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source: vbox/trunk/src/libs/ffmpeg-20060710/libavcodec/ac3enc.c@ 9441

Last change on this file since 9441 was 5776, checked in by vboxsync, 17 years ago

ffmpeg: exported to OSE
File size: 42.6 KB
Line 
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., 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 "crc.h"
29#include "ac3.h"
30
31typedef struct AC3EncodeContext {
32 PutBitContext pb;
33 int nb_channels;
34 int nb_all_channels;
35 int lfe_channel;
36 int bit_rate;
37 unsigned int sample_rate;
38 unsigned int bsid;
39 unsigned int frame_size_min; /* minimum frame size in case rounding is necessary */
40 unsigned int frame_size; /* current frame size in words */
41 unsigned int bits_written;
42 unsigned int samples_written;
43 int halfratecod;
44 unsigned int frmsizecod;
45 unsigned int fscod; /* frequency */
46 unsigned int acmod;
47 int lfe;
48 unsigned int bsmod;
49 short last_samples[AC3_MAX_CHANNELS][256];
50 unsigned int chbwcod[AC3_MAX_CHANNELS];
51 int nb_coefs[AC3_MAX_CHANNELS];
52
53 /* bitrate allocation control */
54 int sgaincod, sdecaycod, fdecaycod, dbkneecod, floorcod;
55 AC3BitAllocParameters bit_alloc;
56 int csnroffst;
57 int fgaincod[AC3_MAX_CHANNELS];
58 int fsnroffst[AC3_MAX_CHANNELS];
59 /* mantissa encoding */
60 int mant1_cnt, mant2_cnt, mant4_cnt;
61} AC3EncodeContext;
62
63#include "ac3tab.h"
64
65#define MDCT_NBITS 9
66#define N (1 << MDCT_NBITS)
67
68/* new exponents are sent if their Norm 1 exceed this number */
69#define EXP_DIFF_THRESHOLD 1000
70
71static void fft_init(int ln);
72
73static inline int16_t fix15(float a)
74{
75 int v;
76 v = (int)(a * (float)(1 << 15));
77 if (v < -32767)
78 v = -32767;
79 else if (v > 32767)
80 v = 32767;
81 return v;
82}
83
84static inline int calc_lowcomp1(int a, int b0, int b1)
85{
86 if ((b0 + 256) == b1) {
87 a = 384 ;
88 } else if (b0 > b1) {
89 a = a - 64;
90 if (a < 0) a=0;
91 }
92 return a;
93}
94
95static inline int calc_lowcomp(int a, int b0, int b1, int bin)
96{
97 if (bin < 7) {
98 if ((b0 + 256) == b1) {
99 a = 384 ;
100 } else if (b0 > b1) {
101 a = a - 64;
102 if (a < 0) a=0;
103 }
104 } else if (bin < 20) {
105 if ((b0 + 256) == b1) {
106 a = 320 ;
107 } else if (b0 > b1) {
108 a= a - 64;
109 if (a < 0) a=0;
110 }
111 } else {
112 a = a - 128;
113 if (a < 0) a=0;
114 }
115 return a;
116}
117
118/* AC3 bit allocation. The algorithm is the one described in the AC3
119 spec. */
120void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
121 int8_t *exp, int start, int end,
122 int snroffset, int fgain, int is_lfe,
123 int deltbae,int deltnseg,
124 uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba)
125{
126 int bin,i,j,k,end1,v,v1,bndstrt,bndend,lowcomp,begin;
127 int fastleak,slowleak,address,tmp;
128 int16_t psd[256]; /* scaled exponents */
129 int16_t bndpsd[50]; /* interpolated exponents */
130 int16_t excite[50]; /* excitation */
131 int16_t mask[50]; /* masking value */
132
133 /* exponent mapping to PSD */
134 for(bin=start;bin<end;bin++) {
135 psd[bin]=(3072 - (exp[bin] << 7));
136 }
137
138 /* PSD integration */
139 j=start;
140 k=masktab[start];
141 do {
142 v=psd[j];
143 j++;
144 end1=bndtab[k+1];
145 if (end1 > end) end1=end;
146 for(i=j;i<end1;i++) {
147 int c,adr;
148 /* logadd */
149 v1=psd[j];
150 c=v-v1;
151 if (c >= 0) {
152 adr=c >> 1;
153 if (adr > 255) adr=255;
154 v=v + latab[adr];
155 } else {
156 adr=(-c) >> 1;
157 if (adr > 255) adr=255;
158 v=v1 + latab[adr];
159 }
160 j++;
161 }
162 bndpsd[k]=v;
163 k++;
164 } while (end > bndtab[k]);
165
166 /* excitation function */
167 bndstrt = masktab[start];
168 bndend = masktab[end-1] + 1;
169
170 if (bndstrt == 0) {
171 lowcomp = 0;
172 lowcomp = calc_lowcomp1(lowcomp, bndpsd[0], bndpsd[1]) ;
173 excite[0] = bndpsd[0] - fgain - lowcomp ;
174 lowcomp = calc_lowcomp1(lowcomp, bndpsd[1], bndpsd[2]) ;
175 excite[1] = bndpsd[1] - fgain - lowcomp ;
176 begin = 7 ;
177 for (bin = 2; bin < 7; bin++) {
178 if (!(is_lfe && bin == 6))
179 lowcomp = calc_lowcomp1(lowcomp, bndpsd[bin], bndpsd[bin+1]) ;
180 fastleak = bndpsd[bin] - fgain ;
181 slowleak = bndpsd[bin] - s->sgain ;
182 excite[bin] = fastleak - lowcomp ;
183 if (!(is_lfe && bin == 6)) {
184 if (bndpsd[bin] <= bndpsd[bin+1]) {
185 begin = bin + 1 ;
186 break ;
187 }
188 }
189 }
190
191 end1=bndend;
192 if (end1 > 22) end1=22;
193
194 for (bin = begin; bin < end1; bin++) {
195 if (!(is_lfe && bin == 6))
196 lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin) ;
197
198 fastleak -= s->fdecay ;
199 v = bndpsd[bin] - fgain;
200 if (fastleak < v) fastleak = v;
201
202 slowleak -= s->sdecay ;
203 v = bndpsd[bin] - s->sgain;
204 if (slowleak < v) slowleak = v;
205
206 v=fastleak - lowcomp;
207 if (slowleak > v) v=slowleak;
208
209 excite[bin] = v;
210 }
211 begin = 22;
