ffmpeg / libavcodec / ac3enc.c @ 687671f0
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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.

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*

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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.

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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 
/**

23 
* @file 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" 
30 
#include "bitstream.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 inline int16_t fix15(float a) 
77 
{ 
78 
int v;

79 
v = (int)(a * (float)(1 << 15)); 
80 
if (v < 32767) 
81 
v = 32767;

82 
else if (v > 32767) 
83 
v = 32767;

84 
return v;

85 
} 
86  
87 
typedef struct IComplex { 
88 
short re,im;

89 
} IComplex; 
90  
91 
static void fft_init(int ln) 
92 
{ 
93 
int i, n;

94 
float alpha;

95  
96 
n = 1 << ln;

97  
98 
for(i=0;i<(n/2);i++) { 
99 
alpha = 2 * M_PI * (float)i / (float)n; 
100 
costab[i] = fix15(cos(alpha)); 
101 
sintab[i] = fix15(sin(alpha)); 
102 
} 
103 
} 
104  
105 
/* butter fly op */

106 
#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \

107 
{\ 
108 
int ax, ay, bx, by;\

109 
bx=pre1;\ 
110 
by=pim1;\ 
111 
ax=qre1;\ 
112 
ay=qim1;\ 
113 
pre = (bx + ax) >> 1;\

114 
pim = (by + ay) >> 1;\

115 
qre = (bx  ax) >> 1;\

116 
qim = (by  ay) >> 1;\

117 
} 
118  
119 
#define MUL16(a,b) ((a) * (b))

120  
121 
#define CMUL(pre, pim, are, aim, bre, bim) \

122 
{\ 
123 
pre = (MUL16(are, bre)  MUL16(aim, bim)) >> 15;\

124 
pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\

125 
} 
126  
127  
128 
/* do a 2^n point complex fft on 2^ln points. */

129 
static void fft(IComplex *z, int ln) 
130 
{ 
131 
int j, l, np, np2;

132 
int nblocks, nloops;

133 
register IComplex *p,*q;

134 
int tmp_re, tmp_im;

135  
136 
np = 1 << ln;

137  
138 
/* reverse */

139 
for(j=0;j<np;j++) { 
140 
int k = ff_reverse[j] >> (8  ln); 
141 
if (k < j)

142 
FFSWAP(IComplex, z[k], z[j]); 
143 
} 
144  
145 
/* pass 0 */

146  
147 
p=&z[0];

148 
j=(np >> 1);

149 
do {

150 
BF(p[0].re, p[0].im, p[1].re, p[1].im, 
151 
p[0].re, p[0].im, p[1].re, p[1].im); 
152 
p+=2;

153 
} while (j != 0); 
154  
155 
/* pass 1 */

156  
157 
p=&z[0];

158 
j=np >> 2;

159 
do {

160 
BF(p[0].re, p[0].im, p[2].re, p[2].im, 
161 
p[0].re, p[0].im, p[2].re, p[2].im); 
162 
BF(p[1].re, p[1].im, p[3].re, p[3].im, 
163 
p[1].re, p[1].im, p[3].im, p[3].re); 
164 
p+=4;

165 
} while (j != 0); 
166  
167 
/* pass 2 .. ln1 */

168  
169 
nblocks = np >> 3;

170 
nloops = 1 << 2; 
171 
np2 = np >> 1;

172 
do {

173 
p = z; 
174 
q = z + nloops; 
175 
for (j = 0; j < nblocks; ++j) { 
176  
177 
BF(p>re, p>im, q>re, q>im, 
178 
p>re, p>im, q>re, q>im); 
179  
180 
p++; 
181 
q++; 
182 
for(l = nblocks; l < np2; l += nblocks) {

183 
CMUL(tmp_re, tmp_im, costab[l], sintab[l], q>re, q>im); 
184 
BF(p>re, p>im, q>re, q>im, 
185 
p>re, p>im, tmp_re, tmp_im); 
186 
p++; 
187 
q++; 
188 
} 
189 
p += nloops; 
190 
q += nloops; 
191 
} 
192 
nblocks = nblocks >> 1;

193 
nloops = nloops << 1;

194 
} while (nblocks != 0); 
195 
} 
196  
197 
/* do a 512 point mdct */

198 
static void mdct512(int32_t *out, int16_t *in) 
199 
{ 
200 
int i, re, im, re1, im1;

201 
int16_t rot[N]; 
202 
IComplex x[N/4];

203  
204 
/* shift to simplify computations */

205 
for(i=0;i<N/4;i++) 
206 
rot[i] = in[i + 3*N/4]; 
207 
for(i=N/4;i<N;i++) 
208 
rot[i] = in[i  N/4];

209  
210 
/* pre rotation */

211 
for(i=0;i<N/4;i++) { 
212 
re = ((int)rot[2*i]  (int)rot[N12*i]) >> 1; 
213 
im = ((int)rot[N/2+2*i]  (int)rot[N/212*i]) >> 1; 
214 
CMUL(x[i].re, x[i].im, re, im, xcos1[i], xsin1[i]); 
215 
} 
216  
217 
fft(x, MDCT_NBITS  2);

218  
219 
/* post rotation */

220 
for(i=0;i<N/4;i++) { 
221 
re = x[i].re; 
222 
im = x[i].im; 
223 
CMUL(re1, im1, re, im, xsin1[i], xcos1[i]); 
224 
out[2*i] = im1;

225 
out[N/212*i] = re1; 
226 
} 
227 
} 
228  
229 
/* XXX: use another norm ? */

230 
static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n) 
231 
{ 
232 
int sum, i;

233 
sum = 0;

234 
for(i=0;i<n;i++) { 
235 
sum += abs(exp1[i]  exp2[i]); 
236 
} 
237 
return sum;

238 
} 
239  
240 
static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], 
241 
uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

242 
int ch, int is_lfe) 
243 
{ 
244 
int i, j;

245 
int exp_diff;

246  
247 
/* estimate if the exponent variation & decide if they should be

248 
reused in the next frame */

249 
exp_strategy[0][ch] = EXP_NEW;

