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1
/*
2
 * The simplest AC3 encoder
3
 * Copyright (c) 2000 Fabrice Bellard.
4
 *
5
 * This library is free software; you can redistribute it and/or
6
 * modify it under the terms of the GNU Lesser General Public
7
 * License as published by the Free Software Foundation; either
8
 * version 2 of the License, or (at your option) any later version.
9
 *
10
 * This library is distributed in the hope that it will be useful,
11
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13
 * Lesser General Public License for more details.
14
 *
15
 * You should have received a copy of the GNU Lesser General Public
16
 * License along with this library; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
18
 */
19

    
20
/**
21
 * @file ac3enc.c
22
 * The simplest AC3 encoder.
23
 */
24
//#define DEBUG
25
//#define DEBUG_BITALLOC
26
#include "avcodec.h"
27
#include "bitstream.h"
28
#include "ac3.h"
29

    
30
typedef struct AC3EncodeContext {
31
    PutBitContext pb;
32
    int nb_channels;
33
    int nb_all_channels;
34
    int lfe_channel;
35
    int bit_rate;
36
    unsigned int sample_rate;
37
    unsigned int bsid;
38
    unsigned int frame_size_min; /* minimum frame size in case rounding is necessary */
39
    unsigned int frame_size; /* current frame size in words */
40
    int halfratecod;
41
    unsigned int frmsizecod;
42
    unsigned int fscod; /* frequency */
43
    unsigned int acmod;
44
    int lfe;
45
    unsigned int bsmod;
46
    short last_samples[AC3_MAX_CHANNELS][256];
47
    unsigned int chbwcod[AC3_MAX_CHANNELS];
48
    int nb_coefs[AC3_MAX_CHANNELS];
49

    
50
    /* bitrate allocation control */
51
    int sgaincod, sdecaycod, fdecaycod, dbkneecod, floorcod;
52
    AC3BitAllocParameters bit_alloc;
53
    int csnroffst;
54
    int fgaincod[AC3_MAX_CHANNELS];
55
    int fsnroffst[AC3_MAX_CHANNELS];
56
    /* mantissa encoding */
57
    int mant1_cnt, mant2_cnt, mant4_cnt;
58
} AC3EncodeContext;
59

    
60
#include "ac3tab.h"
61

    
62
#define MDCT_NBITS 9
63
#define N         (1 << MDCT_NBITS)
64

    
65
/* new exponents are sent if their Norm 1 exceed this number */
66
#define EXP_DIFF_THRESHOLD 1000
67

    
68
static void fft_init(int ln);
69
static void ac3_crc_init(void);
70

    
71
static inline int16_t fix15(float a)
72
{
73
    int v;
74
    v = (int)(a * (float)(1 << 15));
75
    if (v < -32767)
76
        v = -32767;
77
    else if (v > 32767)
78
        v = 32767;
79
    return v;
80
}
81

    
82
static inline int calc_lowcomp1(int a, int b0, int b1)
83
{
84
    if ((b0 + 256) == b1) {
85
        a = 384 ;
86
    } else if (b0 > b1) {
87
        a = a - 64;
88
        if (a < 0) a=0;
89
    }
90
    return a;
91
}
92

    
93
static inline int calc_lowcomp(int a, int b0, int b1, int bin)
94
{
95
    if (bin < 7) {
96
        if ((b0 + 256) == b1) {
97
            a = 384 ;
98
        } else if (b0 > b1) {
99
            a = a - 64;
100
            if (a < 0) a=0;
101
        }
102
    } else if (bin < 20) {
103
        if ((b0 + 256) == b1) {
104
            a = 320 ;
105
        } else if (b0 > b1) {
106
            a= a - 64;
107
            if (a < 0) a=0;
108
        }
109
    } else {
110
        a = a - 128;
111
        if (a < 0) a=0;
112
    }
113
    return a;
114
}
115

    
116
/* AC3 bit allocation. The algorithm is the one described in the AC3
117
   spec. */
118
void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
119
                                   int8_t *exp, int start, int end,
120
                                   int snroffset, int fgain, int is_lfe,
121
                                   int deltbae,int deltnseg,
122
                                   uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba)
123
{
124
    int bin,i,j,k,end1,v,v1,bndstrt,bndend,lowcomp,begin;
125
    int fastleak,slowleak,address,tmp;
126
    int16_t psd[256]; /* scaled exponents */
127
    int16_t bndpsd[50]; /* interpolated exponents */
128
    int16_t excite[50]; /* excitation */
129
    int16_t mask[50];   /* masking value */
130

    
131
    /* exponent mapping to PSD */
132
    for(bin=start;bin<end;bin++) {
133
        psd[bin]=(3072 - (exp[bin] << 7));
134
    }
135

    
136
    /* PSD integration */
137
    j=start;
138
    k=masktab[start];
139
    do {
140
        v=psd[j];
141
        j++;
142
        end1=bndtab[k+1];
143
        if (end1 > end) end1=end;
144
        for(i=j;i<end1;i++) {
145
            int c,adr;
146
            /* logadd */
147
            v1=psd[j];
148
            c=v-v1;
149
            if (c >= 0) {
150
                adr=c >> 1;
151
                if (adr > 255) adr=255;
152
                v=v + latab[adr];
153
            } else {
154
                adr=(-c) >> 1;
155
                if (adr > 255) adr=255;
156
                v=v1 + latab[adr];
157
            }
158
            j++;
159
        }
160
        bndpsd[k]=v;
161
        k++;
162
    } while (end > bndtab[k]);
163

    
164
    /* excitation function */
165
    bndstrt = masktab[start];
166
    bndend = masktab[end-1] + 1;
167

    
168
    if (bndstrt == 0) {
169
        lowcomp = 0;
170
        lowcomp = calc_lowcomp1(lowcomp, bndpsd[0], bndpsd[1]) ;
171
        excite[0] = bndpsd[0] - fgain - lowcomp ;
172
        lowcomp = calc_lowcomp1(lowcomp, bndpsd[1], bndpsd[2]) ;
173
        excite[1] = bndpsd[1] - fgain - lowcomp ;
174
        begin = 7 ;
175
        for (bin = 2; bin < 7; bin++) {
176
            if (!(is_lfe && bin == 6))
177
                lowcomp = calc_lowcomp1(lowcomp, bndpsd[bin], bndpsd[bin+1]) ;
178
            fastleak = bndpsd[bin] - fgain ;
179
            slowleak = bndpsd[bin] - s->sgain ;
180
            excite[bin] = fastleak - lowcomp ;
181
            if (!(is_lfe && bin == 6)) {
182
                if (bndpsd[bin] <= bndpsd[bin+1]) {
183
                    begin = bin + 1 ;
184
                    break ;
185
                }
186
            }
187
        }
188

    
189
        end1=bndend;
190
        if (end1 > 22) end1=22;
191

    
192
        for (bin = begin; bin < end1; bin++) {
193
            if (!(is_lfe && bin == 6))
194
                lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin) ;
195

