ffmpeg / libavcodec / ac3enc.c @ 9106a698
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1 
/*


2 
* The simplest AC3 encoder

3 
* Copyright (c) 2000 Fabrice Bellard

4 
*

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* This file is part of FFmpeg.

6 
*

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* FFmpeg is free software; you can redistribute it and/or

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* modify it under the terms of the GNU Lesser General Public

9 
* License as published by the Free Software Foundation; either

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* version 2.1 of the License, or (at your option) any later version.

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*

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* FFmpeg is distributed in the hope that it will be useful,

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* but WITHOUT ANY WARRANTY; without even the implied warranty of

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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

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* Lesser General Public License for more details.

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*

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* You should have received a copy of the GNU Lesser General Public

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* License along with FFmpeg; if not, write to the Free Software

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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 021101301 USA

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*/

21  
22 
/**

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* @file libavcodec/ac3enc.c

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* The simplest AC3 encoder.

25 
*/

26 
//#define DEBUG

27 
//#define DEBUG_BITALLOC

28 
#include "libavutil/crc.h" 
29 
#include "avcodec.h" 
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#include "get_bits.h" // for ff_reverse 
31 
#include "put_bits.h" 
32 
#include "ac3.h" 
33  
34 
typedef struct AC3EncodeContext { 
35 
PutBitContext pb; 
36 
int nb_channels;

37 
int nb_all_channels;

38 
int lfe_channel;

39 
int bit_rate;

40 
unsigned int sample_rate; 
41 
unsigned int bitstream_id; 
42 
unsigned int frame_size_min; /* minimum frame size in case rounding is necessary */ 
43 
unsigned int frame_size; /* current frame size in words */ 
44 
unsigned int bits_written; 
45 
unsigned int samples_written; 
46 
int sr_shift;

47 
unsigned int frame_size_code; 
48 
unsigned int sr_code; /* frequency */ 
49 
unsigned int channel_mode; 
50 
int lfe;

51 
unsigned int bitstream_mode; 
52 
short last_samples[AC3_MAX_CHANNELS][256]; 
53 
unsigned int chbwcod[AC3_MAX_CHANNELS]; 
54 
int nb_coefs[AC3_MAX_CHANNELS];

55  
56 
/* bitrate allocation control */

57 
int slow_gain_code, slow_decay_code, fast_decay_code, db_per_bit_code, floor_code;

58 
AC3BitAllocParameters bit_alloc; 
59 
int coarse_snr_offset;

60 
int fast_gain_code[AC3_MAX_CHANNELS];

61 
int fine_snr_offset[AC3_MAX_CHANNELS];

62 
/* mantissa encoding */

63 
int mant1_cnt, mant2_cnt, mant4_cnt;

64 
} AC3EncodeContext; 
65  
66 
static int16_t costab[64]; 
67 
static int16_t sintab[64]; 
68 
static int16_t xcos1[128]; 
69 
static int16_t xsin1[128]; 
70  
71 
#define MDCT_NBITS 9 
72 
#define N (1 << MDCT_NBITS) 
73  
74 
/* new exponents are sent if their Norm 1 exceed this number */

75 
#define EXP_DIFF_THRESHOLD 1000 
76  
77 
static inline int16_t fix15(float a) 
78 
{ 
79 
int v;

80 
v = (int)(a * (float)(1 << 15)); 
81 
if (v < 32767) 
82 
v = 32767;

83 
else if (v > 32767) 
84 
v = 32767;

85 
return v;

86 
} 
87  
88 
typedef struct IComplex { 
89 
short re,im;

90 
} IComplex; 
91  
92 
static av_cold void fft_init(int ln) 
93 
{ 
94 
int i, n;

95 
float alpha;

96  
97 
n = 1 << ln;

98  
99 
for(i=0;i<(n/2);i++) { 
100 
alpha = 2 * M_PI * (float)i / (float)n; 
101 
costab[i] = fix15(cos(alpha)); 
102 
sintab[i] = fix15(sin(alpha)); 
103 
} 
104 
} 
105  
106 
/* butter fly op */

107 
#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \

108 
{\ 
109 
int ax, ay, bx, by;\

110 
bx=pre1;\ 
111 
by=pim1;\ 
112 
ax=qre1;\ 
113 
ay=qim1;\ 
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pre = (bx + ax) >> 1;\

115 
pim = (by + ay) >> 1;\

116 
qre = (bx  ax) >> 1;\

117 
qim = (by  ay) >> 1;\

118 
} 
119  
120 
#define CMUL(pre, pim, are, aim, bre, bim) \

121 
{\ 
122 
pre = (MUL16(are, bre)  MUL16(aim, bim)) >> 15;\

123 
pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\

124 
} 
125  
126  
127 
/* do a 2^n point complex fft on 2^ln points. */

128 
static void fft(IComplex *z, int ln) 
129 
{ 
130 
int j, l, np, np2;

131 
int nblocks, nloops;

132 
register IComplex *p,*q;

133 
int tmp_re, tmp_im;

134  
135 
np = 1 << ln;

136  
137 
/* reverse */

138 
for(j=0;j<np;j++) { 
139 
int k = ff_reverse[j] >> (8  ln); 
140 
if (k < j)

141 
FFSWAP(IComplex, z[k], z[j]); 
142 
} 
143  
144 
/* pass 0 */

145  
146 
p=&z[0];

147 
j=(np >> 1);

148 
do {

149 
BF(p[0].re, p[0].im, p[1].re, p[1].im, 
150 
p[0].re, p[0].im, p[1].re, p[1].im); 
151 
p+=2;

152 
} while (j != 0); 
153  
154 
/* pass 1 */

155  
156 
p=&z[0];

157 
j=np >> 2;

158 
do {

159 
BF(p[0].re, p[0].im, p[2].re, p[2].im, 
160 
p[0].re, p[0].im, p[2].re, p[2].im); 
161 
BF(p[1].re, p[1].im, p[3].re, p[3].im, 
162 
p[1].re, p[1].im, p[3].im, p[3].re); 
163 
p+=4;

164 
} while (j != 0); 
165  
166 
/* pass 2 .. ln1 */

167  
168 
nblocks = np >> 3;

169 
nloops = 1 << 2; 
170 
np2 = np >> 1;

