is at the beginning of the data... */
1165
    frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
1166
    crc1 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
1167
                           frame + 4, 2 * frame_size_58 - 4));
1168
    /* XXX: could precompute crc_inv */
1169
    crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
1170
    crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
1171
    AV_WB16(frame+2,crc1);
1172

    
1173
    crc2 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
1174
                           frame + 2 * frame_size_58,
1175
                           (frame_size - frame_size_58) * 2 - 2));
1176
    AV_WB16(frame+2*frame_size-2,crc2);
1177

    
1178
    //    printf("n=%d frame_size=%d\n", n, frame_size);
1179
    return frame_size * 2;
1180
}
1181

    
1182
static int AC3_encode_frame(AVCodecContext *avctx,
1183
                            unsigned char *frame, int buf_size, void *data)
1184
{
1185
    AC3EncodeContext *s = avctx->priv_data;
1186
    int16_t *samples = data;
1187
    int i, j, k, v, ch;
1188
    int16_t input_samples[N];
1189
    int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1190
    uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1191
    uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
1192
    uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1193
    uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1194
    int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
1195
    int frame_bits;
1196

    
1197
    frame_bits = 0;
1198
    for(ch=0;ch<s->nb_all_channels;ch++) {
1199
        int ich = s->channel_map[ch];
1200
        /* fixed mdct to the six sub blocks & exponent computation */
1201
        for(i=0;i<NB_BLOCKS;i++) {
1202
            int16_t *sptr;
1203
            int sinc;
1204

    
1205
            /* compute input samples */
1206
            memcpy(input_samples, s->last_samples[ich], N/2 * sizeof(int16_t));
1207
            sinc = s->nb_all_channels;
1208
            sptr = samples + (sinc * (N/2) * i) + ich;
1209
            for(j=0;j<N/2;j++) {
1210
                v = *sptr;
1211
                input_samples[j + N/2] = v;
1212
                s->last_samples[ich][j] = v;
1213
                sptr += sinc;
1214
            }
1215

    
1216
            /* apply the MDCT window */
1217
            for(j=0;j<N/2;j++) {
1218
                input_samples[j] = MUL16(input_samples[j],
1219
                                         ff_ac3_window[j]) >> 15;
1220
                input_samples[N-j-1] = MUL16(input_samples[N-j-1],
1221
                                             ff_ac3_window[j]) >> 15;
1222
            }
1223

    
1224
            /* Normalize the samples to use the maximum available
1225
               precision */
1226
            v = 14 - log2_tab(input_samples, N);
1227
            if (v < 0)
1228
                v = 0;
1229
            exp_samples[i][ch] = v - 9;
1230
            lshift_tab(input_samples, N, v);
1231

    
1232
            /* do the MDCT */
1233
            mdct512(mdct_coef[i][ch], input_samples);
1234

    
1235
            /* compute "exponents". We take into account the
1236
               normalization there */
1237
            for(j=0;j<N/2;j++) {
1238
                int e;
1239
                v = abs(mdct_coef[i][ch][j]);
1240
                if (v == 0)
1241
                    e = 24;
1242
                else {
1243
                    e = 23 - av_log2(v) + exp_samples[i][ch];
1244
                    if (e >= 24) {
1245
                        e = 24;
1246
                        mdct_coef[i][ch][j] = 0;
1247
                    }
1248
                }
1249
                exp[i][ch][j] = e;
1250
            }
1251
        }
1252

    
1253
        compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);
1254

    
1255
        /* compute the exponents as the decoder will see them. The
1256
           EXP_REUSE case must be handled carefully : we select the
1257
           min of the exponents */
1258
        i = 0;
1259
        while (i < NB_BLOCKS) {
1260
            j = i + 1;
1261
            while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
1262
                exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
1263
                j++;
1264
            }
1265
            frame_bits += encode_exp(encoded_exp[i][ch],
1266
                                     exp[i][ch], s->nb_coefs[ch],
1267
                                     exp_strategy[i][ch]);
1268
            /* copy encoded exponents for reuse case */
1269
            for(k=i+1;k<j;k++) {
1270
                memcpy(encoded_exp[k][ch], encoded_exp[i][ch],
1271
                       s->nb_coefs[ch] * sizeof(uint8_t));
1272
            }
1273
            i = j;
1274
        }
1275
    }
1276

    
1277
    /* adjust for fractional frame sizes */
1278
    while(s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
1279
        s->bits_written -= s->bit_rate;
1280
        s->samples_written -= s->sample_rate;
1281
    }
1282
    s->frame_size = s->frame_size_min + (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
1283
    s->bits_written += s->frame_size * 16;
1284
    s->samples_written += AC3_FRAME_SIZE;
1285

    
1286
    compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
1287
    /* everything is known... let's output the frame */
1288
    output_frame_header(s, frame);
1289