    
196
            fastleak -= s->fdecay ;
197
            v = bndpsd[bin] - fgain;
198
            if (fastleak < v) fastleak = v;
199

    
200
            slowleak -= s->sdecay ;
201
            v = bndpsd[bin] - s->sgain;
202
            if (slowleak < v) slowleak = v;
203

    
204
            v=fastleak - lowcomp;
205
            if (slowleak > v) v=slowleak;
206

    
207
            excite[bin] = v;
208
        }
209
        begin = 22;
210
    } else {
211
        /* coupling channel */
212
        begin = bndstrt;
213

    
214
        fastleak = (s->cplfleak << 8) + 768;
215
        slowleak = (s->cplsleak << 8) + 768;
216
    }
217

    
218
    for (bin = begin; bin < bndend; bin++) {
219
        fastleak -= s->fdecay ;
220
        v = bndpsd[bin] - fgain;
221
        if (fastleak < v) fastleak = v;
222
        slowleak -= s->sdecay ;
223
        v = bndpsd[bin] - s->sgain;
224
        if (slowleak < v) slowleak = v;
225

    
226
        v=fastleak;
227
        if (slowleak > v) v = slowleak;
228
        excite[bin] = v;
229
    }
230

    
231
    /* compute masking curve */
232

    
233
    for (bin = bndstrt; bin < bndend; bin++) {
234
        v1 = excite[bin];
235
        tmp = s->dbknee - bndpsd[bin];
236
        if (tmp > 0) {
237
            v1 += tmp >> 2;
238
        }
239
        v=hth[bin >> s->halfratecod][s->fscod];
240
        if (v1 > v) v=v1;
241
        mask[bin] = v;
242
    }
243

    
244
    /* delta bit allocation */
245

    
246
    if (deltbae == 0 || deltbae == 1) {
247
        int band, seg, delta;
248
        band = 0 ;
249
        for (seg = 0; seg < deltnseg; seg++) {
250
            band += deltoffst[seg] ;
251
            if (deltba[seg] >= 4) {
252
                delta = (deltba[seg] - 3) << 7;
253
            } else {
254
                delta = (deltba[seg] - 4) << 7;
255
            }
256
            for (k = 0; k < deltlen[seg]; k++) {
257
                mask[band] += delta ;
258
                band++ ;
259
            }
260
        }
261
    }
262

    
263
    /* compute bit allocation */
264

    
265
    i = start ;
266
    j = masktab[start] ;
267
    do {
268
        v=mask[j];
269
        v -= snroffset ;
270
        v -= s->floor ;
271
        if (v < 0) v = 0;
272
        v &= 0x1fe0 ;
273
        v += s->floor ;
274

    
275
        end1=bndtab[j] + bndsz[j];
276
        if (end1 > end) end1=end;
277

    
278
        for (k = i; k < end1; k++) {
279
            address = (psd[i] - v) >> 5 ;
280
            if (address < 0) address=0;
281
            else if (address > 63) address=63;
282
            bap[i] = baptab[address];
283
            i++;
284
        }
285
    } while (end > bndtab[j++]) ;
286
}
287

    
288
typedef struct IComplex {
289
    short re,im;
290
} IComplex;
291

    
292
static void fft_init(int ln)
293
{
294
    int i, j, m, n;
295
    float alpha;
296

    
297
    n = 1 << ln;
298

    
299
    for(i=0;i<(n/2);i++) {
300
        alpha = 2 * M_PI * (float)i / (float)n;
301
        costab[i] = fix15(cos(alpha));
302
        sintab[i] = fix15(sin(alpha));
303
    }
304

    
305
    for(i=0;i<n;i++) {
306
        m=0;
307
        for(j=0;j<ln;j++) {
308
            m |= ((i >> j) & 1) << (ln-j-1);
309
        }
310
        fft_rev[i]=m;
311
    }
312
}
313

    
314
/* butter fly op */
315
#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
316
{\
317
  int ax, ay, bx, by;\
318
  bx=pre1;\
319
  by=pim1;\
320
  ax=qre1;\
321
  ay=qim1;\
322
  pre = (bx + ax) >> 1;\
323
  pim = (by + ay) >> 1;\
324
  qre = (bx - ax) >> 1;\
325
  qim = (by - ay) >> 1;\
326
}
327

    
328
#define MUL16(a,b) ((a) * (b))
329

    
330
#define CMUL(pre, pim, are, aim, bre, bim) \
331
{\
332
   pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\
333
   pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\
334
}
335

    
336

    
337
/* do a 2^n point complex fft on 2^ln points. */
338
static void fft(IComplex *z, int ln)
339
{
340
    int        j, l, np, np2;
341
    int        nblocks, nloops;
342
    register IComplex *p,*q;
343
    int tmp_re, tmp_im;
344

    
345
    np = 1 << ln;
346

    
347
    /* reverse */
348
    for(j=0;j<np;j++) {
349
        int k;
350
        IComplex tmp;
351
        k = fft_rev[j];
352
        if (k < j) {
353
            tmp = z[k];
354
            z[k] = z[j];
355
            z[j] = tmp;
356
        }
357
    }
358

    
359
    /* pass 0 */
360

    
361
    p=&z[0];
362
    j=(np >> 1);
363
    do {
364
        BF(p[0].re, p[0].im, p[1].re, p[1].im,
365
           p[0].re, p[0].im, p[1].re, p[1].im);
366
        p+=2;
367
    } while (--j != 0);
368

    
369
    /* pass 1 */
370

    
371
    p=&z[0];
372
    j=np >> 2;
373
    do {
374
        BF(p[0].re, p[0].im, p[2].re, p[2].im,
375
           p[0].re, p[0].im, p[2].re, p[2].im);
376
        BF(p[1].re, p[1].im, p[3].re, p[3].im,
377
           p[1].re, p[1].im, p[3].im, -p[3].re);
378
        p+=4;
379
    } while (--j != 0);
380

    
381
    /* pass 2 .. ln-1 */
382

    
383
    nblocks = np >> 3;
384
    nloops = 1 << 2;
385
    np2 = np >> 1;
386
    do {
387
        p = z;
388
        q = z + nloops;
389
        for (j = 0; j < nblocks; ++j) {
390

    
391
            BF(p->re, p->im, q->re, q->im,
392
               p->re, p->im, q->re, q->im);
393

    
394
            p++;
395
            q++;
396
            for(l = nblocks; l < np2; l += nblocks) {
397
                CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
398
                BF(p->re, p->im, q->re, q->im,
399
                   p->re, p->im, tmp_re, tmp_im);
400
                p++;
401
                q++;
402
            }
403
            p += nloops;
404
            q += nloops;
405
        }
406
        nblocks = nblocks >> 1;
407
        nloops = nloops << 1;
408
    } while (nblocks != 0);
409
}
410

