ffmpeg / libavcodec / ac3enc.c @ 33a7d549
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1 
/*


2 
* The simplest AC3 encoder

3 
* Copyright (c) 2000 Fabrice Bellard

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*

5 
* 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

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

10 
* 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

24 
* The simplest AC3 encoder.

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*/

26  
27 
//#define DEBUG

28  
29 
#include "libavcore/audioconvert.h" 
30 
#include "libavutil/crc.h" 
31 
#include "avcodec.h" 
32 
#include "put_bits.h" 
33 
#include "ac3.h" 
34 
#include "audioconvert.h" 
35  
36  
37 
#define MDCT_NBITS 9 
38 
#define MDCT_SAMPLES (1 << MDCT_NBITS) 
39  
40 
/** Maximum number of exponent groups. +1 for separate DC exponent. */

41 
#define AC3_MAX_EXP_GROUPS 85 
42  
43 
/** Scale a float value by 2^bits and convert to an integer. */

44 
#define SCALE_FLOAT(a, bits) lrintf((a) * (float)(1 << (bits))) 
45  
46 
/** Scale a float value by 2^15, convert to an integer, and clip to int16_t range. */

47 
#define FIX15(a) av_clip_int16(SCALE_FLOAT(a, 15)) 
48  
49  
50 
/**

51 
* Compex number.

52 
* Used in fixedpoint MDCT calculation.

53 
*/

54 
typedef struct IComplex { 
55 
int16_t re,im; 
56 
} IComplex; 
57  
58 
/**

59 
* AC3 encoder private context.

60 
*/

61 
typedef struct AC3EncodeContext { 
62 
PutBitContext pb; ///< bitstream writer context

63  
64 
int bitstream_id; ///< bitstream id (bsid) 
65 
int bitstream_mode; ///< bitstream mode (bsmod) 
66  
67 
int bit_rate; ///< target bit rate, in bitspersecond 
68 
int sample_rate; ///< sampling frequency, in Hz 
69  
70 
int frame_size_min; ///< minimum frame size in case rounding is necessary 
71 
int frame_size; ///< current frame size in bytes 
72 
int frame_size_code; ///< frame size code (frmsizecod) 
73 
int bits_written; ///< bit count (used to avg. bitrate) 
74 
int samples_written; ///< sample count (used to avg. bitrate) 
75  
76 
int fbw_channels; ///< number of fullbandwidth channels (nfchans) 
77 
int channels; ///< total number of channels (nchans) 
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int lfe_on; ///< indicates if there is an LFE channel (lfeon) 
79 
int lfe_channel; ///< channel index of the LFE channel 
80 
int channel_mode; ///< channel mode (acmod) 
81 
const uint8_t *channel_map; ///< channel map used to reorder channels 
82  
83 
int bandwidth_code[AC3_MAX_CHANNELS]; ///< bandwidth code (0 to 60) (chbwcod) 
84 
int nb_coefs[AC3_MAX_CHANNELS];

85  
86 
/* bitrate allocation control */

87 
int slow_gain_code; ///< slow gain code (sgaincod) 
88 
int slow_decay_code; ///< slow decay code (sdcycod) 
89 
int fast_decay_code; ///< fast decay code (fdcycod) 
90 
int db_per_bit_code; ///< dB/bit code (dbpbcod) 
91 
int floor_code; ///< floor code (floorcod) 
92 
AC3BitAllocParameters bit_alloc; ///< bit allocation parameters

93 
int coarse_snr_offset; ///< coarse SNR offsets (csnroffst) 
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int fast_gain_code[AC3_MAX_CHANNELS]; ///< fast gain codes (signaltomask ratio) (fgaincod) 
95 
int fine_snr_offset[AC3_MAX_CHANNELS]; ///< fine SNR offsets (fsnroffst) 
96  
97 
/* mantissa encoding */

98 
int mant1_cnt, mant2_cnt, mant4_cnt; ///< mantissa counts for bap=1,2,4 
99 
uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; ///< mantissa pointers for bap=1,2,4

100  
101 
int16_t last_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< last 256 samples from previous frame

102 
} AC3EncodeContext; 
103  
104  
105 
/** MDCT and FFT tables */

106 
static int16_t costab[64]; 
107 
static int16_t sintab[64]; 
108 
static int16_t xcos1[128]; 
109 
static int16_t xsin1[128]; 
110  
111  
112 
/**

113 
* Adjust the frame size to make the average bit rate match the target bit rate.

114 
* This is only needed for 11025, 22050, and 44100 sample rates.

115 
*/

116 
static void adjust_frame_size(AC3EncodeContext *s) 
117 
{ 
118 
while (s>bits_written >= s>bit_rate && s>samples_written >= s>sample_rate) {

119 
s>bits_written = s>bit_rate; 
120 
s>samples_written = s>sample_rate; 
121 
} 
122 
s>frame_size = s>frame_size_min + 2 * (s>bits_written * s>sample_rate < s>samples_written * s>bit_rate);

123 
s>bits_written += s>frame_size * 8;

124 
s>samples_written += AC3_FRAME_SIZE; 
125 
} 
126  
127  
128 
/**

129 
* Deinterleave input samples.

130 
* Channels are reordered from FFmpeg's default order to AC3 order.

131 
*/

132 
static void deinterleave_input_samples(AC3EncodeContext *s, 
133 
const int16_t *samples,

134 
int16_t planar_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE+AC3_FRAME_SIZE]) 
135 
{ 
136 
int ch, i;

137  
138 
/* deinterleave and remap input samples */

139 
for (ch = 0; ch < s>channels; ch++) { 
140 
const int16_t *sptr;

141 
int sinc;

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143 
/* copy last 256 samples of previous frame to the start of the current frame */

144 
memcpy(&planar_samples[ch][0], s>last_samples[ch],

145 
AC3_BLOCK_SIZE * sizeof(planar_samples[0][0])); 
146  
147 
/* deinterleave */

148 
sinc = s>channels; 
149 
sptr = samples + s>channel_map[ch]; 
150 
for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) {

151 
planar_samples[ch][i] = *sptr; 
152 
sptr += sinc; 
153 
} 
154  
155 
/* save last 256 samples for next frame */

156 
memcpy(s>last_samples[ch], &planar_samples[ch][6* AC3_BLOCK_SIZE],

157 
AC3_BLOCK_SIZE * sizeof(planar_samples[0][0])); 
158 
} 
159 
} 
160  
161  
162 
/**

163 
* Initialize FFT tables.

164 
* @param ln log2(FFT size)

165 
*/

166 
static av_cold void fft_init(int ln) 
167 
{ 
168 
int i, n, n2;

169 
float alpha;

170  
171 
n = 1 << ln;

172 
n2 = n >> 1;

173  
174 
for (i = 0; i < n2; i++) { 
175 
alpha = 2.0 * M_PI * i / n; 
176 
costab[i] = FIX15(cos(alpha)); 
177 
sintab[i] = FIX15(sin(alpha)); 
178 
} 
179 
} 
180  
181  
182 
/**

183 
* Initialize MDCT tables.

184 
* @param nbits log2(MDCT size)

185 
*/

186 
static av_cold void mdct_init(int nbits) 
187 
{ 
188 
int i, n, n4;

189  
190 
n = 1 << nbits;

191 
n4 = n >> 2;

192  
193 
fft_init(nbits  2);

194  
195 
for (i = 0; i < n4; i++) { 
196 
float alpha = 2.0 * M_PI * (i + 1.0 / 8.0) / n; 
197 
xcos1[i] = FIX15(cos(alpha)); 
198 
xsin1[i] = FIX15(sin(alpha)); 
199 
} 
200 
} 
201  
202  
203 
/** Butterfly op */

204 
#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \

205 
{ \ 
206 
int ax, ay, bx, by; \

207 
bx = pre1; \ 
208 
by = pim1; \ 
209 
ax = qre1; \ 
210 
ay = qim1; \ 
211 
pre = (bx + ax) >> 1; \

212 
pim = (by + ay) >> 1; \

213 
qre = (bx  ax) >> 1; \

214 
qim = (by  ay) >> 1; \

215 
} 
216  
217  
218 
/** Complex multiply */

219 
#define CMUL(pre, pim, are, aim, bre, bim) \

220 
{ \ 
221 
pre = (MUL16(are, bre)  MUL16(aim, bim)) >> 15; \

222 
pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15; \

223 
} 
224  
225  
226 
/**

227 
* Calculate a 2^n point complex FFT on 2^ln points.