212 } else {
213 /* coupling channel */
214 begin = bndstrt;
215
216 fastleak = (s->cplfleak << 8) + 768;
217 slowleak = (s->cplsleak << 8) + 768;
218 }
219
220 for (bin = begin; bin < bndend; bin++) {
221 fastleak -= s->fdecay ;
222 v = bndpsd[bin] - fgain;
223 if (fastleak < v) fastleak = v;
224 slowleak -= s->sdecay ;
225 v = bndpsd[bin] - s->sgain;
226 if (slowleak < v) slowleak = v;
227
228 v=fastleak;
229 if (slowleak > v) v = slowleak;
230 excite[bin] = v;
231 }
232
233 /* compute masking curve */
234
235 for (bin = bndstrt; bin < bndend; bin++) {
236 v1 = excite[bin];
237 tmp = s->dbknee - bndpsd[bin];
238 if (tmp > 0) {
239 v1 += tmp >> 2;
240 }
241 v=hth[bin >> s->halfratecod][s->fscod];
242 if (v1 > v) v=v1;
243 mask[bin] = v;
244 }
245
246 /* delta bit allocation */
247
248 if (deltbae == 0 || deltbae == 1) {
249 int band, seg, delta;
250 band = 0 ;
251 for (seg = 0; seg < deltnseg; seg++) {
252 band += deltoffst[seg] ;
253 if (deltba[seg] >= 4) {
254 delta = (deltba[seg] - 3) << 7;
255 } else {
256 delta = (deltba[seg] - 4) << 7;
257 }
258 for (k = 0; k < deltlen[seg]; k++) {
259 mask[band] += delta ;
260 band++ ;
261 }
262 }
263 }
264
265 /* compute bit allocation */
266
267 i = start ;
268 j = masktab[start] ;
269 do {
270 v=mask[j];
271 v -= snroffset ;
272 v -= s->floor ;
273 if (v < 0) v = 0;
274 v &= 0x1fe0 ;
275 v += s->floor ;
276
277 end1=bndtab[j] + bndsz[j];
278 if (end1 > end) end1=end;
279
280 for (k = i; k < end1; k++) {
281 address = (psd[i] - v) >> 5 ;
282 if (address < 0) address=0;
283 else if (address > 63) address=63;
284 bap[i] = baptab[address];
285 i++;
286 }
287 } while (end > bndtab[j++]) ;
288}
289
290typedef struct IComplex {
291 short re,im;
292} IComplex;
293
294static void fft_init(int ln)
295{
296 int i, j, m, n;
297 float alpha;
298
299 n = 1 << ln;
300
301 for(i=0;i<(n/2);i++) {
302 alpha = 2 * M_PI * (float)i / (float)n;
303 costab[i] = fix15(cos(alpha));
304 sintab[i] = fix15(sin(alpha));
305 }
306
307 for(i=0;i<n;i++) {
308 m=0;
309 for(j=0;j<ln;j++) {
310 m |= ((i >> j) & 1) << (ln-j-1);
311 }
312 fft_rev[i]=m;
313 }
314}
315
316/* butter fly op */
317#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
318{\
319 int ax, ay, bx, by;\
320 bx=pre1;\
321 by=pim1;\
322 ax=qre1;\
323 ay=qim1;\
324 pre = (bx + ax) >> 1;\
325 pim = (by + ay) >> 1;\
326 qre = (bx - ax) >> 1;\
327 qim = (by - ay) >> 1;\
328}
329
330#define MUL16(a,b) ((a) * (b))
331
332#define CMUL(pre, pim, are, aim, bre, bim) \
333{\
334 pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\
335 pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\
336}
337
338
339/* do a 2^n point complex fft on 2^ln points. */
340static void fft(IComplex *z, int ln)
341{
342 int j, l, np, np2;
343 int nblocks, nloops;
344 register IComplex *p,*q;
345 int tmp_re, tmp_im;
346
347 np = 1 << ln;
348
349 /* reverse */
350 for(j=0;j<np;j++) {
351 int k;
352 IComplex tmp;
353 k = fft_rev[j];
354 if (k < j) {
355 tmp = z[k];
356 z[k] = z[j];
357 z[j] = tmp;
358 }
359 }
360
361 /* pass 0 */
362
363 p=&z[0];
364 j=(np >> 1);
365 do {
366 BF(p[0].re, p[0].im, p[1].re, p[1].im,
367 p[0].re, p[0].im, p[1].re, p[1].im);
368 p+=2;
369 } while (--j != 0);
370
371 /* pass 1 */
372
373 p=&z[0];
374 j=np >> 2;
375 do {
376 BF(p[0].re, p[0].im, p[2].re, p[2].im,
377 p[0].re, p[0].im, p[2].re, p[2].im);
378 BF(p[1].re, p[1].im, p[3].re, p[3].im,
379 p[1].re, p[1].im, p[3].im, -p[3].re);
380 p+=4;
381 } while (--j != 0);
382
383 /* pass 2 .. ln-1 */
384
385 nblocks = np >> 3;
386 nloops = 1 << 2;
387 np2 = np >> 1;
388 do {
389 p = z;
390 q = z + nloops;
391 for (j = 0; j < nblocks; ++j) {
392
393 BF(p->re, p->im, q->re, q->im,
394 p->re, p->im, q->re, q->im);
395
396 p++;
397 q++;
398 for(l = nblocks; l < np2; l += nblocks) {
399 CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
400 BF(p->re, p->im, q->re, q->im,
401 p->re, p->im, tmp_re, tmp_im);
402 p++;
403 q++;
404 }
405 p += nloops;
406 q += nloops;
407 }
408 nblocks = nblocks >> 1;
409 nloops = nloops << 1;
410 } while (nblocks != 0);
411}
412
413/* do a 512 point mdct */
414static void mdct512(int32_t *out, int16_t *in)
415{
416 int i, re, im, re1, im1;
417 int16_t rot[N];
418 IComplex x[N/4];
419
420 /* shift to simplify computations */
421 for(i=0;i<N/4;i++)
422 rot[i] = -in[i + 3*N/4];
423 for(i=N/4;i<N;i++)
424 rot[i] = in[i - N/4];
425
426 /* pre rotation */
427 for(i=0;i<N/4;i++) {
428 re = ((int)rot[2*i] - (int)rot[N-1-2*i]) >> 1;
429 im = -((int)rot[N/2+2*i] - (int)rot[N/2-1-2*i]) >> 1;
430 CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
431 }
432
433 fft(x, MDCT_NBITS - 2);
434
435 /* post rotation */
436 for(i=0;i<N/4;i++) {
437 re = x[i].re;
438 im = x[i].im;
439 CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
440 out[2*i] = im1;
441 out[N/2-1-2*i] = re1;
442 }