    
411
/* do a 512 point mdct */
412
static void mdct512(int32_t *out, int16_t *in)
413
{
414
    int i, re, im, re1, im1;
415
    int16_t rot[N];
416
    IComplex x[N/4];
417

    
418
    /* shift to simplify computations */
419
    for(i=0;i<N/4;i++)
420
        rot[i] = -in[i + 3*N/4];
421
    for(i=N/4;i<N;i++)
422
        rot[i] = in[i - N/4];
423

    
424
    /* pre rotation */
425
    for(i=0;i<N/4;i++) {
426
        re = ((int)rot[2*i] - (int)rot[N-1-2*i]) >> 1;
427
        im = -((int)rot[N/2+2*i] - (int)rot[N/2-1-2*i]) >> 1;
428
        CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
429
    }
430

    
431
    fft(x, MDCT_NBITS - 2);
432

    
433
    /* post rotation */
434
    for(i=0;i<N/4;i++) {
435
        re = x[i].re;
436
        im = x[i].im;
437
        CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
438
        out[2*i] = im1;
439
        out[N/2-1-2*i] = re1;
440
    }
441
}
442

    
443
/* XXX: use another norm ? */
444
static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)
445
{
446
    int sum, i;
447
    sum = 0;
448
    for(i=0;i<n;i++) {
449
        sum += abs(exp1[i] - exp2[i]);
450
    }
451
    return sum;
452
}
453

    
454
static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
455
                                 uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
456
                                 int ch, int is_lfe)
457
{
458
    int i, j;
459
    int exp_diff;
460

    
461
    /* estimate if the exponent variation & decide if they should be
462
       reused in the next frame */
463
    exp_strategy[0][ch] = EXP_NEW;
464
    for(i=1;i<NB_BLOCKS;i++) {
465
        exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);
466
#ifdef DEBUG
467
        av_log(NULL, AV_LOG_DEBUG, "exp_diff=%d\n", exp_diff);
468
#endif
469
        if (exp_diff > EXP_DIFF_THRESHOLD)
470
            exp_strategy[i][ch] = EXP_NEW;
471
        else
472
            exp_strategy[i][ch] = EXP_REUSE;
473
    }
474
    if (is_lfe)
475
        return;
476

    
477
    /* now select the encoding strategy type : if exponents are often
478
       recoded, we use a coarse encoding */
479
    i = 0;
480
    while (i < NB_BLOCKS) {
481
        j = i + 1;
482
        while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)
483
            j++;
484
        switch(j - i) {
485
        case 1:
486
            exp_strategy[i][ch] = EXP_D45;
487
            break;
488
        case 2:
489
        case 3:
490
            exp_strategy[i][ch] = EXP_D25;
491
            break;
492
        default:
493
            exp_strategy[i][ch] = EXP_D15;
494
            break;
495
        }
496
        i = j;
497
    }
498
}
499

    
500
/* set exp[i] to min(exp[i], exp1[i]) */
501
static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n)
502
{
503
    int i;
504

    
505
    for(i=0;i<n;i++) {
506
        if (exp1[i] < exp[i])
507
            exp[i] = exp1[i];
508
    }
509
}
510

    
511
/* update the exponents so that they are the ones the decoder will
512
   decode. Return the number of bits used to code the exponents */
513
static int encode_exp(uint8_t encoded_exp[N/2],
514
                      uint8_t exp[N/2],
515
                      int nb_exps,
516
                      int exp_strategy)
517
{
518
    int group_size, nb_groups, i, j, k, exp_min;
519
    uint8_t exp1[N/2];
520

    
521
    switch(exp_strategy) {
522
    case EXP_D15:
523
        group_size = 1;
524
        break;
525
    case EXP_D25:
526
        group_size = 2;
527
        break;
528
    default:
529
    case EXP_D45:
530
        group_size = 4;
531
        break;
532
    }
533
    nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
534

    
535
    /* for each group, compute the minimum exponent */
536
    exp1[0] = exp[0]; /* DC exponent is handled separately */
537
    k = 1;
538
    for(i=1;i<=nb_groups;i++) {
539
        exp_min = exp[k];
540
        assert(exp_min >= 0 && exp_min <= 24);
541
        for(j=1;j<group_size;j++) {
542
            if (exp[k+j] < exp_min)
543
                exp_min = exp[k+j];
544
        }
545
        exp1[i] = exp_min;
546
        k += group_size;
547
    }
548

    
549
    /* constraint for DC exponent */
550
    if (exp1[0] > 15)
551
        exp1[0] = 15;
552

    
553
    /* Decrease the delta between each groups to within 2
554
     * so that they can be differentially encoded */
555
    for (i=1;i<=nb_groups;i++)
556
        exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
557
    for (i=nb_groups-1;i>=0;i--)
558
        exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
559

    
560
    /* now we have the exponent values the decoder will see */
561
    encoded_exp[0] = exp1[0];
562
    k = 1;
563
    for(i=1;i<=nb_groups;i++) {
564
        for(j=0;j<group_size;j++) {
565
            encoded_exp[k+j] = exp1[i];
566
        }
567
        k += group_size;
568
    }
569

    
570
#if defined(DEBUG)
571
    av_log(NULL, AV_LOG_DEBUG, "exponents: strategy=%d\n", exp_strategy);
572
    for(i=0;i<=nb_groups * group_size;i++) {
573
        av_log(NULL, AV_LOG_DEBUG, "%d ", encoded_exp[i]);
574
    }
575
    av_log(NULL, AV_LOG_DEBUG, "\n");
576
#endif
577

    
578
    return 4 + (nb_groups / 3) * 7;
579
}
580

    
581
/* return the size in bits taken by the mantissa */
582
static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
583
{
584
    int bits, mant, i;
585

    
586
    bits = 0;
587
    for(i=0;i<nb_coefs;i++) {
588
        mant = m[i];
589
        switch(mant) {
590
        case 0:
591
            /* nothing */
592
            break;
593
        case 1:
594
            /* 3 mantissa in 5 bits */
595
            if (s->mant1_cnt == 0)
596
                bits += 5;
597
            if (++s->mant1_cnt == 3)
598
                s->mant1_cnt = 0;
599
            break;
600
        case 2:
601
            /* 3 mantissa in 7 bits */
602
            if (s->mant2_cnt == 0)
603
                bits += 7;
604
            if (++s->mant2_cnt == 3)
605
                s->mant2_cnt = 0;
606
            break;
607
        case 3:
608
            bits += 3;
609
            break;
610
        case 4:
611
            /* 2 mantissa in 7 bits */
612
            if (s->mant4_cnt == 0)
613
                bits += 7;
614
            if (++s->mant4_cnt == 2)
615
                s->mant4_cnt = 0;
616
            break;
617
        case 14:
618
            bits += 14;
619
            break;
620
        case 15:
621
            bits += 16;
622
            break;
623
        default:
624
            bits += mant - 1;
625
            break;
626
        }
627
    }
628
    return bits;
629
}
630