228 
* @param z complex input/output samples

229 
* @param ln log2(FFT size)

230 
*/

231 
static void fft(IComplex *z, int ln) 
232 
{ 
233 
int j, l, np, np2;

234 
int nblocks, nloops;

235 
register IComplex *p,*q;

236 
int tmp_re, tmp_im;

237  
238 
np = 1 << ln;

239  
240 
/* reverse */

241 
for (j = 0; j < np; j++) { 
242 
int k = av_reverse[j] >> (8  ln); 
243 
if (k < j)

244 
FFSWAP(IComplex, z[k], z[j]); 
245 
} 
246  
247 
/* pass 0 */

248  
249 
p = &z[0];

250 
j = np >> 1;

251 
do {

252 
BF(p[0].re, p[0].im, p[1].re, p[1].im, 
253 
p[0].re, p[0].im, p[1].re, p[1].im); 
254 
p += 2;

255 
} while (j);

256  
257 
/* pass 1 */

258  
259 
p = &z[0];

260 
j = np >> 2;

261 
do {

262 
BF(p[0].re, p[0].im, p[2].re, p[2].im, 
263 
p[0].re, p[0].im, p[2].re, p[2].im); 
264 
BF(p[1].re, p[1].im, p[3].re, p[3].im, 
265 
p[1].re, p[1].im, p[3].im, p[3].re); 
266 
p+=4;

267 
} while (j);

268  
269 
/* pass 2 .. ln1 */

270  
271 
nblocks = np >> 3;

272 
nloops = 1 << 2; 
273 
np2 = np >> 1;

274 
do {

275 
p = z; 
276 
q = z + nloops; 
277 
for (j = 0; j < nblocks; j++) { 
278 
BF(p>re, p>im, q>re, q>im, 
279 
p>re, p>im, q>re, q>im); 
280 
p++; 
281 
q++; 
282 
for(l = nblocks; l < np2; l += nblocks) {

283 
CMUL(tmp_re, tmp_im, costab[l], sintab[l], q>re, q>im); 
284 
BF(p>re, p>im, q>re, q>im, 
285 
p>re, p>im, tmp_re, tmp_im); 
286 
p++; 
287 
q++; 
288 
} 
289 
p += nloops; 
290 
q += nloops; 
291 
} 
292 
nblocks = nblocks >> 1;

293 
nloops = nloops << 1;

294 
} while (nblocks);

295 
} 
296  
297  
298 
/**

299 
* Calculate a 512point MDCT

300 
* @param out 256 output frequency coefficients

301 
* @param in 512 windowed input audio samples

302 
*/

303 
static void mdct512(int32_t *out, int16_t *in) 
304 
{ 
305 
int i, re, im, re1, im1;

306 
int16_t rot[MDCT_SAMPLES]; 
307 
IComplex x[MDCT_SAMPLES/4];

308  
309 
/* shift to simplify computations */

310 
for (i = 0; i < MDCT_SAMPLES/4; i++) 
311 
rot[i] = in[i + 3*MDCT_SAMPLES/4]; 
312 
for (;i < MDCT_SAMPLES; i++)

313 
rot[i] = in[i  MDCT_SAMPLES/4];

314  
315 
/* pre rotation */

316 
for (i = 0; i < MDCT_SAMPLES/4; i++) { 
317 
re = ((int)rot[ 2*i]  (int)rot[MDCT_SAMPLES 12*i]) >> 1; 
318 
im = ((int)rot[MDCT_SAMPLES/2+2*i]  (int)rot[MDCT_SAMPLES/212*i]) >> 1; 
319 
CMUL(x[i].re, x[i].im, re, im, xcos1[i], xsin1[i]); 
320 
} 
321  
322 
fft(x, MDCT_NBITS  2);

323  
324 
/* post rotation */

325 
for (i = 0; i < MDCT_SAMPLES/4; i++) { 
326 
re = x[i].re; 
327 
im = x[i].im; 
328 
CMUL(re1, im1, re, im, xsin1[i], xcos1[i]); 
329 
out[ 2*i] = im1;

330 
out[MDCT_SAMPLES/212*i] = re1; 
331 
} 
332 
} 
333  
334  
335 
/**

336 
* Apply KBD window to input samples prior to MDCT.

337 
*/

338 
static void apply_window(int16_t *output, const int16_t *input, 
339 
const int16_t *window, int n) 
340 
{ 
341 
int i;

342 
int n2 = n >> 1; 
343  
344 
for (i = 0; i < n2; i++) { 
345 
output[i] = MUL16(input[i], window[i]) >> 15;

346 
output[ni1] = MUL16(input[ni1], window[i]) >> 15; 
347 
} 
348 
} 
349  
350  
351 
/**

352 
* Calculate the log2() of the maximum absolute value in an array.

353 
* @param tab input array

354 
* @param n number of values in the array

355 
* @return log2(max(abs(tab[])))

356 
*/

357 
static int log2_tab(int16_t *tab, int n) 
358 
{ 
359 
int i, v;

360  
361 
v = 0;

362 
for (i = 0; i < n; i++) 
363 
v = abs(tab[i]); 
364  
365 
return av_log2(v);

366 
} 
367  
368  
369 
/**

370 
* Leftshift each value in an array by a specified amount.

371 
* @param tab input array

372 
* @param n number of values in the array

373 
* @param lshift left shift amount. a negative value means right shift.

374 
*/

375 
static void lshift_tab(int16_t *tab, int n, int lshift) 
376 
{ 
377 
int i;

378  
379 
if (lshift > 0) { 
380 
for(i = 0; i < n; i++) 
381 
tab[i] <<= lshift; 
382 
} else if (lshift < 0) { 
383 
lshift = lshift; 
384 
for (i = 0; i < n; i++) 
385 
tab[i] >>= lshift; 
386 
} 
387 
} 
388  
389  
390 
/**

391 
* Normalize the input samples to use the maximum available precision.

392 
* This assumes signed 16bit input samples. Exponents are reduced by 9 to

393 
* match the 24bit internal precision for MDCT coefficients.

394 
*

395 
* @return exponent shift

396 
*/

397 
static int normalize_samples(AC3EncodeContext *s, 
398 
int16_t windowed_samples[AC3_WINDOW_SIZE]) 
399 
{ 
400 
int v = 14  log2_tab(windowed_samples, AC3_WINDOW_SIZE); 
401 
v = FFMAX(0, v);

402 
lshift_tab(windowed_samples, AC3_WINDOW_SIZE, v); 
403 
return v  9; 
404 
} 
405  
406  
407 
/**

408 
* Apply the MDCT to input samples to generate frequency coefficients.

409 
* This applies the KBD window and normalizes the input to reduce precision

410 
* loss due to fixedpoint calculations.

411 
*/

412 
static void apply_mdct(AC3EncodeContext *s, 
413 
int16_t planar_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE+AC3_FRAME_SIZE], 
414 
int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
415 
int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS]) 
416 
{ 
417 
int blk, ch;

418 
int16_t windowed_samples[AC3_WINDOW_SIZE]; 
419  
420 
for (ch = 0; ch < s>channels; ch++) { 
421 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
422 
const int16_t *input_samples = &planar_samples[ch][blk * AC3_BLOCK_SIZE];

423  
424 
apply_window(windowed_samples, input_samples, ff_ac3_window, AC3_WINDOW_SIZE); 
425  
426 
exp_shift[blk][ch] = normalize_samples(s, windowed_samples); 
427  
428 
mdct512(mdct_coef[blk][ch], windowed_samples); 
429 
} 
430 
} 
431 
} 
432  
433  
434 
/**

435 
* Extract exponents from the MDCT coefficients.

436 
* This takes into account the normalization that was done to the input samples

437 
* by adjusting the exponents by the exponent shift values.

438 
*/

439 
static void extract_exponents(AC3EncodeContext *s, 
440 
int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
441 
int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
442 
uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS]) 
443 
{ 
444 
int blk, ch, i;

445  
446 
/* extract exponents */

447 
for (ch = 0; ch < s>channels; ch++) { 
448 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
449 
/* compute "exponents". We take into account the normalization there */

450 
for (i = 0; i < AC3_MAX_COEFS; i++) { 
451 
int e;

452 
int v = abs(mdct_coef[blk][ch][i]);

453 
if (v == 0) 
454 
e = 24;

455 
else {

456 
e = 23  av_log2(v) + exp_shift[blk][ch];

457 
if (e >= 24) { 
458 
e = 24;

459 
mdct_coef[blk][ch][i] = 0;

460 
} 
461 
} 
462 
exp[blk][ch][i] = e; 
463 
} 
464 
} 
465 
} 
466 
} 
467  
468  
469 
/**

470 
* Calculate the sum of absolute differences (SAD) between 2 sets of exponents.