443}
444
445/* XXX: use another norm ? */
446static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)
447{
448 int sum, i;
449 sum = 0;
450 for(i=0;i<n;i++) {
451 sum += abs(exp1[i] - exp2[i]);
452 }
453 return sum;
454}
455
456static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
457 uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
458 int ch, int is_lfe)
459{
460 int i, j;
461 int exp_diff;
462
463 /* estimate if the exponent variation & decide if they should be
464 reused in the next frame */
465 exp_strategy[0][ch] = EXP_NEW;
466 for(i=1;i<NB_BLOCKS;i++) {
467 exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);
468#ifdef DEBUG
469 av_log(NULL, AV_LOG_DEBUG, "exp_diff=%d\n", exp_diff);
470#endif
471 if (exp_diff > EXP_DIFF_THRESHOLD)
472 exp_strategy[i][ch] = EXP_NEW;
473 else
474 exp_strategy[i][ch] = EXP_REUSE;
475 }
476 if (is_lfe)
477 return;
478
479 /* now select the encoding strategy type : if exponents are often
480 recoded, we use a coarse encoding */
481 i = 0;
482 while (i < NB_BLOCKS) {
483 j = i + 1;
484 while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)
485 j++;
486 switch(j - i) {
487 case 1:
488 exp_strategy[i][ch] = EXP_D45;
489 break;
490 case 2:
491 case 3:
492 exp_strategy[i][ch] = EXP_D25;
493 break;
494 default:
495 exp_strategy[i][ch] = EXP_D15;
496 break;
497 }
498 i = j;
499 }
500}
501
502/* set exp[i] to min(exp[i], exp1[i]) */
503static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n)
504{
505 int i;
506
507 for(i=0;i<n;i++) {
508 if (exp1[i] < exp[i])
509 exp[i] = exp1[i];
510 }
511}
512
513/* update the exponents so that they are the ones the decoder will
514 decode. Return the number of bits used to code the exponents */
515static int encode_exp(uint8_t encoded_exp[N/2],
516 uint8_t exp[N/2],
517 int nb_exps,
518 int exp_strategy)
519{
520 int group_size, nb_groups, i, j, k, exp_min;
521 uint8_t exp1[N/2];
522
523 switch(exp_strategy) {
524 case EXP_D15:
525 group_size = 1;
526 break;
527 case EXP_D25:
528 group_size = 2;
529 break;
530 default:
531 case EXP_D45:
532 group_size = 4;
533 break;
534 }
535 nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
536
537 /* for each group, compute the minimum exponent */
538 exp1[0] = exp[0]; /* DC exponent is handled separately */
539 k = 1;
540 for(i=1;i<=nb_groups;i++) {
541 exp_min = exp[k];
542 assert(exp_min >= 0 && exp_min <= 24);
543 for(j=1;j<group_size;j++) {
544 if (exp[k+j] < exp_min)
545 exp_min = exp[k+j];
546 }
547 exp1[i] = exp_min;
548 k += group_size;
549 }
550
551 /* constraint for DC exponent */
552 if (exp1[0] > 15)
553 exp1[0] = 15;
554
555 /* Decrease the delta between each groups to within 2
556 * so that they can be differentially encoded */
557 for (i=1;i<=nb_groups;i++)
558 exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
559 for (i=nb_groups-1;i>=0;i--)
560 exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
561
562 /* now we have the exponent values the decoder will see */
563 encoded_exp[0] = exp1[0];
564 k = 1;
565 for(i=1;i<=nb_groups;i++) {
566 for(j=0;j<group_size;j++) {
567 encoded_exp[k+j] = exp1[i];
568 }
569 k += group_size;
570 }
571
572#if defined(DEBUG)
573 av_log(NULL, AV_LOG_DEBUG, "exponents: strategy=%d\n", exp_strategy);
574 for(i=0;i<=nb_groups * group_size;i++) {
575 av_log(NULL, AV_LOG_DEBUG, "%d ", encoded_exp[i]);
576 }
577 av_log(NULL, AV_LOG_DEBUG, "\n");
578#endif
579
580 return 4 + (nb_groups / 3) * 7;
581}
582
583/* return the size in bits taken by the mantissa */
584static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
585{
586 int bits, mant, i;
587
588 bits = 0;
589 for(i=0;i<nb_coefs;i++) {
590 mant = m[i];
591 switch(mant) {
592 case 0:
593 /* nothing */
594 break;
595 case 1:
596 /* 3 mantissa in 5 bits */
597 if (s->mant1_cnt == 0)
598 bits += 5;
599 if (++s->mant1_cnt == 3)
600 s->mant1_cnt = 0;
601 break;
602 case 2:
603 /* 3 mantissa in 7 bits */
604 if (s->mant2_cnt == 0)
605 bits += 7;
606 if (++s->mant2_cnt == 3)
607 s->mant2_cnt = 0;
608 break;
609 case 3:
610 bits += 3;
611 break;
612 case 4:
613 /* 2 mantissa in 7 bits */
614 if (s->mant4_cnt == 0)
615 bits += 7;
616 if (++s->mant4_cnt == 2)
617 s->mant4_cnt = 0;
618 break;
619 case 14:
620 bits += 14;
621 break;
622 case 15:
623 bits += 16;
624 break;
625 default:
626 bits += mant - 1;
627 break;
628 }
629 }
630 return bits;
631}
632
633
634static int bit_alloc(AC3EncodeContext *s,
635 uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
636 uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
637 uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
638 int frame_bits, int csnroffst, int fsnroffst)
639{
640 int i, ch;
641
642 /* compute size */
643 for(i=0;i<NB_BLOCKS;i++) {
644 s->mant1_cnt = 0;
645 s->mant2_cnt = 0;
646 s->mant4_cnt = 0;
647 for(ch=0;ch<s->nb_all_channels;ch++) {
