ffmpeg / libavcodec / ac3enc.c @ 2be209b2
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/*


2 
* The simplest AC3 encoder

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* Copyright (c) 2000 Fabrice Bellard

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*

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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

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* 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 
/**

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* @file

24 
* The simplest AC3 encoder.

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*/

26 
//#define DEBUG

27 
//#define DEBUG_BITALLOC

28 
#include "libavcore/audioconvert.h" 
29 
#include "libavutil/crc.h" 
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#include "avcodec.h" 
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#include "libavutil/common.h" /* for av_reverse */ 
32 
#include "put_bits.h" 
33 
#include "ac3.h" 
34 
#include "audioconvert.h" 
35  
36 
typedef struct AC3EncodeContext { 
37 
PutBitContext pb; 
38  
39 
int bitstream_id;

40 
int bitstream_mode;

41  
42 
int bit_rate;

43 
int sample_rate;

44 
int sr_shift;

45 
int sr_code; /* frequency */ 
46  
47 
int frame_size_min; /* minimum frame size in case rounding is necessary */ 
48 
int frame_size; /* current frame size in words */ 
49 
int frame_size_code;

50 
int bits_written;

51 
int samples_written;

52  
53 
int nb_all_channels;

54 
int nb_channels;

55 
int lfe;

56 
int lfe_channel;

57 
int channel_mode;

58 
const uint8_t *channel_map;

59  
60 
int chbwcod[AC3_MAX_CHANNELS];

61 
int nb_coefs[AC3_MAX_CHANNELS];

62  
63 
/* bitrate allocation control */

64 
int slow_gain_code, slow_decay_code, fast_decay_code, db_per_bit_code, floor_code;

65 
AC3BitAllocParameters bit_alloc; 
66 
int coarse_snr_offset;

67 
int fast_gain_code[AC3_MAX_CHANNELS];

68 
int fine_snr_offset[AC3_MAX_CHANNELS];

69  
70 
/* mantissa encoding */

71 
int mant1_cnt, mant2_cnt, mant4_cnt;

72  
73 
short last_samples[AC3_MAX_CHANNELS][256]; 
74 
} AC3EncodeContext; 
75  
76 
static int16_t costab[64]; 
77 
static int16_t sintab[64]; 
78 
static int16_t xcos1[128]; 
79 
static int16_t xsin1[128]; 
80  
81 
#define MDCT_NBITS 9 
82 
#define N (1 << MDCT_NBITS) 
83  
84 
/* new exponents are sent if their Norm 1 exceed this number */

85 
#define EXP_DIFF_THRESHOLD 1000 
86  
87 
static inline int16_t fix15(float a) 
88 
{ 
89 
int v;

90 
v = (int)(a * (float)(1 << 15)); 
91 
if (v < 32767) 
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v = 32767;

93 
else if (v > 32767) 
94 
v = 32767;

95 
return v;

96 
} 
97  
98 
typedef struct IComplex { 
99 
short re,im;

100 
} IComplex; 
101  
102 
static av_cold void fft_init(int ln) 
103 
{ 
104 
int i, n;

105 
float alpha;

106  
107 
n = 1 << ln;

108  
109 
for(i=0;i<(n/2);i++) { 
110 
alpha = 2 * M_PI * (float)i / (float)n; 
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costab[i] = fix15(cos(alpha)); 
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sintab[i] = fix15(sin(alpha)); 
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} 
114 
} 
115  
116 
/* butter fly op */

117 
#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \

118 
{\ 
119 
int ax, ay, bx, by;\

120 
bx=pre1;\ 
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by=pim1;\ 
122 
ax=qre1;\ 
123 
ay=qim1;\ 
124 
pre = (bx + ax) >> 1;\

125 
pim = (by + ay) >> 1;\

126 
qre = (bx  ax) >> 1;\

127 
qim = (by  ay) >> 1;\

128 
} 
129  
130 
#define CMUL(pre, pim, are, aim, bre, bim) \

131 
{\ 
132 
pre = (MUL16(are, bre)  MUL16(aim, bim)) >> 15;\

133 
pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\

134 
} 
135  
136  
137 
/* do a 2^n point complex fft on 2^ln points. */

138 
static void fft(IComplex *z, int ln) 
139 
{ 
140 
int j, l, np, np2;

141 
int nblocks, nloops;

142 
register IComplex *p,*q;

143 
int tmp_re, tmp_im;

144  
145 
np = 1 << ln;

146  
147 
/* reverse */

148 
for(j=0;j<np;j++) { 
149 
int k = av_reverse[j] >> (8  ln); 
150 
if (k < j)

151 
FFSWAP(IComplex, z[k], z[j]); 
152 
} 
153  
154 
/* pass 0 */

155  
156 
p=&z[0];

157 
j=(np >> 1);

158 
do {

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

162 
} while (j != 0); 
163  
164 
/* pass 1 */

165  
166 
p=&z[0];

167 
j=np >> 2;

168 
do {

169 
BF(p[0].re, p[0].im, p[2].re, p[2].im, 
170 
p[0].re, p[0].im, p[2].re, p[2].im); 
171 
BF(p[1].re, p[1].im, p[3].re, p[3].im, 
172 
p[1].re, p[1].im, p[3].im, p[3].re); 
173 
p+=4;

174 
} while (j != 0); 
175  
176 
/* pass 2 .. ln1 */

177  
178 
nblocks = np >> 3;

179 
nloops = 1 << 2; 
180 
np2 = np >> 1;

181 
do {

182 
p = z; 
183 
q = z + nloops; 
184 
for (j = 0; j < nblocks; ++j) { 
185  
186 
BF(p>re, p>im, q>re, q>im, 
187 
p>re, p>im, q>re, q>im); 
188  
189 
p++; 
190 
q++; 
191 
for(l = nblocks; l < np2; l += nblocks) {

192 
CMUL(tmp_re, tmp_im, costab[l], sintab[l], q>re, q>im); 
193 
BF(p>re, p>im, q>re, q>im, 
194 
p>re, p>im, tmp_re, tmp_im); 
195 
p++; 
196 
q++; 
197 
} 
198 
p += nloops; 
199 
q += nloops; 
200 
} 
201 
nblocks = nblocks >> 1;

202 
nloops = nloops << 1;

203 
} while (nblocks != 0); 
204 
} 
205  
206 
/* do a 512 point mdct */

207 
static void mdct512(int32_t *out, int16_t *in) 
208 
{ 
209 
int i, re, im, re1, im1;

210 
int16_t rot[N]; 
211 
IComplex x[N/4];

212  
213 
/* shift to simplify computations */

214 
for(i=0;i<N/4;i++) 
215 
rot[i] = in[i + 3*N/4]; 
216 
for(i=N/4;i<N;i++) 
217 
rot[i] = in[i  N/4];