250 
for(i=1;i<NB_BLOCKS;i++) { 
251 
exp_diff = calc_exp_diff(exp[i][ch], exp[i1][ch], N/2); 
252 
#ifdef DEBUG

253 
av_log(NULL, AV_LOG_DEBUG, "exp_diff=%d\n", exp_diff); 
254 
#endif

255 
if (exp_diff > EXP_DIFF_THRESHOLD)

256 
exp_strategy[i][ch] = EXP_NEW; 
257 
else

258 
exp_strategy[i][ch] = EXP_REUSE; 
259 
} 
260 
if (is_lfe)

261 
return;

262  
263 
/* now select the encoding strategy type : if exponents are often

264 
recoded, we use a coarse encoding */

265 
i = 0;

266 
while (i < NB_BLOCKS) {

267 
j = i + 1;

268 
while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)

269 
j++; 
270 
switch(j  i) {

271 
case 1: 
272 
exp_strategy[i][ch] = EXP_D45; 
273 
break;

274 
case 2: 
275 
case 3: 
276 
exp_strategy[i][ch] = EXP_D25; 
277 
break;

278 
default:

279 
exp_strategy[i][ch] = EXP_D15; 
280 
break;

281 
} 
282 
i = j; 
283 
} 
284 
} 
285  
286 
/* set exp[i] to min(exp[i], exp1[i]) */

287 
static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n) 
288 
{ 
289 
int i;

290  
291 
for(i=0;i<n;i++) { 
292 
if (exp1[i] < exp[i])

293 
exp[i] = exp1[i]; 
294 
} 
295 
} 
296  
297 
/* update the exponents so that they are the ones the decoder will

298 
decode. Return the number of bits used to code the exponents */

299 
static int encode_exp(uint8_t encoded_exp[N/2], 
300 
uint8_t exp[N/2],

301 
int nb_exps,

302 
int exp_strategy)

303 
{ 
304 
int group_size, nb_groups, i, j, k, exp_min;

305 
uint8_t exp1[N/2];

306  
307 
switch(exp_strategy) {

308 
case EXP_D15:

309 
group_size = 1;

310 
break;

311 
case EXP_D25:

312 
group_size = 2;

313 
break;

314 
default:

315 
case EXP_D45:

316 
group_size = 4;

317 
break;

318 
} 
319 
nb_groups = ((nb_exps + (group_size * 3)  4) / (3 * group_size)) * 3; 
320  
321 
/* for each group, compute the minimum exponent */

322 
exp1[0] = exp[0]; /* DC exponent is handled separately */ 
323 
k = 1;

324 
for(i=1;i<=nb_groups;i++) { 
325 
exp_min = exp[k]; 
326 
assert(exp_min >= 0 && exp_min <= 24); 
327 
for(j=1;j<group_size;j++) { 
328 
if (exp[k+j] < exp_min)

329 
exp_min = exp[k+j]; 
330 
} 
331 
exp1[i] = exp_min; 
332 
k += group_size; 
333 
} 
334  
335 
/* constraint for DC exponent */

336 
if (exp1[0] > 15) 
337 
exp1[0] = 15; 
338  
339 
/* Decrease the delta between each groups to within 2

340 
* so that they can be differentially encoded */

341 
for (i=1;i<=nb_groups;i++) 
342 
exp1[i] = FFMIN(exp1[i], exp1[i1] + 2); 
343 
for (i=nb_groups1;i>=0;i) 
344 
exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2); 
345  
346 
/* now we have the exponent values the decoder will see */

347 
encoded_exp[0] = exp1[0]; 
348 
k = 1;

349 
for(i=1;i<=nb_groups;i++) { 
350 
for(j=0;j<group_size;j++) { 
351 
encoded_exp[k+j] = exp1[i]; 
352 
} 
353 
k += group_size; 
354 
} 
355  
356 
#if defined(DEBUG)

357 
av_log(NULL, AV_LOG_DEBUG, "exponents: strategy=%d\n", exp_strategy); 
358 
for(i=0;i<=nb_groups * group_size;i++) { 
359 
av_log(NULL, AV_LOG_DEBUG, "%d ", encoded_exp[i]); 
360 
} 
361 
av_log(NULL, AV_LOG_DEBUG, "\n"); 
362 
#endif

363  
364 
return 4 + (nb_groups / 3) * 7; 
365 
} 
366  
367 
/* return the size in bits taken by the mantissa */

368 
static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs) 
369 
{ 
370 
int bits, mant, i;

371  
372 
bits = 0;

373 
for(i=0;i<nb_coefs;i++) { 
374 
mant = m[i]; 
375 
switch(mant) {

376 
case 0: 
377 
/* nothing */

378 
break;

379 
case 1: 
380 
/* 3 mantissa in 5 bits */

381 
if (s>mant1_cnt == 0) 
382 
bits += 5;

383 
if (++s>mant1_cnt == 3) 
384 
s>mant1_cnt = 0;

385 
break;

386 
case 2: 
387 
/* 3 mantissa in 7 bits */

388 
if (s>mant2_cnt == 0) 
389 
bits += 7;

390 
if (++s>mant2_cnt == 3) 
391 
s>mant2_cnt = 0;

392 
break;

393 
case 3: 
394 
bits += 3;

395 
break;

396 
case 4: 
397 
/* 2 mantissa in 7 bits */

398 
if (s>mant4_cnt == 0) 
399 
bits += 7;

400 
if (++s>mant4_cnt == 2) 
401 
s>mant4_cnt = 0;

402 
break;

403 
case 14: 
404 
bits += 14;

405 
break;

406 
case 15: 
407 
bits += 16;

408 
break;

409 
default:

410 
bits += mant  1;

411 
break;

412 
} 
413 
} 
414 
return bits;

415 
} 
416  
417  
418 
static void bit_alloc_masking(AC3EncodeContext *s, 
419 
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

420 
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], 
421 
int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

422 
int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50])

423 
{ 
424 
int blk, ch;

425 
int16_t band_psd[NB_BLOCKS][AC3_MAX_CHANNELS][50];