171 
do {

172 
p = z; 
173 
q = z + nloops; 
174 
for (j = 0; j < nblocks; ++j) { 
175  
176 
BF(p>re, p>im, q>re, q>im, 
177 
p>re, p>im, q>re, q>im); 
178  
179 
p++; 
180 
q++; 
181 
for(l = nblocks; l < np2; l += nblocks) {

182 
CMUL(tmp_re, tmp_im, costab[l], sintab[l], q>re, q>im); 
183 
BF(p>re, p>im, q>re, q>im, 
184 
p>re, p>im, tmp_re, tmp_im); 
185 
p++; 
186 
q++; 
187 
} 
188 
p += nloops; 
189 
q += nloops; 
190 
} 
191 
nblocks = nblocks >> 1;

192 
nloops = nloops << 1;

193 
} while (nblocks != 0); 
194 
} 
195  
196 
/* do a 512 point mdct */

197 
static void mdct512(int32_t *out, int16_t *in) 
198 
{ 
199 
int i, re, im, re1, im1;

200 
int16_t rot[N]; 
201 
IComplex x[N/4];

202  
203 
/* shift to simplify computations */

204 
for(i=0;i<N/4;i++) 
205 
rot[i] = in[i + 3*N/4]; 
206 
for(i=N/4;i<N;i++) 
207 
rot[i] = in[i  N/4];

208  
209 
/* pre rotation */

210 
for(i=0;i<N/4;i++) { 
211 
re = ((int)rot[2*i]  (int)rot[N12*i]) >> 1; 
212 
im = ((int)rot[N/2+2*i]  (int)rot[N/212*i]) >> 1; 
213 
CMUL(x[i].re, x[i].im, re, im, xcos1[i], xsin1[i]); 
214 
} 
215  
216 
fft(x, MDCT_NBITS  2);

217  
218 
/* post rotation */

219 
for(i=0;i<N/4;i++) { 
220 
re = x[i].re; 
221 
im = x[i].im; 
222 
CMUL(re1, im1, re, im, xsin1[i], xcos1[i]); 
223 
out[2*i] = im1;

224 
out[N/212*i] = re1; 
225 
} 
226 
} 
227  
228 
/* XXX: use another norm ? */

229 
static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n) 
230 
{ 
231 
int sum, i;

232 
sum = 0;

233 
for(i=0;i<n;i++) { 
234 
sum += abs(exp1[i]  exp2[i]); 
235 
} 
236 
return sum;

237 
} 
238  
239 
static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], 
240 
uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

241 
int ch, int is_lfe) 
242 
{ 
243 
int i, j;

244 
int exp_diff;

245  
246 
/* estimate if the exponent variation & decide if they should be

247 
reused in the next frame */

248 
exp_strategy[0][ch] = EXP_NEW;

249 
for(i=1;i<NB_BLOCKS;i++) { 
250 
exp_diff = calc_exp_diff(exp[i][ch], exp[i1][ch], N/2); 
251 
#ifdef DEBUG

252 
av_log(NULL, AV_LOG_DEBUG, "exp_diff=%d\n", exp_diff); 
253 
#endif

254 
if (exp_diff > EXP_DIFF_THRESHOLD)

255 
exp_strategy[i][ch] = EXP_NEW; 
256 
else

257 
exp_strategy[i][ch] = EXP_REUSE; 
258 
} 
259 
if (is_lfe)

260 
return;

261  
262 
/* now select the encoding strategy type : if exponents are often

263 
recoded, we use a coarse encoding */

264 
i = 0;

265 
while (i < NB_BLOCKS) {

266 
j = i + 1;

267 
while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)

268 
j++; 
269 
switch(j  i) {

270 
case 1: 
271 
exp_strategy[i][ch] = EXP_D45; 
272 
break;

273 
case 2: 
274 
case 3: 
275 
exp_strategy[i][ch] = EXP_D25; 
276 
break;

277 
default:

278 
exp_strategy[i][ch] = EXP_D15; 
279 
break;

280 
} 
281 
i = j; 
282 
} 
283 
} 
284  
285 
/* set exp[i] to min(exp[i], exp1[i]) */

286 
static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n) 
287 
{ 
288 
int i;

289  
290 
for(i=0;i<n;i++) { 
291 
if (exp1[i] < exp[i])

292 
exp[i] = exp1[i]; 
293 
} 
294 
} 
295  
296 
/* update the exponents so that they are the ones the decoder will

297 
decode. Return the number of bits used to code the exponents */

298 
static int encode_exp(uint8_t encoded_exp[N/2], 
299 
uint8_t exp[N/2],

300 
int nb_exps,

301 
int exp_strategy)

302 
{ 
303 
int group_size, nb_groups, i, j, k, exp_min;

304 
uint8_t exp1[N/2];

305  
306 
switch(exp_strategy) {

307 
case EXP_D15:

308 
group_size = 1;

309 
break;

310 
case EXP_D25:

311 
group_size = 2;

312 
break;

313 
default:

314 
case EXP_D45:

315 
group_size = 4;

316 
break;

317 
} 
318 
nb_groups = ((nb_exps + (group_size * 3)  4) / (3 * group_size)) * 3; 
319  
320 
/* for each group, compute the minimum exponent */

321 
exp1[0] = exp[0]; /* DC exponent is handled separately */ 
322 
k = 1;

323 
for(i=1;i<=nb_groups;i++) { 
324 
exp_min = exp[k]; 
325 
assert(exp_min >= 0 && exp_min <= 24); 
326 
for(j=1;j<group_size;j++) { 
327 
if (exp[k+j] < exp_min)

328 
exp_min = exp[k+j]; 
329 
} 
330 
exp1[i] = exp_min; 
331 
k += group_size; 
332 
} 
333  
334 
/* constraint for DC exponent */

335 
if (exp1[0] > 15) 
336 
exp1[0] = 15; 
337  
338 
/* Decrease the delta between each groups to within 2

339 
* so that they can be differentially encoded */

340 
for (i=1;i<=nb_groups;i++) 
341 
exp1[i] = FFMIN(exp1[i], exp1[i1] + 2); 
342 
for (i=nb_groups1;i>=0;i) 
343 
exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2); 
344  
345 
/* now we have the exponent values the decoder will see */

346 
encoded_exp[0] = exp1[0]; 
347 
k = 1;

348 
for(i=1;i<=nb_groups;i++) { 
349 
for(j=0;j<group_size;j++) { 
350 
encoded_exp[k+j] = exp1[i]; 
351 
} 
352 
k += group_size; 
353 
} 
354  
355 
#if defined(DEBUG)