218  
219 
/* pre rotation */

220 
for(i=0;i<N/4;i++) { 
221 
re = ((int)rot[2*i]  (int)rot[N12*i]) >> 1; 
222 
im = ((int)rot[N/2+2*i]  (int)rot[N/212*i]) >> 1; 
223 
CMUL(x[i].re, x[i].im, re, im, xcos1[i], xsin1[i]); 
224 
} 
225  
226 
fft(x, MDCT_NBITS  2);

227  
228 
/* post rotation */

229 
for(i=0;i<N/4;i++) { 
230 
re = x[i].re; 
231 
im = x[i].im; 
232 
CMUL(re1, im1, re, im, xsin1[i], xcos1[i]); 
233 
out[2*i] = im1;

234 
out[N/212*i] = re1; 
235 
} 
236 
} 
237  
238 
/* XXX: use another norm ? */

239 
static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n) 
240 
{ 
241 
int sum, i;

242 
sum = 0;

243 
for(i=0;i<n;i++) { 
244 
sum += abs(exp1[i]  exp2[i]); 
245 
} 
246 
return sum;

247 
} 
248  
249 
static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], 
250 
uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

251 
int ch, int is_lfe) 
252 
{ 
253 
int i, j;

254 
int exp_diff;

255  
256 
/* estimate if the exponent variation & decide if they should be

257 
reused in the next frame */

258 
exp_strategy[0][ch] = EXP_NEW;

259 
for(i=1;i<NB_BLOCKS;i++) { 
260 
exp_diff = calc_exp_diff(exp[i][ch], exp[i1][ch], N/2); 
261 
dprintf(NULL, "exp_diff=%d\n", exp_diff); 
262 
if (exp_diff > EXP_DIFF_THRESHOLD)

263 
exp_strategy[i][ch] = EXP_NEW; 
264 
else

265 
exp_strategy[i][ch] = EXP_REUSE; 
266 
} 
267 
if (is_lfe)

268 
return;

269  
270 
/* now select the encoding strategy type : if exponents are often

271 
recoded, we use a coarse encoding */

272 
i = 0;

273 
while (i < NB_BLOCKS) {

274 
j = i + 1;

275 
while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)

276 
j++; 
277 
switch(j  i) {

278 
case 1: 
279 
exp_strategy[i][ch] = EXP_D45; 
280 
break;

281 
case 2: 
282 
case 3: 
283 
exp_strategy[i][ch] = EXP_D25; 
284 
break;

285 
default:

286 
exp_strategy[i][ch] = EXP_D15; 
287 
break;

288 
} 
289 
i = j; 
290 
} 
291 
} 
292  
293 
/* set exp[i] to min(exp[i], exp1[i]) */

294 
static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n) 
295 
{ 
296 
int i;

297  
298 
for(i=0;i<n;i++) { 
299 
if (exp1[i] < exp[i])

300 
exp[i] = exp1[i]; 
301 
} 
302 
} 
303  
304 
/* update the exponents so that they are the ones the decoder will

305 
decode. Return the number of bits used to code the exponents */

306 
static int encode_exp(uint8_t encoded_exp[N/2], 
307 
uint8_t exp[N/2],

308 
int nb_exps,

309 
int exp_strategy)

310 
{ 
311 
int group_size, nb_groups, i, j, k, exp_min;

312 
uint8_t exp1[N/2];

313  
314 
switch(exp_strategy) {

315 
case EXP_D15:

316 
group_size = 1;

317 
break;

318 
case EXP_D25:

319 
group_size = 2;

320 
break;

321 
default:

322 
case EXP_D45:

323 
group_size = 4;

324 
break;

325 
} 
326 
nb_groups = ((nb_exps + (group_size * 3)  4) / (3 * group_size)) * 3; 
327  
328 
/* for each group, compute the minimum exponent */

329 
exp1[0] = exp[0]; /* DC exponent is handled separately */ 
330 
k = 1;

331 
for(i=1;i<=nb_groups;i++) { 
332 
exp_min = exp[k]; 
333 
assert(exp_min >= 0 && exp_min <= 24); 
334 
for(j=1;j<group_size;j++) { 
335 
if (exp[k+j] < exp_min)

336 
exp_min = exp[k+j]; 
337 
} 
338 
exp1[i] = exp_min; 
339 
k += group_size; 
340 
} 
341  
342 
/* constraint for DC exponent */

343 
if (exp1[0] > 15) 
344 
exp1[0] = 15; 
345  
346 
/* Decrease the delta between each groups to within 2

347 
* so that they can be differentially encoded */

348 
for (i=1;i<=nb_groups;i++) 
349 
exp1[i] = FFMIN(exp1[i], exp1[i1] + 2); 
350 
for (i=nb_groups1;i>=0;i) 
351 
exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2); 
352  
353 
/* now we have the exponent values the decoder will see */

354 
encoded_exp[0] = exp1[0]; 
355 
k = 1;

356 
for(i=1;i<=nb_groups;i++) { 
357 
for(j=0;j<group_size;j++) { 
358 
encoded_exp[k+j] = exp1[i]; 
359 
} 
360 
k += group_size; 
361 
} 
362  
363 
#if defined(DEBUG)

364 
av_log(NULL, AV_LOG_DEBUG, "exponents: strategy=%d\n", exp_strategy); 
365 
for(i=0;i<=nb_groups * group_size;i++) { 
366 
av_log(NULL, AV_LOG_DEBUG, "%d ", encoded_exp[i]); 
367 
} 
368 
av_log(NULL, AV_LOG_DEBUG, "\n"); 
369 
#endif

370  
371 
return 4 + (nb_groups / 3) * 7; 
372 
} 
373  
374 
/* return the size in bits taken by the mantissa */

375 
static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs) 
376 
{ 
377 
int bits, mant, i;

378  
379 
bits = 0;

380 
for(i=0;i<nb_coefs;i++) { 
381 
mant = m[i]; 
382 
switch(mant) {

383 
case 0: 
384 
/* nothing */

385 
break;

386 
case 1: 
387 
/* 3 mantissa in 5 bits */

388 
if (s>mant1_cnt == 0) 
389 
bits += 5;

390 
if (++s>mant1_cnt == 3) 
391 
s>mant1_cnt = 0;

392 
break;

393 
case 2: 
394 
/* 3 mantissa in 7 bits */

395 
if (s>mant2_cnt == 0) 
396 
bits += 7;

397 
if (++s>mant2_cnt == 3) 
398 
s>mant2_cnt = 0;

399 
break;

400 
case 3: 
401 
bits += 3;

402 
break;

403 
case 4: 
404 
/* 2 mantissa in 7 bits */

405 
if (s>mant4_cnt == 0) 
406 
bits += 7;

407 
if (++s>mant4_cnt == 2) 
408 
s>mant4_cnt = 0;

409 
break;

410 
case 14: 
411 
bits += 14;