426  
427 
for(blk=0; blk<NB_BLOCKS; blk++) { 
428 
for(ch=0;ch<s>nb_all_channels;ch++) { 
429 
if(exp_strategy[blk][ch] == EXP_REUSE) {

430 
memcpy(psd[blk][ch], psd[blk1][ch], (N/2)*sizeof(int16_t)); 
431 
memcpy(mask[blk][ch], mask[blk1][ch], 50*sizeof(int16_t)); 
432 
} else {

433 
ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,

434 
s>nb_coefs[ch], 
435 
psd[blk][ch], band_psd[blk][ch]); 
436 
ff_ac3_bit_alloc_calc_mask(&s>bit_alloc, band_psd[blk][ch], 
437 
0, s>nb_coefs[ch],

438 
ff_ac3_fast_gain_tab[s>fast_gain_code[ch]], 
439 
ch == s>lfe_channel, 
440 
DBA_NONE, 0, NULL, NULL, NULL, 
441 
mask[blk][ch]); 
442 
} 
443 
} 
444 
} 
445 
} 
446  
447 
static int bit_alloc(AC3EncodeContext *s, 
448 
int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50],

449 
int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

450 
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

451 
int frame_bits, int coarse_snr_offset, int fine_snr_offset) 
452 
{ 
453 
int i, ch;

454 
int snr_offset;

455  
456 
snr_offset = (((coarse_snr_offset  15) << 4) + fine_snr_offset) << 2; 
457  
458 
/* compute size */

459 
for(i=0;i<NB_BLOCKS;i++) { 
460 
s>mant1_cnt = 0;

461 
s>mant2_cnt = 0;

462 
s>mant4_cnt = 0;

463 
for(ch=0;ch<s>nb_all_channels;ch++) { 
464 
ff_ac3_bit_alloc_calc_bap(mask[i][ch], psd[i][ch], 0,

465 
s>nb_coefs[ch], snr_offset, 
466 
s>bit_alloc.floor, ff_ac3_bap_tab, 
467 
bap[i][ch]); 
468 
frame_bits += compute_mantissa_size(s, bap[i][ch], 
469 
s>nb_coefs[ch]); 
470 
} 
471 
} 
472 
#if 0

473 
printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",

474 
coarse_snr_offset, fine_snr_offset, frame_bits,

475 
16 * s>frame_size  ((frame_bits + 7) & ~7));

476 
#endif

477 
return 16 * s>frame_size  frame_bits; 
478 
} 
479  
480 
#define SNR_INC1 4 
481  
482 
static int compute_bit_allocation(AC3EncodeContext *s, 
483 
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

484 
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

485 
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], 
486 
int frame_bits)

487 
{ 
488 
int i, ch;

489 
int coarse_snr_offset, fine_snr_offset;

490 
uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

491 
int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

492 
int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50];

493 
static int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 }; 
494  
495 
/* init default parameters */

496 
s>slow_decay_code = 2;

497 
s>fast_decay_code = 1;

498 
s>slow_gain_code = 1;

499 
s>db_per_bit_code = 2;

500 
s>floor_code = 4;

501 
for(ch=0;ch<s>nb_all_channels;ch++) 
502 
s>fast_gain_code[ch] = 4;

503  
504 
/* compute real values */

505 
s>bit_alloc.sr_code = s>sr_code; 
506 
s>bit_alloc.sr_shift = s>sr_shift; 
507 
s>bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s>slow_decay_code] >> s>sr_shift; 
508 
s>bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s>fast_decay_code] >> s>sr_shift; 
509 
s>bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s>slow_gain_code]; 
510 
s>bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s>db_per_bit_code]; 
511 
s>bit_alloc.floor = ff_ac3_floor_tab[s>floor_code]; 
512  
513 
/* header size */

514 
frame_bits += 65;

515 
// if (s>channel_mode == 2)

516 
// frame_bits += 2;

517 
frame_bits += frame_bits_inc[s>channel_mode]; 
518  
519 
/* audio blocks */

520 
for(i=0;i<NB_BLOCKS;i++) { 
521 
frame_bits += s>nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */ 
522 
if (s>channel_mode == AC3_CHMODE_STEREO) {

523 
frame_bits++; /* rematstr */

524 
if(i==0) frame_bits += 4; 
525 
} 
526 
frame_bits += 2 * s>nb_channels; /* chexpstr[2] * c */ 
527 
if (s>lfe)

528 
frame_bits++; /* lfeexpstr */

529 
for(ch=0;ch<s>nb_channels;ch++) { 
530 
if (exp_strategy[i][ch] != EXP_REUSE)

531 
frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */ 
532 
} 
533 
frame_bits++; /* baie */

534 
frame_bits++; /* snr */

535 
frame_bits += 2; /* delta / skip */ 
536 
} 
537 
frame_bits++; /* cplinu for block 0 */

538 
/* bit alloc info */

539 
/* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */

540 
/* csnroffset[6] */

541 
/* (fsnoffset[4] + fgaincod[4]) * c */

542 
frame_bits += 2*4 + 3 + 6 + s>nb_all_channels * (4 + 3); 
543  
544 
/* auxdatae, crcrsv */

545 
frame_bits += 2;

546  
547 
/* CRC */

548 
frame_bits += 16;

549  
550 
/* calculate psd and masking curve before doing bit allocation */

551 
bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask); 
552  
553 
/* now the big work begins : do the bit allocation. Modify the snr

554 
offset until we can pack everything in the requested frame size */

555  
556 
coarse_snr_offset = s>coarse_snr_offset; 
557 
while (coarse_snr_offset >= 0 && 
558 
bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0) 
559 
coarse_snr_offset = SNR_INC1; 
560 
if (coarse_snr_offset < 0) { 
561 
av_log(NULL, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n"); 
562 
return 1; 
563 
} 
564 
while ((coarse_snr_offset + SNR_INC1) <= 63 && 
565 
bit_alloc(s, mask, psd, bap1, frame_bits, 
566 
coarse_snr_offset + SNR_INC1, 0) >= 0) { 
567 
coarse_snr_offset += SNR_INC1; 
568 
memcpy(bap, bap1, sizeof(bap1));