471 
*/

472 
static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n) 
473 
{ 
474 
int sum, i;

475 
sum = 0;

476 
for (i = 0; i < n; i++) 
477 
sum += abs(exp1[i]  exp2[i]); 
478 
return sum;

479 
} 
480  
481  
482 
/**

483 
* Exponent Difference Threshold.

484 
* New exponents are sent if their SAD exceed this number.

485 
*/

486 
#define EXP_DIFF_THRESHOLD 1000 
487  
488  
489 
/**

490 
* Calculate exponent strategies for all blocks in a single channel.

491 
*/

492 
static void compute_exp_strategy_ch(uint8_t *exp_strategy, uint8_t **exp) 
493 
{ 
494 
int blk, blk1;

495 
int exp_diff;

496  
497 
/* estimate if the exponent variation & decide if they should be

498 
reused in the next frame */

499 
exp_strategy[0] = EXP_NEW;

500 
for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) { 
501 
exp_diff = calc_exp_diff(exp[blk], exp[blk1], AC3_MAX_COEFS);

502 
if (exp_diff > EXP_DIFF_THRESHOLD)

503 
exp_strategy[blk] = EXP_NEW; 
504 
else

505 
exp_strategy[blk] = EXP_REUSE; 
506 
} 
507  
508 
/* now select the encoding strategy type : if exponents are often

509 
recoded, we use a coarse encoding */

510 
blk = 0;

511 
while (blk < AC3_MAX_BLOCKS) {

512 
blk1 = blk + 1;

513 
while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)

514 
blk1++; 
515 
switch (blk1  blk) {

516 
case 1: exp_strategy[blk] = EXP_D45; break; 
517 
case 2: 
518 
case 3: exp_strategy[blk] = EXP_D25; break; 
519 
default: exp_strategy[blk] = EXP_D15; break; 
520 
} 
521 
blk = blk1; 
522 
} 
523 
} 
524  
525  
526 
/**

527 
* Calculate exponent strategies for all channels.

528 
* Array arrangement is reversed to simplify the perchannel calculation.

529 
*/

530 
static void compute_exp_strategy(AC3EncodeContext *s, 
531 
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
532 
uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS]) 
533 
{ 
534 
uint8_t *exp1[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS]; 
535 
uint8_t exp_str1[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS]; 
536 
int ch, blk;

537  
538 
for (ch = 0; ch < s>fbw_channels; ch++) { 
539 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
540 
exp1[ch][blk] = exp[blk][ch]; 
541 
exp_str1[ch][blk] = exp_strategy[blk][ch]; 
542 
} 
543  
544 
compute_exp_strategy_ch(exp_str1[ch], exp1[ch]); 
545  
546 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) 
547 
exp_strategy[blk][ch] = exp_str1[ch][blk]; 
548 
} 
549 
if (s>lfe_on) {

550 
ch = s>lfe_channel; 
551 
exp_strategy[0][ch] = EXP_D15;

552 
for (blk = 1; blk < 5; blk++) 
553 
exp_strategy[blk][ch] = EXP_REUSE; 
554 
} 
555 
} 
556  
557  
558 
/**

559 
* Set each encoded exponent in a block to the minimum of itself and the

560 
* exponent in the same frequency bin of a following block.

561 
* exp[i] = min(exp[i], exp1[i]

562 
*/

563 
static void exponent_min(uint8_t exp[AC3_MAX_COEFS], uint8_t exp1[AC3_MAX_COEFS], int n) 
564 
{ 
565 
int i;

566 
for (i = 0; i < n; i++) { 
567 
if (exp1[i] < exp[i])

568 
exp[i] = exp1[i]; 
569 
} 
570 
} 
571  
572  
573 
/**

574 
* Update the exponents so that they are the ones the decoder will decode.

575 
*/

576 
static void encode_exponents_blk_ch(uint8_t encoded_exp[AC3_MAX_COEFS], 
577 
uint8_t exp[AC3_MAX_COEFS], 
578 
int nb_exps, int exp_strategy, 
579 
uint8_t *num_exp_groups) 
580 
{ 
581 
int group_size, nb_groups, i, j, k, exp_min;

582 
uint8_t exp1[AC3_MAX_COEFS]; 
583  
584 
group_size = exp_strategy + (exp_strategy == EXP_D45); 
585 
*num_exp_groups = (nb_exps + (group_size * 3)  4) / (3 * group_size); 
586 
nb_groups = *num_exp_groups * 3;

587  
588 
/* for each group, compute the minimum exponent */

589 
exp1[0] = exp[0]; /* DC exponent is handled separately */ 
590 
k = 1;

591 
for (i = 1; i <= nb_groups; i++) { 
592 
exp_min = exp[k]; 
593 
assert(exp_min >= 0 && exp_min <= 24); 
594 
for (j = 1; j < group_size; j++) { 
595 
if (exp[k+j] < exp_min)

596 
exp_min = exp[k+j]; 
597 
} 
598 
exp1[i] = exp_min; 
599 
k += group_size; 
600 
} 
601  
602 
/* constraint for DC exponent */

603 
if (exp1[0] > 15) 
604 
exp1[0] = 15; 
605  
606 
/* decrease the delta between each groups to within 2 so that they can be

607 
differentially encoded */

608 
for (i = 1; i <= nb_groups; i++) 
609 
exp1[i] = FFMIN(exp1[i], exp1[i1] + 2); 
610 
for (i = nb_groups1; i >= 0; i) 
611 
exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2); 
612  
613 
/* now we have the exponent values the decoder will see */

614 
encoded_exp[0] = exp1[0]; 
615 
k = 1;

616 
for (i = 1; i <= nb_groups; i++) { 
617 
for (j = 0; j < group_size; j++) 
618 
encoded_exp[k+j] = exp1[i]; 
619 
k += group_size; 
620 
} 
621 
} 
622  
623  
624 
/**

625 
* Encode exponents from original extracted form to what the decoder will see.

626 
* This copies and groups exponents based on exponent strategy and reduces

627 
* deltas between adjacent exponent groups so that they can be differentially

628 
* encoded.

629 
*/

630 
static void encode_exponents(AC3EncodeContext *s, 
631 
uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
632 
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
633 
uint8_t num_exp_groups[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
634 
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS]) 
635 
{ 
636 
int blk, blk1, blk2, ch;

637  
638 
for (ch = 0; ch < s>channels; ch++) { 
639 
/* for the EXP_REUSE case we select the min of the exponents */

640 
blk = 0;

641 
while (blk < AC3_MAX_BLOCKS) {

642 
blk1 = blk + 1;

643 
while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1][ch] == EXP_REUSE) {

644 
exponent_min(exp[blk][ch], exp[blk1][ch], s>nb_coefs[ch]); 
645 
blk1++; 
646 
} 
647 
encode_exponents_blk_ch(encoded_exp[blk][ch], 
648 
exp[blk][ch], s>nb_coefs[ch], 
649 
exp_strategy[blk][ch], 
650 
&num_exp_groups[blk][ch]); 
651 
/* copy encoded exponents for reuse case */

652 
for (blk2 = blk+1; blk2 < blk1; blk2++) { 
653 
memcpy(encoded_exp[blk2][ch], encoded_exp[blk][ch], 
654 
s>nb_coefs[ch] * sizeof(uint8_t));

655 
} 
656 
blk = blk1; 
657 
} 
658 
} 
659 
} 
660  
661  
662 
/**

663 
* Group exponents.

664 
* 3 deltaencoded exponents are in each 7bit group. The number of groups

665 
* varies depending on exponent strategy and bandwidth.