412 
break;

413 
case 15: 
414 
bits += 16;

415 
break;

416 
default:

417 
bits += mant  1;

418 
break;

419 
} 
420 
} 
421 
return bits;

422 
} 
423  
424  
425 
static void bit_alloc_masking(AC3EncodeContext *s, 
426 
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

427 
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], 
428 
int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

429 
int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50])

430 
{ 
431 
int blk, ch;

432 
int16_t band_psd[NB_BLOCKS][AC3_MAX_CHANNELS][50];

433  
434 
for(blk=0; blk<NB_BLOCKS; blk++) { 
435 
for(ch=0;ch<s>nb_all_channels;ch++) { 
436 
if(exp_strategy[blk][ch] == EXP_REUSE) {

437 
memcpy(psd[blk][ch], psd[blk1][ch], (N/2)*sizeof(int16_t)); 
438 
memcpy(mask[blk][ch], mask[blk1][ch], 50*sizeof(int16_t)); 
439 
} else {

440 
ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,

441 
s>nb_coefs[ch], 
442 
psd[blk][ch], band_psd[blk][ch]); 
443 
ff_ac3_bit_alloc_calc_mask(&s>bit_alloc, band_psd[blk][ch], 
444 
0, s>nb_coefs[ch],

445 
ff_ac3_fast_gain_tab[s>fast_gain_code[ch]], 
446 
ch == s>lfe_channel, 
447 
DBA_NONE, 0, NULL, NULL, NULL, 
448 
mask[blk][ch]); 
449 
} 
450 
} 
451 
} 
452 
} 
453  
454 
static int bit_alloc(AC3EncodeContext *s, 
455 
int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50],

456 
int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

457 
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

458 
int frame_bits, int coarse_snr_offset, int fine_snr_offset) 
459 
{ 
460 
int i, ch;

461 
int snr_offset;

462  
463 
snr_offset = (((coarse_snr_offset  15) << 4) + fine_snr_offset) << 2; 
464  
465 
/* compute size */

466 
for(i=0;i<NB_BLOCKS;i++) { 
467 
s>mant1_cnt = 0;

468 
s>mant2_cnt = 0;

469 
s>mant4_cnt = 0;

470 
for(ch=0;ch<s>nb_all_channels;ch++) { 
471 
ff_ac3_bit_alloc_calc_bap(mask[i][ch], psd[i][ch], 0,

472 
s>nb_coefs[ch], snr_offset, 
473 
s>bit_alloc.floor, ff_ac3_bap_tab, 
474 
bap[i][ch]); 
475 
frame_bits += compute_mantissa_size(s, bap[i][ch], 
476 
s>nb_coefs[ch]); 
477 
} 
478 
} 
479 
#if 0

480 
printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",

481 
coarse_snr_offset, fine_snr_offset, frame_bits,

482 
16 * s>frame_size  ((frame_bits + 7) & ~7));

483 
#endif

484 
return 16 * s>frame_size  frame_bits; 
485 
} 
486  
487 
#define SNR_INC1 4 
488  
489 
static int compute_bit_allocation(AC3EncodeContext *s, 
490 
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

491 
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],

492 
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS], 
493 
int frame_bits)

494 
{ 
495 
int i, ch;

496 
int coarse_snr_offset, fine_snr_offset;

497 
uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

498 
int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

499 
int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50];

500 
static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 }; 
501  
502 
/* init default parameters */

503 
s>slow_decay_code = 2;

504 
s>fast_decay_code = 1;

505 
s>slow_gain_code = 1;

506 
s>db_per_bit_code = 2;

507 
s>floor_code = 4;

508 
for(ch=0;ch<s>nb_all_channels;ch++) 
509 
s>fast_gain_code[ch] = 4;

510  
511 
/* compute real values */

512 
s>bit_alloc.sr_code = s>sr_code; 
513 
s>bit_alloc.sr_shift = s>sr_shift; 
514 
s>bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s>slow_decay_code] >> s>sr_shift; 
515 
s>bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s>fast_decay_code] >> s>sr_shift; 
516 
s>bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s>slow_gain_code]; 
517 
s>bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s>db_per_bit_code]; 
518 
s>bit_alloc.floor = ff_ac3_floor_tab[s>floor_code]; 
519  
520 
/* header size */

521 
frame_bits += 65;

522 
// if (s>channel_mode == 2)

523 
// frame_bits += 2;

524 
frame_bits += frame_bits_inc[s>channel_mode]; 
525  
526 
/* audio blocks */

527 
for(i=0;i<NB_BLOCKS;i++) { 
528 
frame_bits += s>nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */ 
529 
if (s>channel_mode == AC3_CHMODE_STEREO) {

530 
frame_bits++; /* rematstr */

531 
if(i==0) frame_bits += 4; 
532 
} 
533 
frame_bits += 2 * s>nb_channels; /* chexpstr[2] * c */ 
534 
if (s>lfe)

535 
frame_bits++; /* lfeexpstr */

536 
for(ch=0;ch<s>nb_channels;ch++) { 
537 
if (exp_strategy[i][ch] != EXP_REUSE)

538 
frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */ 
539 
} 
540 
frame_bits++; /* baie */

541 
frame_bits++; /* snr */

542 
frame_bits += 2; /* delta / skip */ 
543 
} 
544 
frame_bits++; /* cplinu for block 0 */

545 
/* bit alloc info */

546 
/* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */

547 
/* csnroffset[6] */

548 
/* (fsnoffset[4] + fgaincod[4]) * c */

549 
frame_bits += 2*4 + 3 + 6 + s>nb_all_channels * (4 + 3); 
550  
551 
/* auxdatae, crcrsv */

552 
frame_bits += 2;

553  
554 
/* CRC */

555 
frame_bits += 16;

556  
557 
/* calculate psd and masking curve before doing bit allocation */

558 
bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask); 
559  
560 
/* now the big work begins : do the bit allocation. Modify the snr

561 
offset until we can pack everything in the requested frame size */

562  
563 
coarse_snr_offset = s>coarse_snr_offset; 
564 
while (coarse_snr_offset >= 0 && 
565 
bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0) 
566 
coarse_snr_offset = SNR_INC1; 
567 
if (coarse_snr_offset < 0) { 
568 
av_log(NULL, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n"); 
569 
return 1; 
570 
} 
571 
while ((coarse_snr_offset + SNR_INC1) <= 63 && 
572 
bit_alloc(s, mask, psd, bap1, frame_bits, 
573 
coarse_snr_offset + SNR_INC1, 0) >= 0) { 
574 
coarse_snr_offset += SNR_INC1; 
575 
memcpy(bap, bap1, sizeof(bap1));

576 
} 
577 
while ((coarse_snr_offset + 1) <= 63 && 
578 
bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) { 
579 
coarse_snr_offset++; 
580 
memcpy(bap, bap1, sizeof(bap1));

