ffmpeg / libavcodec / ac3enc.c @ 99fac080
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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

8 
* modify it under the terms of the GNU Lesser General Public

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* License as published by the Free Software Foundation; either

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

11 
*

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

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

14 
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

15 
* Lesser General Public License for more details.

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*

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

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

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

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*/

21  
22 
/**

23 
* @file ac3enc.c

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* The simplest AC3 encoder.

25 
*/

26 
//#define DEBUG

27 
//#define DEBUG_BITALLOC

28 
#include "avcodec.h" 
29 
#include "bitstream.h" 
30 
#include "crc.h" 
31 
#include "ac3.h" 
32  
33 
typedef struct AC3EncodeContext { 
34 
PutBitContext pb; 
35 
int nb_channels;

36 
int nb_all_channels;

37 
int lfe_channel;

38 
int bit_rate;

39 
unsigned int sample_rate; 
40 
unsigned int bitstream_id; 
41 
unsigned int frame_size_min; /* minimum frame size in case rounding is necessary */ 
42 
unsigned int frame_size; /* current frame size in words */ 
43 
unsigned int bits_written; 
44 
unsigned int samples_written; 
45 
int sr_shift;

46 
unsigned int frame_size_code; 
47 
unsigned int sr_code; /* frequency */ 
48 
unsigned int channel_mode; 
49 
int lfe;

50 
unsigned int bitstream_mode; 
51 
short last_samples[AC3_MAX_CHANNELS][256]; 
52 
unsigned int chbwcod[AC3_MAX_CHANNELS]; 
53 
int nb_coefs[AC3_MAX_CHANNELS];

54  
55 
/* bitrate allocation control */

56 
int slow_gain_code, slow_decay_code, fast_decay_code, db_per_bit_code, floor_code;

57 
AC3BitAllocParameters bit_alloc; 
58 
int coarse_snr_offset;

59 
int fast_gain_code[AC3_MAX_CHANNELS];

60 
int fine_snr_offset[AC3_MAX_CHANNELS];

61 
/* mantissa encoding */

62 
int mant1_cnt, mant2_cnt, mant4_cnt;

63 
} AC3EncodeContext; 
64  
65 
static int16_t costab[64]; 
66 
static int16_t sintab[64]; 
67 
static int16_t xcos1[128]; 
68 
static int16_t xsin1[128]; 
69  
70 
#define MDCT_NBITS 9 
71 
#define N (1 << MDCT_NBITS) 
72  
73 
/* new exponents are sent if their Norm 1 exceed this number */

74 
#define EXP_DIFF_THRESHOLD 1000 
75  
76 
static void fft_init(int ln); 
77  
78 
static inline int16_t fix15(float a) 
79 
{ 
80 
int v;

81 
v = (int)(a * (float)(1 << 15)); 
82 
if (v < 32767) 
83 
v = 32767;

84 
else if (v > 32767) 
85 
v = 32767;

86 
return v;

87 
} 
88  
89 
typedef struct IComplex { 
90 
short re,im;

91 
} IComplex; 
92  
93 
static void fft_init(int ln) 
94 
{ 
95 
int i, j, m, n;

96 
float alpha;

97  
98 
n = 1 << ln;

99  
100 
for(i=0;i<(n/2);i++) { 
101 
alpha = 2 * M_PI * (float)i / (float)n; 
102 
costab[i] = fix15(cos(alpha)); 
103 
sintab[i] = fix15(sin(alpha)); 
104 
} 
105 
} 
106  
107 
/* butter fly op */

108 
#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \

109 
{\ 
110 
int ax, ay, bx, by;\

111 
bx=pre1;\ 
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by=pim1;\ 
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ax=qre1;\ 
114 
ay=qim1;\ 
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pre = (bx + ax) >> 1;\

116 
pim = (by + ay) >> 1;\

117 
qre = (bx  ax) >> 1;\

118 
qim = (by  ay) >> 1;\

119 
} 
120  
121 
#define MUL16(a,b) ((a) * (b))

122  
123 
#define CMUL(pre, pim, are, aim, bre, bim) \

124 
{\ 
125 
pre = (MUL16(are, bre)  MUL16(aim, bim)) >> 15;\

126 
pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\

127 
} 
128  
129  
130 
/* do a 2^n point complex fft on 2^ln points. */

131 
static void fft(IComplex *z, int ln) 
132 
{ 
133 
int j, l, np, np2;

134 
int nblocks, nloops;

135 
register IComplex *p,*q;

136 
int tmp_re, tmp_im;

137  
138 
np = 1 << ln;

139  
140 
/* reverse */

141 
for(j=0;j<np;j++) { 
142 
int k = ff_reverse[j] >> (8  ln); 
143 
if (k < j)

144 
FFSWAP(IComplex, z[k], z[j]); 
145 
} 
146  
147 
/* pass 0 */

148  
149 
p=&z[0];

150 
j=(np >> 1);

151 
do {

152 
BF(p[0].re, p[0].im, p[1].re, p[1].im, 
153 
p[0].re, p[0].im, p[1].re, p[1].im); 
154 
p+=2;

155 
} while (j != 0); 
156  
157 
/* pass 1 */

158  
159 
p=&z[0];

160 
j=np >> 2;

161 
do {

162 
BF(p[0].re, p[0].im, p[2].re, p[2].im, 
163 
p[0].re, p[0].im, p[2].re, p[2].im); 
164 
BF(p[1].re, p[1].im, p[3].re, p[3].im, 
165 
p[1].re, p[1].im, p[3].im, p[3].re); 
166 
p+=4;

167 
} while (j != 0); 
168  
169 
/* pass 2 .. ln1 */

170  
171 
nblocks = np >> 3;

172 
nloops = 1 << 2; 
173 
np2 = np >> 1;

174 
do {

175 
p = z; 
176 
q = z + nloops; 
177 
for (j = 0; j < nblocks; ++j) { 
178  
179 
BF(p>re, p>im, q>re, q>im, 
180 
p>re, p>im, q>re, q>im); 
181  
182 
p++; 
183 
q++; 
184 
for(l = nblocks; l < np2; l += nblocks) {

185 
CMUL(tmp_re, tmp_im, costab[l], sintab[l], q>re, q>im); 
186 
BF(p>re, p>im, q>re, q>im, 
187 
p>re, p>im, tmp_re, tmp_im); 
188 
p++; 
189 
q++; 
190 
} 
191 
p += nloops; 
192 
q += nloops; 
193 
} 
194 
nblocks = nblocks >> 1;