    
631

    
632
static int bit_alloc(AC3EncodeContext *s,
633
                     uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
634
                     uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
635
                     uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
636
                     int frame_bits, int csnroffst, int fsnroffst)
637
{
638
    int i, ch;
639

    
640
    /* compute size */
641
    for(i=0;i<NB_BLOCKS;i++) {
642
        s->mant1_cnt = 0;
643
        s->mant2_cnt = 0;
644
        s->mant4_cnt = 0;
645
        for(ch=0;ch<s->nb_all_channels;ch++) {
646
            ac3_parametric_bit_allocation(&s->bit_alloc,
647
                                          bap[i][ch], (int8_t *)encoded_exp[i][ch],
648
                                          0, s->nb_coefs[ch],
649
                                          (((csnroffst-15) << 4) +
650
                                           fsnroffst) << 2,
651
                                          fgaintab[s->fgaincod[ch]],
652
                                          ch == s->lfe_channel,
653
                                          2, 0, NULL, NULL, NULL);
654
            frame_bits += compute_mantissa_size(s, bap[i][ch],
655
                                                 s->nb_coefs[ch]);
656
        }
657
    }
658
#if 0
659
    printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",
660
           csnroffst, fsnroffst, frame_bits,
661
           16 * s->frame_size - ((frame_bits + 7) & ~7));
662
#endif
663
    return 16 * s->frame_size - frame_bits;
664
}
665

    
666
#define SNR_INC1 4
667

    
668
static int compute_bit_allocation(AC3EncodeContext *s,
669
                                  uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
670
                                  uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
671
                                  uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
672
                                  int frame_bits)
673
{
674
    int i, ch;
675
    int csnroffst, fsnroffst;
676
    uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
677
    static int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
678

    
679
    /* init default parameters */
680
    s->sdecaycod = 2;
681
    s->fdecaycod = 1;
682
    s->sgaincod = 1;
683
    s->dbkneecod = 2;
684
    s->floorcod = 4;
685
    for(ch=0;ch<s->nb_all_channels;ch++)
686
        s->fgaincod[ch] = 4;
687

    
688
    /* compute real values */
689
    s->bit_alloc.fscod = s->fscod;
690
    s->bit_alloc.halfratecod = s->halfratecod;
691
    s->bit_alloc.sdecay = sdecaytab[s->sdecaycod] >> s->halfratecod;
692
    s->bit_alloc.fdecay = fdecaytab[s->fdecaycod] >> s->halfratecod;
693
    s->bit_alloc.sgain = sgaintab[s->sgaincod];
694
    s->bit_alloc.dbknee = dbkneetab[s->dbkneecod];
695
    s->bit_alloc.floor = floortab[s->floorcod];
696

    
697
    /* header size */
698
    frame_bits += 65;
699
    // if (s->acmod == 2)
700
    //    frame_bits += 2;
701
    frame_bits += frame_bits_inc[s->acmod];
702

    
703
    /* audio blocks */
704
    for(i=0;i<NB_BLOCKS;i++) {
705
        frame_bits += s->nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
706
        if (s->acmod == 2) {
707
            frame_bits++; /* rematstr */
708
            if(i==0) frame_bits += 4;
709
        }
710
        frame_bits += 2 * s->nb_channels; /* chexpstr[2] * c */
711
        if (s->lfe)
712
            frame_bits++; /* lfeexpstr */
713
        for(ch=0;ch<s->nb_channels;ch++) {
714
            if (exp_strategy[i][ch] != EXP_REUSE)
715
                frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
716
        }
717
        frame_bits++; /* baie */
718
        frame_bits++; /* snr */
719
        frame_bits += 2; /* delta / skip */
720
    }
721
    frame_bits++; /* cplinu for block 0 */
722
    /* bit alloc info */
723
    /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
724
    /* csnroffset[6] */
725
    /* (fsnoffset[4] + fgaincod[4]) * c */
726
    frame_bits += 2*4 + 3 + 6 + s->nb_all_channels * (4 + 3);
727

    
728
    /* auxdatae, crcrsv */
729
    frame_bits += 2;
730

    
731
    /* CRC */
732
    frame_bits += 16;
733

    
734
    /* now the big work begins : do the bit allocation. Modify the snr
735
       offset until we can pack everything in the requested frame size */
736

    
737
    csnroffst = s->csnroffst;
738
    while (csnroffst >= 0 &&
739
           bit_alloc(s, bap, encoded_exp, exp_strategy, frame_bits, csnroffst, 0) < 0)
740
        csnroffst -= SNR_INC1;
741
    if (csnroffst < 0) {
742
        av_log(NULL, AV_LOG_ERROR, "Yack, Error !!!\n");
743
        return -1;
744
    }
745
    while ((csnroffst + SNR_INC1) <= 63 &&
746
           bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,
747
                     csnroffst + SNR_INC1, 0) >= 0) {
748
        csnroffst += SNR_INC1;
749
        memcpy(bap, bap1, sizeof(bap1));
750
    }
751
    while ((csnroffst + 1) <= 63 &&
752
           bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits, csnroffst + 1, 0) >= 0) {
753
        csnroffst++;
754
        memcpy(bap, bap1, sizeof(bap1));
755
    }
756

    
757
    fsnroffst = 0;
758
    while ((fsnroffst + SNR_INC1) <= 15 &&
759
           bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,
760
                     csnroffst, fsnroffst + SNR_INC1) >= 0) {
761
        fsnroffst += SNR_INC1;
762
        memcpy(bap, bap1, sizeof(bap1));
763
    }
764
    while ((fsnroffst + 1) <= 15 &&
765
           bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,
766
                     csnroffst, fsnroffst + 1) >= 0) {
767
        fsnroffst++;
768
        memcpy(bap, bap1, sizeof(bap1));
769
    }
770

    
771
    s->csnroffst = csnroffst;
772
    for(ch=0;ch<s->nb_all_channels;ch++)
773
        s->fsnroffst[ch] = fsnroffst;
774
#if defined(DEBUG_BITALLOC)
775
    {
776
        int j;
777

    
778
        for(i=0;i<6;i++) {
779
            for(ch=0;ch<s->nb_all_channels;ch++) {
780
                printf("Block #%d Ch%d:\n", i, ch);
781
                printf("bap=");
782
                for(j=0;j<s->nb_coefs[ch];j++) {
783
                    printf("%d ",bap[i][ch][j]);
784
                }
785
                printf("\n");
786
            }
787
        }
788
    }
789
#endif
790
    return 0;
791
}
792

    
793
void ac3_common_init(void)
794
{
795
    int i, j, k, l, v;
796
    /* compute bndtab and masktab from bandsz */
797
    k = 0;
798
    l = 0;
799
    for(i=0;i<50;i++) {
800
        bndtab[i] = l;
801
        v = bndsz[i];
802
        for(j=0;j<v;j++) masktab[k++]=i;
803
        l += v;
804
    }
805
    bndtab[50] = 0;
806
}
807