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

362  
363 
return 4 + (nb_groups / 3) * 7; 
364 
} 
365  
366 
/* return the size in bits taken by the mantissa */

367 
static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs) 
368 
{ 
369 
int bits, mant, i;

370  
371 
bits = 0;

372 
for(i=0;i<nb_coefs;i++) { 
373 
mant = m[i]; 
374 
switch(mant) {

375 
case 0: 
376 
/* nothing */

377 
break;

378 
case 1: 
379 
/* 3 mantissa in 5 bits */

380 
if (s>mant1_cnt == 0) 
381 
bits += 5;

382 
if (++s>mant1_cnt == 3) 
383 
s>mant1_cnt = 0;

384 
break;

385 
case 2: 
386 
/* 3 mantissa in 7 bits */

387 
if (s>mant2_cnt == 0) 
388 
bits += 7;

389 
if (++s>mant2_cnt == 3) 
390 
s>mant2_cnt = 0;

391 
break;

392 
case 3: 
393 
bits += 3;

394 
break;

395 
case 4: 
396 
/* 2 mantissa in 7 bits */

397 
if (s>mant4_cnt == 0) 
398 
bits += 7;

399 
if (++s>mant4_cnt == 2) 
400 
s>mant4_cnt = 0;

401 
break;

402 
case 14: 
403 
bits += 14;

404 
break;

405 
case 15: 
406 
bits += 16;

407 
break;

408 
default:

409 
bits += mant  1;

410 
break;

411 
} 
412 
} 
413 
return bits;

414 
} 
415  
416  
417 
static void bit_alloc_masking(AC3EncodeContext *s, 
418 
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

419 
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], 
420 
int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

421 
int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50])

422 
{ 
423 
int blk, ch;

424 
int16_t band_psd[NB_BLOCKS][AC3_MAX_CHANNELS][50];

425  
426 
for(blk=0; blk<NB_BLOCKS; blk++) { 
427 
for(ch=0;ch<s>nb_all_channels;ch++) { 
428 
if(exp_strategy[blk][ch] == EXP_REUSE) {

429 
memcpy(psd[blk][ch], psd[blk1][ch], (N/2)*sizeof(int16_t)); 
430 
memcpy(mask[blk][ch], mask[blk1][ch], 50*sizeof(int16_t)); 
431 
} else {

432 
ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,

433 
s>nb_coefs[ch], 
434 
psd[blk][ch], band_psd[blk][ch]); 
435 
ff_ac3_bit_alloc_calc_mask(&s>bit_alloc, band_psd[blk][ch], 
436 
0, s>nb_coefs[ch],

437 
ff_ac3_fast_gain_tab[s>fast_gain_code[ch]], 
438 
ch == s>lfe_channel, 
439 
DBA_NONE, 0, NULL, NULL, NULL, 
440 
mask[blk][ch]); 
441 
} 
442 
} 
443 
} 
444 
} 
445  
446 
static int bit_alloc(AC3EncodeContext *s, 
447 
int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50],

448 
int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

449 
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

450 
int frame_bits, int coarse_snr_offset, int fine_snr_offset) 
451 
{ 
452 
int i, ch;

453 
int snr_offset;

454  
455 
snr_offset = (((coarse_snr_offset  15) << 4) + fine_snr_offset) << 2; 
456  
457 
/* compute size */

458 
for(i=0;i<NB_BLOCKS;i++) { 
459 
s>mant1_cnt = 0;

460 
s>mant2_cnt = 0;

461 
s>mant4_cnt = 0;

462 
for(ch=0;ch<s>nb_all_channels;ch++) { 
463 
ff_ac3_bit_alloc_calc_bap(mask[i][ch], psd[i][ch], 0,

464 
s>nb_coefs[ch], snr_offset, 
465 
s>bit_alloc.floor, ff_ac3_bap_tab, 
466 
bap[i][ch]); 
467 
frame_bits += compute_mantissa_size(s, bap[i][ch], 
468 
s>nb_coefs[ch]); 
469 
} 
470 
} 
471 
#if 0

472 
printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",

473 
coarse_snr_offset, fine_snr_offset, frame_bits,

474 
16 * s>frame_size  ((frame_bits + 7) & ~7));

475 
#endif

476 
return 16 * s>frame_size  frame_bits; 
477 
} 
478  
479 
#define SNR_INC1 4 
480  
481 
static int compute_bit_allocation(AC3EncodeContext *s, 
482 
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

483 
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

484 
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], 
485 
int frame_bits)

486 
{ 
487 
int i, ch;

488 
int coarse_snr_offset, fine_snr_offset;

489 
uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

490 
int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

491 
int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50];

492 
static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 }; 
493  
494 
/* init default parameters */

495 
s>slow_decay_code = 2;

496 
s>fast_decay_code = 1;

497 
s>slow_gain_code = 1;

498 
s>db_per_bit_code = 2;

499 
s>floor_code = 4;

500 
for(ch=0;ch<s>nb_all_channels;ch++) 
501 
s>fast_gain_code[ch] = 4;

502  
503 
/* compute real values */

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

513 
frame_bits += 65;

514 
// if (s>channel_mode == 2)

515 
// frame_bits += 2;

516 
frame_bits += frame_bits_inc[s>channel_mode]; 
517  
518 
/* audio blocks */

519 
for(i=0;i<NB_BLOCKS;i++) { 
520 
frame_bits += s>nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */ 
521 
if (s>channel_mode == AC3_CHMODE_STEREO) {

522 
frame_bits++; /* rematstr */

523 
if(i==0) frame_bits += 4; 
524 
} 
525 
frame_bits += 2 * s>nb_channels; /* chexpstr[2] * c */ 
526 
if (s>lfe)

527 
frame_bits++; /* lfeexpstr */

528 
for(ch=0;ch<s>nb_channels;ch++) { 
529 
if (exp_strategy[i][ch] != EXP_REUSE)

530 
frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */ 
531 
} 
532 
frame_bits++; /* baie */

533 
frame_bits++; /* snr */

534 
frame_bits += 2; /* delta / skip */ 
535 
} 
536 
frame_bits++; /* cplinu for block 0 */

537 
/* bit alloc info */

538 
/* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */

539 
/* csnroffset[6] */

540 
/* (fsnoffset[4] + fgaincod[4]) * c */

541 
frame_bits += 2*4 + 3 + 6 + s>nb_all_channels * (4 + 3); 
542  
543 
/* auxdatae, crcrsv */