581 
} 
582  
583 
fine_snr_offset = 0;

584 
while ((fine_snr_offset + SNR_INC1) <= 15 && 
585 
bit_alloc(s, mask, psd, bap1, frame_bits, 
586 
coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {

587 
fine_snr_offset += SNR_INC1; 
588 
memcpy(bap, bap1, sizeof(bap1));

589 
} 
590 
while ((fine_snr_offset + 1) <= 15 && 
591 
bit_alloc(s, mask, psd, bap1, frame_bits, 
592 
coarse_snr_offset, fine_snr_offset + 1) >= 0) { 
593 
fine_snr_offset++; 
594 
memcpy(bap, bap1, sizeof(bap1));

595 
} 
596  
597 
s>coarse_snr_offset = coarse_snr_offset; 
598 
for(ch=0;ch<s>nb_all_channels;ch++) 
599 
s>fine_snr_offset[ch] = fine_snr_offset; 
600 
#if defined(DEBUG_BITALLOC)

601 
{ 
602 
int j;

603  
604 
for(i=0;i<6;i++) { 
605 
for(ch=0;ch<s>nb_all_channels;ch++) { 
606 
printf("Block #%d Ch%d:\n", i, ch);

607 
printf("bap=");

608 
for(j=0;j<s>nb_coefs[ch];j++) { 
609 
printf("%d ",bap[i][ch][j]);

610 
} 
611 
printf("\n");

612 
} 
613 
} 
614 
} 
615 
#endif

616 
return 0; 
617 
} 
618  
619 
static av_cold int set_channel_info(AC3EncodeContext *s, int channels, 
620 
int64_t *channel_layout) 
621 
{ 
622 
int ch_layout;

623  
624 
if (channels < 1  channels > AC3_MAX_CHANNELS) 
625 
return 1; 
626 
if ((uint64_t)*channel_layout > 0x7FF) 
627 
return 1; 
628 
ch_layout = *channel_layout; 
629 
if (!ch_layout)

630 
ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);

631 
if (av_get_channel_layout_nb_channels(ch_layout) != channels)

632 
return 1; 
633  
634 
s>lfe = !!(ch_layout & AV_CH_LOW_FREQUENCY); 
635 
s>nb_all_channels = channels; 
636 
s>nb_channels = channels  s>lfe; 
637 
s>lfe_channel = s>lfe ? s>nb_channels : 1;

638 
if (s>lfe)

639 
ch_layout = AV_CH_LOW_FREQUENCY; 
640  
641 
switch (ch_layout) {

642 
case AV_CH_LAYOUT_MONO: s>channel_mode = AC3_CHMODE_MONO; break; 
643 
case AV_CH_LAYOUT_STEREO: s>channel_mode = AC3_CHMODE_STEREO; break; 
644 
case AV_CH_LAYOUT_SURROUND: s>channel_mode = AC3_CHMODE_3F; break; 
645 
case AV_CH_LAYOUT_2_1: s>channel_mode = AC3_CHMODE_2F1R; break; 
646 
case AV_CH_LAYOUT_4POINT0: s>channel_mode = AC3_CHMODE_3F1R; break; 
647 
case AV_CH_LAYOUT_QUAD:

648 
case AV_CH_LAYOUT_2_2: s>channel_mode = AC3_CHMODE_2F2R; break; 
649 
case AV_CH_LAYOUT_5POINT0:

650 
case AV_CH_LAYOUT_5POINT0_BACK: s>channel_mode = AC3_CHMODE_3F2R; break; 
651 
default:

652 
return 1; 
653 
} 
654  
655 
s>channel_map = ff_ac3_enc_channel_map[s>channel_mode][s>lfe]; 
656 
*channel_layout = ch_layout; 
657 
if (s>lfe)

658 
*channel_layout = AV_CH_LOW_FREQUENCY; 
659  
660 
return 0; 
661 
} 
662  
663 
static av_cold int AC3_encode_init(AVCodecContext *avctx) 
664 
{ 
665 
int freq = avctx>sample_rate;

666 
int bitrate = avctx>bit_rate;

667 
AC3EncodeContext *s = avctx>priv_data; 
668 
int i, j, ch;

669 
float alpha;

670 
int bw_code;

671  
672 
avctx>frame_size = AC3_FRAME_SIZE; 
673  
674 
ac3_common_init(); 
675  
676 
if (!avctx>channel_layout) {

677 
av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "

678 
"encoder will guess the layout, but it "

679 
"might be incorrect.\n");

680 
} 
681 
if (set_channel_info(s, avctx>channels, &avctx>channel_layout)) {

682 
av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");

683 
return 1; 
684 
} 
685  
686 
/* frequency */

687 
for(i=0;i<3;i++) { 
688 
for(j=0;j<3;j++) 
689 
if ((ff_ac3_sample_rate_tab[j] >> i) == freq)

690 
goto found;

691 
} 
692 
return 1; 
693 
found:

694 
s>sample_rate = freq; 
695 
s>sr_shift = i; 
696 
s>sr_code = j; 
697 
s>bitstream_id = 8 + s>sr_shift;

698 
s>bitstream_mode = 0; /* complete main audio service */ 
699  
700 
/* bitrate & frame size */

701 
for(i=0;i<19;i++) { 
702 
if ((ff_ac3_bitrate_tab[i] >> s>sr_shift)*1000 == bitrate) 
703 
break;

704 
} 
705 
if (i == 19) 
706 
return 1; 
707 
s>bit_rate = bitrate; 
708 
s>frame_size_code = i << 1;

709 
s>frame_size_min = ff_ac3_frame_size_tab[s>frame_size_code][s>sr_code]; 
710 
s>bits_written = 0;

711 
s>samples_written = 0;

712 
s>frame_size = s>frame_size_min; 
713  
714 
/* bit allocation init */

715 
if(avctx>cutoff) {

716 
/* calculate bandwidth based on userspecified cutoff frequency */

717 
int cutoff = av_clip(avctx>cutoff, 1, s>sample_rate >> 1); 
718 
int fbw_coeffs = cutoff * 512 / s>sample_rate; 
719 
bw_code = av_clip((fbw_coeffs  73) / 3, 0, 60); 
720 
} else {

721 
/* use default bandwidth setting */

722 
/* XXX: should compute the bandwidth according to the frame

723 
size, so that we avoid annoying high frequency artifacts */

724 
bw_code = 50;

725 
} 
726 
for(ch=0;ch<s>nb_channels;ch++) { 
727 
/* bandwidth for each channel */

728 
s>chbwcod[ch] = bw_code; 
729 
s>nb_coefs[ch] = bw_code * 3 + 73; 
730 
} 
731 
if (s>lfe) {

732 
s>nb_coefs[s>lfe_channel] = 7; /* fixed */ 
733 
} 
734 
/* initial snr offset */