195 
nloops = nloops << 1;

196 
} while (nblocks != 0); 
197 
} 
198  
199 
/* do a 512 point mdct */

200 
static void mdct512(int32_t *out, int16_t *in) 
201 
{ 
202 
int i, re, im, re1, im1;

203 
int16_t rot[N]; 
204 
IComplex x[N/4];

205  
206 
/* shift to simplify computations */

207 
for(i=0;i<N/4;i++) 
208 
rot[i] = in[i + 3*N/4]; 
209 
for(i=N/4;i<N;i++) 
210 
rot[i] = in[i  N/4];

211  
212 
/* pre rotation */

213 
for(i=0;i<N/4;i++) { 
214 
re = ((int)rot[2*i]  (int)rot[N12*i]) >> 1; 
215 
im = ((int)rot[N/2+2*i]  (int)rot[N/212*i]) >> 1; 
216 
CMUL(x[i].re, x[i].im, re, im, xcos1[i], xsin1[i]); 
217 
} 
218  
219 
fft(x, MDCT_NBITS  2);

220  
221 
/* post rotation */

222 
for(i=0;i<N/4;i++) { 
223 
re = x[i].re; 
224 
im = x[i].im; 
225 
CMUL(re1, im1, re, im, xsin1[i], xcos1[i]); 
226 
out[2*i] = im1;

227 
out[N/212*i] = re1; 
228 
} 
229 
} 
230  
231 
/* XXX: use another norm ? */

232 
static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n) 
233 
{ 
234 
int sum, i;

235 
sum = 0;

236 
for(i=0;i<n;i++) { 
237 
sum += abs(exp1[i]  exp2[i]); 
238 
} 
239 
return sum;

240 
} 
241  
242 
static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], 
243 
uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

244 
int ch, int is_lfe) 
245 
{ 
246 
int i, j;

247 
int exp_diff;

248  
249 
/* estimate if the exponent variation & decide if they should be

250 
reused in the next frame */

251 
exp_strategy[0][ch] = EXP_NEW;

252 
for(i=1;i<NB_BLOCKS;i++) { 
253 
exp_diff = calc_exp_diff(exp[i][ch], exp[i1][ch], N/2); 
254 
#ifdef DEBUG

255 
av_log(NULL, AV_LOG_DEBUG, "exp_diff=%d\n", exp_diff); 
256 
#endif

257 
if (exp_diff > EXP_DIFF_THRESHOLD)

258 
exp_strategy[i][ch] = EXP_NEW; 
259 
else

260 
exp_strategy[i][ch] = EXP_REUSE; 
261 
} 
262 
if (is_lfe)

263 
return;

264  
265 
/* now select the encoding strategy type : if exponents are often

266 
recoded, we use a coarse encoding */

267 
i = 0;

268 
while (i < NB_BLOCKS) {

269 
j = i + 1;

270 
while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)

271 
j++; 
272 
switch(j  i) {

273 
case 1: 
274 
exp_strategy[i][ch] = EXP_D45; 
275 
break;

276 
case 2: 
277 
case 3: 
278 
exp_strategy[i][ch] = EXP_D25; 
279 
break;

280 
default:

281 
exp_strategy[i][ch] = EXP_D15; 
282 
break;

283 
} 
284 
i = j; 
285 
} 
286 
} 
287  
288 
/* set exp[i] to min(exp[i], exp1[i]) */

289 
static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n) 
290 
{ 
291 
int i;

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

295 
exp[i] = exp1[i]; 
296 
} 
297 
} 
298  
299 
/* update the exponents so that they are the ones the decoder will

300 
decode. Return the number of bits used to code the exponents */

301 
static int encode_exp(uint8_t encoded_exp[N/2], 
302 
uint8_t exp[N/2],

303 
int nb_exps,

304 
int exp_strategy)

305 
{ 
306 
int group_size, nb_groups, i, j, k, exp_min;

307 
uint8_t exp1[N/2];

308  
309 
switch(exp_strategy) {

310 
case EXP_D15:

311 
group_size = 1;

312 
break;

313 
case EXP_D25:

314 
group_size = 2;

315 
break;

316 
default:

317 
case EXP_D45:

318 
group_size = 4;

319 
break;

320 
} 
321 
nb_groups = ((nb_exps + (group_size * 3)  4) / (3 * group_size)) * 3; 
322  
323 
/* for each group, compute the minimum exponent */

324 
exp1[0] = exp[0]; /* DC exponent is handled separately */ 
325 
k = 1;

326 
for(i=1;i<=nb_groups;i++) { 
327 
exp_min = exp[k]; 
328 
assert(exp_min >= 0 && exp_min <= 24); 
329 
for(j=1;j<group_size;j++) { 
330 
if (exp[k+j] < exp_min)

331 
exp_min = exp[k+j]; 
332 
} 
333 
exp1[i] = exp_min; 
334 
k += group_size; 
335 
} 
336  
337 
/* constraint for DC exponent */

338 
if (exp1[0] > 15) 
339 
exp1[0] = 15; 
340  
341 
/* Decrease the delta between each groups to within 2

342 
* so that they can be differentially encoded */

343 
for (i=1;i<=nb_groups;i++) 
344 
exp1[i] = FFMIN(exp1[i], exp1[i1] + 2); 
345 
for (i=nb_groups1;i>=0;i) 
346 
exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2); 
347  
348 
/* now we have the exponent values the decoder will see */

349 
encoded_exp[0] = exp1[0]; 
350 
k = 1;

351 
for(i=1;i<=nb_groups;i++) { 
352 
for(j=0;j<group_size;j++) { 
353 
encoded_exp[k+j] = exp1[i]; 
354 
} 
355 
k += group_size; 
356 
} 
357  
358 
#if defined(DEBUG)

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

365  
366 
return 4 + (nb_groups / 3) * 7; 
367 
} 
368  
369 
/* return the size in bits taken by the mantissa */

370 
static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs) 
371 
{ 
372 
int bits, mant, i;

373  
374 
bits = 0;

375 
for(i=0;i<nb_coefs;i++) { 
376 
mant = m[i]; 
377 
switch(mant) {

378 
case 0: 
379 
/* nothing */

380 
break;