666 
* @return bits needed to encode the exponents

667 
*/

668 
static int group_exponents(AC3EncodeContext *s, 
669 
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
670 
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
671 
uint8_t num_exp_groups[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
672 
uint8_t grouped_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS]) 
673 
{ 
674 
int blk, ch, i;

675 
int group_size, bit_count;

676 
uint8_t *p; 
677 
int delta0, delta1, delta2;

678 
int exp0, exp1;

679  
680 
bit_count = 0;

681 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
682 
for (ch = 0; ch < s>channels; ch++) { 
683 
if (exp_strategy[blk][ch] == EXP_REUSE) {

684 
num_exp_groups[blk][ch] = 0;

685 
continue;

686 
} 
687 
group_size = exp_strategy[blk][ch] + (exp_strategy[blk][ch] == EXP_D45); 
688 
bit_count += 4 + (num_exp_groups[blk][ch] * 7); 
689 
p = encoded_exp[blk][ch]; 
690  
691 
/* DC exponent */

692 
exp1 = *p++; 
693 
grouped_exp[blk][ch][0] = exp1;

694  
695 
/* remaining exponents are delta encoded */

696 
for (i = 1; i <= num_exp_groups[blk][ch]; i++) { 
697 
/* merge three delta in one code */

698 
exp0 = exp1; 
699 
exp1 = p[0];

700 
p += group_size; 
701 
delta0 = exp1  exp0 + 2;

702  
703 
exp0 = exp1; 
704 
exp1 = p[0];

705 
p += group_size; 
706 
delta1 = exp1  exp0 + 2;

707  
708 
exp0 = exp1; 
709 
exp1 = p[0];

710 
p += group_size; 
711 
delta2 = exp1  exp0 + 2;

712  
713 
grouped_exp[blk][ch][i] = ((delta0 * 5 + delta1) * 5) + delta2; 
714 
} 
715 
} 
716 
} 
717  
718 
return bit_count;

719 
} 
720  
721  
722 
/**

723 
* Calculate final exponents from the supplied MDCT coefficients and exponent shift.

724 
* Extract exponents from MDCT coefficients, calculate exponent strategies,

725 
* and encode final exponents.

726 
* @return bits needed to encode the exponents

727 
*/

728 
static int process_exponents(AC3EncodeContext *s, 
729 
int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
730 
int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
731 
uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
732 
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
733 
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
734 
uint8_t num_exp_groups[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
735 
uint8_t grouped_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS]) 
736 
{ 
737 
extract_exponents(s, mdct_coef, exp_shift, exp); 
738  
739 
compute_exp_strategy(s, exp_strategy, exp); 
740  
741 
encode_exponents(s, exp, exp_strategy, num_exp_groups, encoded_exp); 
742  
743 
return group_exponents(s, encoded_exp, exp_strategy, num_exp_groups, grouped_exp);

744 
} 
745  
746  
747 
/**

748 
* Calculate the number of bits needed to encode a set of mantissas.

749 
*/

750 
static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs) 
751 
{ 
752 
int bits, mant, i;

753  
754 
bits = 0;

755 
for (i = 0; i < nb_coefs; i++) { 
756 
mant = m[i]; 
757 
switch (mant) {

758 
case 0: 
759 
/* nothing */

760 
break;

761 
case 1: 
762 
/* 3 mantissa in 5 bits */

763 
if (s>mant1_cnt == 0) 
764 
bits += 5;

765 
if (++s>mant1_cnt == 3) 
766 
s>mant1_cnt = 0;

767 
break;

768 
case 2: 
769 
/* 3 mantissa in 7 bits */

770 
if (s>mant2_cnt == 0) 
771 
bits += 7;

772 
if (++s>mant2_cnt == 3) 
773 
s>mant2_cnt = 0;

774 
break;

775 
case 3: 
776 
bits += 3;

777 
break;

778 
case 4: 
779 
/* 2 mantissa in 7 bits */

780 
if (s>mant4_cnt == 0) 
781 
bits += 7;

782 
if (++s>mant4_cnt == 2) 
783 
s>mant4_cnt = 0;

784 
break;

785 
case 14: 
786 
bits += 14;

787 
break;

788 
case 15: 
789 
bits += 16;

790 
break;

791 
default:

792 
bits += mant  1;

793 
break;

794 
} 
795 
} 
796 
return bits;

797 
} 
798  
799  
800 
/**

801 
* Calculate masking curve based on the final exponents.

802 
* Also calculate the power spectral densities to use in future calculations.

803 
*/

804 
static void bit_alloc_masking(AC3EncodeContext *s, 
805 
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
806 
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
807 
int16_t psd[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
808 
int16_t mask[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]) 
809 
{ 
810 
int blk, ch;

811 
int16_t band_psd[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]; 
812  
813 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
814 
for (ch = 0; ch < s>channels; ch++) { 
815 
if(exp_strategy[blk][ch] == EXP_REUSE) {

816 
memcpy(psd[blk][ch], psd[blk1][ch], AC3_MAX_COEFS*sizeof(psd[0][0][0])); 
817 
memcpy(mask[blk][ch], mask[blk1][ch], AC3_CRITICAL_BANDS*sizeof(mask[0][0][0])); 
818 
} else {

819 
ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,

820 
s>nb_coefs[ch], 
821 
psd[blk][ch], band_psd[blk][ch]); 
822 
ff_ac3_bit_alloc_calc_mask(&s>bit_alloc, band_psd[blk][ch], 
823 
0, s>nb_coefs[ch],

824 
ff_ac3_fast_gain_tab[s>fast_gain_code[ch]], 
825 
ch == s>lfe_channel, 
826 
DBA_NONE, 0, NULL, NULL, NULL, 
827 
mask[blk][ch]); 
828 
} 
829 
} 
830 
} 
831 
} 
832  
833  
834 
/**

835 
* Run the bit allocation with a given SNR offset.

836 
* This calculates the bit allocation pointers that will be used to determine

837 
* the quantization of each mantissa.

838 
* @return the number of remaining bits (positive or negative) if the given

839 
* SNR offset is used to quantize the mantissas.

840 
*/

841 
static int bit_alloc(AC3EncodeContext *s, 
842 
int16_t mask[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS], 
843 
int16_t psd[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
844 
uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
845 
int frame_bits, int coarse_snr_offset, int fine_snr_offset) 
846 
{ 
847 
int blk, ch;

848 
int snr_offset;

849  
850 
snr_offset = (((coarse_snr_offset  15) << 4) + fine_snr_offset) << 2; 
851  
852 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
853 
s>mant1_cnt = 0;

854 
s>mant2_cnt = 0;

855 
s>mant4_cnt = 0;

856 
for (ch = 0; ch < s>channels; ch++) { 
857 
ff_ac3_bit_alloc_calc_bap(mask[blk][ch], psd[blk][ch], 0,

858 
s>nb_coefs[ch], snr_offset, 
859 
s>bit_alloc.floor, ff_ac3_bap_tab, 
860 
bap[blk][ch]); 
861 
frame_bits += compute_mantissa_size(s, bap[blk][ch], s>nb_coefs[ch]); 
862 
} 
863 
} 
864 
return 8 * s>frame_size  frame_bits; 
865 
} 
866  
867  
868 
#define SNR_INC1 4 
869  
870 
/**

871 
* Perform bit allocation search.

872 
* Finds the SNR offset value that maximizes quality and fits in the specified

873 
* frame size. Output is the SNR offset and a set of bit allocation pointers

874 
* used to quantize the mantissas.

875 
*/

876 
static int compute_bit_allocation(AC3EncodeContext *s, 
877 
uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
878 
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
879 
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
880 
int frame_bits)

881 
{ 
882 
int blk, ch;

883 
int coarse_snr_offset, fine_snr_offset;

884 
uint8_t bap1[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS]; 
885 
int16_t psd[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS]; 
886 
int16_t mask[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]; 
887 
static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 }; 
888  
889 
/* init default parameters */

890 
s>slow_decay_code = 2;

891 
s>fast_decay_code = 1;

892 
s>slow_gain_code = 1;

893 
s>db_per_bit_code = 2;

894 
s>floor_code = 4;

895 
for (ch = 0; ch < s>channels; ch++) 
896 
s>fast_gain_code[ch] = 4;

897  
898 
/* compute real values */

899 
s>bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s>slow_decay_code] >> s>bit_alloc.sr_shift; 
900 
s>bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s>fast_decay_code] >> s>bit_alloc.sr_shift; 
901 
s>bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s>slow_gain_code]; 
902 
s>bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s>db_per_bit_code]; 
903 
s>bit_alloc.floor = ff_ac3_floor_tab[s>floor_code]; 
904  
905 
/* header size */

906 
frame_bits += 65;

907 
// if (s>channel_mode == 2)

908 
// frame_bits += 2;

909 
frame_bits += frame_bits_inc[s>channel_mode]; 
910  
911 
/* audio blocks */

912 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
913 
frame_bits += s>fbw_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */ 
914 
if (s>channel_mode == AC3_CHMODE_STEREO) {

915 
frame_bits++; /* rematstr */

916 
if (!blk)

917 
frame_bits += 4;

918 
} 
919 
frame_bits += 2 * s>fbw_channels; /* chexpstr[2] * c */ 
920 
if (s>lfe_on)