569 
} 
570 
while ((coarse_snr_offset + 1) <= 63 && 
571 
bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) { 
572 
coarse_snr_offset++; 
573 
memcpy(bap, bap1, sizeof(bap1));

574 
} 
575  
576 
fine_snr_offset = 0;

577 
while ((fine_snr_offset + SNR_INC1) <= 15 && 
578 
bit_alloc(s, mask, psd, bap1, frame_bits, 
579 
coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {

580 
fine_snr_offset += SNR_INC1; 
581 
memcpy(bap, bap1, sizeof(bap1));

582 
} 
583 
while ((fine_snr_offset + 1) <= 15 && 
584 
bit_alloc(s, mask, psd, bap1, frame_bits, 
585 
coarse_snr_offset, fine_snr_offset + 1) >= 0) { 
586 
fine_snr_offset++; 
587 
memcpy(bap, bap1, sizeof(bap1));

588 
} 
589  
590 
s>coarse_snr_offset = coarse_snr_offset; 
591 
for(ch=0;ch<s>nb_all_channels;ch++) 
592 
s>fine_snr_offset[ch] = fine_snr_offset; 
593 
#if defined(DEBUG_BITALLOC)

594 
{ 
595 
int j;

596  
597 
for(i=0;i<6;i++) { 
598 
for(ch=0;ch<s>nb_all_channels;ch++) { 
599 
printf("Block #%d Ch%d:\n", i, ch);

600 
printf("bap=");

601 
for(j=0;j<s>nb_coefs[ch];j++) { 
602 
printf("%d ",bap[i][ch][j]);

603 
} 
604 
printf("\n");

605 
} 
606 
} 
607 
} 
608 
#endif

609 
return 0; 
610 
} 
611  
612 
static av_cold int AC3_encode_init(AVCodecContext *avctx) 
613 
{ 
614 
int freq = avctx>sample_rate;

615 
int bitrate = avctx>bit_rate;

616 
int channels = avctx>channels;

617 
AC3EncodeContext *s = avctx>priv_data; 
618 
int i, j, ch;

619 
float alpha;

620 
int bw_code;

621 
static const uint8_t channel_mode_defs[6] = { 
622 
0x01, /* C */ 
623 
0x02, /* L R */ 
624 
0x03, /* L C R */ 
625 
0x06, /* L R SL SR */ 
626 
0x07, /* L C R SL SR */ 
627 
0x07, /* L C R SL SR (+LFE) */ 
628 
}; 
629  
630 
avctx>frame_size = AC3_FRAME_SIZE; 
631  
632 
ac3_common_init(); 
633  
634 
/* number of channels */

635 
if (channels < 1  channels > 6) 
636 
return 1; 
637 
s>channel_mode = channel_mode_defs[channels  1];

638 
s>lfe = (channels == 6) ? 1 : 0; 
639 
s>nb_all_channels = channels; 
640 
s>nb_channels = channels > 5 ? 5 : channels; 
641 
s>lfe_channel = s>lfe ? 5 : 1; 
642  
643 
/* frequency */

644 
for(i=0;i<3;i++) { 
645 
for(j=0;j<3;j++) 
646 
if ((ff_ac3_sample_rate_tab[j] >> i) == freq)

647 
goto found;

648 
} 
649 
return 1; 
650 
found:

651 
s>sample_rate = freq; 
652 
s>sr_shift = i; 
653 
s>sr_code = j; 
654 
s>bitstream_id = 8 + s>sr_shift;

655 
s>bitstream_mode = 0; /* complete main audio service */ 
656  
657 
/* bitrate & frame size */

658 
for(i=0;i<19;i++) { 
659 
if ((ff_ac3_bitrate_tab[i] >> s>sr_shift)*1000 == bitrate) 
660 
break;

661 
} 
662 
if (i == 19) 
663 
return 1; 
664 
s>bit_rate = bitrate; 
665 
s>frame_size_code = i << 1;

666 
s>frame_size_min = ff_ac3_frame_size_tab[s>frame_size_code][s>sr_code]; 
667 
s>bits_written = 0;

668 
s>samples_written = 0;

669 
s>frame_size = s>frame_size_min; 
670  
671 
/* bit allocation init */

672 
if(avctx>cutoff) {

673 
/* calculate bandwidth based on userspecified cutoff frequency */

674 
int cutoff = av_clip(avctx>cutoff, 1, s>sample_rate >> 1); 
675 
int fbw_coeffs = cutoff * 512 / s>sample_rate; 
676 
bw_code = av_clip((fbw_coeffs  73) / 3, 0, 60); 
677 
} else {

678 
/* use default bandwidth setting */

679 
/* XXX: should compute the bandwidth according to the frame

680 
size, so that we avoid annoying high frequency artifacts */

681 
bw_code = 50;

682 
} 
683 
for(ch=0;ch<s>nb_channels;ch++) { 
684 
/* bandwidth for each channel */

685 
s>chbwcod[ch] = bw_code; 
686 
s>nb_coefs[ch] = bw_code * 3 + 73; 
687 
} 
688 
if (s>lfe) {

689 
s>nb_coefs[s>lfe_channel] = 7; /* fixed */ 
690 
} 
691 
/* initial snr offset */

692 
s>coarse_snr_offset = 40;

693  
694 
/* mdct init */

695 
fft_init(MDCT_NBITS  2);

696 
for(i=0;i<N/4;i++) { 
697 
alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N; 
698 
xcos1[i] = fix15(cos(alpha)); 
699 
xsin1[i] = fix15(sin(alpha)); 
700 
} 
701  
702 
avctx>coded_frame= avcodec_alloc_frame(); 
703 
avctx>coded_frame>key_frame= 1;

704  
705 
return 0; 
706 
} 
707  
708 
/* output the AC3 frame header */

709 
static void output_frame_header(AC3EncodeContext *s, unsigned char *frame) 
710 
{ 
711 
init_put_bits(&s>pb, frame, AC3_MAX_CODED_FRAME_SIZE); 
712  
713 
put_bits(&s>pb, 16, 0x0b77); /* frame header */ 
714 
put_bits(&s>pb, 16, 0); /* crc1: will be filled later */ 
715 
put_bits(&s>pb, 2, s>sr_code);