381 
case 1: 
382 
/* 3 mantissa in 5 bits */

383 
if (s>mant1_cnt == 0) 
384 
bits += 5;

385 
if (++s>mant1_cnt == 3) 
386 
s>mant1_cnt = 0;

387 
break;

388 
case 2: 
389 
/* 3 mantissa in 7 bits */

390 
if (s>mant2_cnt == 0) 
391 
bits += 7;

392 
if (++s>mant2_cnt == 3) 
393 
s>mant2_cnt = 0;

394 
break;

395 
case 3: 
396 
bits += 3;

397 
break;

398 
case 4: 
399 
/* 2 mantissa in 7 bits */

400 
if (s>mant4_cnt == 0) 
401 
bits += 7;

402 
if (++s>mant4_cnt == 2) 
403 
s>mant4_cnt = 0;

404 
break;

405 
case 14: 
406 
bits += 14;

407 
break;

408 
case 15: 
409 
bits += 16;

410 
break;

411 
default:

412 
bits += mant  1;

413 
break;

414 
} 
415 
} 
416 
return bits;

417 
} 
418  
419  
420 
static void bit_alloc_masking(AC3EncodeContext *s, 
421 
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

422 
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], 
423 
int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

424 
int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50])

425 
{ 
426 
int blk, ch;

427 
int16_t band_psd[NB_BLOCKS][AC3_MAX_CHANNELS][50];

428  
429 
for(blk=0; blk<NB_BLOCKS; blk++) { 
430 
for(ch=0;ch<s>nb_all_channels;ch++) { 
431 
if(exp_strategy[blk][ch] == EXP_REUSE) {

432 
memcpy(psd[blk][ch], psd[blk1][ch], (N/2)*sizeof(int16_t)); 
433 
memcpy(mask[blk][ch], mask[blk1][ch], 50*sizeof(int16_t)); 
434 
} else {

435 
ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,

436 
s>nb_coefs[ch], 
437 
psd[blk][ch], band_psd[blk][ch]); 
438 
ff_ac3_bit_alloc_calc_mask(&s>bit_alloc, band_psd[blk][ch], 
439 
0, s>nb_coefs[ch],

440 
ff_ac3_fast_gain_tab[s>fast_gain_code[ch]], 
441 
ch == s>lfe_channel, 
442 
DBA_NONE, 0, NULL, NULL, NULL, 
443 
mask[blk][ch]); 
444 
} 
445 
} 
446 
} 
447 
} 
448  
449 
static int bit_alloc(AC3EncodeContext *s, 
450 
int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50],

451 
int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

452 
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

453 
int frame_bits, int coarse_snr_offset, int fine_snr_offset) 
454 
{ 
455 
int i, ch;

456 
int snr_offset;

457  
458 
snr_offset = (((coarse_snr_offset  15) << 4) + fine_snr_offset) << 2; 
459  
460 
/* compute size */

461 
for(i=0;i<NB_BLOCKS;i++) { 
462 
s>mant1_cnt = 0;

463 
s>mant2_cnt = 0;

464 
s>mant4_cnt = 0;

465 
for(ch=0;ch<s>nb_all_channels;ch++) { 
466 
ff_ac3_bit_alloc_calc_bap(mask[i][ch], psd[i][ch], 0,

467 
s>nb_coefs[ch], snr_offset, 
468 
s>bit_alloc.floor, bap[i][ch]); 
469 
frame_bits += compute_mantissa_size(s, bap[i][ch], 
470 
s>nb_coefs[ch]); 
471 
} 
472 
} 
473 
#if 0

474 
printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",

475 
coarse_snr_offset, fine_snr_offset, frame_bits,

476 
16 * s>frame_size  ((frame_bits + 7) & ~7));

477 
#endif

478 
return 16 * s>frame_size  frame_bits; 
479 
} 
480  
481 
#define SNR_INC1 4 
482  
483 
static int compute_bit_allocation(AC3EncodeContext *s, 
484 
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

485 
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

486 
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], 
487 
int frame_bits)

488 
{ 
489 
int i, ch;

490 
int coarse_snr_offset, fine_snr_offset;

491 
uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

492 
int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

493 
int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50];

494 
static int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 }; 
495  
496 
/* init default parameters */

497 
s>slow_decay_code = 2;

498 
s>fast_decay_code = 1;

499 
s>slow_gain_code = 1;

500 
s>db_per_bit_code = 2;

501 
s>floor_code = 4;

502 
for(ch=0;ch<s>nb_all_channels;ch++) 
503 
s>fast_gain_code[ch] = 4;

504  
505 
/* compute real values */

506 
s>bit_alloc.sr_code = s>sr_code; 
507 
s>bit_alloc.sr_shift = s>sr_shift; 
508 
s>bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s>slow_decay_code] >> s>sr_shift; 
509 
s>bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s>fast_decay_code] >> s>sr_shift; 
510 
s>bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s>slow_gain_code]; 
511 
s>bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s>db_per_bit_code]; 
512 
s>bit_alloc.floor = ff_ac3_floor_tab[s>floor_code]; 
513  
514 
/* header size */

515 
frame_bits += 65;

516 
// if (s>channel_mode == 2)

517 
// frame_bits += 2;

518 
frame_bits += frame_bits_inc[s>channel_mode]; 
519  
520 
/* audio blocks */

521 
for(i=0;i<NB_BLOCKS;i++) { 
522 
frame_bits += s>nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */ 
523 
if (s>channel_mode == AC3_CHMODE_STEREO) {

524 
frame_bits++; /* rematstr */

525 
if(i==0) frame_bits += 4; 
526 
} 
527 
frame_bits += 2 * s>nb_channels; /* chexpstr[2] * c */ 
528 
if (s>lfe)

529 
frame_bits++; /* lfeexpstr */

530 
for(ch=0;ch<s>nb_channels;ch++) { 
531 
if (exp_strategy[i][ch] != EXP_REUSE)

532 
frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */ 
533 
} 
534 
frame_bits++; /* baie */

535 
frame_bits++; /* snr */

536 
frame_bits += 2; /* delta / skip */ 
537 
} 
538 
frame_bits++; /* cplinu for block 0 */

539 
/* bit alloc info */

540 
/* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */

541 
/* csnroffset[6] */

542 
/* (fsnoffset[4] + fgaincod[4]) * c */

543 
frame_bits += 2*4 + 3 + 6 + s>nb_all_channels * (4 + 3); 
544  
545 
/* auxdatae, crcrsv */