735 
s>coarse_snr_offset = 40;

736  
737 
/* mdct init */

738 
fft_init(MDCT_NBITS  2);

739 
for(i=0;i<N/4;i++) { 
740 
alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N; 
741 
xcos1[i] = fix15(cos(alpha)); 
742 
xsin1[i] = fix15(sin(alpha)); 
743 
} 
744  
745 
avctx>coded_frame= avcodec_alloc_frame(); 
746 
avctx>coded_frame>key_frame= 1;

747  
748 
return 0; 
749 
} 
750  
751 
/* output the AC3 frame header */

752 
static void output_frame_header(AC3EncodeContext *s, unsigned char *frame) 
753 
{ 
754 
init_put_bits(&s>pb, frame, AC3_MAX_CODED_FRAME_SIZE); 
755  
756 
put_bits(&s>pb, 16, 0x0b77); /* frame header */ 
757 
put_bits(&s>pb, 16, 0); /* crc1: will be filled later */ 
758 
put_bits(&s>pb, 2, s>sr_code);

759 
put_bits(&s>pb, 6, s>frame_size_code + (s>frame_size  s>frame_size_min));

760 
put_bits(&s>pb, 5, s>bitstream_id);

761 
put_bits(&s>pb, 3, s>bitstream_mode);

762 
put_bits(&s>pb, 3, s>channel_mode);

763 
if ((s>channel_mode & 0x01) && s>channel_mode != AC3_CHMODE_MONO) 
764 
put_bits(&s>pb, 2, 1); /* XXX 4.5 dB */ 
765 
if (s>channel_mode & 0x04) 
766 
put_bits(&s>pb, 2, 1); /* XXX 6 dB */ 
767 
if (s>channel_mode == AC3_CHMODE_STEREO)

768 
put_bits(&s>pb, 2, 0); /* surround not indicated */ 
769 
put_bits(&s>pb, 1, s>lfe); /* LFE */ 
770 
put_bits(&s>pb, 5, 31); /* dialog norm: 31 db */ 
771 
put_bits(&s>pb, 1, 0); /* no compression control word */ 
772 
put_bits(&s>pb, 1, 0); /* no lang code */ 
773 
put_bits(&s>pb, 1, 0); /* no audio production info */ 
774 
put_bits(&s>pb, 1, 0); /* no copyright */ 
775 
put_bits(&s>pb, 1, 1); /* original bitstream */ 
776 
put_bits(&s>pb, 1, 0); /* no time code 1 */ 
777 
put_bits(&s>pb, 1, 0); /* no time code 2 */ 
778 
put_bits(&s>pb, 1, 0); /* no additional bit stream info */ 
779 
} 
780  
781 
/* symetric quantization on 'levels' levels */

782 
static inline int sym_quant(int c, int e, int levels) 
783 
{ 
784 
int v;

785  
786 
if (c >= 0) { 
787 
v = (levels * (c << e)) >> 24;

788 
v = (v + 1) >> 1; 
789 
v = (levels >> 1) + v;

790 
} else {

791 
v = (levels * ((c) << e)) >> 24;

792 
v = (v + 1) >> 1; 
793 
v = (levels >> 1)  v;

794 
} 
795 
assert (v >= 0 && v < levels);

796 
return v;

797 
} 
798  
799 
/* asymetric quantization on 2^qbits levels */

800 
static inline int asym_quant(int c, int e, int qbits) 
801 
{ 
802 
int lshift, m, v;

803  
804 
lshift = e + qbits  24;

805 
if (lshift >= 0) 
806 
v = c << lshift; 
807 
else

808 
v = c >> (lshift); 
809 
/* rounding */

810 
v = (v + 1) >> 1; 
811 
m = (1 << (qbits1)); 
812 
if (v >= m)

813 
v = m  1;

814 
assert(v >= m); 
815 
return v & ((1 << qbits)1); 
816 
} 
817  
818 
/* Output one audio block. There are NB_BLOCKS audio blocks in one AC3

819 
frame */

820 
static void output_audio_block(AC3EncodeContext *s, 
821 
uint8_t exp_strategy[AC3_MAX_CHANNELS], 
822 
uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],

823 
uint8_t bap[AC3_MAX_CHANNELS][N/2],

824 
int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],

825 
int8_t global_exp[AC3_MAX_CHANNELS], 
826 
int block_num)

827 
{ 
828 
int ch, nb_groups, group_size, i, baie, rbnd;

829 
uint8_t *p; 
830 
uint16_t qmant[AC3_MAX_CHANNELS][N/2];

831 
int exp0, exp1;

832 
int mant1_cnt, mant2_cnt, mant4_cnt;

833 
uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; 
834 
int delta0, delta1, delta2;

835  
836 
for(ch=0;ch<s>nb_channels;ch++) 
837 
put_bits(&s>pb, 1, 0); /* 512 point MDCT */ 
838 
for(ch=0;ch<s>nb_channels;ch++) 
839 
put_bits(&s>pb, 1, 1); /* no dither */ 
840 
put_bits(&s>pb, 1, 0); /* no dynamic range */ 
841 
if (block_num == 0) { 
842 
/* for block 0, even if no coupling, we must say it. This is a

843 
waste of bit :) */

844 
put_bits(&s>pb, 1, 1); /* coupling strategy present */ 
845 
put_bits(&s>pb, 1, 0); /* no coupling strategy */ 
846 
} else {

847 
put_bits(&s>pb, 1, 0); /* no new coupling strategy */ 
848 
} 
849  
850 
if (s>channel_mode == AC3_CHMODE_STEREO)

851 
{ 
852 
if(block_num==0) 
853 
{ 
854 
/* first block must define rematrixing (rematstr) */

855 
put_bits(&s>pb, 1, 1); 
856  
857 
/* dummy rematrixing rematflg(1:4)=0 */

858 
for (rbnd=0;rbnd<4;rbnd++) 
859 
put_bits(&s>pb, 1, 0); 
860 
} 
861 
else

862 
{ 
863 
/* no matrixing (but should be used in the future) */

864 
put_bits(&s>pb, 1, 0); 
865 
} 
866 
} 
867  
868 
#if defined(DEBUG)

869 
{ 
870 
static int count = 0; 
871 
av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++); 
872 
} 
873 
#endif

874 
/* exponent strategy */

875 
for(ch=0;ch<s>nb_channels;ch++) { 
876 
put_bits(&s>pb, 2, exp_strategy[ch]);

877 
} 
878  
879 
if (s>lfe) {

880 
put_bits(&s>pb, 1, exp_strategy[s>lfe_channel]);

881 
} 
882  
883 
for(ch=0;ch<s>nb_channels;ch++) { 
884 
if (exp_strategy[ch] != EXP_REUSE)

885 
put_bits(&s>pb, 6, s>chbwcod[ch]);