921 
frame_bits++; /* lfeexpstr */

922 
for (ch = 0; ch < s>fbw_channels; ch++) { 
923 
if (exp_strategy[blk][ch] != EXP_REUSE)

924 
frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */ 
925 
} 
926 
frame_bits++; /* baie */

927 
frame_bits++; /* snr */

928 
frame_bits += 2; /* delta / skip */ 
929 
} 
930 
frame_bits++; /* cplinu for block 0 */

931 
/* bit alloc info */

932 
/* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */

933 
/* csnroffset[6] */

934 
/* (fsnoffset[4] + fgaincod[4]) * c */

935 
frame_bits += 2*4 + 3 + 6 + s>channels * (4 + 3); 
936  
937 
/* auxdatae, crcrsv */

938 
frame_bits += 2;

939  
940 
/* CRC */

941 
frame_bits += 16;

942  
943 
/* calculate psd and masking curve before doing bit allocation */

944 
bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask); 
945  
946 
/* now the big work begins : do the bit allocation. Modify the snr

947 
offset until we can pack everything in the requested frame size */

948  
949 
coarse_snr_offset = s>coarse_snr_offset; 
950 
while (coarse_snr_offset >= 0 && 
951 
bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0) 
952 
coarse_snr_offset = SNR_INC1; 
953 
if (coarse_snr_offset < 0) { 
954 
return AVERROR(EINVAL);

955 
} 
956 
while (coarse_snr_offset + SNR_INC1 <= 63 && 
957 
bit_alloc(s, mask, psd, bap1, frame_bits, 
958 
coarse_snr_offset + SNR_INC1, 0) >= 0) { 
959 
coarse_snr_offset += SNR_INC1; 
960 
memcpy(bap, bap1, sizeof(bap1));

961 
} 
962 
while (coarse_snr_offset + 1 <= 63 && 
963 
bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) { 
964 
coarse_snr_offset++; 
965 
memcpy(bap, bap1, sizeof(bap1));

966 
} 
967  
968 
fine_snr_offset = 0;

969 
while (fine_snr_offset + SNR_INC1 <= 15 && 
970 
bit_alloc(s, mask, psd, bap1, frame_bits, 
971 
coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {

972 
fine_snr_offset += SNR_INC1; 
973 
memcpy(bap, bap1, sizeof(bap1));

974 
} 
975 
while (fine_snr_offset + 1 <= 15 && 
976 
bit_alloc(s, mask, psd, bap1, frame_bits, 
977 
coarse_snr_offset, fine_snr_offset + 1) >= 0) { 
978 
fine_snr_offset++; 
979 
memcpy(bap, bap1, sizeof(bap1));

980 
} 
981  
982 
s>coarse_snr_offset = coarse_snr_offset; 
983 
for (ch = 0; ch < s>channels; ch++) 
984 
s>fine_snr_offset[ch] = fine_snr_offset; 
985  
986 
return 0; 
987 
} 
988  
989  
990 
/**

991 
* Symmetric quantization on 'levels' levels.

992 
*/

993 
static inline int sym_quant(int c, int e, int levels) 
994 
{ 
995 
int v;

996  
997 
if (c >= 0) { 
998 
v = (levels * (c << e)) >> 24;

999 
v = (v + 1) >> 1; 
1000 
v = (levels >> 1) + v;

1001 
} else {

1002 
v = (levels * ((c) << e)) >> 24;

1003 
v = (v + 1) >> 1; 
1004 
v = (levels >> 1)  v;

1005 
} 
1006 
assert (v >= 0 && v < levels);

1007 
return v;

1008 
} 
1009  
1010  
1011 
/**

1012 
* Asymmetric quantization on 2^qbits levels.

1013 
*/

1014 
static inline int asym_quant(int c, int e, int qbits) 
1015 
{ 
1016 
int lshift, m, v;

1017  
1018 
lshift = e + qbits  24;

1019 
if (lshift >= 0) 
1020 
v = c << lshift; 
1021 
else

1022 
v = c >> (lshift); 
1023 
/* rounding */

1024 
v = (v + 1) >> 1; 
1025 
m = (1 << (qbits1)); 
1026 
if (v >= m)

1027 
v = m  1;

1028 
assert(v >= m); 
1029 
return v & ((1 << qbits)1); 
1030 
} 
1031  
1032  
1033 
/**

1034 
* Quantize a set of mantissas for a single channel in a single block.

1035 
*/

1036 
static void quantize_mantissas_blk_ch(AC3EncodeContext *s, 
1037 
int32_t *mdct_coef, int8_t exp_shift, 
1038 
uint8_t *encoded_exp, uint8_t *bap, 
1039 
uint16_t *qmant, int n)

1040 
{ 
1041 
int i;

1042  
1043 
for (i = 0; i < n; i++) { 
1044 
int v;

1045 
int c = mdct_coef[i];

1046 
int e = encoded_exp[i]  exp_shift;

1047 
int b = bap[i];

1048 
switch (b) {

1049 
case 0: 
1050 
v = 0;

1051 
break;

1052 
case 1: 
1053 
v = sym_quant(c, e, 3);

1054 
switch (s>mant1_cnt) {

1055 
case 0: 
1056 
s>qmant1_ptr = &qmant[i]; 
1057 
v = 9 * v;

1058 
s>mant1_cnt = 1;

1059 
break;

1060 
case 1: 
1061 
*s>qmant1_ptr += 3 * v;

1062 
s>mant1_cnt = 2;

1063 
v = 128;

1064 
break;

1065 
default:

1066 
*s>qmant1_ptr += v; 
1067 
s>mant1_cnt = 0;

1068 
v = 128;

1069 
break;

1070 
} 
1071 
break;

1072 
case 2: 
1073 
v = sym_quant(c, e, 5);

1074 
switch (s>mant2_cnt) {

1075 
case 0: 
1076 
s>qmant2_ptr = &qmant[i]; 
1077 
v = 25 * v;

1078 
s>mant2_cnt = 1;

1079 
break;

1080 
case 1: 
1081 
*s>qmant2_ptr += 5 * v;

1082 
s>mant2_cnt = 2;

1083 
v = 128;

1084 
break;

1085 
default:

1086 
*s>qmant2_ptr += v; 
1087 
s>mant2_cnt = 0;

1088 
v = 128;

1089 
break;

1090 
} 
1091 
break;

1092 
case 3: 
1093 
v = sym_quant(c, e, 7);

1094 
break;

1095 
case 4: 
1096 
v = sym_quant(c, e, 11);

1097 
switch (s>mant4_cnt) {

1098 
case 0: 
1099 
s>qmant4_ptr = &qmant[i]; 
1100 
v = 11 * v;

1101 
s>mant4_cnt = 1;

1102 
break;

1103 
default:

1104 
*s>qmant4_ptr += v; 
1105 
s>mant4_cnt = 0;

1106 
v = 128;

1107 
break;

1108 
} 
1109 
break;

1110 
case 5: 
1111 
v = sym_quant(c, e, 15);

1112 
break;

1113 
case 14: 
1114 
v = asym_quant(c, e, 14);

1115 
break;

1116 
case 15: 
1117 
v = asym_quant(c, e, 16);

1118 
break;

1119 
default:

1120 
v = asym_quant(c, e, b  1);

1121 
break;

1122 
} 
1123 
qmant[i] = v; 
1124 
} 
1125 
} 
1126  
1127  
1128 
/**

1129 
* Quantize mantissas using coefficients, exponents, and bit allocation pointers.

1130 
*/

1131 
static void quantize_mantissas(AC3EncodeContext *s, 
1132 
int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
1133 
int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
1134 
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
1135 
uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
1136 
uint16_t qmant[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS]) 
1137 
{ 
1138 
int blk, ch;

1139  
1140  
1141 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
1142 
s>mant1_cnt = s>mant2_cnt = s>mant4_cnt = 0;

1143 
s>qmant1_ptr = s>qmant2_ptr = s>qmant4_ptr = NULL;

1144  
1145 
for (ch = 0; ch < s>channels; ch++) { 
1146 
quantize_mantissas_blk_ch(s, mdct_coef[blk][ch], exp_shift[blk][ch], 
1147 
encoded_exp[blk][ch], bap[blk][ch], 
1148 
qmant[blk][ch], s>nb_coefs[ch]); 
1149 
} 
1150 
} 
1151 
} 
1152  
1153  
1154 
/**

1155 
* Write the AC3 frame header to the output bitstream.