544 
frame_bits += 2;

545  
546 
/* CRC */

547 
frame_bits += 16;

548  
549 
/* calculate psd and masking curve before doing bit allocation */

550 
bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask); 
551  
552 
/* now the big work begins : do the bit allocation. Modify the snr

553 
offset until we can pack everything in the requested frame size */

554  
555 
coarse_snr_offset = s>coarse_snr_offset; 
556 
while (coarse_snr_offset >= 0 && 
557 
bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0) 
558 
coarse_snr_offset = SNR_INC1; 
559 
if (coarse_snr_offset < 0) { 
560 
av_log(NULL, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n"); 
561 
return 1; 
562 
} 
563 
while ((coarse_snr_offset + SNR_INC1) <= 63 && 
564 
bit_alloc(s, mask, psd, bap1, frame_bits, 
565 
coarse_snr_offset + SNR_INC1, 0) >= 0) { 
566 
coarse_snr_offset += SNR_INC1; 
567 
memcpy(bap, bap1, sizeof(bap1));

568 
} 
569 
while ((coarse_snr_offset + 1) <= 63 && 
570 
bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) { 
571 
coarse_snr_offset++; 
572 
memcpy(bap, bap1, sizeof(bap1));

573 
} 
574  
575 
fine_snr_offset = 0;

576 
while ((fine_snr_offset + SNR_INC1) <= 15 && 
577 
bit_alloc(s, mask, psd, bap1, frame_bits, 
578 
coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {

579 
fine_snr_offset += SNR_INC1; 
580 
memcpy(bap, bap1, sizeof(bap1));

581 
} 
582 
while ((fine_snr_offset + 1) <= 15 && 
583 
bit_alloc(s, mask, psd, bap1, frame_bits, 
584 
coarse_snr_offset, fine_snr_offset + 1) >= 0) { 
585 
fine_snr_offset++; 
586 
memcpy(bap, bap1, sizeof(bap1));

587 
} 
588  
589 
s>coarse_snr_offset = coarse_snr_offset; 
590 
for(ch=0;ch<s>nb_all_channels;ch++) 
591 
s>fine_snr_offset[ch] = fine_snr_offset; 
592 
#if defined(DEBUG_BITALLOC)

593 
{ 
594 
int j;

595  
596 
for(i=0;i<6;i++) { 
597 
for(ch=0;ch<s>nb_all_channels;ch++) { 
598 
printf("Block #%d Ch%d:\n", i, ch);

599 
printf("bap=");

600 
for(j=0;j<s>nb_coefs[ch];j++) { 
601 
printf("%d ",bap[i][ch][j]);

602 
} 
603 
printf("\n");

604 
} 
605 
} 
606 
} 
607 
#endif

608 
return 0; 
609 
} 
610  
611 
static av_cold int AC3_encode_init(AVCodecContext *avctx) 
612 
{ 
613 
int freq = avctx>sample_rate;

614 
int bitrate = avctx>bit_rate;

615 
int channels = avctx>channels;

616 
AC3EncodeContext *s = avctx>priv_data; 
617 
int i, j, ch;

618 
float alpha;

619 
int bw_code;

620 
static const uint8_t channel_mode_defs[6] = { 
621 
0x01, /* C */ 
622 
0x02, /* L R */ 
623 
0x03, /* L C R */ 
624 
0x06, /* L R SL SR */ 
625 
0x07, /* L C R SL SR */ 
626 
0x07, /* L C R SL SR (+LFE) */ 
627 
}; 
628  
629 
avctx>frame_size = AC3_FRAME_SIZE; 
630  
631 
ac3_common_init(); 
632  
633 
/* number of channels */

634 
if (channels < 1  channels > 6) 
635 
return 1; 
636 
s>channel_mode = channel_mode_defs[channels  1];

637 
s>lfe = (channels == 6) ? 1 : 0; 
638 
s>nb_all_channels = channels; 
639 
s>nb_channels = channels > 5 ? 5 : channels; 
640 
s>lfe_channel = s>lfe ? 5 : 1; 
641  
642 
/* frequency */

643 
for(i=0;i<3;i++) { 
644 
for(j=0;j<3;j++) 
645 
if ((ff_ac3_sample_rate_tab[j] >> i) == freq)

646 
goto found;

647 
} 
648 
return 1; 
649 
found:

650 
s>sample_rate = freq; 
651 
s>sr_shift = i; 
652 
s>sr_code = j; 
653 
s>bitstream_id = 8 + s>sr_shift;

654 
s>bitstream_mode = 0; /* complete main audio service */ 
655  
656 
/* bitrate & frame size */

657 
for(i=0;i<19;i++) { 
658 
if ((ff_ac3_bitrate_tab[i] >> s>sr_shift)*1000 == bitrate) 
659 
break;

660 
} 
661 
if (i == 19) 
662 
return 1; 
663 
s>bit_rate = bitrate; 
664 
s>frame_size_code = i << 1;

665 
s>frame_size_min = ff_ac3_frame_size_tab[s>frame_size_code][s>sr_code]; 
666 
s>bits_written = 0;

667 
s>samples_written = 0;

668 
s>frame_size = s>frame_size_min; 
669  
670 
/* bit allocation init */

671 
if(avctx>cutoff) {

672 
/* calculate bandwidth based on userspecified cutoff frequency */

673 
int cutoff = av_clip(avctx>cutoff, 1, s>sample_rate >> 1); 
674 
int fbw_coeffs = cutoff * 512 / s>sample_rate; 
675 
bw_code = av_clip((fbw_coeffs  73) / 3, 0, 60); 
676 
} else {

677 
/* use default bandwidth setting */

678 
/* XXX: should compute the bandwidth according to the frame

679 
size, so that we avoid annoying high frequency artifacts */

680 
bw_code = 50;

681 
} 
682 
for(ch=0;ch<s>nb_channels;ch++) { 
683 
/* bandwidth for each channel */

684 
s>chbwcod[ch] = bw_code; 
685 
s>nb_coefs[ch] = bw_code * 3 + 73; 
686 
} 
687 
if (s>lfe) {

688 
s>nb_coefs[s>lfe_channel] = 7; /* fixed */ 
689 
} 
690 
/* initial snr offset */

691 
s>coarse_snr_offset = 40;