546 
frame_bits += 2;

547  
548 
/* CRC */

549 
frame_bits += 16;

550  
551 
/* calculate psd and masking curve before doing bit allocation */

552 
bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask); 
553  
554 
/* now the big work begins : do the bit allocation. Modify the snr

555 
offset until we can pack everything in the requested frame size */

556  
557 
coarse_snr_offset = s>coarse_snr_offset; 
558 
while (coarse_snr_offset >= 0 && 
559 
bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0) 
560 
coarse_snr_offset = SNR_INC1; 
561 
if (coarse_snr_offset < 0) { 
562 
av_log(NULL, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n"); 
563 
return 1; 
564 
} 
565 
while ((coarse_snr_offset + SNR_INC1) <= 63 && 
566 
bit_alloc(s, mask, psd, bap1, frame_bits, 
567 
coarse_snr_offset + SNR_INC1, 0) >= 0) { 
568 
coarse_snr_offset += SNR_INC1; 
569 
memcpy(bap, bap1, sizeof(bap1));

570 
} 
571 
while ((coarse_snr_offset + 1) <= 63 && 
572 
bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) { 
573 
coarse_snr_offset++; 
574 
memcpy(bap, bap1, sizeof(bap1));

575 
} 
576  
577 
fine_snr_offset = 0;

578 
while ((fine_snr_offset + SNR_INC1) <= 15 && 
579 
bit_alloc(s, mask, psd, bap1, frame_bits, 
580 
coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {

581 
fine_snr_offset += SNR_INC1; 
582 
memcpy(bap, bap1, sizeof(bap1));

583 
} 
584 
while ((fine_snr_offset + 1) <= 15 && 
585 
bit_alloc(s, mask, psd, bap1, frame_bits, 
586 
coarse_snr_offset, fine_snr_offset + 1) >= 0) { 
587 
fine_snr_offset++; 
588 
memcpy(bap, bap1, sizeof(bap1));

589 
} 
590  
591 
s>coarse_snr_offset = coarse_snr_offset; 
592 
for(ch=0;ch<s>nb_all_channels;ch++) 
593 
s>fine_snr_offset[ch] = fine_snr_offset; 
594 
#if defined(DEBUG_BITALLOC)

595 
{ 
596 
int j;

597  
598 
for(i=0;i<6;i++) { 
599 
for(ch=0;ch<s>nb_all_channels;ch++) { 
600 
printf("Block #%d Ch%d:\n", i, ch);

601 
printf("bap=");

602 
for(j=0;j<s>nb_coefs[ch];j++) { 
603 
printf("%d ",bap[i][ch][j]);

604 
} 
605 
printf("\n");

606 
} 
607 
} 
608 
} 
609 
#endif

610 
return 0; 
611 
} 
612  
613 
static int AC3_encode_init(AVCodecContext *avctx) 
614 
{ 
615 
int freq = avctx>sample_rate;

616 
int bitrate = avctx>bit_rate;

617 
int channels = avctx>channels;

618 
AC3EncodeContext *s = avctx>priv_data; 
619 
int i, j, ch;

620 
float alpha;

621 
int bw_code;

622 
static const uint8_t channel_mode_defs[6] = { 
623 
0x01, /* C */ 
624 
0x02, /* L R */ 
625 
0x03, /* L C R */ 
626 
0x06, /* L R SL SR */ 
627 
0x07, /* L C R SL SR */ 
628 
0x07, /* L C R SL SR (+LFE) */ 
629 
}; 
630  
631 
avctx>frame_size = AC3_FRAME_SIZE; 
632  
633 
ac3_common_init(); 
634  
635 
/* number of channels */

636 
if (channels < 1  channels > 6) 
637 
return 1; 
638 
s>channel_mode = channel_mode_defs[channels  1];

639 
s>lfe = (channels == 6) ? 1 : 0; 
640 
s>nb_all_channels = channels; 
641 
s>nb_channels = channels > 5 ? 5 : channels; 
642 
s>lfe_channel = s>lfe ? 5 : 1; 
643  
644 
/* frequency */

645 
for(i=0;i<3;i++) { 
646 
for(j=0;j<3;j++) 
647 
if ((ff_ac3_sample_rate_tab[j] >> i) == freq)

648 
goto found;

649 
} 
650 
return 1; 
651 
found:

652 
s>sample_rate = freq; 
653 
s>sr_shift = i; 
654 
s>sr_code = j; 
655 
s>bitstream_id = 8 + s>sr_shift;

656 
s>bitstream_mode = 0; /* complete main audio service */ 
657  
658 
/* bitrate & frame size */

659 
for(i=0;i<19;i++) { 
660 
if ((ff_ac3_bitrate_tab[i] >> s>sr_shift)*1000 == bitrate) 
661 
break;

662 
} 
663 
if (i == 19) 
664 
return 1; 
665 
s>bit_rate = bitrate; 
666 
s>frame_size_code = i << 1;

667 
s>frame_size_min = ff_ac3_frame_size_tab[s>frame_size_code][s>sr_code]; 
668 
s>bits_written = 0;

669 
s>samples_written = 0;

670 
s>frame_size = s>frame_size_min; 
671  
672 
/* bit allocation init */

673 
if(avctx>cutoff) {

674 
/* calculate bandwidth based on userspecified cutoff frequency */

675 
int cutoff = av_clip(avctx>cutoff, 1, s>sample_rate >> 1); 
676 
int fbw_coeffs = cutoff * 512 / s>sample_rate; 
677 
bw_code = av_clip((fbw_coeffs  73) / 3, 0, 60); 
678 
} else {

679 
/* use default bandwidth setting */

680 
/* XXX: should compute the bandwidth according to the frame

681 
size, so that we avoid anoying high freq artefacts */

682 
bw_code = 50;

683 
} 
684 
for(ch=0;ch<s>nb_channels;ch++) { 
685 
/* bandwidth for each channel */

686 
s>chbwcod[ch] = bw_code; 
687 
s>nb_coefs[ch] = bw_code * 3 + 73; 
688 
} 
689 
if (s>lfe) {

690 
s>nb_coefs[s>lfe_channel] = 7; /* fixed */ 
691 
} 
692 
/* initial snr offset */