648 ac3_parametric_bit_allocation(&s->bit_alloc,
649 bap[i][ch], (int8_t *)encoded_exp[i][ch],
650 0, s->nb_coefs[ch],
651 (((csnroffst-15) << 4) +
652 fsnroffst) << 2,
653 fgaintab[s->fgaincod[ch]],
654 ch == s->lfe_channel,
655 2, 0, NULL, NULL, NULL);
656 frame_bits += compute_mantissa_size(s, bap[i][ch],
657 s->nb_coefs[ch]);
658 }
659 }
660#if 0
661 printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",
662 csnroffst, fsnroffst, frame_bits,
663 16 * s->frame_size - ((frame_bits + 7) & ~7));
664#endif
665 return 16 * s->frame_size - frame_bits;
666}
667
668#define SNR_INC1 4
669
670static int compute_bit_allocation(AC3EncodeContext *s,
671 uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
672 uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
673 uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
674 int frame_bits)
675{
676 int i, ch;
677 int csnroffst, fsnroffst;
678 uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
679 static int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
680
681 /* init default parameters */
682 s->sdecaycod = 2;
683 s->fdecaycod = 1;
684 s->sgaincod = 1;
685 s->dbkneecod = 2;
686 s->floorcod = 4;
687 for(ch=0;ch<s->nb_all_channels;ch++)
688 s->fgaincod[ch] = 4;
689
690 /* compute real values */
691 s->bit_alloc.fscod = s->fscod;
692 s->bit_alloc.halfratecod = s->halfratecod;
693 s->bit_alloc.sdecay = sdecaytab[s->sdecaycod] >> s->halfratecod;
694 s->bit_alloc.fdecay = fdecaytab[s->fdecaycod] >> s->halfratecod;
695 s->bit_alloc.sgain = sgaintab[s->sgaincod];
696 s->bit_alloc.dbknee = dbkneetab[s->dbkneecod];
697 s->bit_alloc.floor = floortab[s->floorcod];
698
699 /* header size */
700 frame_bits += 65;
701 // if (s->acmod == 2)
702 // frame_bits += 2;
703 frame_bits += frame_bits_inc[s->acmod];
704
705 /* audio blocks */
706 for(i=0;i<NB_BLOCKS;i++) {
707 frame_bits += s->nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
708 if (s->acmod == 2) {
709 frame_bits++; /* rematstr */
710 if(i==0) frame_bits += 4;
711 }
712 frame_bits += 2 * s->nb_channels; /* chexpstr[2] * c */
713 if (s->lfe)
714 frame_bits++; /* lfeexpstr */
715 for(ch=0;ch<s->nb_channels;ch++) {
716 if (exp_strategy[i][ch] != EXP_REUSE)
717 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
718 }
719 frame_bits++; /* baie */
720 frame_bits++; /* snr */
721 frame_bits += 2; /* delta / skip */
722 }
723 frame_bits++; /* cplinu for block 0 */
724 /* bit alloc info */
725 /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
726 /* csnroffset[6] */
727 /* (fsnoffset[4] + fgaincod[4]) * c */
728 frame_bits += 2*4 + 3 + 6 + s->nb_all_channels * (4 + 3);
729
730 /* auxdatae, crcrsv */
731 frame_bits += 2;
732
733 /* CRC */
734 frame_bits += 16;
735
736 /* now the big work begins : do the bit allocation. Modify the snr
737 offset until we can pack everything in the requested frame size */
738
739 csnroffst = s->csnroffst;
740 while (csnroffst >= 0 &&
741 bit_alloc(s, bap, encoded_exp, exp_strategy, frame_bits, csnroffst, 0) < 0)
742 csnroffst -= SNR_INC1;
743 if (csnroffst < 0) {
744 av_log(NULL, AV_LOG_ERROR, "Bit allocation failed, try increasing the bitrate, -ab 384 for example!\n");
745 return -1;
746 }
747 while ((csnroffst + SNR_INC1) <= 63 &&
748 bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,
749 csnroffst + SNR_INC1, 0) >= 0) {
750 csnroffst += SNR_INC1;
751 memcpy(bap, bap1, sizeof(bap1));
752 }
753 while ((csnroffst + 1) <= 63 &&
754 bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits, csnroffst + 1, 0) >= 0) {
755 csnroffst++;
756 memcpy(bap, bap1, sizeof(bap1));
757 }
758
759 fsnroffst = 0;
760 while ((fsnroffst + SNR_INC1) <= 15 &&
761 bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,
762 csnroffst, fsnroffst + SNR_INC1) >= 0) {
763 fsnroffst += SNR_INC1;
764 memcpy(bap, bap1, sizeof(bap1));
765 }
766 while ((fsnroffst + 1) <= 15 &&
767 bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,
768 csnroffst, fsnroffst + 1) >= 0) {
769 fsnroffst++;
770 memcpy(bap, bap1, sizeof(bap1));
771 }
772
773 s->csnroffst = csnroffst;
774 for(ch=0;ch<s->nb_all_channels;ch++)
775 s->fsnroffst[ch] = fsnroffst;
776#if defined(DEBUG_BITALLOC)
777 {
778 int j;
779
780 for(i=0;i<6;i++) {
781 for(ch=0;ch<s->nb_all_channels;ch++) {
782 printf("Block #%d Ch%d:\n", i, ch);
783 printf("bap=");
784 for(j=0;j<s->nb_coefs[ch];j++) {
785 printf("%d ",bap[i][ch][j]);
786 }
787 printf("\n");
788 }
789 }
790 }
791#endif
792 return 0;
793}
794
795void ac3_common_init(void)
796{
797 int i, j, k, l, v;
798 /* compute bndtab and masktab from bandsz */
799 k = 0;
800 l = 0;
801 for(i=0;i<50;i++) {
802 bndtab[i] = l;
803 v = bndsz[i];
804 for(j=0;j<v;j++) masktab[k++]=i;
805 l += v;
806 }
807 bndtab[50] = 0;
808}
809
810
811static int AC3_encode_init(AVCodecContext *avctx)
812{
813 int freq = avctx->sample_rate;