716 
put_bits(&s>pb, 6, s>frame_size_code + (s>frame_size  s>frame_size_min));

717 
put_bits(&s>pb, 5, s>bitstream_id);

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

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

720 
if ((s>channel_mode & 0x01) && s>channel_mode != AC3_CHMODE_MONO) 
721 
put_bits(&s>pb, 2, 1); /* XXX 4.5 dB */ 
722 
if (s>channel_mode & 0x04) 
723 
put_bits(&s>pb, 2, 1); /* XXX 6 dB */ 
724 
if (s>channel_mode == AC3_CHMODE_STEREO)

725 
put_bits(&s>pb, 2, 0); /* surround not indicated */ 
726 
put_bits(&s>pb, 1, s>lfe); /* LFE */ 
727 
put_bits(&s>pb, 5, 31); /* dialog norm: 31 db */ 
728 
put_bits(&s>pb, 1, 0); /* no compression control word */ 
729 
put_bits(&s>pb, 1, 0); /* no lang code */ 
730 
put_bits(&s>pb, 1, 0); /* no audio production info */ 
731 
put_bits(&s>pb, 1, 0); /* no copyright */ 
732 
put_bits(&s>pb, 1, 1); /* original bitstream */ 
733 
put_bits(&s>pb, 1, 0); /* no time code 1 */ 
734 
put_bits(&s>pb, 1, 0); /* no time code 2 */ 
735 
put_bits(&s>pb, 1, 0); /* no additional bit stream info */ 
736 
} 
737  
738 
/* symetric quantization on 'levels' levels */

739 
static inline int sym_quant(int c, int e, int levels) 
740 
{ 
741 
int v;

742  
743 
if (c >= 0) { 
744 
v = (levels * (c << e)) >> 24;

745 
v = (v + 1) >> 1; 
746 
v = (levels >> 1) + v;

747 
} else {

748 
v = (levels * ((c) << e)) >> 24;

749 
v = (v + 1) >> 1; 
750 
v = (levels >> 1)  v;

751 
} 
752 
assert (v >= 0 && v < levels);

753 
return v;

754 
} 
755  
756 
/* asymetric quantization on 2^qbits levels */

757 
static inline int asym_quant(int c, int e, int qbits) 
758 
{ 
759 
int lshift, m, v;

760  
761 
lshift = e + qbits  24;

762 
if (lshift >= 0) 
763 
v = c << lshift; 
764 
else

765 
v = c >> (lshift); 
766 
/* rounding */

767 
v = (v + 1) >> 1; 
768 
m = (1 << (qbits1)); 
769 
if (v >= m)

770 
v = m  1;

771 
assert(v >= m); 
772 
return v & ((1 << qbits)1); 
773 
} 
774  
775 
/* Output one audio block. There are NB_BLOCKS audio blocks in one AC3

776 
frame */

777 
static void output_audio_block(AC3EncodeContext *s, 
778 
uint8_t exp_strategy[AC3_MAX_CHANNELS], 
779 
uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],

780 
uint8_t bap[AC3_MAX_CHANNELS][N/2],

781 
int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],

782 
int8_t global_exp[AC3_MAX_CHANNELS], 
783 
int block_num)

784 
{ 
785 
int ch, nb_groups, group_size, i, baie, rbnd;

786 
uint8_t *p; 
787 
uint16_t qmant[AC3_MAX_CHANNELS][N/2];

788 
int exp0, exp1;

789 
int mant1_cnt, mant2_cnt, mant4_cnt;

790 
uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; 
791 
int delta0, delta1, delta2;

792  
793 
for(ch=0;ch<s>nb_channels;ch++) 
794 
put_bits(&s>pb, 1, 0); /* 512 point MDCT */ 
795 
for(ch=0;ch<s>nb_channels;ch++) 
796 
put_bits(&s>pb, 1, 1); /* no dither */ 
797 
put_bits(&s>pb, 1, 0); /* no dynamic range */ 
798 
if (block_num == 0) { 
799 
/* for block 0, even if no coupling, we must say it. This is a

800 
waste of bit :) */

801 
put_bits(&s>pb, 1, 1); /* coupling strategy present */ 
802 
put_bits(&s>pb, 1, 0); /* no coupling strategy */ 
803 
} else {

804 
put_bits(&s>pb, 1, 0); /* no new coupling strategy */ 
805 
} 
806  
807 
if (s>channel_mode == AC3_CHMODE_STEREO)

808 
{ 
809 
if(block_num==0) 
810 
{ 
811 
/* first block must define rematrixing (rematstr) */

812 
put_bits(&s>pb, 1, 1); 
813  
814 
/* dummy rematrixing rematflg(1:4)=0 */

815 
for (rbnd=0;rbnd<4;rbnd++) 
816 
put_bits(&s>pb, 1, 0); 
817 
} 
818 
else

819 
{ 
820 
/* no matrixing (but should be used in the future) */

821 
put_bits(&s>pb, 1, 0); 
822 
} 
823 
} 
824  
825 
#if defined(DEBUG)

826 
{ 
827 
static int count = 0; 
828 
av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++); 
829 
} 
830 
#endif

831 
/* exponent strategy */

832 
for(ch=0;ch<s>nb_channels;ch++) { 
833 
put_bits(&s>pb, 2, exp_strategy[ch]);

834 
} 
835  
836 
if (s>lfe) {

837 
put_bits(&s>pb, 1, exp_strategy[s>lfe_channel]);

838 
} 
839  
840 
for(ch=0;ch<s>nb_channels;ch++) { 
841 
if (exp_strategy[ch] != EXP_REUSE)

842 
put_bits(&s>pb, 6, s>chbwcod[ch]);

843 
} 
844  
845 
/* exponents */

846 
for (ch = 0; ch < s>nb_all_channels; ch++) { 
847 
switch(exp_strategy[ch]) {