692  
693 
/* mdct init */

694 
fft_init(MDCT_NBITS  2);

695 
for(i=0;i<N/4;i++) { 
696 
alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N; 
697 
xcos1[i] = fix15(cos(alpha)); 
698 
xsin1[i] = fix15(sin(alpha)); 
699 
} 
700  
701 
avctx>coded_frame= avcodec_alloc_frame(); 
702 
avctx>coded_frame>key_frame= 1;

703  
704 
return 0; 
705 
} 
706  
707 
/* output the AC3 frame header */

708 
static void output_frame_header(AC3EncodeContext *s, unsigned char *frame) 
709 
{ 
710 
init_put_bits(&s>pb, frame, AC3_MAX_CODED_FRAME_SIZE); 
711  
712 
put_bits(&s>pb, 16, 0x0b77); /* frame header */ 
713 
put_bits(&s>pb, 16, 0); /* crc1: will be filled later */ 
714 
put_bits(&s>pb, 2, s>sr_code);

715 
put_bits(&s>pb, 6, s>frame_size_code + (s>frame_size  s>frame_size_min));

716 
put_bits(&s>pb, 5, s>bitstream_id);

717 
put_bits(&s>pb, 3, s>bitstream_mode);

718 
put_bits(&s>pb, 3, s>channel_mode);

719 
if ((s>channel_mode & 0x01) && s>channel_mode != AC3_CHMODE_MONO) 
720 
put_bits(&s>pb, 2, 1); /* XXX 4.5 dB */ 
721 
if (s>channel_mode & 0x04) 
722 
put_bits(&s>pb, 2, 1); /* XXX 6 dB */ 
723 
if (s>channel_mode == AC3_CHMODE_STEREO)

724 
put_bits(&s>pb, 2, 0); /* surround not indicated */ 
725 
put_bits(&s>pb, 1, s>lfe); /* LFE */ 
726 
put_bits(&s>pb, 5, 31); /* dialog norm: 31 db */ 
727 
put_bits(&s>pb, 1, 0); /* no compression control word */ 
728 
put_bits(&s>pb, 1, 0); /* no lang code */ 
729 
put_bits(&s>pb, 1, 0); /* no audio production info */ 
730 
put_bits(&s>pb, 1, 0); /* no copyright */ 
731 
put_bits(&s>pb, 1, 1); /* original bitstream */ 
732 
put_bits(&s>pb, 1, 0); /* no time code 1 */ 
733 
put_bits(&s>pb, 1, 0); /* no time code 2 */ 
734 
put_bits(&s>pb, 1, 0); /* no additional bit stream info */ 
735 
} 
736  
737 
/* symetric quantization on 'levels' levels */

738 
static inline int sym_quant(int c, int e, int levels) 
739 
{ 
740 
int v;

741  
742 
if (c >= 0) { 
743 
v = (levels * (c << e)) >> 24;

744 
v = (v + 1) >> 1; 
745 
v = (levels >> 1) + v;

746 
} else {

747 
v = (levels * ((c) << e)) >> 24;

748 
v = (v + 1) >> 1; 
749 
v = (levels >> 1)  v;

750 
} 
751 
assert (v >= 0 && v < levels);

752 
return v;

753 
} 
754  
755 
/* asymetric quantization on 2^qbits levels */

756 
static inline int asym_quant(int c, int e, int qbits) 
757 
{ 
758 
int lshift, m, v;

759  
760 
lshift = e + qbits  24;

761 
if (lshift >= 0) 
762 
v = c << lshift; 
763 
else

764 
v = c >> (lshift); 
765 
/* rounding */

766 
v = (v + 1) >> 1; 
767 
m = (1 << (qbits1)); 
768 
if (v >= m)

769 
v = m  1;

770 
assert(v >= m); 
771 
return v & ((1 << qbits)1); 
772 
} 
773  
774 
/* Output one audio block. There are NB_BLOCKS audio blocks in one AC3

775 
frame */

776 
static void output_audio_block(AC3EncodeContext *s, 
777 
uint8_t exp_strategy[AC3_MAX_CHANNELS], 
778 
uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],

779 
uint8_t bap[AC3_MAX_CHANNELS][N/2],

780 
int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],

781 
int8_t global_exp[AC3_MAX_CHANNELS], 
782 
int block_num)

783 
{ 
784 
int ch, nb_groups, group_size, i, baie, rbnd;

785 
uint8_t *p; 
786 
uint16_t qmant[AC3_MAX_CHANNELS][N/2];

787 
int exp0, exp1;

788 
int mant1_cnt, mant2_cnt, mant4_cnt;

789 
uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; 
790 
int delta0, delta1, delta2;

791  
792 
for(ch=0;ch<s>nb_channels;ch++) 
793 
put_bits(&s>pb, 1, 0); /* 512 point MDCT */ 
794 
for(ch=0;ch<s>nb_channels;ch++) 
795 
put_bits(&s>pb, 1, 1); /* no dither */ 
796 
put_bits(&s>pb, 1, 0); /* no dynamic range */ 
797 
if (block_num == 0) { 
798 
/* for block 0, even if no coupling, we must say it. This is a

799 
waste of bit :) */

800 
put_bits(&s>pb, 1, 1); /* coupling strategy present */ 
801 
put_bits(&s>pb, 1, 0); /* no coupling strategy */ 
802 
} else {

803 
put_bits(&s>pb, 1, 0); /* no new coupling strategy */ 
804 
} 
805  
806 
if (s>channel_mode == AC3_CHMODE_STEREO)

807 
{ 
808 
if(block_num==0) 
809 
{ 
810 
/* first block must define rematrixing (rematstr) */

811 
put_bits(&s>pb, 1, 1); 
812  
813 
/* dummy rematrixing rematflg(1:4)=0 */

814 
for (rbnd=0;rbnd<4;rbnd++) 
815 
put_bits(&s>pb, 1, 0); 
816 
} 
817 
else

818 
{ 
819 
/* no matrixing (but should be used in the future) */

820 
put_bits(&s>pb, 1, 0); 
821 
} 
822 
} 
823  
824 
#if defined(DEBUG)

825 
{ 
826 
static int count = 0; 
827 
av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++); 
828 
} 
829 
#endif

830 
/* exponent strategy */

831 
for(ch=0;ch<s>nb_channels;ch++) { 
832 
put_bits(&s>pb, 2, exp_strategy[ch]);