814 int bitrate = avctx->bit_rate;
815 int channels = avctx->channels;
816 AC3EncodeContext *s = avctx->priv_data;
817 int i, j, ch;
818 float alpha;
819 static const uint8_t acmod_defs[6] = {
820 0x01, /* C */
821 0x02, /* L R */
822 0x03, /* L C R */
823 0x06, /* L R SL SR */
824 0x07, /* L C R SL SR */
825 0x07, /* L C R SL SR (+LFE) */
826 };
827
828 avctx->frame_size = AC3_FRAME_SIZE;
829
830 /* number of channels */
831 if (channels < 1 || channels > 6)
832 return -1;
833 s->acmod = acmod_defs[channels - 1];
834 s->lfe = (channels == 6) ? 1 : 0;
835 s->nb_all_channels = channels;
836 s->nb_channels = channels > 5 ? 5 : channels;
837 s->lfe_channel = s->lfe ? 5 : -1;
838
839 /* frequency */
840 for(i=0;i<3;i++) {
841 for(j=0;j<3;j++)
842 if ((ac3_freqs[j] >> i) == freq)
843 goto found;
844 }
845 return -1;
846 found:
847 s->sample_rate = freq;
848 s->halfratecod = i;
849 s->fscod = j;
850 s->bsid = 8 + s->halfratecod;
851 s->bsmod = 0; /* complete main audio service */
852
853 /* bitrate & frame size */
854 bitrate /= 1000;
855 for(i=0;i<19;i++) {
856 if ((ac3_bitratetab[i] >> s->halfratecod) == bitrate)
857 break;
858 }
859 if (i == 19)
860 return -1;
861 s->bit_rate = bitrate;
862 s->frmsizecod = i << 1;
863 s->frame_size_min = (bitrate * 1000 * AC3_FRAME_SIZE) / (freq * 16);
864 s->bits_written = 0;
865 s->samples_written = 0;
866 s->frame_size = s->frame_size_min;
867
868 /* bit allocation init */
869 for(ch=0;ch<s->nb_channels;ch++) {
870 /* bandwidth for each channel */
871 /* XXX: should compute the bandwidth according to the frame
872 size, so that we avoid anoying high freq artefacts */
873 s->chbwcod[ch] = 50; /* sample bandwidth as mpeg audio layer 2 table 0 */
874 s->nb_coefs[ch] = ((s->chbwcod[ch] + 12) * 3) + 37;
875 }
876 if (s->lfe) {
877 s->nb_coefs[s->lfe_channel] = 7; /* fixed */
878 }
879 /* initial snr offset */
880 s->csnroffst = 40;
881
882 ac3_common_init();
883
884 /* mdct init */
885 fft_init(MDCT_NBITS - 2);
886 for(i=0;i<N/4;i++) {
887 alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
888 xcos1[i] = fix15(-cos(alpha));
889 xsin1[i] = fix15(-sin(alpha));
890 }
891
892 avctx->coded_frame= avcodec_alloc_frame();
893 avctx->coded_frame->key_frame= 1;
894
895 return 0;
896}
897
898/* output the AC3 frame header */
899static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
900{
901 init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
902
903 put_bits(&s->pb, 16, 0x0b77); /* frame header */
904 put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
905 put_bits(&s->pb, 2, s->fscod);
906 put_bits(&s->pb, 6, s->frmsizecod + (s->frame_size - s->frame_size_min));
907 put_bits(&s->pb, 5, s->bsid);
908 put_bits(&s->pb, 3, s->bsmod);
909 put_bits(&s->pb, 3, s->acmod);
910 if ((s->acmod & 0x01) && s->acmod != 0x01)
911 put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
912 if (s->acmod & 0x04)
913 put_bits(&s->pb, 2, 1); /* XXX -6 dB */
914 if (s->acmod == 0x02)
915 put_bits(&s->pb, 2, 0); /* surround not indicated */
916 put_bits(&s->pb, 1, s->lfe); /* LFE */
917 put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
918 put_bits(&s->pb, 1, 0); /* no compression control word */
919 put_bits(&s->pb, 1, 0); /* no lang code */
920 put_bits(&s->pb, 1, 0); /* no audio production info */
921 put_bits(&s->pb, 1, 0); /* no copyright */
922 put_bits(&s->pb, 1, 1); /* original bitstream */
923 put_bits(&s->pb, 1, 0); /* no time code 1 */
924 put_bits(&s->pb, 1, 0); /* no time code 2 */
925 put_bits(&s->pb, 1, 0); /* no addtional bit stream info */
926}
927
928/* symetric quantization on 'levels' levels */
929static inline int sym_quant(int c, int e, int levels)
930{
931 int v;
932
933 if (c >= 0) {
934 v = (levels * (c << e)) >> 24;
935 v = (v + 1) >> 1;
936 v = (levels >> 1) + v;
937 } else {
938 v = (levels * ((-c) << e)) >> 24;
939 v = (v + 1) >> 1;
940 v = (levels >> 1) - v;
941 }
942 assert (v >= 0 && v < levels);
943 return v;
944}
945
946/* asymetric quantization on 2^qbits levels */
947static inline int asym_quant(int c, int e, int qbits)
948{
949 int lshift, m, v;
950
951 lshift = e + qbits - 24;
952 if (lshift >= 0)
953 v = c << lshift;
954 else
955 v = c >> (-lshift);
956 /* rounding */
957 v = (v + 1) >> 1;
958 m = (1 << (qbits-1));
959 if (v >= m)
960 v = m - 1;
961 assert(v >= -m);
962 return v & ((1 << qbits)-1);
963}
964
965/* Output one audio block. There are NB_BLOCKS audio blocks in one AC3
966 frame */
967static void output_audio_block(AC3EncodeContext *s,
968 uint8_t exp_strategy[AC3_MAX_CHANNELS],
969 uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],
970 uint8_t bap[AC3_MAX_CHANNELS][N/2],
971 int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],
972 int8_t global_exp[AC3_MAX_CHANNELS],
973 int block_num)
974{
975 int ch, nb_groups, group_size, i, baie, rbnd;