1156 
*/

1157 
static void output_frame_header(AC3EncodeContext *s) 
1158 
{ 
1159 
put_bits(&s>pb, 16, 0x0b77); /* frame header */ 
1160 
put_bits(&s>pb, 16, 0); /* crc1: will be filled later */ 
1161 
put_bits(&s>pb, 2, s>bit_alloc.sr_code);

1162 
put_bits(&s>pb, 6, s>frame_size_code + (s>frame_size  s>frame_size_min) / 2); 
1163 
put_bits(&s>pb, 5, s>bitstream_id);

1164 
put_bits(&s>pb, 3, s>bitstream_mode);

1165 
put_bits(&s>pb, 3, s>channel_mode);

1166 
if ((s>channel_mode & 0x01) && s>channel_mode != AC3_CHMODE_MONO) 
1167 
put_bits(&s>pb, 2, 1); /* XXX 4.5 dB */ 
1168 
if (s>channel_mode & 0x04) 
1169 
put_bits(&s>pb, 2, 1); /* XXX 6 dB */ 
1170 
if (s>channel_mode == AC3_CHMODE_STEREO)

1171 
put_bits(&s>pb, 2, 0); /* surround not indicated */ 
1172 
put_bits(&s>pb, 1, s>lfe_on); /* LFE */ 
1173 
put_bits(&s>pb, 5, 31); /* dialog norm: 31 db */ 
1174 
put_bits(&s>pb, 1, 0); /* no compression control word */ 
1175 
put_bits(&s>pb, 1, 0); /* no lang code */ 
1176 
put_bits(&s>pb, 1, 0); /* no audio production info */ 
1177 
put_bits(&s>pb, 1, 0); /* no copyright */ 
1178 
put_bits(&s>pb, 1, 1); /* original bitstream */ 
1179 
put_bits(&s>pb, 1, 0); /* no time code 1 */ 
1180 
put_bits(&s>pb, 1, 0); /* no time code 2 */ 
1181 
put_bits(&s>pb, 1, 0); /* no additional bit stream info */ 
1182 
} 
1183  
1184  
1185 
/**

1186 
* Write one audio block to the output bitstream.

1187 
*/

1188 
static void output_audio_block(AC3EncodeContext *s, 
1189 
uint8_t exp_strategy[AC3_MAX_CHANNELS], 
1190 
uint8_t num_exp_groups[AC3_MAX_CHANNELS], 
1191 
uint8_t grouped_exp[AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS], 
1192 
uint8_t bap[AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
1193 
uint16_t qmant[AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
1194 
int block_num)

1195 
{ 
1196 
int ch, i, baie, rbnd;

1197  
1198 
for (ch = 0; ch < s>fbw_channels; ch++) 
1199 
put_bits(&s>pb, 1, 0); /* no block switching */ 
1200 
for (ch = 0; ch < s>fbw_channels; ch++) 
1201 
put_bits(&s>pb, 1, 1); /* no dither */ 
1202 
put_bits(&s>pb, 1, 0); /* no dynamic range */ 
1203 
if (!block_num) {

1204 
put_bits(&s>pb, 1, 1); /* coupling strategy present */ 
1205 
put_bits(&s>pb, 1, 0); /* no coupling strategy */ 
1206 
} else {

1207 
put_bits(&s>pb, 1, 0); /* no new coupling strategy */ 
1208 
} 
1209  
1210 
if (s>channel_mode == AC3_CHMODE_STEREO) {

1211 
if (!block_num) {

1212 
/* first block must define rematrixing (rematstr) */

1213 
put_bits(&s>pb, 1, 1); 
1214  
1215 
/* dummy rematrixing rematflg(1:4)=0 */

1216 
for (rbnd = 0; rbnd < 4; rbnd++) 
1217 
put_bits(&s>pb, 1, 0); 
1218 
} else {

1219 
/* no matrixing (but should be used in the future) */

1220 
put_bits(&s>pb, 1, 0); 
1221 
} 
1222 
} 
1223  
1224 
/* exponent strategy */

1225 
for (ch = 0; ch < s>fbw_channels; ch++) 
1226 
put_bits(&s>pb, 2, exp_strategy[ch]);

1227  
1228 
if (s>lfe_on)

1229 
put_bits(&s>pb, 1, exp_strategy[s>lfe_channel]);

1230  
1231 
/* bandwidth */

1232 
for (ch = 0; ch < s>fbw_channels; ch++) { 
1233 
if (exp_strategy[ch] != EXP_REUSE)

1234 
put_bits(&s>pb, 6, s>bandwidth_code[ch]);

1235 
} 
1236  
1237 
/* exponents */

1238 
for (ch = 0; ch < s>channels; ch++) { 
1239 
if (exp_strategy[ch] == EXP_REUSE)

1240 
continue;

1241  
1242 
/* first exponent */

1243 
put_bits(&s>pb, 4, grouped_exp[ch][0]); 
1244  
1245 
/* next ones are deltaencoded and grouped */

1246 
for (i = 1; i <= num_exp_groups[ch]; i++) 
1247 
put_bits(&s>pb, 7, grouped_exp[ch][i]);

1248  
1249 
if (ch != s>lfe_channel)

1250 
put_bits(&s>pb, 2, 0); /* no gain range info */ 
1251 
} 
1252  
1253 
/* bit allocation info */

1254 
baie = (block_num == 0);

1255 
put_bits(&s>pb, 1, baie);

1256 
if (baie) {

1257 
put_bits(&s>pb, 2, s>slow_decay_code);

1258 
put_bits(&s>pb, 2, s>fast_decay_code);

1259 
put_bits(&s>pb, 2, s>slow_gain_code);

1260 
put_bits(&s>pb, 2, s>db_per_bit_code);

1261 
put_bits(&s>pb, 3, s>floor_code);

1262 
} 
1263  
1264 
/* snr offset */

1265 
put_bits(&s>pb, 1, baie);

1266 
if (baie) {

1267 
put_bits(&s>pb, 6, s>coarse_snr_offset);

1268 
for (ch = 0; ch < s>channels; ch++) { 
1269 
put_bits(&s>pb, 4, s>fine_snr_offset[ch]);

1270 
put_bits(&s>pb, 3, s>fast_gain_code[ch]);

1271 
} 
1272 
} 
1273  
1274 
put_bits(&s>pb, 1, 0); /* no delta bit allocation */ 
1275 
put_bits(&s>pb, 1, 0); /* no data to skip */ 
1276  
1277 
/* mantissa encoding */

1278 
for (ch = 0; ch < s>channels; ch++) { 
1279 
int b, q;

1280  
1281 
for (i = 0; i < s>nb_coefs[ch]; i++) { 
1282 
q = qmant[ch][i]; 
1283 
b = bap[ch][i]; 
1284 
switch (b) {

1285 
case 0: break; 
1286 
case 1: if (q != 128) put_bits(&s>pb, 5, q); break; 
1287 
case 2: if (q != 128) put_bits(&s>pb, 7, q); break; 
1288 
case 3: put_bits(&s>pb, 3, q); break; 
1289 
case 4: if (q != 128) put_bits(&s>pb, 7, q); break; 
1290 
case 14: put_bits(&s>pb, 14, q); break; 
1291 
case 15: put_bits(&s>pb, 16, q); break; 
1292 
default: put_bits(&s>pb, b1, q); break; 
1293 
} 
1294 
} 
1295 
} 
1296 
} 
1297  
1298  
1299 
/** CRC16 Polynomial */

1300 
#define CRC16_POLY ((1 << 0)  (1 << 2)  (1 << 15)  (1 << 16)) 
1301  
1302  
1303 
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly) 
1304 
{ 
1305 
unsigned int c; 
1306  
1307 
c = 0;

1308 
while (a) {

1309 
if (a & 1) 
1310 
c ^= b; 
1311 
a = a >> 1;

1312 
b = b << 1;

1313 
if (b & (1 << 16)) 
1314 
b ^= poly; 
1315 
} 
1316 
return c;

1317 
} 
1318  
1319  
1320 
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly) 
1321 
{ 
1322 
unsigned int r; 
1323 
r = 1;

1324 
while (n) {

1325 
if (n & 1) 
1326 
r = mul_poly(r, a, poly); 
1327 
a = mul_poly(a, a, poly); 
1328 
n >>= 1;

1329 
} 
1330 
return r;

1331 
} 
1332  
1333  
1334 
/**

1335 
* Fill the end of the frame with 0's and compute the two CRCs.