848 
case EXP_REUSE:

849 
continue;

850 
case EXP_D15:

851 
group_size = 1;

852 
break;

853 
case EXP_D25:

854 
group_size = 2;

855 
break;

856 
default:

857 
case EXP_D45:

858 
group_size = 4;

859 
break;

860 
} 
861 
nb_groups = (s>nb_coefs[ch] + (group_size * 3)  4) / (3 * group_size); 
862 
p = encoded_exp[ch]; 
863  
864 
/* first exponent */

865 
exp1 = *p++; 
866 
put_bits(&s>pb, 4, exp1);

867  
868 
/* next ones are delta encoded */

869 
for(i=0;i<nb_groups;i++) { 
870 
/* merge three delta in one code */

871 
exp0 = exp1; 
872 
exp1 = p[0];

873 
p += group_size; 
874 
delta0 = exp1  exp0 + 2;

875  
876 
exp0 = exp1; 
877 
exp1 = p[0];

878 
p += group_size; 
879 
delta1 = exp1  exp0 + 2;

880  
881 
exp0 = exp1; 
882 
exp1 = p[0];

883 
p += group_size; 
884 
delta2 = exp1  exp0 + 2;

885  
886 
put_bits(&s>pb, 7, ((delta0 * 5 + delta1) * 5) + delta2); 
887 
} 
888  
889 
if (ch != s>lfe_channel)

890 
put_bits(&s>pb, 2, 0); /* no gain range info */ 
891 
} 
892  
893 
/* bit allocation info */

894 
baie = (block_num == 0);

895 
put_bits(&s>pb, 1, baie);

896 
if (baie) {

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

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

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

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

901 
put_bits(&s>pb, 3, s>floor_code);

902 
} 
903  
904 
/* snr offset */

905 
put_bits(&s>pb, 1, baie); /* always present with bai */ 
906 
if (baie) {

907 
put_bits(&s>pb, 6, s>coarse_snr_offset);

908 
for(ch=0;ch<s>nb_all_channels;ch++) { 
909 
put_bits(&s>pb, 4, s>fine_snr_offset[ch]);

910 
put_bits(&s>pb, 3, s>fast_gain_code[ch]);

911 
} 
912 
} 
913  
914 
put_bits(&s>pb, 1, 0); /* no delta bit allocation */ 
915 
put_bits(&s>pb, 1, 0); /* no data to skip */ 
916  
917 
/* mantissa encoding : we use two passes to handle the grouping. A

918 
one pass method may be faster, but it would necessitate to

919 
modify the output stream. */

920  
921 
/* first pass: quantize */

922 
mant1_cnt = mant2_cnt = mant4_cnt = 0;

923 
qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;

924  
925 
for (ch = 0; ch < s>nb_all_channels; ch++) { 
926 
int b, c, e, v;

927  
928 
for(i=0;i<s>nb_coefs[ch];i++) { 
929 
c = mdct_coefs[ch][i]; 
930 
e = encoded_exp[ch][i]  global_exp[ch]; 
931 
b = bap[ch][i]; 
932 
switch(b) {

933 
case 0: 
934 
v = 0;

935 
break;

936 
case 1: 
937 
v = sym_quant(c, e, 3);

938 
switch(mant1_cnt) {

939 
case 0: 
940 
qmant1_ptr = &qmant[ch][i]; 
941 
v = 9 * v;

942 
mant1_cnt = 1;

943 
break;

944 
case 1: 
945 
*qmant1_ptr += 3 * v;

946 
mant1_cnt = 2;

947 
v = 128;

948 
break;

949 
default:

950 
*qmant1_ptr += v; 
951 
mant1_cnt = 0;

952 
v = 128;

953 
break;

954 
} 
955 
break;

956 
case 2: 
957 
v = sym_quant(c, e, 5);

958 
switch(mant2_cnt) {

959 
case 0: 
960 
qmant2_ptr = &qmant[ch][i]; 
961 
v = 25 * v;

962 
mant2_cnt = 1;

963 
break;

964 
case 1: 
965 
*qmant2_ptr += 5 * v;

966 
mant2_cnt = 2;

967 
v = 128;

968 
break;

969 
default:

970 
*qmant2_ptr += v; 
971 
mant2_cnt = 0;

972 
v = 128;

973 
break;

974 
} 
975 
break;

976 
case 3: 
977 
v = sym_quant(c, e, 7);

978 
break;

979 
case 4: 
980 
v = sym_quant(c, e, 11);

981 
switch(mant4_cnt) {

982 
case 0: 
983 
qmant4_ptr = &qmant[ch][i]; 
984 
v = 11 * v;

985 
mant4_cnt = 1;

986 
break;

987 
default:

988 
*qmant4_ptr += v; 
989 
mant4_cnt = 0;

990 
v = 128;

991 
break;

992 
} 
993 
break;

994 
case 5: 
995 
v = sym_quant(c, e, 15);

996 
break;

997 
case 14: 
998 
v = asym_quant(c, e, 14);

999 
break;

1000 
case 15: 
1001 
v = asym_quant(c, e, 16);

1002 
break;

1003 
default:

1004 
v = asym_quant(c, e, b  1);

1005 
break;

1006 
} 
1007 
qmant[ch][i] = v; 
1008 
} 
1009 
} 
1010  
1011 
/* second pass : output the values */

1012 
for (ch = 0; ch < s>nb_all_channels; ch++) { 
1013 
int b, q;

1014  
1015 
for(i=0;i<s>nb_coefs[ch];i++) { 
1016 
q = qmant[ch][i]; 
1017 
b = bap[ch][i]; 
1018 
switch(b) {

1019 
case 0: 
1020 
break;

1021 
case 1: 
1022 
if (q != 128) 
1023 
put_bits(&s>pb, 5, q);

1024 
break;

1025 
case 2: 
1026 
if (q != 128) 
1027 
put_bits(&s>pb, 7, q);

1028 
break;

1029 
case 3: 
1030 
put_bits(&s>pb, 3, q);

1031 
break;

