COSMETICS: Remove all trailing whitespace.
[libav.git] / libavcodec / ac3enc.c
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
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 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 };