    
808

    
809
static int AC3_encode_init(AVCodecContext *avctx)
810
{
811
    int freq = avctx->sample_rate;
812
    int bitrate = avctx->bit_rate;
813
    int channels = avctx->channels;
814
    AC3EncodeContext *s = avctx->priv_data;
815
    int i, j, ch;
816
    float alpha;
817
    static const uint8_t acmod_defs[6] = {
818
        0x01, /* C */
819
        0x02, /* L R */
820
        0x03, /* L C R */
821
        0x06, /* L R SL SR */
822
        0x07, /* L C R SL SR */
823
        0x07, /* L C R SL SR (+LFE) */
824
    };
825

    
826
    avctx->frame_size = AC3_FRAME_SIZE;
827

    
828
    /* number of channels */
829
    if (channels < 1 || channels > 6)
830
        return -1;
831
    s->acmod = acmod_defs[channels - 1];
832
    s->lfe = (channels == 6) ? 1 : 0;
833
    s->nb_all_channels = channels;
834
    s->nb_channels = channels > 5 ? 5 : channels;
835
    s->lfe_channel = s->lfe ? 5 : -1;
836

    
837
    /* frequency */
838
    for(i=0;i<3;i++) {
839
        for(j=0;j<3;j++)
840
            if ((ac3_freqs[j] >> i) == freq)
841
                goto found;
842
    }
843
    return -1;
844
 found:
845
    s->sample_rate = freq;
846
    s->halfratecod = i;
847
    s->fscod = j;
848
    s->bsid = 8 + s->halfratecod;
849
    s->bsmod = 0; /* complete main audio service */
850

    
851
    /* bitrate & frame size */
852
    bitrate /= 1000;
853
    for(i=0;i<19;i++) {
854
        if ((ac3_bitratetab[i] >> s->halfratecod) == bitrate)
855
            break;
856
    }
857
    if (i == 19)
858
        return -1;
859
    s->bit_rate = bitrate;
860
    s->frmsizecod = i << 1;
861
    s->frame_size_min = (bitrate * 1000 * AC3_FRAME_SIZE) / (freq * 16);
862
    /* for now we do not handle fractional sizes */
863
    s->frame_size = s->frame_size_min;
864

    
865
    /* bit allocation init */
866
    for(ch=0;ch<s->nb_channels;ch++) {
867
        /* bandwidth for each channel */
868
        /* XXX: should compute the bandwidth according to the frame
869
           size, so that we avoid anoying high freq artefacts */
870
        s->chbwcod[ch] = 50; /* sample bandwidth as mpeg audio layer 2 table 0 */
871
        s->nb_coefs[ch] = ((s->chbwcod[ch] + 12) * 3) + 37;
872
    }
873
    if (s->lfe) {
874
        s->nb_coefs[s->lfe_channel] = 7; /* fixed */
875
    }
876
    /* initial snr offset */
877
    s->csnroffst = 40;
878

    
879
    ac3_common_init();
880

    
881
    /* mdct init */
882
    fft_init(MDCT_NBITS - 2);
883
    for(i=0;i<N/4;i++) {
884
        alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
885
        xcos1[i] = fix15(-cos(alpha));
886
        xsin1[i] = fix15(-sin(alpha));
887
    }
888

    
889
    ac3_crc_init();
890

    
891
    avctx->coded_frame= avcodec_alloc_frame();
892
    avctx->coded_frame->key_frame= 1;
893

    
894
    return 0;
895
}
896

    
897
/* output the AC3 frame header */
898
static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
899
{
900
    init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
901

    
902
    put_bits(&s->pb, 16, 0x0b77); /* frame header */
903
    put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
904
    put_bits(&s->pb, 2, s->fscod);
905
    put_bits(&s->pb, 6, s->frmsizecod + (s->frame_size - s->frame_size_min));
906
    put_bits(&s->pb, 5, s->bsid);
907
    put_bits(&s->pb, 3, s->bsmod);
908
    put_bits(&s->pb, 3, s->acmod);
909
    if ((s->acmod & 0x01) && s->acmod != 0x01)
910
        put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
911
    if (s->acmod & 0x04)
912
        put_bits(&s->pb, 2, 1); /* XXX -6 dB */
913
    if (s->acmod == 0x02)
914
        put_bits(&s->pb, 2, 0); /* surround not indicated */
915
    put_bits(&s->pb, 1, s->lfe); /* LFE */
916
    put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
917
    put_bits(&s->pb, 1, 0); /* no compression control word */
918
    put_bits(&s->pb, 1, 0); /* no lang code */
919
    put_bits(&s->pb, 1, 0); /* no audio production info */
920
    put_bits(&s->pb, 1, 0); /* no copyright */
921
    put_bits(&s->pb, 1, 1); /* original bitstream */
922
    put_bits(&s->pb, 1, 0); /* no time code 1 */
923
    put_bits(&s->pb, 1, 0); /* no time code 2 */
924
    put_bits(&s->pb, 1, 0); /* no addtional bit stream info */
925
}
926

    
927
/* symetric quantization on 'levels' levels */
928
static inline int sym_quant(int c, int e, int levels)
929
{
930
    int v;
931

    
932
    if (c >= 0) {
933
        v = (levels * (c << e)) >> 24;
934
        v = (v + 1) >> 1;
935
        v = (levels >> 1) + v;
936
    } else {
937
        v = (levels * ((-c) << e)) >> 24;
938
        v = (v + 1) >> 1;
939
        v = (levels >> 1) - v;
940
    }
941
    assert (v >= 0 && v < levels);
942
    return v;
943
}
944

    
945
/* asymetric quantization on 2^qbits levels */
946
static inline int asym_quant(int c, int e, int qbits)
947
{
948
    int lshift, m, v;
949

    
950
    lshift = e + qbits - 24;
951
    if (lshift >= 0)
952
        v = c << lshift;
953
    else
954
        v = c >> (-lshift);
955
    /* rounding */
956
    v = (v + 1) >> 1;
957
    m = (1 << (qbits-1));
958
    if (v >= m)
959
        v = m - 1;
960
    assert(v >= -m);
961
    return v & ((1 << qbits)-1);
962
}
963

    
964
/* Output one audio block. There are NB_BLOCKS audio blocks in one AC3
965
   frame */
966
static void output_audio_block(AC3EncodeContext *s,
967
                               uint8_t exp_strategy[AC3_MAX_CHANNELS],
968
                               uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],
969
                               uint8_t bap[AC3_MAX_CHANNELS][N/2],
970
                               int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],
971
                               int8_t global_exp[AC3_MAX_CHANNELS],
972
                               int block_num)
973
{
974
    int ch, nb_groups, group_size, i, baie, rbnd;
975
    uint8_t *p;
976
    uint16_t qmant[AC3_MAX_CHANNELS][N/2];
977
    int exp0, exp1;
978
    int mant1_cnt, mant2_cnt, mant4_cnt;
979
    uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
980
    int delta0, delta1, delta2;
981