1032 
case 4: 
1033 
if (q != 128) 
1034 
put_bits(&s>pb, 7, q);

1035 
break;

1036 
case 14: 
1037 
put_bits(&s>pb, 14, q);

1038 
break;

1039 
case 15: 
1040 
put_bits(&s>pb, 16, q);

1041 
break;

1042 
default:

1043 
put_bits(&s>pb, b  1, q);

1044 
break;

1045 
} 
1046 
} 
1047 
} 
1048 
} 
1049  
1050 
#define CRC16_POLY ((1 << 0)  (1 << 2)  (1 << 15)  (1 << 16)) 
1051  
1052 
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly) 
1053 
{ 
1054 
unsigned int c; 
1055  
1056 
c = 0;

1057 
while (a) {

1058 
if (a & 1) 
1059 
c ^= b; 
1060 
a = a >> 1;

1061 
b = b << 1;

1062 
if (b & (1 << 16)) 
1063 
b ^= poly; 
1064 
} 
1065 
return c;

1066 
} 
1067  
1068 
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly) 
1069 
{ 
1070 
unsigned int r; 
1071 
r = 1;

1072 
while (n) {

1073 
if (n & 1) 
1074 
r = mul_poly(r, a, poly); 
1075 
a = mul_poly(a, a, poly); 
1076 
n >>= 1;

1077 
} 
1078 
return r;

1079 
} 
1080  
1081  
1082 
/* compute log2(max(abs(tab[]))) */

1083 
static int log2_tab(int16_t *tab, int n) 
1084 
{ 
1085 
int i, v;

1086  
1087 
v = 0;

1088 
for(i=0;i<n;i++) { 
1089 
v = abs(tab[i]); 
1090 
} 
1091 
return av_log2(v);

1092 
} 
1093  
1094 
static void lshift_tab(int16_t *tab, int n, int lshift) 
1095 
{ 
1096 
int i;

1097  
1098 
if (lshift > 0) { 
1099 
for(i=0;i<n;i++) { 
1100 
tab[i] <<= lshift; 
1101 
} 
1102 
} else if (lshift < 0) { 
1103 
lshift = lshift; 
1104 
for(i=0;i<n;i++) { 
1105 
tab[i] >>= lshift; 
1106 
} 
1107 
} 
1108 
} 
1109  
1110 
/* fill the end of the frame and compute the two crcs */

1111 
static int output_frame_end(AC3EncodeContext *s) 
1112 
{ 
1113 
int frame_size, frame_size_58, n, crc1, crc2, crc_inv;

1114 
uint8_t *frame; 
1115  
1116 
frame_size = s>frame_size; /* frame size in words */

1117 
/* align to 8 bits */

1118 
flush_put_bits(&s>pb); 
1119 
/* add zero bytes to reach the frame size */

1120 
frame = s>pb.buf; 
1121 
n = 2 * s>frame_size  (pbBufPtr(&s>pb)  frame)  2; 
1122 
assert(n >= 0);

1123 
if(n>0) 
1124 
memset(pbBufPtr(&s>pb), 0, n);

1125  
1126 
/* Now we must compute both crcs : this is not so easy for crc1

1127 
because it is at the beginning of the data... */

1128 
frame_size_58 = (frame_size >> 1) + (frame_size >> 3); 
1129 
crc1 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,

1130 
frame + 4, 2 * frame_size_58  4)); 
1131 
/* XXX: could precompute crc_inv */

1132 
crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58)  16, CRC16_POLY); 
1133 
crc1 = mul_poly(crc_inv, crc1, CRC16_POLY); 
1134 
AV_WB16(frame+2,crc1);

1135  
1136 
crc2 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,

1137 
frame + 2 * frame_size_58,

1138 
(frame_size  frame_size_58) * 2  2)); 
1139 
AV_WB16(frame+2*frame_size2,crc2); 
1140  
1141 
// printf("n=%d frame_size=%d\n", n, frame_size);

1142 
return frame_size * 2; 
1143 
} 
1144  
1145 
static int AC3_encode_frame(AVCodecContext *avctx, 
1146 
unsigned char *frame, int buf_size, void *data) 
1147 
{ 
1148 
AC3EncodeContext *s = avctx>priv_data; 
1149 
int16_t *samples = data; 
1150 
int i, j, k, v, ch;

1151 
int16_t input_samples[N]; 
1152 
int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1153 
uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1154 
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS]; 
1155 
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1156 
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1157 
int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS]; 
1158 
int frame_bits;

1159  
1160 
frame_bits = 0;

1161 
for(ch=0;ch<s>nb_all_channels;ch++) { 
1162 
/* fixed mdct to the six sub blocks & exponent computation */

1163 
for(i=0;i<NB_BLOCKS;i++) { 
1164 
int16_t *sptr; 
1165 
int sinc;

1166  
1167 
/* compute input samples */

1168 
memcpy(input_samples, s>last_samples[ch], N/2 * sizeof(int16_t)); 
1169 
sinc = s>nb_all_channels; 
1170 
sptr = samples + (sinc * (N/2) * i) + ch;

1171 
for(j=0;j<N/2;j++) { 
1172 
v = *sptr; 
1173 
input_samples[j + N/2] = v;

1174 
s>last_samples[ch][j] = v; 
1175 
sptr += sinc; 
1176 
} 
1177  
1178 
/* apply the MDCT window */

1179 
for(j=0;j<N/2;j++) { 
1180 
input_samples[j] = MUL16(input_samples[j], 
1181 
ff_ac3_window[j]) >> 15;

1182 
input_samples[Nj1] = MUL16(input_samples[Nj1], 
1183 
ff_ac3_window[j]) >> 15;

1184 
} 
1185  
1186 
/* Normalize the samples to use the maximum available

1187 
precision */

1188 
v = 14  log2_tab(input_samples, N);

1189 
if (v < 0) 
1190 
v = 0;

1191 
exp_samples[i][ch] = v  9;

1192 
lshift_tab(input_samples, N, v); 
1193  
1194 
/* do the MDCT */

1195 
mdct512(mdct_coef[i][ch], input_samples); 
1196  
1197 
/* compute "exponents". We take into account the