693 
s>coarse_snr_offset = 40;

694  
695 
/* mdct init */

696 
fft_init(MDCT_NBITS  2);

697 
for(i=0;i<N/4;i++) { 
698 
alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N; 
699 
xcos1[i] = fix15(cos(alpha)); 
700 
xsin1[i] = fix15(sin(alpha)); 
701 
} 
702  
703 
avctx>coded_frame= avcodec_alloc_frame(); 
704 
avctx>coded_frame>key_frame= 1;

705  
706 
return 0; 
707 
} 
708  
709 
/* output the AC3 frame header */

710 
static void output_frame_header(AC3EncodeContext *s, unsigned char *frame) 
711 
{ 
712 
init_put_bits(&s>pb, frame, AC3_MAX_CODED_FRAME_SIZE); 
713  
714 
put_bits(&s>pb, 16, 0x0b77); /* frame header */ 
715 
put_bits(&s>pb, 16, 0); /* crc1: will be filled later */ 
716 
put_bits(&s>pb, 2, s>sr_code);

717 
put_bits(&s>pb, 6, s>frame_size_code + (s>frame_size  s>frame_size_min));

718 
put_bits(&s>pb, 5, s>bitstream_id);

719 
put_bits(&s>pb, 3, s>bitstream_mode);

720 
put_bits(&s>pb, 3, s>channel_mode);

721 
if ((s>channel_mode & 0x01) && s>channel_mode != AC3_CHMODE_MONO) 
722 
put_bits(&s>pb, 2, 1); /* XXX 4.5 dB */ 
723 
if (s>channel_mode & 0x04) 
724 
put_bits(&s>pb, 2, 1); /* XXX 6 dB */ 
725 
if (s>channel_mode == AC3_CHMODE_STEREO)

726 
put_bits(&s>pb, 2, 0); /* surround not indicated */ 
727 
put_bits(&s>pb, 1, s>lfe); /* LFE */ 
728 
put_bits(&s>pb, 5, 31); /* dialog norm: 31 db */ 
729 
put_bits(&s>pb, 1, 0); /* no compression control word */ 
730 
put_bits(&s>pb, 1, 0); /* no lang code */ 
731 
put_bits(&s>pb, 1, 0); /* no audio production info */ 
732 
put_bits(&s>pb, 1, 0); /* no copyright */ 
733 
put_bits(&s>pb, 1, 1); /* original bitstream */ 
734 
put_bits(&s>pb, 1, 0); /* no time code 1 */ 
735 
put_bits(&s>pb, 1, 0); /* no time code 2 */ 
736 
put_bits(&s>pb, 1, 0); /* no additional bit stream info */ 
737 
} 
738  
739 
/* symetric quantization on 'levels' levels */

740 
static inline int sym_quant(int c, int e, int levels) 
741 
{ 
742 
int v;

743  
744 
if (c >= 0) { 
745 
v = (levels * (c << e)) >> 24;

746 
v = (v + 1) >> 1; 
747 
v = (levels >> 1) + v;

748 
} else {

749 
v = (levels * ((c) << e)) >> 24;

750 
v = (v + 1) >> 1; 
751 
v = (levels >> 1)  v;

752 
} 
753 
assert (v >= 0 && v < levels);

754 
return v;

755 
} 
756  
757 
/* asymetric quantization on 2^qbits levels */

758 
static inline int asym_quant(int c, int e, int qbits) 
759 
{ 
760 
int lshift, m, v;

761  
762 
lshift = e + qbits  24;

763 
if (lshift >= 0) 
764 
v = c << lshift; 
765 
else

766 
v = c >> (lshift); 
767 
/* rounding */

768 
v = (v + 1) >> 1; 
769 
m = (1 << (qbits1)); 
770 
if (v >= m)

771 
v = m  1;

772 
assert(v >= m); 
773 
return v & ((1 << qbits)1); 
774 
} 
775  
776 
/* Output one audio block. There are NB_BLOCKS audio blocks in one AC3

777 
frame */

778 
static void output_audio_block(AC3EncodeContext *s, 
779 
uint8_t exp_strategy[AC3_MAX_CHANNELS], 
780 
uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],

781 
uint8_t bap[AC3_MAX_CHANNELS][N/2],

782 
int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],

783 
int8_t global_exp[AC3_MAX_CHANNELS], 
784 
int block_num)

785 
{ 
786 
int ch, nb_groups, group_size, i, baie, rbnd;

787 
uint8_t *p; 
788 
uint16_t qmant[AC3_MAX_CHANNELS][N/2];

789 
int exp0, exp1;

790 
int mant1_cnt, mant2_cnt, mant4_cnt;

791 
uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; 
792 
int delta0, delta1, delta2;

793  
794 
for(ch=0;ch<s>nb_channels;ch++) 
795 
put_bits(&s>pb, 1, 0); /* 512 point MDCT */ 
796 
for(ch=0;ch<s>nb_channels;ch++) 
797 
put_bits(&s>pb, 1, 1); /* no dither */ 
798 
put_bits(&s>pb, 1, 0); /* no dynamic range */ 
799 
if (block_num == 0) { 
800 
/* for block 0, even if no coupling, we must say it. This is a

801 
waste of bit :) */

802 
put_bits(&s>pb, 1, 1); /* coupling strategy present */ 
803 
put_bits(&s>pb, 1, 0); /* no coupling strategy */ 
804 
} else {

805 
put_bits(&s>pb, 1, 0); /* no new coupling strategy */ 
806 
} 
807  
808 
if (s>channel_mode == AC3_CHMODE_STEREO)

809 
{ 
810 
if(block_num==0) 
811 
{ 
812 
/* first block must define rematrixing (rematstr) */

813 
put_bits(&s>pb, 1, 1); 
814  
815 
/* dummy rematrixing rematflg(1:4)=0 */

816 
for (rbnd=0;rbnd<4;rbnd++) 
817 
put_bits(&s>pb, 1, 0); 
818 
} 
819 
else

820 
{ 
821 
/* no matrixing (but should be used in the future) */

822 
put_bits(&s>pb, 1, 0); 
823 
} 
824 
} 
825  
826 
#if defined(DEBUG)

827 
{ 
828 
static int count = 0; 
829 
av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++); 
830 
} 
831 
#endif

832 
/* exponent strategy */

833 
for(ch=0;ch<s>nb_channels;ch++) { 
834 
put_bits(&s>pb, 2, exp_strategy[ch]);