833 
} 
834  
835 
if (s>lfe) {

836 
put_bits(&s>pb, 1, exp_strategy[s>lfe_channel]);

837 
} 
838  
839 
for(ch=0;ch<s>nb_channels;ch++) { 
840 
if (exp_strategy[ch] != EXP_REUSE)

841 
put_bits(&s>pb, 6, s>chbwcod[ch]);

842 
} 
843  
844 
/* exponents */

845 
for (ch = 0; ch < s>nb_all_channels; ch++) { 
846 
switch(exp_strategy[ch]) {

847 
case EXP_REUSE:

848 
continue;

849 
case EXP_D15:

850 
group_size = 1;

851 
break;

852 
case EXP_D25:

853 
group_size = 2;

854 
break;

855 
default:

856 
case EXP_D45:

857 
group_size = 4;

858 
break;

859 
} 
860 
nb_groups = (s>nb_coefs[ch] + (group_size * 3)  4) / (3 * group_size); 
861 
p = encoded_exp[ch]; 
862  
863 
/* first exponent */

864 
exp1 = *p++; 
865 
put_bits(&s>pb, 4, exp1);

866  
867 
/* next ones are delta encoded */

868 
for(i=0;i<nb_groups;i++) { 
869 
/* merge three delta in one code */

870 
exp0 = exp1; 
871 
exp1 = p[0];

872 
p += group_size; 
873 
delta0 = exp1  exp0 + 2;

874  
875 
exp0 = exp1; 
876 
exp1 = p[0];

877 
p += group_size; 
878 
delta1 = exp1  exp0 + 2;

879  
880 
exp0 = exp1; 
881 
exp1 = p[0];

882 
p += group_size; 
883 
delta2 = exp1  exp0 + 2;

884  
885 
put_bits(&s>pb, 7, ((delta0 * 5 + delta1) * 5) + delta2); 
886 
} 
887  
888 
if (ch != s>lfe_channel)

889 
put_bits(&s>pb, 2, 0); /* no gain range info */ 
890 
} 
891  
892 
/* bit allocation info */

893 
baie = (block_num == 0);

894 
put_bits(&s>pb, 1, baie);

895 
if (baie) {

896 
put_bits(&s>pb, 2, s>slow_decay_code);

897 
put_bits(&s>pb, 2, s>fast_decay_code);

898 
put_bits(&s>pb, 2, s>slow_gain_code);

899 
put_bits(&s>pb, 2, s>db_per_bit_code);

900 
put_bits(&s>pb, 3, s>floor_code);

901 
} 
902  
903 
/* snr offset */

904 
put_bits(&s>pb, 1, baie); /* always present with bai */ 
905 
if (baie) {

906 
put_bits(&s>pb, 6, s>coarse_snr_offset);

907 
for(ch=0;ch<s>nb_all_channels;ch++) { 
908 
put_bits(&s>pb, 4, s>fine_snr_offset[ch]);

909 
put_bits(&s>pb, 3, s>fast_gain_code[ch]);

910 
} 
911 
} 
912  
913 
put_bits(&s>pb, 1, 0); /* no delta bit allocation */ 
914 
put_bits(&s>pb, 1, 0); /* no data to skip */ 
915  
916 
/* mantissa encoding : we use two passes to handle the grouping. A

917 
one pass method may be faster, but it would necessitate to

918 
modify the output stream. */

919  
920 
/* first pass: quantize */

921 
mant1_cnt = mant2_cnt = mant4_cnt = 0;

922 
qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;

923  
924 
for (ch = 0; ch < s>nb_all_channels; ch++) { 
925 
int b, c, e, v;

926  
927 
for(i=0;i<s>nb_coefs[ch];i++) { 
928 
c = mdct_coefs[ch][i]; 
929 
e = encoded_exp[ch][i]  global_exp[ch]; 
930 
b = bap[ch][i]; 
931 
switch(b) {

932 
case 0: 
933 
v = 0;

934 
break;

935 
case 1: 
936 
v = sym_quant(c, e, 3);

937 
switch(mant1_cnt) {

938 
case 0: 
939 
qmant1_ptr = &qmant[ch][i]; 
940 
v = 9 * v;

941 
mant1_cnt = 1;

942 
break;

943 
case 1: 
944 
*qmant1_ptr += 3 * v;

945 
mant1_cnt = 2;

946 
v = 128;

947 
break;

948 
default:

949 
*qmant1_ptr += v; 
950 
mant1_cnt = 0;

951 
v = 128;

952 
break;

953 
} 
954 
break;

955 
case 2: 
956 
v = sym_quant(c, e, 5);

957 
switch(mant2_cnt) {

958 
case 0: 
959 
qmant2_ptr = &qmant[ch][i]; 
960 
v = 25 * v;

961 
mant2_cnt = 1;

962 
break;

963 
case 1: 
964 
*qmant2_ptr += 5 * v;

965 
mant2_cnt = 2;

966 
v = 128;

967 
break;

968 
default:

969 
*qmant2_ptr += v; 
970 
mant2_cnt = 0;

971 
v = 128;

972 
break;

973 
} 
974 
break;

975 
case 3: 
976 
v = sym_quant(c, e, 7);

977 
break;

978 
case 4: 
979 
v = sym_quant(c, e, 11);

980 
switch(mant4_cnt) {

981 
case 0: 
982 
qmant4_ptr = &qmant[ch][i]; 
983 
v = 11 * v;

984 
mant4_cnt = 1;

985 
break;

986 
default:

987 
*qmant4_ptr += v; 
988 
mant4_cnt = 0;

989 
v = 128;

990 
break;

991 
} 
992 
break;

993 
case 5: 
994 
v = sym_quant(c, e, 15);

995 
break;

996 
case 14: 
997 
v = asym_quant(c, e, 14);

998 
break;

999 
case 15: 
1000 
v = asym_quant(c, e, 16);

1001 
break;

1002 
default:

1003 
v = asym_quant(c, e, b  1);

1004 
break;

1005 
} 
1006 
qmant[ch][i] = v; 
1007 
} 
1008 
} 
1009  
1010 
/* second pass : output the values */

1011 
for (ch = 0; ch < s>nb_all_channels; ch++) { 
1012 
int b, q;

1013  
1014 
for(i=0;i<s>nb_coefs[ch];i++) { 
1015 
q = qmant[ch][i]; 
1016 
b = bap[ch][i]; 
1017 
switch(b) {