886 
} 
887  
888 
/* exponents */

889 
for (ch = 0; ch < s>nb_all_channels; ch++) { 
890 
switch(exp_strategy[ch]) {

891 
case EXP_REUSE:

892 
continue;

893 
case EXP_D15:

894 
group_size = 1;

895 
break;

896 
case EXP_D25:

897 
group_size = 2;

898 
break;

899 
default:

900 
case EXP_D45:

901 
group_size = 4;

902 
break;

903 
} 
904 
nb_groups = (s>nb_coefs[ch] + (group_size * 3)  4) / (3 * group_size); 
905 
p = encoded_exp[ch]; 
906  
907 
/* first exponent */

908 
exp1 = *p++; 
909 
put_bits(&s>pb, 4, exp1);

910  
911 
/* next ones are delta encoded */

912 
for(i=0;i<nb_groups;i++) { 
913 
/* merge three delta in one code */

914 
exp0 = exp1; 
915 
exp1 = p[0];

916 
p += group_size; 
917 
delta0 = exp1  exp0 + 2;

918  
919 
exp0 = exp1; 
920 
exp1 = p[0];

921 
p += group_size; 
922 
delta1 = exp1  exp0 + 2;

923  
924 
exp0 = exp1; 
925 
exp1 = p[0];

926 
p += group_size; 
927 
delta2 = exp1  exp0 + 2;

928  
929 
put_bits(&s>pb, 7, ((delta0 * 5 + delta1) * 5) + delta2); 
930 
} 
931  
932 
if (ch != s>lfe_channel)

933 
put_bits(&s>pb, 2, 0); /* no gain range info */ 
934 
} 
935  
936 
/* bit allocation info */

937 
baie = (block_num == 0);

938 
put_bits(&s>pb, 1, baie);

939 
if (baie) {

940 
put_bits(&s>pb, 2, s>slow_decay_code);

941 
put_bits(&s>pb, 2, s>fast_decay_code);

942 
put_bits(&s>pb, 2, s>slow_gain_code);

943 
put_bits(&s>pb, 2, s>db_per_bit_code);

944 
put_bits(&s>pb, 3, s>floor_code);

945 
} 
946  
947 
/* snr offset */

948 
put_bits(&s>pb, 1, baie); /* always present with bai */ 
949 
if (baie) {

950 
put_bits(&s>pb, 6, s>coarse_snr_offset);

951 
for(ch=0;ch<s>nb_all_channels;ch++) { 
952 
put_bits(&s>pb, 4, s>fine_snr_offset[ch]);

953 
put_bits(&s>pb, 3, s>fast_gain_code[ch]);

954 
} 
955 
} 
956  
957 
put_bits(&s>pb, 1, 0); /* no delta bit allocation */ 
958 
put_bits(&s>pb, 1, 0); /* no data to skip */ 
959  
960 
/* mantissa encoding : we use two passes to handle the grouping. A

961 
one pass method may be faster, but it would necessitate to

962 
modify the output stream. */

963  
964 
/* first pass: quantize */

965 
mant1_cnt = mant2_cnt = mant4_cnt = 0;

966 
qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;

967  
968 
for (ch = 0; ch < s>nb_all_channels; ch++) { 
969 
int b, c, e, v;

970  
971 
for(i=0;i<s>nb_coefs[ch];i++) { 
972 
c = mdct_coefs[ch][i]; 
973 
e = encoded_exp[ch][i]  global_exp[ch]; 
974 
b = bap[ch][i]; 
975 
switch(b) {

976 
case 0: 
977 
v = 0;

978 
break;

979 
case 1: 
980 
v = sym_quant(c, e, 3);

981 
switch(mant1_cnt) {

982 
case 0: 
983 
qmant1_ptr = &qmant[ch][i]; 
984 
v = 9 * v;

985 
mant1_cnt = 1;

986 
break;

987 
case 1: 
988 
*qmant1_ptr += 3 * v;

989 
mant1_cnt = 2;

990 
v = 128;

991 
break;

992 
default:

993 
*qmant1_ptr += v; 
994 
mant1_cnt = 0;

995 
v = 128;

996 
break;

997 
} 
998 
break;

999 
case 2: 
1000 
v = sym_quant(c, e, 5);

1001 
switch(mant2_cnt) {

1002 
case 0: 
1003 
qmant2_ptr = &qmant[ch][i]; 
1004 
v = 25 * v;

1005 
mant2_cnt = 1;

1006 
break;

1007 
case 1: 
1008 
*qmant2_ptr += 5 * v;

1009 
mant2_cnt = 2;

1010 
v = 128;

1011 
break;

1012 
default:

1013 
*qmant2_ptr += v; 
1014 
mant2_cnt = 0;

1015 
v = 128;

1016 
break;

1017 
} 
1018 
break;

1019 
case 3: 
1020 
v = sym_quant(c, e, 7);

1021 
break;

1022 
case 4: 
1023 
v = sym_quant(c, e, 11);

1024 
switch(mant4_cnt) {

1025 
case 0: 
1026 
qmant4_ptr = &qmant[ch][i]; 
1027 
v = 11 * v;

1028 
mant4_cnt = 1;

1029 
break;

1030 
default:

1031 
*qmant4_ptr += v; 
1032 
mant4_cnt = 0;

1033 
v = 128;

1034 
break;

1035 
} 
1036 
break;

1037 
case 5: 
1038 
v = sym_quant(c, e, 15);

1039 
break;

1040 
case 14: 
1041 
v = asym_quant(c, e, 14);

1042 
break;

1043 
case 15: 
1044 
v = asym_quant(c, e, 16);

1045 
break;

1046 
default:

1047 
v = asym_quant(c, e, b  1);

1048 
break;

1049 
} 
1050 
qmant[ch][i] = v; 
1051 
} 
1052 
} 
1053  
1054 
/* second pass : output the values */

1055 
for (ch = 0; ch < s>nb_all_channels; ch++) { 
1056 
int b, q;

1057  
1058 
for(i=0;i<s>nb_coefs[ch];i++) { 
1059 
q = qmant[ch][i]; 
1060 
b = bap[ch][i]; 
1061 
switch(b) {

1062 
case 0: 
1063 
break;

1064 
case 1: 
1065 
if (q != 128) 
1066 
put_bits(&s>pb, 5, q);

1067 
break;

1068 
case 2: 
1069 
if (q != 128) 
1070 
put_bits(&s>pb, 7, q);

1071 
break;

1072 
case 3: 
1073 
put_bits(&s>pb, 3, q);

1074 
break;

1075 
case 4: 
1076 
if (q != 128) 
1077 
put_bits(&s>pb, 7, q);

1078 
break;

1079 
case 14: 
1080 
put_bits(&s>pb, 14, q);

1081 
break;

1082 
case 15: 
1083 
put_bits(&s>pb, 16, q);