835 
} 
836  
837 
if (s>lfe) {

838 
put_bits(&s>pb, 1, exp_strategy[s>lfe_channel]);

839 
} 
840  
841 
for(ch=0;ch<s>nb_channels;ch++) { 
842 
if (exp_strategy[ch] != EXP_REUSE)

843 
put_bits(&s>pb, 6, s>chbwcod[ch]);

844 
} 
845  
846 
/* exponents */

847 
for (ch = 0; ch < s>nb_all_channels; ch++) { 
848 
switch(exp_strategy[ch]) {

849 
case EXP_REUSE:

850 
continue;

851 
case EXP_D15:

852 
group_size = 1;

853 
break;

854 
case EXP_D25:

855 
group_size = 2;

856 
break;

857 
default:

858 
case EXP_D45:

859 
group_size = 4;

860 
break;

861 
} 
862 
nb_groups = (s>nb_coefs[ch] + (group_size * 3)  4) / (3 * group_size); 
863 
p = encoded_exp[ch]; 
864  
865 
/* first exponent */

866 
exp1 = *p++; 
867 
put_bits(&s>pb, 4, exp1);

868  
869 
/* next ones are delta encoded */

870 
for(i=0;i<nb_groups;i++) { 
871 
/* merge three delta in one code */

872 
exp0 = exp1; 
873 
exp1 = p[0];

874 
p += group_size; 
875 
delta0 = exp1  exp0 + 2;

876  
877 
exp0 = exp1; 
878 
exp1 = p[0];

879 
p += group_size; 
880 
delta1 = exp1  exp0 + 2;

881  
882 
exp0 = exp1; 
883 
exp1 = p[0];

884 
p += group_size; 
885 
delta2 = exp1  exp0 + 2;

886  
887 
put_bits(&s>pb, 7, ((delta0 * 5 + delta1) * 5) + delta2); 
888 
} 
889  
890 
if (ch != s>lfe_channel)

891 
put_bits(&s>pb, 2, 0); /* no gain range info */ 
892 
} 
893  
894 
/* bit allocation info */

895 
baie = (block_num == 0);

896 
put_bits(&s>pb, 1, baie);

897 
if (baie) {

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

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

900 
put_bits(&s>pb, 2, s>slow_gain_code);

901 
put_bits(&s>pb, 2, s>db_per_bit_code);

902 
put_bits(&s>pb, 3, s>floor_code);

903 
} 
904  
905 
/* snr offset */

906 
put_bits(&s>pb, 1, baie); /* always present with bai */ 
907 
if (baie) {

908 
put_bits(&s>pb, 6, s>coarse_snr_offset);

909 
for(ch=0;ch<s>nb_all_channels;ch++) { 
910 
put_bits(&s>pb, 4, s>fine_snr_offset[ch]);

911 
put_bits(&s>pb, 3, s>fast_gain_code[ch]);

912 
} 
913 
} 
914  
915 
put_bits(&s>pb, 1, 0); /* no delta bit allocation */ 
916 
put_bits(&s>pb, 1, 0); /* no data to skip */ 
917  
918 
/* mantissa encoding : we use two passes to handle the grouping. A

919 
one pass method may be faster, but it would necessitate to

920 
modify the output stream. */

921  
922 
/* first pass: quantize */

923 
mant1_cnt = mant2_cnt = mant4_cnt = 0;

924 
qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;

925  
926 
for (ch = 0; ch < s>nb_all_channels; ch++) { 
927 
int b, c, e, v;

928  
929 
for(i=0;i<s>nb_coefs[ch];i++) { 
930 
c = mdct_coefs[ch][i]; 
931 
e = encoded_exp[ch][i]  global_exp[ch]; 
932 
b = bap[ch][i]; 
933 
switch(b) {

934 
case 0: 
935 
v = 0;

936 
break;

937 
case 1: 
938 
v = sym_quant(c, e, 3);

939 
switch(mant1_cnt) {

940 
case 0: 
941 
qmant1_ptr = &qmant[ch][i]; 
942 
v = 9 * v;

943 
mant1_cnt = 1;

944 
break;

945 
case 1: 
946 
*qmant1_ptr += 3 * v;

947 
mant1_cnt = 2;

948 
v = 128;

949 
break;

950 
default:

951 
*qmant1_ptr += v; 
952 
mant1_cnt = 0;

953 
v = 128;

954 
break;

955 
} 
956 
break;

957 
case 2: 
958 
v = sym_quant(c, e, 5);

959 
switch(mant2_cnt) {

960 
case 0: 
961 
qmant2_ptr = &qmant[ch][i]; 
962 
v = 25 * v;

963 
mant2_cnt = 1;

964 
break;

965 
case 1: 
966 
*qmant2_ptr += 5 * v;

967 
mant2_cnt = 2;

968 
v = 128;

969 
break;

970 
default:

971 
*qmant2_ptr += v; 
972 
mant2_cnt = 0;

973 
v = 128;

974 
break;

975 
} 
976 
break;

977 
case 3: 
978 
v = sym_quant(c, e, 7);

979 
break;

980 
case 4: 
981 
v = sym_quant(c, e, 11);

982 
switch(mant4_cnt) {

983 
case 0: 
984 
qmant4_ptr = &qmant[ch][i]; 
985 
v = 11 * v;

986 
mant4_cnt = 1;

987 
break;

988 
default:

989 
*qmant4_ptr += v; 
990 
mant4_cnt = 0;

991 
v = 128;

992 
break;

993 
} 
994 
break;

995 
case 5: 
996 
v = sym_quant(c, e, 15);

997 
break;

998 
case 14: 
999 
v = asym_quant(c, e, 14);

1000 
break;

1001 
case 15: 
1002 
v = asym_quant(c, e, 16);

1003 
break;

1004 
default:

1005 
v = asym_quant(c, e, b  1);

1006 
break;

1007 
} 
1008 
qmant[ch][i] = v; 
1009 
} 
1010 
} 
1011  
1012 
/* second pass : output the values */

1013 
for (ch = 0; ch < s>nb_all_channels; ch++) { 
1014 
int b, q;

1015  
1016 
for(i=0;i<s>nb_coefs[ch];i++) { 
1017 
q = qmant[ch][i]; 
1018 
b = bap[ch][i]; 
1019 
switch(b) {