1018 
case 0: 
1019 
break;

1020 
case 1: 
1021 
if (q != 128) 
1022 
put_bits(&s>pb, 5, q);

1023 
break;

1024 
case 2: 
1025 
if (q != 128) 
1026 
put_bits(&s>pb, 7, q);

1027 
break;

1028 
case 3: 
1029 
put_bits(&s>pb, 3, q);

1030 
break;

1031 
case 4: 
1032 
if (q != 128) 
1033 
put_bits(&s>pb, 7, q);

1034 
break;

1035 
case 14: 
1036 
put_bits(&s>pb, 14, q);

1037 
break;

1038 
case 15: 
1039 
put_bits(&s>pb, 16, q);

1040 
break;

1041 
default:

1042 
put_bits(&s>pb, b  1, q);

1043 
break;

1044 
} 
1045 
} 
1046 
} 
1047 
} 
1048  
1049 
#define CRC16_POLY ((1 << 0)  (1 << 2)  (1 << 15)  (1 << 16)) 
1050  
1051 
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly) 
1052 
{ 
1053 
unsigned int c; 
1054  
1055 
c = 0;

1056 
while (a) {

1057 
if (a & 1) 
1058 
c ^= b; 
1059 
a = a >> 1;

1060 
b = b << 1;

1061 
if (b & (1 << 16)) 
1062 
b ^= poly; 
1063 
} 
1064 
return c;

1065 
} 
1066  
1067 
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly) 
1068 
{ 
1069 
unsigned int r; 
1070 
r = 1;

1071 
while (n) {

1072 
if (n & 1) 
1073 
r = mul_poly(r, a, poly); 
1074 
a = mul_poly(a, a, poly); 
1075 
n >>= 1;

1076 
} 
1077 
return r;

1078 
} 
1079  
1080  
1081 
/* compute log2(max(abs(tab[]))) */

1082 
static int log2_tab(int16_t *tab, int n) 
1083 
{ 
1084 
int i, v;

1085  
1086 
v = 0;

1087 
for(i=0;i<n;i++) { 
1088 
v = abs(tab[i]); 
1089 
} 
1090 
return av_log2(v);

1091 
} 
1092  
1093 
static void lshift_tab(int16_t *tab, int n, int lshift) 
1094 
{ 
1095 
int i;

1096  
1097 
if (lshift > 0) { 
1098 
for(i=0;i<n;i++) { 
1099 
tab[i] <<= lshift; 
1100 
} 
1101 
} else if (lshift < 0) { 
1102 
lshift = lshift; 
1103 
for(i=0;i<n;i++) { 
1104 
tab[i] >>= lshift; 
1105 
} 
1106 
} 
1107 
} 
1108  
1109 
/* fill the end of the frame and compute the two crcs */

1110 
static int output_frame_end(AC3EncodeContext *s) 
1111 
{ 
1112 
int frame_size, frame_size_58, n, crc1, crc2, crc_inv;

1113 
uint8_t *frame; 
1114  
1115 
frame_size = s>frame_size; /* frame size in words */

1116 
/* align to 8 bits */

1117 
flush_put_bits(&s>pb); 
1118 
/* add zero bytes to reach the frame size */

1119 
frame = s>pb.buf; 
1120 
n = 2 * s>frame_size  (pbBufPtr(&s>pb)  frame)  2; 
1121 
assert(n >= 0);

1122 
if(n>0) 
1123 
memset(pbBufPtr(&s>pb), 0, n);

1124  
1125 
/* Now we must compute both crcs : this is not so easy for crc1

1126 
because it is at the beginning of the data... */

1127 
frame_size_58 = (frame_size >> 1) + (frame_size >> 3); 
1128 
crc1 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,

1129 
frame + 4, 2 * frame_size_58  4)); 
1130 
/* XXX: could precompute crc_inv */

1131 
crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58)  16, CRC16_POLY); 
1132 
crc1 = mul_poly(crc_inv, crc1, CRC16_POLY); 
1133 
AV_WB16(frame+2,crc1);

1134  
1135 
crc2 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,

1136 
frame + 2 * frame_size_58,

1137 
(frame_size  frame_size_58) * 2  2)); 
1138 
AV_WB16(frame+2*frame_size2,crc2); 
1139  
1140 
// printf("n=%d frame_size=%d\n", n, frame_size);

1141 
return frame_size * 2; 
1142 
} 
1143  
1144 
static int AC3_encode_frame(AVCodecContext *avctx, 
1145 
unsigned char *frame, int buf_size, void *data) 
1146 
{ 
1147 
AC3EncodeContext *s = avctx>priv_data; 
1148 
int16_t *samples = data; 
1149 
int i, j, k, v, ch;

1150 
int16_t input_samples[N]; 
1151 
int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1152 
uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1153 
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS]; 
1154 
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1155 
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1156 
int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS]; 
1157 
int frame_bits;

1158  
1159 
frame_bits = 0;

1160 
for(ch=0;ch<s>nb_all_channels;ch++) { 
1161 
/* fixed mdct to the six sub blocks & exponent computation */

1162 
for(i=0;i<NB_BLOCKS;i++) { 
1163 
int16_t *sptr; 
1164 
int sinc;

1165  
1166 
/* compute input samples */

1167 
memcpy(input_samples, s>last_samples[ch], N/2 * sizeof(int16_t)); 
1168 
sinc = s>nb_all_channels; 
1169 
sptr = samples + (sinc * (N/2) * i) + ch;

1170 
for(j=0;j<N/2;j++) { 
1171 
v = *sptr; 
1172 
input_samples[j + N/2] = v;

1173 
s>last_samples[ch][j] = v; 
1174 
sptr += sinc; 
1175 
} 
1176  
1177 
/* apply the MDCT window */

1178 
for(j=0;j<N/2;j++) { 
1179 
input_samples[j] = MUL16(input_samples[j], 
1180 
ff_ac3_window[j]) >> 15;

1181 
input_samples[Nj1] = MUL16(input_samples[Nj1], 
1182 
ff_ac3_window[j]) >> 15;

1183 
} 
1184  
1185 
/* Normalize the samples to use the maximum available

1186 
precision */

1187 
v = 14  log2_tab(input_samples, N);

1188 
if (v < 0) 
1189 
v = 0;

1190 
exp_samples[i][ch] = v  9;