1198 
normalization there */

1199 
for(j=0;j<N/2;j++) { 
1200 
int e;

1201 
v = abs(mdct_coef[i][ch][j]); 
1202 
if (v == 0) 
1203 
e = 24;

1204 
else {

1205 
e = 23  av_log2(v) + exp_samples[i][ch];

1206 
if (e >= 24) { 
1207 
e = 24;

1208 
mdct_coef[i][ch][j] = 0;

1209 
} 
1210 
} 
1211 
exp[i][ch][j] = e; 
1212 
} 
1213 
} 
1214  
1215 
compute_exp_strategy(exp_strategy, exp, ch, ch == s>lfe_channel); 
1216  
1217 
/* compute the exponents as the decoder will see them. The

1218 
EXP_REUSE case must be handled carefully : we select the

1219 
min of the exponents */

1220 
i = 0;

1221 
while (i < NB_BLOCKS) {

1222 
j = i + 1;

1223 
while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {

1224 
exponent_min(exp[i][ch], exp[j][ch], s>nb_coefs[ch]); 
1225 
j++; 
1226 
} 
1227 
frame_bits += encode_exp(encoded_exp[i][ch], 
1228 
exp[i][ch], s>nb_coefs[ch], 
1229 
exp_strategy[i][ch]); 
1230 
/* copy encoded exponents for reuse case */

1231 
for(k=i+1;k<j;k++) { 
1232 
memcpy(encoded_exp[k][ch], encoded_exp[i][ch], 
1233 
s>nb_coefs[ch] * sizeof(uint8_t));

1234 
} 
1235 
i = j; 
1236 
} 
1237 
} 
1238  
1239 
/* adjust for fractional frame sizes */

1240 
while(s>bits_written >= s>bit_rate && s>samples_written >= s>sample_rate) {

1241 
s>bits_written = s>bit_rate; 
1242 
s>samples_written = s>sample_rate; 
1243 
} 
1244 
s>frame_size = s>frame_size_min + (s>bits_written * s>sample_rate < s>samples_written * s>bit_rate); 
1245 
s>bits_written += s>frame_size * 16;

1246 
s>samples_written += AC3_FRAME_SIZE; 
1247  
1248 
compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits); 
1249 
/* everything is known... let's output the frame */

1250 
output_frame_header(s, frame); 
1251  
1252 
for(i=0;i<NB_BLOCKS;i++) { 
1253 
output_audio_block(s, exp_strategy[i], encoded_exp[i], 
1254 
bap[i], mdct_coef[i], exp_samples[i], i); 
1255 
} 
1256 
return output_frame_end(s);

1257 
} 
1258  
1259 
static av_cold int AC3_encode_close(AVCodecContext *avctx) 
1260 
{ 
1261 
av_freep(&avctx>coded_frame); 
1262 
return 0; 
1263 
} 
1264  
1265 
#if 0

1266 
/*************************************************************************/

1267 
/* TEST */

1268 

1269 
#undef random

1270 
#define FN (N/4)

1271 

1272 
void fft_test(void)

1273 
{

1274 
IComplex in[FN], in1[FN];

1275 
int k, n, i;

1276 
float sum_re, sum_im, a;

1277 

1278 
/* FFT test */

1279 

1280 
for(i=0;i<FN;i++) {

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

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

1283 
in1[i] = in[i];

1284 
}

1285 
fft(in, 7);

1286 

1287 
/* do it by hand */

1288 
for(k=0;k<FN;k++) {

1289 
sum_re = 0;

1290 
sum_im = 0;

1291 
for(n=0;n<FN;n++) {

1292 
a = 2 * M_PI * (n * k) / FN;

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

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

1295 
}

1296 
printf("%3d: %6d,%6d %6.0f,%6.0f\n",

1297 
k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);

1298 
}

1299 
}

1300 

1301 
void mdct_test(void)

1302 
{

1303 
int16_t input[N];

1304 
int32_t output[N/2];

1305 
float input1[N];

1306 
float output1[N/2];

1307 
float s, a, err, e, emax;

1308 
int i, k, n;

1309 

1310 
for(i=0;i<N;i++) {

1311 
input[i] = (random() % 65535  32767) * 9 / 10;

1312 
input1[i] = input[i];

1313 
}

1314 

1315 
mdct512(output, input);

1316 

1317 
/* do it by hand */

1318 
for(k=0;k<N/2;k++) {

1319 
s = 0;

1320 
for(n=0;n<N;n++) {

1321 
a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));

1322 
s += input1[n] * cos(a);

1323 
}

1324 
output1[k] = 2 * s / N;

1325 
}

1326 

1327 
err = 0;

1328 
emax = 0;

1329 
for(i=0;i<N/2;i++) {

1330 
printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);

1331 
e = output[i]  output1[i];

1332 
if (e > emax)

1333 
emax = e;

1334 
err += e * e;

1335 
}

1336 
printf("err2=%f emax=%f\n", err / (N/2), emax);

1337 
}

1338 

1339 
void test_ac3(void)

1340 
{

1341 
AC3EncodeContext ctx;

1342 
unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];

1343 
short samples[AC3_FRAME_SIZE];

1344 
int ret, i;

1345 

1346 
AC3_encode_init(&ctx, 44100, 64000, 1);

1347 

1348 
fft_test();

1349 
mdct_test();

1350 

1351 
for(i=0;i<AC3_FRAME_SIZE;i++)

1352 
samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);

1353 
ret = AC3_encode_frame(&ctx, frame, samples);

1354 
printf("ret=%d\n", ret);

1355 
}

1356 
#endif

1357  
1358 
AVCodec ac3_encoder = { 
1359 
"ac3",

1360 
CODEC_TYPE_AUDIO, 
1361 
CODEC_ID_AC3, 
1362 
sizeof(AC3EncodeContext),

1363 
AC3_encode_init, 
1364 
AC3_encode_frame, 
1365 
AC3_encode_close, 
1366 
NULL,

1367 
.long_name = "ATSC A/52 / AC3",

1368 
}; 