1020 
case 0: 
1021 
break;

1022 
case 1: 
1023 
if (q != 128) 
1024 
put_bits(&s>pb, 5, q);

1025 
break;

1026 
case 2: 
1027 
if (q != 128) 
1028 
put_bits(&s>pb, 7, q);

1029 
break;

1030 
case 3: 
1031 
put_bits(&s>pb, 3, q);

1032 
break;

1033 
case 4: 
1034 
if (q != 128) 
1035 
put_bits(&s>pb, 7, q);

1036 
break;

1037 
case 14: 
1038 
put_bits(&s>pb, 14, q);

1039 
break;

1040 
case 15: 
1041 
put_bits(&s>pb, 16, q);

1042 
break;

1043 
default:

1044 
put_bits(&s>pb, b  1, q);

1045 
break;

1046 
} 
1047 
} 
1048 
} 
1049 
} 
1050  
1051 
#define CRC16_POLY ((1 << 0)  (1 << 2)  (1 << 15)  (1 << 16)) 
1052  
1053 
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly) 
1054 
{ 
1055 
unsigned int c; 
1056  
1057 
c = 0;

1058 
while (a) {

1059 
if (a & 1) 
1060 
c ^= b; 
1061 
a = a >> 1;

1062 
b = b << 1;

1063 
if (b & (1 << 16)) 
1064 
b ^= poly; 
1065 
} 
1066 
return c;

1067 
} 
1068  
1069 
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly) 
1070 
{ 
1071 
unsigned int r; 
1072 
r = 1;

1073 
while (n) {

1074 
if (n & 1) 
1075 
r = mul_poly(r, a, poly); 
1076 
a = mul_poly(a, a, poly); 
1077 
n >>= 1;

1078 
} 
1079 
return r;

1080 
} 
1081  
1082  
1083 
/* compute log2(max(abs(tab[]))) */

1084 
static int log2_tab(int16_t *tab, int n) 
1085 
{ 
1086 
int i, v;

1087  
1088 
v = 0;

1089 
for(i=0;i<n;i++) { 
1090 
v = abs(tab[i]); 
1091 
} 
1092 
return av_log2(v);

1093 
} 
1094  
1095 
static void lshift_tab(int16_t *tab, int n, int lshift) 
1096 
{ 
1097 
int i;

1098  
1099 
if (lshift > 0) { 
1100 
for(i=0;i<n;i++) { 
1101 
tab[i] <<= lshift; 
1102 
} 
1103 
} else if (lshift < 0) { 
1104 
lshift = lshift; 
1105 
for(i=0;i<n;i++) { 
1106 
tab[i] >>= lshift; 
1107 
} 
1108 
} 
1109 
} 
1110  
1111 
/* fill the end of the frame and compute the two crcs */

1112 
static int output_frame_end(AC3EncodeContext *s) 
1113 
{ 
1114 
int frame_size, frame_size_58, n, crc1, crc2, crc_inv;

1115 
uint8_t *frame; 
1116  
1117 
frame_size = s>frame_size; /* frame size in words */

1118 
/* align to 8 bits */

1119 
flush_put_bits(&s>pb); 
1120 
/* add zero bytes to reach the frame size */

1121 
frame = s>pb.buf; 
1122 
n = 2 * s>frame_size  (pbBufPtr(&s>pb)  frame)  2; 
1123 
assert(n >= 0);

1124 
if(n>0) 
1125 
memset(pbBufPtr(&s>pb), 0, n);

1126  
1127 
/* Now we must compute both crcs : this is not so easy for crc1

1128 
because it is at the beginning of the data... */

1129 
frame_size_58 = (frame_size >> 1) + (frame_size >> 3); 
1130 
crc1 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,

1131 
frame + 4, 2 * frame_size_58  4)); 
1132 
/* XXX: could precompute crc_inv */

1133 
crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58)  16, CRC16_POLY); 
1134 
crc1 = mul_poly(crc_inv, crc1, CRC16_POLY); 
1135 
AV_WB16(frame+2,crc1);

1136  
1137 
crc2 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,

1138 
frame + 2 * frame_size_58,

1139 
(frame_size  frame_size_58) * 2  2)); 
1140 
AV_WB16(frame+2*frame_size2,crc2); 
1141  
1142 
// printf("n=%d frame_size=%d\n", n, frame_size);

1143 
return frame_size * 2; 
1144 
} 
1145  
1146 
static int AC3_encode_frame(AVCodecContext *avctx, 
1147 
unsigned char *frame, int buf_size, void *data) 
1148 
{ 
1149 
AC3EncodeContext *s = avctx>priv_data; 
1150 
int16_t *samples = data; 
1151 
int i, j, k, v, ch;

1152 
int16_t input_samples[N]; 
1153 
int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1154 
uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1155 
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS]; 
1156 
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1157 
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1158 
int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS]; 
1159 
int frame_bits;

1160  
1161 
frame_bits = 0;

1162 
for(ch=0;ch<s>nb_all_channels;ch++) { 
1163 
/* fixed mdct to the six sub blocks & exponent computation */

1164 
for(i=0;i<NB_BLOCKS;i++) { 
1165 
int16_t *sptr; 
1166 
int sinc;

1167  
1168 
/* compute input samples */

1169 
memcpy(input_samples, s>last_samples[ch], N/2 * sizeof(int16_t)); 
1170 
sinc = s>nb_all_channels; 
1171 
sptr = samples + (sinc * (N/2) * i) + ch;

1172 
for(j=0;j<N/2;j++) { 
1173 
v = *sptr; 
1174 
input_samples[j + N/2] = v;

1175 
s>last_samples[ch][j] = v; 
1176 
sptr += sinc; 
1177 
} 
1178  
1179 
/* apply the MDCT window */

1180 
for(j=0;j<N/2;j++) { 
1181 
input_samples[j] = MUL16(input_samples[j], 
1182 
ff_ac3_window[j]) >> 15;

1183 
input_samples[Nj1] = MUL16(input_samples[Nj1], 
1184 
ff_ac3_window[j]) >> 15;

1185 
} 
1186  
1187 
/* Normalize the samples to use the maximum available

1188 
precision */

1189 
v = 14  log2_tab(input_samples, N);

1190 
if (v < 0) 
1191 
v = 0;

1192 
exp_samples[i][ch] = v  9;