1191 
lshift_tab(input_samples, N, v); 
1192  
1193 
/* do the MDCT */

1194 
mdct512(mdct_coef[i][ch], input_samples); 
1195  
1196 
/* compute "exponents". We take into account the

1197 
normalization there */

1198 
for(j=0;j<N/2;j++) { 
1199 
int e;

1200 
v = abs(mdct_coef[i][ch][j]); 
1201 
if (v == 0) 
1202 
e = 24;

1203 
else {

1204 
e = 23  av_log2(v) + exp_samples[i][ch];

1205 
if (e >= 24) { 
1206 
e = 24;

1207 
mdct_coef[i][ch][j] = 0;

1208 
} 
1209 
} 
1210 
exp[i][ch][j] = e; 
1211 
} 
1212 
} 
1213  
1214 
compute_exp_strategy(exp_strategy, exp, ch, ch == s>lfe_channel); 
1215  
1216 
/* compute the exponents as the decoder will see them. The

1217 
EXP_REUSE case must be handled carefully : we select the

1218 
min of the exponents */

1219 
i = 0;

1220 
while (i < NB_BLOCKS) {

1221 
j = i + 1;

1222 
while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {

1223 
exponent_min(exp[i][ch], exp[j][ch], s>nb_coefs[ch]); 
1224 
j++; 
1225 
} 
1226 
frame_bits += encode_exp(encoded_exp[i][ch], 
1227 
exp[i][ch], s>nb_coefs[ch], 
1228 
exp_strategy[i][ch]); 
1229 
/* copy encoded exponents for reuse case */

1230 
for(k=i+1;k<j;k++) { 
1231 
memcpy(encoded_exp[k][ch], encoded_exp[i][ch], 
1232 
s>nb_coefs[ch] * sizeof(uint8_t));

1233 
} 
1234 
i = j; 
1235 
} 
1236 
} 
1237  
1238 
/* adjust for fractional frame sizes */

1239 
while(s>bits_written >= s>bit_rate && s>samples_written >= s>sample_rate) {

1240 
s>bits_written = s>bit_rate; 
1241 
s>samples_written = s>sample_rate; 
1242 
} 
1243 
s>frame_size = s>frame_size_min + (s>bits_written * s>sample_rate < s>samples_written * s>bit_rate); 
1244 
s>bits_written += s>frame_size * 16;

1245 
s>samples_written += AC3_FRAME_SIZE; 
1246  
1247 
compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits); 
1248 
/* everything is known... let's output the frame */

1249 
output_frame_header(s, frame); 
1250  
1251 
for(i=0;i<NB_BLOCKS;i++) { 
1252 
output_audio_block(s, exp_strategy[i], encoded_exp[i], 
1253 
bap[i], mdct_coef[i], exp_samples[i], i); 
1254 
} 
1255 
return output_frame_end(s);

1256 
} 
1257  
1258 
static av_cold int AC3_encode_close(AVCodecContext *avctx) 
1259 
{ 
1260 
av_freep(&avctx>coded_frame); 
1261 
return 0; 
1262 
} 
1263  
1264 
#if 0

1265 
/*************************************************************************/

1266 
/* TEST */

1267 

1268 
#undef random

1269 
#define FN (N/4)

1270 

1271 
void fft_test(void)

1272 
{

1273 
IComplex in[FN], in1[FN];

1274 
int k, n, i;

1275 
float sum_re, sum_im, a;

1276 

1277 
/* FFT test */

1278 

1279 
for(i=0;i<FN;i++) {

1280 
in[i].re = random() % 65535  32767;

1281 
in[i].im = random() % 65535  32767;

1282 
in1[i] = in[i];

1283 
}

1284 
fft(in, 7);

1285 

1286 
/* do it by hand */

1287 
for(k=0;k<FN;k++) {

1288 
sum_re = 0;

1289 
sum_im = 0;

1290 
for(n=0;n<FN;n++) {

1291 
a = 2 * M_PI * (n * k) / FN;

1292 
sum_re += in1[n].re * cos(a)  in1[n].im * sin(a);

1293 
sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);

1294 
}

1295 
printf("%3d: %6d,%6d %6.0f,%6.0f\n",

1296 
k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);

1297 
}

1298 
}

1299 

1300 
void mdct_test(void)

1301 
{

1302 
int16_t input[N];

1303 
int32_t output[N/2];

1304 
float input1[N];

1305 
float output1[N/2];

1306 
float s, a, err, e, emax;

1307 
int i, k, n;

1308 

1309 
for(i=0;i<N;i++) {

1310 
input[i] = (random() % 65535  32767) * 9 / 10;

1311 
input1[i] = input[i];

1312 
}

1313 

1314 
mdct512(output, input);

1315 

1316 
/* do it by hand */

1317 
for(k=0;k<N/2;k++) {

1318 
s = 0;

1319 
for(n=0;n<N;n++) {

1320 
a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));

1321 
s += input1[n] * cos(a);

1322 
}

1323 
output1[k] = 2 * s / N;

1324 
}

1325 

1326 
err = 0;

1327 
emax = 0;

1328 
for(i=0;i<N/2;i++) {

1329 
printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);

1330 
e = output[i]  output1[i];

1331 
if (e > emax)

1332 
emax = e;

1333 
err += e * e;

1334 
}

1335 
printf("err2=%f emax=%f\n", err / (N/2), emax);

1336 
}

1337 

1338 
void test_ac3(void)

1339 
{

1340 
AC3EncodeContext ctx;

1341 
unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];

1342 
short samples[AC3_FRAME_SIZE];

1343 
int ret, i;

1344 

1345 
AC3_encode_init(&ctx, 44100, 64000, 1);

1346 

1347 
fft_test();

1348 
mdct_test();

1349 

1350 
for(i=0;i<AC3_FRAME_SIZE;i++)

1351 
samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);

1352 
ret = AC3_encode_frame(&ctx, frame, samples);

1353 
printf("ret=%d\n", ret);

1354 
}

1355 
#endif

1356  
1357 
AVCodec ac3_encoder = { 
1358 
"ac3",

1359 
CODEC_TYPE_AUDIO, 
1360 
CODEC_ID_AC3, 
1361 
sizeof(AC3EncodeContext),

1362 
AC3_encode_init, 
1363 
AC3_encode_frame, 
1364 
AC3_encode_close, 
1365 
NULL,

1366 
.sample_fmts = (enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},

1367 
.long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC3)"),

1368 
}; 