1084 
break;

1085 
default:

1086 
put_bits(&s>pb, b  1, q);

1087 
break;

1088 
} 
1089 
} 
1090 
} 
1091 
} 
1092  
1093 
#define CRC16_POLY ((1 << 0)  (1 << 2)  (1 << 15)  (1 << 16)) 
1094  
1095 
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly) 
1096 
{ 
1097 
unsigned int c; 
1098  
1099 
c = 0;

1100 
while (a) {

1101 
if (a & 1) 
1102 
c ^= b; 
1103 
a = a >> 1;

1104 
b = b << 1;

1105 
if (b & (1 << 16)) 
1106 
b ^= poly; 
1107 
} 
1108 
return c;

1109 
} 
1110  
1111 
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly) 
1112 
{ 
1113 
unsigned int r; 
1114 
r = 1;

1115 
while (n) {

1116 
if (n & 1) 
1117 
r = mul_poly(r, a, poly); 
1118 
a = mul_poly(a, a, poly); 
1119 
n >>= 1;

1120 
} 
1121 
return r;

1122 
} 
1123  
1124  
1125 
/* compute log2(max(abs(tab[]))) */

1126 
static int log2_tab(int16_t *tab, int n) 
1127 
{ 
1128 
int i, v;

1129  
1130 
v = 0;

1131 
for(i=0;i<n;i++) { 
1132 
v = abs(tab[i]); 
1133 
} 
1134 
return av_log2(v);

1135 
} 
1136  
1137 
static void lshift_tab(int16_t *tab, int n, int lshift) 
1138 
{ 
1139 
int i;

1140  
1141 
if (lshift > 0) { 
1142 
for(i=0;i<n;i++) { 
1143 
tab[i] <<= lshift; 
1144 
} 
1145 
} else if (lshift < 0) { 
1146 
lshift = lshift; 
1147 
for(i=0;i<n;i++) { 
1148 
tab[i] >>= lshift; 
1149 
} 
1150 
} 
1151 
} 
1152  
1153 
/* fill the end of the frame and compute the two crcs */

1154 
static int output_frame_end(AC3EncodeContext *s) 
1155 
{ 
1156 
int frame_size, frame_size_58, n, crc1, crc2, crc_inv;

1157 
uint8_t *frame; 
1158  
1159 
frame_size = s>frame_size; /* frame size in words */

1160 
/* align to 8 bits */

1161 
flush_put_bits(&s>pb); 
1162 
/* add zero bytes to reach the frame size */

1163 
frame = s>pb.buf; 
1164 
n = 2 * s>frame_size  (put_bits_ptr(&s>pb)  frame)  2; 
1165 
assert(n >= 0);

1166 
if(n>0) 
1167 
memset(put_bits_ptr(&s>pb), 0, n);

1168  
1169 
/* Now we must compute both crcs : this is not so easy for crc1

1170 
because it is at the beginning of the data... */

1171 
frame_size_58 = (frame_size >> 1) + (frame_size >> 3); 
1172 
crc1 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,

1173 
frame + 4, 2 * frame_size_58  4)); 
1174 
/* XXX: could precompute crc_inv */

1175 
crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58)  16, CRC16_POLY); 
1176 
crc1 = mul_poly(crc_inv, crc1, CRC16_POLY); 
1177 
AV_WB16(frame+2,crc1);

1178  
1179 
crc2 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,

1180 
frame + 2 * frame_size_58,

1181 
(frame_size  frame_size_58) * 2  2)); 
1182 
AV_WB16(frame+2*frame_size2,crc2); 
1183  
1184 
// printf("n=%d frame_size=%d\n", n, frame_size);

1185 
return frame_size * 2; 
1186 
} 
1187  
1188 
static int AC3_encode_frame(AVCodecContext *avctx, 
1189 
unsigned char *frame, int buf_size, void *data) 
1190 
{ 
1191 
AC3EncodeContext *s = avctx>priv_data; 
1192 
const int16_t *samples = data;

1193 
int i, j, k, v, ch;

1194 
int16_t input_samples[N]; 
1195 
int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1196 
uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1197 
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS]; 
1198 
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1199 
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];

1200 
int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS]; 
1201 
int frame_bits;

1202  
1203 
frame_bits = 0;

1204 
for(ch=0;ch<s>nb_all_channels;ch++) { 
1205 
int ich = s>channel_map[ch];

1206 
/* fixed mdct to the six sub blocks & exponent computation */

1207 
for(i=0;i<NB_BLOCKS;i++) { 
1208 
const int16_t *sptr;

1209 
int sinc;

1210  
1211 
/* compute input samples */

1212 
memcpy(input_samples, s>last_samples[ich], N/2 * sizeof(int16_t)); 
1213 
sinc = s>nb_all_channels; 
1214 
sptr = samples + (sinc * (N/2) * i) + ich;

1215 
for(j=0;j<N/2;j++) { 
1216 
v = *sptr; 
1217 
input_samples[j + N/2] = v;

1218 
s>last_samples[ich][j] = v; 
1219 
sptr += sinc; 
1220 
} 
1221  
1222 
/* apply the MDCT window */

1223 
for(j=0;j<N/2;j++) { 
1224 
input_samples[j] = MUL16(input_samples[j], 
1225 
ff_ac3_window[j]) >> 15;

1226 
input_samples[Nj1] = MUL16(input_samples[Nj1], 
1227 
ff_ac3_window[j]) >> 15;

1228 
} 
1229  
1230 
/* Normalize the samples to use the maximum available

1231 
precision */

1232 
v = 14  log2_tab(input_samples, N);

1233 
if (v < 0) 
1234 
v = 0;

1235 
exp_samples[i][ch] = v  9;

1236 
lshift_tab(input_samples, N, v); 
1237  
1238 
/* do the MDCT */

1239 
mdct512(mdct_coef[i][ch], input_samples); 
1240  
1241 
/* compute "exponents". We take into account the

1242 
normalization there */

1243 
for(j=0;j<N/2;j++) { 
1244 
int e;

1245 
v = abs(mdct_coef[i][ch][j]); 
1246 
if (v == 0) 
1247 
e = 24;

1248 
else {

1249 
e = 23  av_log2(v) + exp_samples[i][ch];

1250 
if (e >= 24) { 
1251 
e = 24;

1252 
mdct_coef[i][ch][j] = 0;

1253 
} 
1254 
} 
1255 
exp[i][ch][j] = e; 
1256 
} 
1257 
} 
1258  
1259 
compute_exp_strategy(exp_strategy, exp, ch, ch == s>lfe_channel); 
1260  
1261 
/* compute the exponents as the decoder will see them. The

1262 
EXP_REUSE case must be handled carefully : we select the

1263 
min of the exponents */

1264 
i = 0;

1265 
while (i < NB_BLOCKS) {

1266 
j = i + 1;