1193 
lshift_tab(input_samples, N, v); 
1194  
1195 
/* do the MDCT */

1196 
mdct512(mdct_coef[i][ch], input_samples); 
1197  
1198 
/* compute "exponents". We take into account the

1199 
normalization there */

1200 
for(j=0;j<N/2;j++) { 
1201 
int e;

1202 
v = abs(mdct_coef[i][ch][j]); 
1203 
if (v == 0) 
1204 
e = 24;

1205 
else {

1206 
e = 23  av_log2(v) + exp_samples[i][ch];

1207 
if (e >= 24) { 
1208 
e = 24;

1209 
mdct_coef[i][ch][j] = 0;

1210 
} 
1211 
} 
1212 
exp[i][ch][j] = e; 
1213 
} 
1214 
} 
1215  
1216 
compute_exp_strategy(exp_strategy, exp, ch, ch == s>lfe_channel); 
1217  
1218 
/* compute the exponents as the decoder will see them. The

1219 
EXP_REUSE case must be handled carefully : we select the

1220 
min of the exponents */

1221 
i = 0;

1222 
while (i < NB_BLOCKS) {

1223 
j = i + 1;

1224 
while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {

1225 
exponent_min(exp[i][ch], exp[j][ch], s>nb_coefs[ch]); 
1226 
j++; 
1227 
} 
1228 
frame_bits += encode_exp(encoded_exp[i][ch], 
1229 
exp[i][ch], s>nb_coefs[ch], 
1230 
exp_strategy[i][ch]); 
1231 
/* copy encoded exponents for reuse case */

1232 
for(k=i+1;k<j;k++) { 
1233 
memcpy(encoded_exp[k][ch], encoded_exp[i][ch], 
1234 
s>nb_coefs[ch] * sizeof(uint8_t));

1235 
} 
1236 
i = j; 
1237 
} 
1238 
} 
1239  
1240 
/* adjust for fractional frame sizes */

1241 
while(s>bits_written >= s>bit_rate && s>samples_written >= s>sample_rate) {

1242 
s>bits_written = s>bit_rate; 
1243 
s>samples_written = s>sample_rate; 
1244 
} 
1245 
s>frame_size = s>frame_size_min + (s>bits_written * s>sample_rate < s>samples_written * s>bit_rate); 
1246 
s>bits_written += s>frame_size * 16;

1247 
s>samples_written += AC3_FRAME_SIZE; 
1248  
1249 
compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits); 
1250 
/* everything is known... let's output the frame */

1251 
output_frame_header(s, frame); 
1252  
1253 
for(i=0;i<NB_BLOCKS;i++) { 
1254 
output_audio_block(s, exp_strategy[i], encoded_exp[i], 
1255 
bap[i], mdct_coef[i], exp_samples[i], i); 
1256 
} 
1257 
return output_frame_end(s);

1258 
} 
1259  
1260 
static int AC3_encode_close(AVCodecContext *avctx) 
1261 
{ 
1262 
av_freep(&avctx>coded_frame); 
1263 
return 0; 
1264 
} 
1265  
1266 
#if 0

1267 
/*************************************************************************/

1268 
/* TEST */

1269 

1270 
#undef random

1271 
#define FN (N/4)

1272 

1273 
void fft_test(void)

1274 
{

1275 
IComplex in[FN], in1[FN];

1276 
int k, n, i;

1277 
float sum_re, sum_im, a;

1278 

1279 
/* FFT test */

1280 

1281 
for(i=0;i<FN;i++) {

1282 
in[i].re = random() % 65535  32767;

1283 
in[i].im = random() % 65535  32767;

1284 
in1[i] = in[i];

1285 
}

1286 
fft(in, 7);

1287 

1288 
/* do it by hand */

1289 
for(k=0;k<FN;k++) {

1290 
sum_re = 0;

1291 
sum_im = 0;

1292 
for(n=0;n<FN;n++) {

1293 
a = 2 * M_PI * (n * k) / FN;

1294 
sum_re += in1[n].re * cos(a)  in1[n].im * sin(a);

1295 
sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);

1296 
}

1297 
printf("%3d: %6d,%6d %6.0f,%6.0f\n",

1298 
k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);

1299 
}

1300 
}

1301 

1302 
void mdct_test(void)

1303 
{

1304 
int16_t input[N];

1305 
int32_t output[N/2];

1306 
float input1[N];

1307 
float output1[N/2];

1308 
float s, a, err, e, emax;

1309 
int i, k, n;

1310 

1311 
for(i=0;i<N;i++) {

1312 
input[i] = (random() % 65535  32767) * 9 / 10;

1313 
input1[i] = input[i];

1314 
}

1315 

1316 
mdct512(output, input);

1317 

1318 
/* do it by hand */

1319 
for(k=0;k<N/2;k++) {

1320 
s = 0;

1321 
for(n=0;n<N;n++) {

1322 
a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));

1323 
s += input1[n] * cos(a);

1324 
}

1325 
output1[k] = 2 * s / N;

1326 
}

1327 

1328 
err = 0;

1329 
emax = 0;

1330 
for(i=0;i<N/2;i++) {

1331 
printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);

1332 
e = output[i]  output1[i];

1333 
if (e > emax)

1334 
emax = e;

1335 
err += e * e;

1336 
}

1337 
printf("err2=%f emax=%f\n", err / (N/2), emax);

1338 
}

1339 

1340 
void test_ac3(void)

1341 
{

1342 
AC3EncodeContext ctx;

1343 
unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];

1344 
short samples[AC3_FRAME_SIZE];

1345 
int ret, i;

1346 

1347 
AC3_encode_init(&ctx, 44100, 64000, 1);

1348 

1349 
fft_test();

1350 
mdct_test();

1351 

1352 
for(i=0;i<AC3_FRAME_SIZE;i++)

1353 
samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);

1354 
ret = AC3_encode_frame(&ctx, frame, samples);

1355 
printf("ret=%d\n", ret);

1356 
}

1357 
#endif

1358  
1359 
AVCodec ac3_encoder = { 
1360 
"ac3",

1361 
CODEC_TYPE_AUDIO, 
1362 
CODEC_ID_AC3, 
1363 
sizeof(AC3EncodeContext),

1364 
AC3_encode_init, 
1365 
AC3_encode_frame, 
1366 
AC3_encode_close, 
1367 
NULL,

1368 
}; 