1336 
*/

1337 
static void output_frame_end(AC3EncodeContext *s) 
1338 
{ 
1339 
int frame_size, frame_size_58, pad_bytes, crc1, crc2, crc_inv;

1340 
uint8_t *frame; 
1341  
1342 
frame_size = s>frame_size; /* frame size in words */

1343 
/* align to 8 bits */

1344 
flush_put_bits(&s>pb); 
1345 
/* add zero bytes to reach the frame size */

1346 
frame = s>pb.buf; 
1347 
pad_bytes = s>frame_size  (put_bits_ptr(&s>pb)  frame)  2;

1348 
assert(pad_bytes >= 0);

1349 
if (pad_bytes > 0) 
1350 
memset(put_bits_ptr(&s>pb), 0, pad_bytes);

1351  
1352 
/* Now we must compute both crcs : this is not so easy for crc1

1353 
because it is at the beginning of the data... */

1354 
frame_size_58 = ((frame_size >> 2) + (frame_size >> 4)) << 1; 
1355  
1356 
crc1 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,

1357 
frame + 4, frame_size_58  4)); 
1358  
1359 
/* XXX: could precompute crc_inv */

1360 
crc_inv = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58)  16, CRC16_POLY); 
1361 
crc1 = mul_poly(crc_inv, crc1, CRC16_POLY); 
1362 
AV_WB16(frame + 2, crc1);

1363  
1364 
crc2 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,

1365 
frame + frame_size_58, 
1366 
frame_size  frame_size_58  2));

1367 
AV_WB16(frame + frame_size  2, crc2);

1368 
} 
1369  
1370  
1371 
/**

1372 
* Write the frame to the output bitstream.

1373 
*/

1374 
static void output_frame(AC3EncodeContext *s, 
1375 
unsigned char *frame, 
1376 
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
1377 
uint8_t num_exp_groups[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS], 
1378 
uint8_t grouped_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS], 
1379 
uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS], 
1380 
uint16_t qmant[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS]) 
1381 
{ 
1382 
int blk;

1383  
1384 
init_put_bits(&s>pb, frame, AC3_MAX_CODED_FRAME_SIZE); 
1385  
1386 
output_frame_header(s); 
1387  
1388 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
1389 
output_audio_block(s, exp_strategy[blk], num_exp_groups[blk], 
1390 
grouped_exp[blk], bap[blk], qmant[blk], blk); 
1391 
} 
1392  
1393 
output_frame_end(s); 
1394 
} 
1395  
1396  
1397 
/**

1398 
* Encode a single AC3 frame.

1399 
*/

1400 
static int ac3_encode_frame(AVCodecContext *avctx, 
1401 
unsigned char *frame, int buf_size, void *data) 
1402 
{ 
1403 
AC3EncodeContext *s = avctx>priv_data; 
1404 
const int16_t *samples = data;

1405 
int16_t planar_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE+AC3_FRAME_SIZE]; 
1406 
int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS]; 
1407 
uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS]; 
1408 
uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS]; 
1409 
uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS]; 
1410 
uint8_t num_exp_groups[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS]; 
1411 
uint8_t grouped_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_EXP_GROUPS]; 
1412 
uint8_t bap[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS]; 
1413 
int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS]; 
1414 
uint16_t qmant[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS]; 
1415 
int frame_bits;

1416 
int ret;

1417  
1418 
if (s>bit_alloc.sr_code == 1) 
1419 
adjust_frame_size(s); 
1420  
1421 
deinterleave_input_samples(s, samples, planar_samples); 
1422  
1423 
apply_mdct(s, planar_samples, exp_shift, mdct_coef); 
1424  
1425 
frame_bits = process_exponents(s, mdct_coef, exp_shift, exp, exp_strategy, 
1426 
encoded_exp, num_exp_groups, grouped_exp); 
1427  
1428 
ret = compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits); 
1429 
if (ret) {

1430 
av_log(avctx, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");

1431 
return ret;

1432 
} 
1433  
1434 
quantize_mantissas(s, mdct_coef, exp_shift, encoded_exp, bap, qmant); 
1435  
1436 
output_frame(s, frame, exp_strategy, num_exp_groups, grouped_exp, bap, qmant); 
1437  
1438 
return s>frame_size;

1439 
} 
1440  
1441  
1442 
/**

1443 
* Finalize encoding and free any memory allocated by the encoder.

1444 
*/

1445 
static av_cold int ac3_encode_close(AVCodecContext *avctx) 
1446 
{ 
1447 
av_freep(&avctx>coded_frame); 
1448 
return 0; 
1449 
} 
1450  
1451  
1452 
/**

1453 
* Set channel information during initialization.

1454 
*/

1455 
static av_cold int set_channel_info(AC3EncodeContext *s, int channels, 
1456 
int64_t *channel_layout) 
1457 
{ 
1458 
int ch_layout;

1459  
1460 
if (channels < 1  channels > AC3_MAX_CHANNELS) 
1461 
return AVERROR(EINVAL);

1462 
if ((uint64_t)*channel_layout > 0x7FF) 
1463 
return AVERROR(EINVAL);

1464 
ch_layout = *channel_layout; 
1465 
if (!ch_layout)

1466 
ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);

1467 
if (av_get_channel_layout_nb_channels(ch_layout) != channels)

1468 
return AVERROR(EINVAL);

1469  
1470 
s>lfe_on = !!(ch_layout & AV_CH_LOW_FREQUENCY); 
1471 
s>channels = channels; 
1472 
s>fbw_channels = channels  s>lfe_on; 
1473 
s>lfe_channel = s>lfe_on ? s>fbw_channels : 1;

1474 
if (s>lfe_on)

1475 
ch_layout = AV_CH_LOW_FREQUENCY; 
1476  
1477 
switch (ch_layout) {

1478 
case AV_CH_LAYOUT_MONO: s>channel_mode = AC3_CHMODE_MONO; break; 
1479 
case AV_CH_LAYOUT_STEREO: s>channel_mode = AC3_CHMODE_STEREO; break; 
1480 
case AV_CH_LAYOUT_SURROUND: s>channel_mode = AC3_CHMODE_3F; break; 
1481 
case AV_CH_LAYOUT_2_1: s>channel_mode = AC3_CHMODE_2F1R; break; 
1482 
case AV_CH_LAYOUT_4POINT0: s>channel_mode = AC3_CHMODE_3F1R; break; 
1483 
case AV_CH_LAYOUT_QUAD:

1484 
case AV_CH_LAYOUT_2_2: s>channel_mode = AC3_CHMODE_2F2R; break; 
1485 
case AV_CH_LAYOUT_5POINT0:

1486 
case AV_CH_LAYOUT_5POINT0_BACK: s>channel_mode = AC3_CHMODE_3F2R; break; 
1487 
default:

1488 
return AVERROR(EINVAL);

1489 
} 
1490  
1491 
s>channel_map = ff_ac3_enc_channel_map[s>channel_mode][s>lfe_on]; 
1492 
*channel_layout = ch_layout; 
1493 
if (s>lfe_on)

1494 
*channel_layout = AV_CH_LOW_FREQUENCY; 
1495  
1496 
return 0; 
1497 
} 
1498  
1499  
1500 
static av_cold int validate_options(AVCodecContext *avctx, AC3EncodeContext *s) 
1501 
{ 
1502 
int i, ret;

1503  
1504 
/* validate channel layout */

1505 
if (!avctx>channel_layout) {

1506 
av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "

1507 
"encoder will guess the layout, but it "

1508 
"might be incorrect.\n");

1509 
} 
1510 
ret = set_channel_info(s, avctx>channels, &avctx>channel_layout); 
1511 
if (ret) {

1512 
av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");

1513 
return ret;

1514 
} 
1515  
1516 
/* validate sample rate */

1517 
for (i = 0; i < 9; i++) { 
1518 
if ((ff_ac3_sample_rate_tab[i / 3] >> (i % 3)) == avctx>sample_rate) 
1519 
break;

1520 
} 
1521 
if (i == 9) { 
1522 
av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");

1523 
return AVERROR(EINVAL);

1524 
} 
1525 
s>sample_rate = avctx>sample_rate; 
1526 
s>bit_alloc.sr_shift = i % 3;

1527 
s>bit_alloc.sr_code = i / 3;

1528  
1529 
/* validate bit rate */

1530 
for (i = 0; i < 19; i++) { 
1531 
if ((ff_ac3_bitrate_tab[i] >> s>bit_alloc.sr_shift)*1000 == avctx>bit_rate) 
1532 
break;

1533 
} 
1534 
if (i == 19) { 
1535 
av_log(avctx, AV_LOG_ERROR, "invalid bit rate\n");

1536 
return AVERROR(EINVAL);

1537 
} 
1538 
s>bit_rate = avctx>bit_rate; 
1539 
s>frame_size_code = i << 1;

1540  
1541 
return 0; 
1542 
} 
1543  
1544  
1545 
/**

1546 
* Set bandwidth for all channels.