    
982
    for(ch=0;ch<s->nb_channels;ch++)
983
        put_bits(&s->pb, 1, 0); /* 512 point MDCT */
984
    for(ch=0;ch<s->nb_channels;ch++)
985
        put_bits(&s->pb, 1, 1); /* no dither */
986
    put_bits(&s->pb, 1, 0); /* no dynamic range */
987
    if (block_num == 0) {
988
        /* for block 0, even if no coupling, we must say it. This is a
989
           waste of bit :-) */
990
        put_bits(&s->pb, 1, 1); /* coupling strategy present */
991
        put_bits(&s->pb, 1, 0); /* no coupling strategy */
992
    } else {
993
        put_bits(&s->pb, 1, 0); /* no new coupling strategy */
994
    }
995

    
996
    if (s->acmod == 2)
997
      {
998
        if(block_num==0)
999
          {
1000
            /* first block must define rematrixing (rematstr)  */
1001
            put_bits(&s->pb, 1, 1);
1002

    
1003
            /* dummy rematrixing rematflg(1:4)=0 */
1004
            for (rbnd=0;rbnd<4;rbnd++)
1005
              put_bits(&s->pb, 1, 0);
1006
          }
1007
        else
1008
          {
1009
            /* no matrixing (but should be used in the future) */
1010
            put_bits(&s->pb, 1, 0);
1011
          }
1012
      }
1013

    
1014
#if defined(DEBUG)
1015
    {
1016
      static int count = 0;
1017
      av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++);
1018
    }
1019
#endif
1020
    /* exponent strategy */
1021
    for(ch=0;ch<s->nb_channels;ch++) {
1022
        put_bits(&s->pb, 2, exp_strategy[ch]);
1023
    }
1024

    
1025
    if (s->lfe) {
1026
        put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
1027
    }
1028

    
1029
    for(ch=0;ch<s->nb_channels;ch++) {
1030
        if (exp_strategy[ch] != EXP_REUSE)
1031
            put_bits(&s->pb, 6, s->chbwcod[ch]);
1032
    }
1033

    
1034
    /* exponents */
1035
    for (ch = 0; ch < s->nb_all_channels; ch++) {
1036
        switch(exp_strategy[ch]) {
1037
        case EXP_REUSE:
1038
            continue;
1039
        case EXP_D15:
1040
            group_size = 1;
1041
            break;
1042
        case EXP_D25:
1043
            group_size = 2;
1044
            break;
1045
        default:
1046
        case EXP_D45:
1047
            group_size = 4;
1048
            break;
1049
        }
1050
        nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
1051
        p = encoded_exp[ch];
1052

    
1053
        /* first exponent */
1054
        exp1 = *p++;
1055
        put_bits(&s->pb, 4, exp1);
1056

    
1057
        /* next ones are delta encoded */
1058
        for(i=0;i<nb_groups;i++) {
1059
            /* merge three delta in one code */
1060
            exp0 = exp1;
1061
            exp1 = p[0];
1062
            p += group_size;
1063
            delta0 = exp1 - exp0 + 2;
1064

    
1065
            exp0 = exp1;
1066
            exp1 = p[0];
1067
            p += group_size;
1068
            delta1 = exp1 - exp0 + 2;
1069

    
1070
            exp0 = exp1;
1071
            exp1 = p[0];
1072
            p += group_size;
1073
            delta2 = exp1 - exp0 + 2;
1074

    
1075
            put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
1076
        }
1077

    
1078
        if (ch != s->lfe_channel)
1079
            put_bits(&s->pb, 2, 0); /* no gain range info */
1080
    }
1081

    
1082
    /* bit allocation info */
1083
    baie = (block_num == 0);
1084
    put_bits(&s->pb, 1, baie);
1085
    if (baie) {
1086
        put_bits(&s->pb, 2, s->sdecaycod);
1087
        put_bits(&s->pb, 2, s->fdecaycod);
1088
        put_bits(&s->pb, 2, s->sgaincod);
1089
        put_bits(&s->pb, 2, s->dbkneecod);
1090
        put_bits(&s->pb, 3, s->floorcod);
1091
    }
1092

    
1093
    /* snr offset */
1094
    put_bits(&s->pb, 1, baie); /* always present with bai */
1095
    if (baie) {
1096
        put_bits(&s->pb, 6, s->csnroffst);
1097
        for(ch=0;ch<s->nb_all_channels;ch++) {
1098
            put_bits(&s->pb, 4, s->fsnroffst[ch]);
1099
            put_bits(&s->pb, 3, s->fgaincod[ch]);
1100
        }
1101
    }
1102

    
1103
    put_bits(&s->pb, 1, 0); /* no delta bit allocation */
1104
    put_bits(&s->pb, 1, 0); /* no data to skip */
1105

    
1106
    /* mantissa encoding : we use two passes to handle the grouping. A
1107
       one pass method may be faster, but it would necessitate to
1108
       modify the output stream. */
1109

    
1110
    /* first pass: quantize */
1111
    mant1_cnt = mant2_cnt = mant4_cnt = 0;
1112
    qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
1113

    
1114
    for (ch = 0; ch < s->nb_all_channels; ch++) {
1115
        int b, c, e, v;
1116

    
1117
        for(i=0;i<s->nb_coefs[ch];i++) {
1118
            c = mdct_coefs[ch][i];
1119
            e = encoded_exp[ch][i] - global_exp[ch];
1120
            b = bap[ch][i];
1121
            switch(b) {
1122
            case 0:
1123
                v = 0;
1124
                break;
1125
            case 1:
1126
                v = sym_quant(c, e, 3);
1127
                switch(mant1_cnt) {
1128
                case 0:
1129
                    qmant1_ptr = &qmant[ch][i];
1130
                    v = 9 * v;
1131
                    mant1_cnt = 1;
1132
                    break;
1133
                case 1:
1134
                    *qmant1_ptr += 3 * v;
1135
                    mant1_cnt = 2;
1136
                    v = 128;
1137
                    break;
1138
                default:
1139
                    *qmant1_ptr += v;
1140
                    mant1_cnt = 0;
1141
                    v = 128;
1142
                    break;
1143
                }
1144
                break;
1145
            case 2:
1146
                v = sym_quant(c, e, 5);
1147
                switch(mant2_cnt) {
1148
                case 0:
1149
                    qmant2_ptr = &qmant[ch][i];
1150
                    v = 25 * v;
1151
                    mant2_cnt = 1;
1152
                    break;
1153
                case 1:
1154
                    *qmant2_ptr += 5 * v;
1155
                    mant2_cnt = 2;
1156
                    v = 128;
1157
                    break;
1158
                default:
1159
                    *qmant2_ptr += v;
1160
                    mant2_cnt = 0;
1161
                    v = 128;
1162
                    break;
1163
                }
1164
                break;
1165
            case 3:
1166
                v = sym_quant(c, e, 7);
1167
                break;
1168
            case 4:
1169
                v = sym_quant(c, e, 11);
1170
                switch(mant4_cnt) {
1171
                case 0:
1172
                    qmant4_ptr = &qmant[ch][i];
1173
                    v = 11 * v;
1174
                    mant4_cnt = 1;
1175
                    break;
1176
                default:
1177
                    *qmant4_ptr += v;
1178
                    mant4_cnt = 0;
1179
                    v = 128;
1180
                    break;
1181
                }
1182
                break;
1183
            case 5:
1184
                v = sym_quant(c, e, 15);
1185
                break;
1186
            case 14:
1187
                v = asym_quant(c, e, 14);
1188
                break;
1189
            case 15:
1190
                v = asym_quant(c, e, 16);
1191
                break;
1192
            default:
1193
                v = asym_quant(c, e, b - 1);
1194
                break;
1195
            }
1196
            qmant[ch][i] = v;
1197
        }
1198
    }
1199