1267 
while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {

1268 
exponent_min(exp[i][ch], exp[j][ch], s>nb_coefs[ch]); 
1269 
j++; 
1270 
} 
1271 
frame_bits += encode_exp(encoded_exp[i][ch], 
1272 
exp[i][ch], s>nb_coefs[ch], 
1273 
exp_strategy[i][ch]); 
1274 
/* copy encoded exponents for reuse case */

1275 
for(k=i+1;k<j;k++) { 
1276 
memcpy(encoded_exp[k][ch], encoded_exp[i][ch], 
1277 
s>nb_coefs[ch] * sizeof(uint8_t));

1278 
} 
1279 
i = j; 
1280 
} 
1281 
} 
1282  
1283 
/* adjust for fractional frame sizes */

1284 
while(s>bits_written >= s>bit_rate && s>samples_written >= s>sample_rate) {

1285 
s>bits_written = s>bit_rate; 
1286 
s>samples_written = s>sample_rate; 
1287 
} 
1288 
s>frame_size = s>frame_size_min + (s>bits_written * s>sample_rate < s>samples_written * s>bit_rate); 
1289 
s>bits_written += s>frame_size * 16;

1290 
s>samples_written += AC3_FRAME_SIZE; 
1291  
1292 
compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits); 
1293 
/* everything is known... let's output the frame */

1294 
output_frame_header(s, frame); 
1295  
1296 
for(i=0;i<NB_BLOCKS;i++) { 
1297 
output_audio_block(s, exp_strategy[i], encoded_exp[i], 
1298 
bap[i], mdct_coef[i], exp_samples[i], i); 
1299 
} 
1300 
return output_frame_end(s);

1301 
} 
1302  
1303 
static av_cold int AC3_encode_close(AVCodecContext *avctx) 
1304 
{ 
1305 
av_freep(&avctx>coded_frame); 
1306 
return 0; 
1307 
} 
1308  
1309 
#if 0

1310 
/*************************************************************************/

1311 
/* TEST */

1312 

1313 
#undef random

1314 
#define FN (N/4)

1315 

1316 
void fft_test(void)

1317 
{

1318 
IComplex in[FN], in1[FN];

1319 
int k, n, i;

1320 
float sum_re, sum_im, a;

1321 

1322 
/* FFT test */

1323 

1324 
for(i=0;i<FN;i++) {

1325 
in[i].re = random() % 65535  32767;

1326 
in[i].im = random() % 65535  32767;

1327 
in1[i] = in[i];

1328 
}

1329 
fft(in, 7);

1330 

1331 
/* do it by hand */

1332 
for(k=0;k<FN;k++) {

1333 
sum_re = 0;

1334 
sum_im = 0;

1335 
for(n=0;n<FN;n++) {

1336 
a = 2 * M_PI * (n * k) / FN;

1337 
sum_re += in1[n].re * cos(a)  in1[n].im * sin(a);

1338 
sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);

1339 
}

1340 
printf("%3d: %6d,%6d %6.0f,%6.0f\n",

1341 
k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);

1342 
}

1343 
}

1344 

1345 
void mdct_test(void)

1346 
{

1347 
int16_t input[N];

1348 
int32_t output[N/2];

1349 
float input1[N];

1350 
float output1[N/2];

1351 
float s, a, err, e, emax;

1352 
int i, k, n;

1353 

1354 
for(i=0;i<N;i++) {

1355 
input[i] = (random() % 65535  32767) * 9 / 10;

1356 
input1[i] = input[i];

1357 
}

1358 

1359 
mdct512(output, input);

1360 

1361 
/* do it by hand */

1362 
for(k=0;k<N/2;k++) {

1363 
s = 0;

1364 
for(n=0;n<N;n++) {

1365 
a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));

1366 
s += input1[n] * cos(a);

1367 
}

1368 
output1[k] = 2 * s / N;

1369 
}

1370 

1371 
err = 0;

1372 
emax = 0;

1373 
for(i=0;i<N/2;i++) {

1374 
printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);

1375 
e = output[i]  output1[i];

1376 
if (e > emax)

1377 
emax = e;

1378 
err += e * e;

1379 
}

1380 
printf("err2=%f emax=%f\n", err / (N/2), emax);

1381 
}

1382 

1383 
void test_ac3(void)

1384 
{

1385 
AC3EncodeContext ctx;

1386 
unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];

1387 
short samples[AC3_FRAME_SIZE];

1388 
int ret, i;

1389 

1390 
AC3_encode_init(&ctx, 44100, 64000, 1);

1391 

1392 
fft_test();

1393 
mdct_test();

1394 

1395 
for(i=0;i<AC3_FRAME_SIZE;i++)

1396 
samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);

1397 
ret = AC3_encode_frame(&ctx, frame, samples);

1398 
printf("ret=%d\n", ret);

1399 
}

1400 
#endif

1401  
1402 
AVCodec ac3_encoder = { 
1403 
"ac3",

1404 
AVMEDIA_TYPE_AUDIO, 
1405 
CODEC_ID_AC3, 
1406 
sizeof(AC3EncodeContext),

1407 
AC3_encode_init, 
1408 
AC3_encode_frame, 
1409 
AC3_encode_close, 
1410 
NULL,

1411 
.sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE}, 
1412 
.long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC3)"),

1413 
.channel_layouts = (const int64_t[]){

1414 
AV_CH_LAYOUT_MONO, 
1415 
AV_CH_LAYOUT_STEREO, 
1416 
AV_CH_LAYOUT_2_1, 
1417 
AV_CH_LAYOUT_SURROUND, 
1418 
AV_CH_LAYOUT_2_2, 
1419 
AV_CH_LAYOUT_QUAD, 
1420 
AV_CH_LAYOUT_4POINT0, 
1421 
AV_CH_LAYOUT_5POINT0, 
1422 
AV_CH_LAYOUT_5POINT0_BACK, 
1423 
(AV_CH_LAYOUT_MONO  AV_CH_LOW_FREQUENCY), 
1424 
(AV_CH_LAYOUT_STEREO  AV_CH_LOW_FREQUENCY), 
1425 
(AV_CH_LAYOUT_2_1  AV_CH_LOW_FREQUENCY), 
1426 
(AV_CH_LAYOUT_SURROUND  AV_CH_LOW_FREQUENCY), 
1427 
(AV_CH_LAYOUT_2_2  AV_CH_LOW_FREQUENCY), 
1428 
(AV_CH_LAYOUT_QUAD  AV_CH_LOW_FREQUENCY), 
1429 
(AV_CH_LAYOUT_4POINT0  AV_CH_LOW_FREQUENCY), 
1430 
AV_CH_LAYOUT_5POINT1, 
1431 
AV_CH_LAYOUT_5POINT1_BACK, 
1432 
0 },

1433 
}; 