    
1290
    for(i=0;i<NB_BLOCKS;i++) {
1291
        output_audio_block(s, exp_strategy[i], encoded_exp[i],
1292
                           bap[i], mdct_coef[i], exp_samples[i], i);
1293
    }
1294
    return output_frame_end(s);
1295
}
1296

    
1297
static av_cold int AC3_encode_close(AVCodecContext *avctx)
1298
{
1299
    av_freep(&avctx->coded_frame);
1300
    return 0;
1301
}
1302

    
1303
#if 0
1304
/*************************************************************************/
1305
/* TEST */
1306

1307
#undef random
1308
#define FN (N/4)
1309

1310
void fft_test(void)
1311
{
1312
    IComplex in[FN], in1[FN];
1313
    int k, n, i;
1314
    float sum_re, sum_im, a;
1315

1316
    /* FFT test */
1317

1318
    for(i=0;i<FN;i++) {
1319
        in[i].re = random() % 65535 - 32767;
1320
        in[i].im = random() % 65535 - 32767;
1321
        in1[i] = in[i];
1322
    }
1323
    fft(in, 7);
1324

1325
    /* do it by hand */
1326
    for(k=0;k<FN;k++) {
1327
        sum_re = 0;
1328
        sum_im = 0;
1329
        for(n=0;n<FN;n++) {
1330
            a = -2 * M_PI * (n * k) / FN;
1331
            sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
1332
            sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
1333
        }
1334
        printf("%3d: %6d,%6d %6.0f,%6.0f\n",
1335
               k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
1336
    }
1337
}
1338

1339
void mdct_test(void)
1340
{
1341
    int16_t input[N];
1342
    int32_t output[N/2];
1343
    float input1[N];
1344
    float output1[N/2];
1345
    float s, a, err, e, emax;
1346
    int i, k, n;
1347

1348
    for(i=0;i<N;i++) {
1349
        input[i] = (random() % 65535 - 32767) * 9 / 10;
1350
        input1[i] = input[i];
1351
    }
1352

1353
    mdct512(output, input);
1354

1355
    /* do it by hand */
1356
    for(k=0;k<N/2;k++) {
1357
        s = 0;
1358
        for(n=0;n<N;n++) {
1359
            a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));
1360
            s += input1[n] * cos(a);
1361
        }
1362
        output1[k] = -2 * s / N;
1363
    }
1364

1365
    err = 0;
1366
    emax = 0;
1367
    for(i=0;i<N/2;i++) {
1368
        printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);
1369
        e = output[i] - output1[i];
1370
        if (e > emax)
1371
            emax = e;
1372
        err += e * e;
1373
    }
1374
    printf("err2=%f emax=%f\n", err / (N/2), emax);
1375
}
1376

1377
void test_ac3(void)
1378
{
1379
    AC3EncodeContext ctx;
1380
    unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];
1381
    short samples[AC3_FRAME_SIZE];
1382
    int ret, i;
1383

1384
    AC3_encode_init(&ctx, 44100, 64000, 1);
1385

1386
    fft_test();
1387
    mdct_test();
1388

1389
    for(i=0;i<AC3_FRAME_SIZE;i++)
1390
        samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);
1391
    ret = AC3_encode_frame(&ctx, frame, samples);
1392
    printf("ret=%d\n", ret);
1393
}
1394
#endif
1395

    
1396
AVCodec ac3_encoder = {
1397
    "ac3",
1398
    CODEC_TYPE_AUDIO,
1399
    CODEC_ID_AC3,
1400
    sizeof(AC3EncodeContext),
1401
    AC3_encode_init,
1402
    AC3_encode_frame,
1403
    AC3_encode_close,
1404
    NULL,
1405
    .sample_fmts = (enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
1406
    .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
1407
    .channel_layouts = (int64_t[]){
1408
        CH_LAYOUT_MONO,
1409
        CH_LAYOUT_STEREO,
1410
        CH_LAYOUT_2_1,
1411
        CH_LAYOUT_SURROUND,
1412
        CH_LAYOUT_2_2,
1413
        CH_LAYOUT_QUAD,
1414
        CH_LAYOUT_4POINT0,
1415
        CH_LAYOUT_5POINT0,
1416
        CH_LAYOUT_5POINT0_BACK,
1417
       (CH_LAYOUT_MONO     | CH_LOW_FREQUENCY),
1418
       (CH_LAYOUT_STEREO   | CH_LOW_FREQUENCY),
1419
       (CH_LAYOUT_2_1      | CH_LOW_FREQUENCY),
1420
       (CH_LAYOUT_SURROUND | CH_LOW_FREQUENCY),
1421
       (CH_LAYOUT_2_2      | CH_LOW_FREQUENCY),
1422
       (CH_LAYOUT_QUAD     | CH_LOW_FREQUENCY),
1423
       (CH_LAYOUT_4POINT0  | CH_LOW_FREQUENCY),
1424
        CH_LAYOUT_5POINT1,
1425
        CH_LAYOUT_5POINT1_BACK,
1426
        0 },
1427
};