976 uint8_t *p;
977 uint16_t qmant[AC3_MAX_CHANNELS][N/2];
978 int exp0, exp1;
979 int mant1_cnt, mant2_cnt, mant4_cnt;
980 uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
981 int delta0, delta1, delta2;
982
983 for(ch=0;ch<s->nb_channels;ch++)
984 put_bits(&s->pb, 1, 0); /* 512 point MDCT */
985 for(ch=0;ch<s->nb_channels;ch++)
986 put_bits(&s->pb, 1, 1); /* no dither */
987 put_bits(&s->pb, 1, 0); /* no dynamic range */
988 if (block_num == 0) {
989 /* for block 0, even if no coupling, we must say it. This is a
990 waste of bit :-) */
991 put_bits(&s->pb, 1, 1); /* coupling strategy present */
992 put_bits(&s->pb, 1, 0); /* no coupling strategy */
993 } else {
994 put_bits(&s->pb, 1, 0); /* no new coupling strategy */
995 }
996
997 if (s->acmod == 2)
998 {
999 if(block_num==0)
1000 {
1001 /* first block must define rematrixing (rematstr) */
1002 put_bits(&s->pb, 1, 1);
1003
1004 /* dummy rematrixing rematflg(1:4)=0 */
1005 for (rbnd=0;rbnd<4;rbnd++)
1006 put_bits(&s->pb, 1, 0);
1007 }
1008 else
1009 {
1010 /* no matrixing (but should be used in the future) */
1011 put_bits(&s->pb, 1, 0);
1012 }
1013 }
1014
1015#if defined(DEBUG)
1016 {
1017 static int count = 0;
1018 av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++);
1019 }
1020#endif
1021 /* exponent strategy */
1022 for(ch=0;ch<s->nb_channels;ch++) {
1023 put_bits(&s->pb, 2, exp_strategy[ch]);
1024 }
1025
1026 if (s->lfe) {
1027 put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
1028 }
1029
1030 for(ch=0;ch<s->nb_channels;ch++) {
1031 if (exp_strategy[ch] != EXP_REUSE)
1032 put_bits(&s->pb, 6, s->chbwcod[ch]);
1033 }
1034
1035 /* exponents */
1036 for (ch = 0; ch < s->nb_all_channels; ch++) {
1037 switch(exp_strategy[ch]) {
1038 case EXP_REUSE:
1039 continue;
1040 case EXP_D15:
1041 group_size = 1;
1042 break;
1043 case EXP_D25:
1044 group_size = 2;
1045 break;
1046 default:
1047 case EXP_D45:
1048 group_size = 4;
1049 break;
1050 }
1051 nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
1052 p = encoded_exp[ch];
1053
1054 /* first exponent */
1055 exp1 = *p++;
1056 put_bits(&s->pb, 4, exp1);
1057
1058 /* next ones are delta encoded */
1059 for(i=0;i<nb_groups;i++) {
1060 /* merge three delta in one code */
1061 exp0 = exp1;
1062 exp1 = p[0];
1063 p += group_size;
1064 delta0 = exp1 - exp0 + 2;
1065
1066 exp0 = exp1;
1067 exp1 = p[0];
1068 p += group_size;
1069 delta1 = exp1 - exp0 + 2;
1070
1071 exp0 = exp1;
1072 exp1 = p[0];
1073 p += group_size;
1074 delta2 = exp1 - exp0 + 2;
1075
1076 put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
1077 }
1078
1079 if (ch != s->lfe_channel)
1080 put_bits(&s->pb, 2, 0); /* no gain range info */
1081 }
1082
1083 /* bit allocation info */
1084 baie = (block_num == 0);
1085 put_bits(&s->pb, 1, baie);
1086 if (baie) {
1087 put_bits(&s->pb, 2, s->sdecaycod);
1088 put_bits(&s->pb, 2, s->fdecaycod);
1089 put_bits(&s->pb, 2, s->sgaincod);
1090 put_bits(&s->pb, 2, s->dbkneecod);
1091 put_bits(&s->pb, 3, s->floorcod);
1092 }
1093
1094 /* snr offset */
1095 put_bits(&s->pb, 1, baie); /* always present with bai */
1096 if (baie) {
1097 put_bits(&s->pb, 6, s->csnroffst);
1098 for(ch=0;ch<s->nb_all_channels;ch++) {
1099 put_bits(&s->pb, 4, s->fsnroffst[ch]);
1100 put_bits(&s->pb, 3, s->fgaincod[ch]);
1101 }
1102 }
1103
1104 put_bits(&s->pb, 1, 0); /* no delta bit allocation */
1105 put_bits(&s->pb, 1, 0); /* no data to skip */
1106
1107 /* mantissa encoding : we use two passes to handle the grouping. A
1108 one pass method may be faster, but it would necessitate to
1109 modify the output stream. */
1110
1111 /* first pass: quantize */
1112 mant1_cnt = mant2_cnt = mant4_cnt = 0;
1113 qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
1114
1115 for (ch = 0; ch < s->nb_all_channels; ch++) {
1116 int b, c, e, v;
1117
1118 for(i=0;i<s->nb_coefs[ch];i++) {
1119 c = mdct_coefs[ch][i];
1120 e = encoded_exp[ch][i] - global_exp[ch];
1121 b = bap[ch][i];
1122 switch(b) {
1123 case 0:
1124 v = 0;
1125 break;
1126 case 1:
1127 v = sym_quant(c, e, 3);
1128 switch(mant1_cnt) {
1129 case 0:
1130 qmant1_ptr = &qmant[ch][i];
1131 v = 9 * v;
1132 mant1_cnt = 1;
1133 break;
1134 case 1:
1135 *qmant1_ptr += 3 * v;
1136 mant1_cnt = 2;
1137 v = 128;
1138 break;
1139 default:
1140 *qmant1_ptr += v;
1141 mant1_cnt = 0;
1142 v = 128;
1143 break;
1144 }
1145 break;
1146 case 2:
1147 v = sym_quant(c, e, 5);
1148 switch(mant2_cnt) {
1149 case 0:
1150 qmant2_ptr = &qmant[ch][i];
1151 v = 25 * v;
1152 mant2_cnt = 1;
1153 break;
1154 case 1:
1155 *qmant2_ptr += 5 * v;
1156 mant2_cnt = 2;
1157 v = 128;
1158 break;
1159 default:
1160 *qmant2_ptr += v;
1161 mant2_cnt = 0;
1162 v = 128;
1163 break;
1164 }
1165 break;
1166 case 3:
1167 v = sym_quant(c, e, 7);
1168 break;
1169 case 4:
1170 v = sym_quant(c, e, 11);
1171 switch(mant4_cnt) {