    
1200
    /* second pass : output the values */
1201
    for (ch = 0; ch < s->nb_all_channels; ch++) {
1202
        int b, q;
1203

    
1204
        for(i=0;i<s->nb_coefs[ch];i++) {
1205
            q = qmant[ch][i];
1206
            b = bap[ch][i];
1207
            switch(b) {
1208
            case 0:
1209
                break;
1210
            case 1:
1211
                if (q != 128)
1212
                    put_bits(&s->pb, 5, q);
1213
                break;
1214
            case 2:
1215
                if (q != 128)
1216
                    put_bits(&s->pb, 7, q);
1217
                break;
1218
            case 3:
1219
                put_bits(&s->pb, 3, q);
1220
                break;
1221
            case 4:
1222
                if (q != 128)
1223
                    put_bits(&s->pb, 7, q);
1224
                break;
1225
            case 14:
1226
                put_bits(&s->pb, 14, q);
1227
                break;
1228
            case 15:
1229
                put_bits(&s->pb, 16, q);
1230
                break;
1231
            default:
1232
                put_bits(&s->pb, b - 1, q);
1233
                break;
1234
            }
1235
        }
1236
    }
1237
}
1238

    
1239
/* compute the ac3 crc */
1240

    
1241
#define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1242

    
1243
static void ac3_crc_init(void)
1244
{
1245
    unsigned int c, n, k;
1246

    
1247
    for(n=0;n<256;n++) {
1248
        c = n << 8;
1249
        for (k = 0; k < 8; k++) {
1250
            if (c & (1 << 15))
1251
                c = ((c << 1) & 0xffff) ^ (CRC16_POLY & 0xffff);
1252
            else
1253
                c = c << 1;
1254
        }
1255
        crc_table[n] = c;
1256
    }
1257
}
1258

    
1259
static unsigned int ac3_crc(uint8_t *data, int n, unsigned int crc)
1260
{
1261
    int i;
1262
    for(i=0;i<n;i++) {
1263
        crc = (crc_table[data[i] ^ (crc >> 8)] ^ (crc << 8)) & 0xffff;
1264
    }
1265
    return crc;
1266
}
1267

    
1268
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1269
{
1270
    unsigned int c;
1271

    
1272
    c = 0;
1273
    while (a) {
1274
        if (a & 1)
1275
            c ^= b;
1276
        a = a >> 1;
1277
        b = b << 1;
1278
        if (b & (1 << 16))
1279
            b ^= poly;
1280
    }
1281
    return c;
1282
}
1283

    
1284
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1285
{
1286
    unsigned int r;
1287
    r = 1;
1288
    while (n) {
1289
        if (n & 1)
1290
            r = mul_poly(r, a, poly);
1291
        a = mul_poly(a, a, poly);
1292
        n >>= 1;
1293
    }
1294
    return r;
1295
}
1296

    
1297

    
1298
/* compute log2(max(abs(tab[]))) */
1299
static int log2_tab(int16_t *tab, int n)
1300
{
1301
    int i, v;
1302

    
1303
    v = 0;
1304
    for(i=0;i<n;i++) {
1305
        v |= abs(tab[i]);
1306
    }
1307
    return av_log2(v);
1308
}
1309

    
1310
static void lshift_tab(int16_t *tab, int n, int lshift)
1311
{
1312
    int i;
1313

    
1314
    if (lshift > 0) {
1315
        for(i=0;i<n;i++) {
1316
            tab[i] <<= lshift;
1317
        }
1318
    } else if (lshift < 0) {
1319
        lshift = -lshift;
1320
        for(i=0;i<n;i++) {
1321
            tab[i] >>= lshift;
1322
        }
1323
    }
1324
}
1325

    
1326
/* fill the end of the frame and compute the two crcs */
1327
static int output_frame_end(AC3EncodeContext *s)
1328
{
1329
    int frame_size, frame_size_58, n, crc1, crc2, crc_inv;
1330
    uint8_t *frame;
1331

    
1332
    frame_size = s->frame_size; /* frame size in words */
1333
    /* align to 8 bits */
1334
    flush_put_bits(&s->pb);
1335
    /* add zero bytes to reach the frame size */
1336
    frame = s->pb.buf;
1337
    n = 2 * s->frame_size - (pbBufPtr(&s->pb) - frame) - 2;
1338
    assert(n >= 0);
1339
    if(n>0)
1340
      memset(pbBufPtr(&s->pb), 0, n);
1341

    
1342
    /* Now we must compute both crcs : this is not so easy for crc1
1343
       because it is at the beginning of the data... */
1344
    frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
1345
    crc1 = ac3_crc(frame + 4, (2 * frame_size_58) - 4, 0);
1346
    /* XXX: could precompute crc_inv */
1347
    crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
1348
    crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
1349
    frame[2] = crc1 >> 8;
1350
    frame[3] = crc1;
1351

    
1352
    crc2 = ac3_crc(frame + 2 * frame_size_58, (frame_size - frame_size_58) * 2 - 2, 0);
1353
    frame[2*frame_size - 2] = crc2 >> 8;
1354
    frame[2*frame_size - 1] = crc2;
1355

    
1356
    //    printf("n=%d frame_size=%d\n", n, frame_size);
1357
    return frame_size * 2;
1358
}
1359

    
1360
static int AC3_encode_frame(AVCodecContext *avctx,
1361
                            unsigned char *frame, int buf_size, void *data)
1362
{
1363
    AC3EncodeContext *s = avctx->priv_data;
1364
    int16_t *samples = data;
1365
    int i, j, k, v, ch;
1366
    int16_t input_samples[N];
1367
    int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1368
    uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1369
    uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
1370
    uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1371
    uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1372
    int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
1373
    int frame_bits;
1374