1172 case 0:
1173 qmant4_ptr = &qmant[ch][i];
1174 v = 11 * v;
1175 mant4_cnt = 1;
1176 break;
1177 default:
1178 *qmant4_ptr += v;
1179 mant4_cnt = 0;
1180 v = 128;
1181 break;
1182 }
1183 break;
1184 case 5:
1185 v = sym_quant(c, e, 15);
1186 break;
1187 case 14:
1188 v = asym_quant(c, e, 14);
1189 break;
1190 case 15:
1191 v = asym_quant(c, e, 16);
1192 break;
1193 default:
1194 v = asym_quant(c, e, b - 1);
1195 break;
1196 }
1197 qmant[ch][i] = v;
1198 }
1199 }
1200
1201 /* second pass : output the values */
1202 for (ch = 0; ch < s->nb_all_channels; ch++) {
1203 int b, q;
1204
1205 for(i=0;i<s->nb_coefs[ch];i++) {
1206 q = qmant[ch][i];
1207 b = bap[ch][i];
1208 switch(b) {
1209 case 0:
1210 break;
1211 case 1:
1212 if (q != 128)
1213 put_bits(&s->pb, 5, q);
1214 break;
1215 case 2:
1216 if (q != 128)
1217 put_bits(&s->pb, 7, q);
1218 break;
1219 case 3:
1220 put_bits(&s->pb, 3, q);
1221 break;
1222 case 4:
1223 if (q != 128)
1224 put_bits(&s->pb, 7, q);
1225 break;
1226 case 14:
1227 put_bits(&s->pb, 14, q);
1228 break;
1229 case 15:
1230 put_bits(&s->pb, 16, q);
1231 break;
1232 default:
1233 put_bits(&s->pb, b - 1, q);
1234 break;
1235 }
1236 }
1237 }
1238}
1239
1240#define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1241
1242static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1243{
1244 unsigned int c;
1245
1246 c = 0;
1247 while (a) {
1248 if (a & 1)
1249 c ^= b;
1250 a = a >> 1;
1251 b = b << 1;
1252 if (b & (1 << 16))
1253 b ^= poly;
1254 }
1255 return c;
1256}
1257
1258static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1259{
1260 unsigned int r;
1261 r = 1;
1262 while (n) {
1263 if (n & 1)
1264 r = mul_poly(r, a, poly);
1265 a = mul_poly(a, a, poly);
1266 n >>= 1;
1267 }
1268 return r;
1269}
1270
1271
1272/* compute log2(max(abs(tab[]))) */
1273static int log2_tab(int16_t *tab, int n)
1274{
1275 int i, v;
1276
1277 v = 0;
1278 for(i=0;i<n;i++) {
1279 v |= abs(tab[i]);
1280 }
1281 return av_log2(v);
1282}
1283
1284static void lshift_tab(int16_t *tab, int n, int lshift)
1285{
1286 int i;
1287
1288 if (lshift > 0) {
1289 for(i=0;i<n;i++) {
1290 tab[i] <<= lshift;
1291 }
1292 } else if (lshift < 0) {
1293 lshift = -lshift;
1294 for(i=0;i<n;i++) {
1295 tab[i] >>= lshift;
1296 }
1297 }
1298}
1299
1300/* fill the end of the frame and compute the two crcs */
1301static int output_frame_end(AC3EncodeContext *s)
1302{
1303 int frame_size, frame_size_58, n, crc1, crc2, crc_inv;
1304 uint8_t *frame;
1305
1306 frame_size = s->frame_size; /* frame size in words */
1307 /* align to 8 bits */
1308 flush_put_bits(&s->pb);
1309 /* add zero bytes to reach the frame size */
1310 frame = s->pb.buf;
1311 n = 2 * s->frame_size - (pbBufPtr(&s->pb) - frame) - 2;
1312 assert(n >= 0);
1313 if(n>0)
1314 memset(pbBufPtr(&s->pb), 0, n);
1315
1316 /* Now we must compute both crcs : this is not so easy for crc1
1317 because it is at the beginning of the data... */
1318 frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
1319 crc1 = bswap_16(av_crc(av_crc8005, 0, frame + 4, 2 * frame_size_58 - 4));
1320 /* XXX: could precompute crc_inv */
1321 crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
1322 crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
1323 frame[2] = crc1 >> 8;
1324 frame[3] = crc1;
1325
1326 crc2 = bswap_16(av_crc(av_crc8005, 0, frame + 2 * frame_size_58, (frame_size - frame_size_58) * 2 - 2));
1327 frame[2*frame_size - 2] = crc2 >> 8;
1328 frame[2*frame_size - 1] = crc2;
1329
1330 // printf("n=%d frame_size=%d\n", n, frame_size);
1331 return frame_size * 2;
1332}
1333
1334static int AC3_encode_frame(AVCodecContext *avctx,
1335 unsigned char *frame, int buf_size, void *data)
1336{
1337 AC3EncodeContext *s = avctx->priv_data;
1338 int16_t *samples = data;
1339 int i, j, k, v, ch;
1340 int16_t input_samples[N];
1341 int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1342 uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1343 uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
1344 uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1345 uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
1346 int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
1347 int frame_bits;
1348
1349 frame_bits = 0;
1350 for(ch=0;ch<s->nb_all_channels;ch++) {
1351 /* fixed mdct to the six sub blocks & exponent computation */
1352 for(i=0;i<NB_BLOCKS;i++) {
1353 int16_t *sptr;
1354 int sinc;
1355
1356 /* compute input samples */
1357 memcpy(input_samples, s->last_samples[ch], N/2 * sizeof(int16_t));
1358 sinc = s->nb_all_channels;
1359 sptr = samples + (sinc * (N/2) * i) + ch;
1360 for(j=0;j<N/2;j++) {
1361 v = *sptr;
1362 input_samples[j + N/2] = v;
1363 s->last_samples[ch][j] = v;
1364 sptr += sinc;
1365 }
1366
1367 /* apply the MDCT window */
1368 for(j=0;j<N/2;j++) {
1369 input_samples[j] = MUL16(input_samples[j],
1370 ac3_window[j]) >> 15;
1371 input_samples[N-j-1] = MUL16(input_samples[N-j-1],
1372 ac3_window[j]) >> 15;
1373 }
1374
1375 /* Normalize the samples to use the maximum available
1376 precision */
1377 v = 14 - log2_tab(input_samples, N);
1378 if (v < 0)
1379 v = 0;
1380 exp_samples[i][ch] = v - 9;
1381 lshift_tab(input_samples, N, v);
1382
1383 /* do the MDCT */
1384 mdct512(mdct_coef[i][ch], input_samples);
1385
1386 /* compute "exponents". We take into account the
1387 normalization there */
1388 for(j=0;j<N/2;j++) {
1389 int e;
1390 v = abs(mdct_coef[i][ch][j]);
1391 if (v == 0)
1392 e = 24;
1393 else {
1394 e = 23 - av_log2(v) + exp_samples[i][ch];
1395 if (e >= 24) {
1396 e = 24;
1397 mdct_coef[i][ch][j] = 0;
1398 }
1399 }
1400 exp[i][ch][j] = e;
1401 }
1402 }
1403
1404 compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);
1405
1406 /* compute the exponents as the decoder will see them. The
1407 EXP_REUSE case must be handled carefully : we select the
1408 min of the exponents */
1409 i = 0;
1410 while (i < NB_BLOCKS) {
1411 j = i + 1;
1412 while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
1413 exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
1414 j++;
1415 }
1416 frame_bits += encode_exp(encoded_exp[i][ch],
1417 exp[i][ch], s->nb_coefs[ch],
1418 exp_strategy[i][ch]);
1419 /* copy encoded exponents for reuse case */
1420 for(k=i+1;k<j;k++) {
1421 memcpy(encoded_exp[k][ch], encoded_exp[i][ch],
1422 s->nb_coefs[ch] * sizeof(uint8_t));
1423 }
1424 i = j;
1425 }
1426 }
1427
1428 /* adjust for fractional frame sizes */
1429 while(s->bits_written >= s->bit_rate*1000 && s->samples_written >= s->sample_rate) {
1430 s->bits_written -= s->bit_rate*1000;
1431 s->samples_written -= s->sample_rate;
1432 }
1433 s->frame_size = s->frame_size_min + (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate*1000);
1434 s->bits_written += s->frame_size * 16;
1435 s->samples_written += AC3_FRAME_SIZE;
1436
1437 compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
1438 /* everything is known... let's output the frame */
1439 output_frame_header(s, frame);
1440
1441 for(i=0;i<NB_BLOCKS;i++) {
1442 output_audio_block(s, exp_strategy[i], encoded_exp[i],
1443 bap[i], mdct_coef[i], exp_samples[i], i);
1444 }
1445 return output_frame_end(s);
1446}
1447
1448static int AC3_encode_close(AVCodecContext *avctx)
1449{
1450 av_freep(&avctx->coded_frame);
1451 return 0;
1452}
1453
1454#if 0
1455/*************************************************************************/
1456/* TEST */
1457
1458#define FN (N/4)
1459
1460void fft_test(void)
1461{
1462 IComplex in[FN], in1[FN];
1463 int k, n, i;
1464 float sum_re, sum_im, a;
1465
1466 /* FFT test */
1467
1468 for(i=0;i<FN;i++) {
1469 in[i].re = random() % 65535 - 32767;
1470 in[i].im = random() % 65535 - 32767;
1471 in1[i] = in[i];
1472 }
1473 fft(in, 7);
1474
1475 /* do it by hand */
1476 for(k=0;k<FN;k++) {
1477 sum_re = 0;
1478 sum_im = 0;
1479 for(n=0;n<FN;n++) {
1480 a = -2 * M_PI * (n * k) / FN;
1481 sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
1482 sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
1483 }
1484 printf("%3d: %6d,%6d %6.0f,%6.0f\n",
1485 k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
1486 }
1487}
1488
1489void mdct_test(void)
1490{
1491 int16_t input[N];
1492 int32_t output[N/2];
1493 float input1[N];
1494 float output1[N/2];
1495 float s, a, err, e, emax;
1496 int i, k, n;
1497
1498 for(i=0;i<N;i++) {
1499 input[i] = (random() % 65535 - 32767) * 9 / 10;
1500 input1[i] = input[i];
1501 }
1502
1503 mdct512(output, input);
1504
1505 /* do it by hand */
1506 for(k=0;k<N/2;k++) {
1507 s = 0;
1508 for(n=0;n<N;n++) {
1509 a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));
1510 s += input1[n] * cos(a);
1511 }
1512 output1[k] = -2 * s / N;
1513 }
1514
1515 err = 0;
1516 emax = 0;
1517 for(i=0;i<N/2;i++) {
1518 printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);
1519 e = output[i] - output1[i];
1520 if (e > emax)
1521 emax = e;
1522 err += e * e;
1523 }
1524 printf("err2=%f emax=%f\n", err / (N/2), emax);
1525}
1526
1527void test_ac3(void)
1528{
1529 AC3EncodeContext ctx;
1530 unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];
1531 short samples[AC3_FRAME_SIZE];
1532 int ret, i;
1533
1534 AC3_encode_init(&ctx, 44100, 64000, 1);
1535
1536 fft_test();
1537 mdct_test();
1538
1539 for(i=0;i<AC3_FRAME_SIZE;i++)
1540 samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);
1541 ret = AC3_encode_frame(&ctx, frame, samples);
1542 printf("ret=%d\n", ret);
1543}
1544#endif
1545
1546AVCodec ac3_encoder = {
1547 "ac3",
1548 CODEC_TYPE_AUDIO,
1549 CODEC_ID_AC3,
1550 sizeof(AC3EncodeContext),
1551 AC3_encode_init,
1552 AC3_encode_frame,
1553 AC3_encode_close,
1554 NULL,
1555};
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