    
1375
    frame_bits = 0;
1376
    for(ch=0;ch<s->nb_all_channels;ch++) {
1377
        /* fixed mdct to the six sub blocks & exponent computation */
1378
        for(i=0;i<NB_BLOCKS;i++) {
1379
            int16_t *sptr;
1380
            int sinc;
1381

    
1382
            /* compute input samples */
1383
            memcpy(input_samples, s->last_samples[ch], N/2 * sizeof(int16_t));
1384
            sinc = s->nb_all_channels;
1385
            sptr = samples + (sinc * (N/2) * i) + ch;
1386
            for(j=0;j<N/2;j++) {
1387
                v = *sptr;
1388
                input_samples[j + N/2] = v;
1389
                s->last_samples[ch][j] = v;
1390
                sptr += sinc;
1391
            }
1392

    
1393
            /* apply the MDCT window */
1394
            for(j=0;j<N/2;j++) {
1395
                input_samples[j] = MUL16(input_samples[j],
1396
                                         ac3_window[j]) >> 15;
1397
                input_samples[N-j-1] = MUL16(input_samples[N-j-1],
1398
                                             ac3_window[j]) >> 15;
1399
            }
1400

    
1401
            /* Normalize the samples to use the maximum available
1402
               precision */
1403
            v = 14 - log2_tab(input_samples, N);
1404
            if (v < 0)
1405
                v = 0;
1406
            exp_samples[i][ch] = v - 8;
1407
            lshift_tab(input_samples, N, v);
1408

    
1409
            /* do the MDCT */
1410
            mdct512(mdct_coef[i][ch], input_samples);
1411

    
1412
            /* compute "exponents". We take into account the
1413
               normalization there */
1414
            for(j=0;j<N/2;j++) {
1415
                int e;
1416
                v = abs(mdct_coef[i][ch][j]);
1417
                if (v == 0)
1418
                    e = 24;
1419
                else {
1420
                    e = 23 - av_log2(v) + exp_samples[i][ch];
1421
                    if (e >= 24) {
1422
                        e = 24;
1423
                        mdct_coef[i][ch][j] = 0;
1424
                    }
1425
                }
1426
                exp[i][ch][j] = e;
1427
            }
1428
        }
1429

    
1430
        compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);
1431

    
1432
        /* compute the exponents as the decoder will see them. The
1433
           EXP_REUSE case must be handled carefully : we select the
1434
           min of the exponents */
1435
        i = 0;
1436
        while (i < NB_BLOCKS) {
1437
            j = i + 1;
1438
            while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
1439
                exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
1440
                j++;
1441
            }
1442
            frame_bits += encode_exp(encoded_exp[i][ch],
1443
                                     exp[i][ch], s->nb_coefs[ch],
1444
                                     exp_strategy[i][ch]);
1445
            /* copy encoded exponents for reuse case */
1446
            for(k=i+1;k<j;k++) {
1447
                memcpy(encoded_exp[k][ch], encoded_exp[i][ch],
1448
                       s->nb_coefs[ch] * sizeof(uint8_t));
1449
            }
1450
            i = j;
1451
        }
1452
    }
1453

    
1454
    compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
1455
    /* everything is known... let's output the frame */
1456
    output_frame_header(s, frame);
1457

    
1458
    for(i=0;i<NB_BLOCKS;i++) {
1459
        output_audio_block(s, exp_strategy[i], encoded_exp[i],
1460
                           bap[i], mdct_coef[i], exp_samples[i], i);
1461
    }
1462
    return output_frame_end(s);
1463
}
1464

    
1465
static int AC3_encode_close(AVCodecContext *avctx)
1466
{
1467
    av_freep(&avctx->coded_frame);
1468
    return 0;
1469
}
1470

    
1471
#if 0
1472
/*************************************************************************/
1473
/* TEST */
1474

1475
#define FN (N/4)
1476

1477
void fft_test(void)
1478
{
1479
    IComplex in[FN], in1[FN];
1480
    int k, n, i;
1481
    float sum_re, sum_im, a;
1482

1483
    /* FFT test */
1484

1485
    for(i=0;i<FN;i++) {
1486
        in[i].re = random() % 65535 - 32767;
1487
        in[i].im = random() % 65535 - 32767;
1488
        in1[i] = in[i];
1489
    }
1490
    fft(in, 7);
1491

1492
    /* do it by hand */
1493
    for(k=0;k<FN;k++) {
1494
        sum_re = 0;
1495
        sum_im = 0;
1496
        for(n=0;n<FN;n++) {
1497
            a = -2 * M_PI * (n * k) / FN;
1498
            sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
1499
            sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
1500
        }
1501
        printf("%3d: %6d,%6d %6.0f,%6.0f\n",
1502
               k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
1503
    }
1504
}
1505

1506
void mdct_test(void)
1507
{
1508
    int16_t input[N];
1509
    int32_t output[N/2];
1510
    float input1[N];
1511
    float output1[N/2];
1512
    float s, a, err, e, emax;
1513
    int i, k, n;
1514

1515
    for(i=0;i<N;i++) {
1516
        input[i] = (random() % 65535 - 32767) * 9 / 10;
1517
        input1[i] = input[i];
1518
    }
1519

1520
    mdct512(output, input);
1521

1522
    /* do it by hand */
1523
    for(k=0;k<N/2;k++) {
1524
        s = 0;
1525
        for(n=0;n<N;n++) {
1526
            a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));
1527
            s += input1[n] * cos(a);
1528
        }
1529
        output1[k] = -2 * s / N;
1530
    }
1531

1532
    err = 0;
1533
    emax = 0;
1534
    for(i=0;i<N/2;i++) {
1535
        printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);
1536
        e = output[i] - output1[i];
1537
        if (e > emax)
1538
            emax = e;
1539
        err += e * e;
1540
    }
1541
    printf("err2=%f emax=%f\n", err / (N/2), emax);
1542
}
1543

1544
void test_ac3(void)
1545
{
1546
    AC3EncodeContext ctx;
1547
    unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];
1548
    short samples[AC3_FRAME_SIZE];
1549
    int ret, i;
1550

1551
    AC3_encode_init(&ctx, 44100, 64000, 1);
1552

1553
    fft_test();
1554
    mdct_test();
1555

1556
    for(i=0;i<AC3_FRAME_SIZE;i++)
1557
        samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);
1558
    ret = AC3_encode_frame(&ctx, frame, samples);
1559
    printf("ret=%d\n", ret);
1560
}
1561
#endif
1562

    
1563
AVCodec ac3_encoder = {
1564
    "ac3",
1565
    CODEC_TYPE_AUDIO,
1566
    CODEC_ID_AC3,
1567
    sizeof(AC3EncodeContext),
1568
    AC3_encode_init,
1569
    AC3_encode_frame,
1570
    AC3_encode_close,
1571
    NULL,
1572
};