1547 
* The user can optionally supply a cutoff frequency. Otherwise an appropriate

1548 
* default value will be used.

1549 
*/

1550 
static av_cold void set_bandwidth(AC3EncodeContext *s, int cutoff) 
1551 
{ 
1552 
int ch, bw_code;

1553  
1554 
if (cutoff) {

1555 
/* calculate bandwidth based on userspecified cutoff frequency */

1556 
int fbw_coeffs;

1557 
cutoff = av_clip(cutoff, 1, s>sample_rate >> 1); 
1558 
fbw_coeffs = cutoff * 2 * AC3_MAX_COEFS / s>sample_rate;

1559 
bw_code = av_clip((fbw_coeffs  73) / 3, 0, 60); 
1560 
} else {

1561 
/* use default bandwidth setting */

1562 
/* XXX: should compute the bandwidth according to the frame

1563 
size, so that we avoid annoying high frequency artifacts */

1564 
bw_code = 50;

1565 
} 
1566  
1567 
/* set number of coefficients for each channel */

1568 
for (ch = 0; ch < s>fbw_channels; ch++) { 
1569 
s>bandwidth_code[ch] = bw_code; 
1570 
s>nb_coefs[ch] = bw_code * 3 + 73; 
1571 
} 
1572 
if (s>lfe_on)

1573 
s>nb_coefs[s>lfe_channel] = 7; /* LFE channel always has 7 coefs */ 
1574 
} 
1575  
1576  
1577 
/**

1578 
* Initialize the encoder.

1579 
*/

1580 
static av_cold int ac3_encode_init(AVCodecContext *avctx) 
1581 
{ 
1582 
AC3EncodeContext *s = avctx>priv_data; 
1583 
int ret;

1584  
1585 
avctx>frame_size = AC3_FRAME_SIZE; 
1586  
1587 
ac3_common_init(); 
1588  
1589 
ret = validate_options(avctx, s); 
1590 
if (ret)

1591 
return ret;

1592  
1593 
s>bitstream_id = 8 + s>bit_alloc.sr_shift;

1594 
s>bitstream_mode = 0; /* complete main audio service */ 
1595  
1596 
s>frame_size_min = 2 * ff_ac3_frame_size_tab[s>frame_size_code][s>bit_alloc.sr_code];

1597 
s>bits_written = 0;

1598 
s>samples_written = 0;

1599 
s>frame_size = s>frame_size_min; 
1600  
1601 
set_bandwidth(s, avctx>cutoff); 
1602  
1603 
/* initial snr offset */

1604 
s>coarse_snr_offset = 40;

1605  
1606 
mdct_init(9);

1607  
1608 
avctx>coded_frame= avcodec_alloc_frame(); 
1609 
avctx>coded_frame>key_frame= 1;

1610  
1611 
return 0; 
1612 
} 
1613  
1614  
1615 
#ifdef TEST

1616 
/*************************************************************************/

1617 
/* TEST */

1618  
1619 
#include "libavutil/lfg.h" 
1620  
1621 
#define FN (MDCT_SAMPLES/4) 
1622  
1623  
1624 
static void fft_test(AVLFG *lfg) 
1625 
{ 
1626 
IComplex in[FN], in1[FN]; 
1627 
int k, n, i;

1628 
float sum_re, sum_im, a;

1629  
1630 
for (i = 0; i < FN; i++) { 
1631 
in[i].re = av_lfg_get(lfg) % 65535  32767; 
1632 
in[i].im = av_lfg_get(lfg) % 65535  32767; 
1633 
in1[i] = in[i]; 
1634 
} 
1635 
fft(in, 7);

1636  
1637 
/* do it by hand */

1638 
for (k = 0; k < FN; k++) { 
1639 
sum_re = 0;

1640 
sum_im = 0;

1641 
for (n = 0; n < FN; n++) { 
1642 
a = 2 * M_PI * (n * k) / FN;

1643 
sum_re += in1[n].re * cos(a)  in1[n].im * sin(a); 
1644 
sum_im += in1[n].re * sin(a) + in1[n].im * cos(a); 
1645 
} 
1646 
av_log(NULL, AV_LOG_DEBUG, "%3d: %6d,%6d %6.0f,%6.0f\n", 
1647 
k, in[k].re, in[k].im, sum_re / FN, sum_im / FN); 
1648 
} 
1649 
} 
1650  
1651  
1652 
static void mdct_test(AVLFG *lfg) 
1653 
{ 
1654 
int16_t input[MDCT_SAMPLES]; 
1655 
int32_t output[AC3_MAX_COEFS]; 
1656 
float input1[MDCT_SAMPLES];

1657 
float output1[AC3_MAX_COEFS];

1658 
float s, a, err, e, emax;

1659 
int i, k, n;

1660  
1661 
for (i = 0; i < MDCT_SAMPLES; i++) { 
1662 
input[i] = (av_lfg_get(lfg) % 65535  32767) * 9 / 10; 
1663 
input1[i] = input[i]; 
1664 
} 
1665  
1666 
mdct512(output, input); 
1667  
1668 
/* do it by hand */

1669 
for (k = 0; k < AC3_MAX_COEFS; k++) { 
1670 
s = 0;

1671 
for (n = 0; n < MDCT_SAMPLES; n++) { 
1672 
a = (2*M_PI*(2*n+1+MDCT_SAMPLES/2)*(2*k+1) / (4 * MDCT_SAMPLES)); 
1673 
s += input1[n] * cos(a); 
1674 
} 
1675 
output1[k] = 2 * s / MDCT_SAMPLES;

1676 
} 
1677  
1678 
err = 0;

1679 
emax = 0;

1680 
for (i = 0; i < AC3_MAX_COEFS; i++) { 
1681 
av_log(NULL, AV_LOG_DEBUG, "%3d: %7d %7.0f\n", i, output[i], output1[i]); 
1682 
e = output[i]  output1[i]; 
1683 
if (e > emax)

1684 
emax = e; 
1685 
err += e * e; 
1686 
} 
1687 
av_log(NULL, AV_LOG_DEBUG, "err2=%f emax=%f\n", err / AC3_MAX_COEFS, emax); 
1688 
} 
1689  
1690  
1691 
int main(void) 
1692 
{ 
1693 
AVLFG lfg; 
1694  
1695 
av_log_set_level(AV_LOG_DEBUG); 
1696 
mdct_init(9);

1697  
1698 
fft_test(&lfg); 
1699 
mdct_test(&lfg); 
1700  
1701 
return 0; 
1702 
} 
1703 
#endif /* TEST */ 
1704  
1705  
1706 
AVCodec ac3_encoder = { 
1707 
"ac3",

1708 
AVMEDIA_TYPE_AUDIO, 
1709 
CODEC_ID_AC3, 
1710 
sizeof(AC3EncodeContext),

1711 
ac3_encode_init, 
1712 
ac3_encode_frame, 
1713 
ac3_encode_close, 
1714 
NULL,

1715 
.sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE}, 
1716 
.long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC3)"),

1717 
.channel_layouts = (const int64_t[]){

1718 
AV_CH_LAYOUT_MONO, 
1719 
AV_CH_LAYOUT_STEREO, 
1720 
AV_CH_LAYOUT_2_1, 
1721 
AV_CH_LAYOUT_SURROUND, 
1722 
AV_CH_LAYOUT_2_2, 
1723 
AV_CH_LAYOUT_QUAD, 
1724 
AV_CH_LAYOUT_4POINT0, 
1725 
AV_CH_LAYOUT_5POINT0, 
1726 
AV_CH_LAYOUT_5POINT0_BACK, 
1727 
(AV_CH_LAYOUT_MONO  AV_CH_LOW_FREQUENCY), 
1728 
(AV_CH_LAYOUT_STEREO  AV_CH_LOW_FREQUENCY), 
1729 
(AV_CH_LAYOUT_2_1  AV_CH_LOW_FREQUENCY), 
1730 
(AV_CH_LAYOUT_SURROUND  AV_CH_LOW_FREQUENCY), 
1731 
(AV_CH_LAYOUT_2_2  AV_CH_LOW_FREQUENCY), 
1732 
(AV_CH_LAYOUT_QUAD  AV_CH_LOW_FREQUENCY), 
1733 
(AV_CH_LAYOUT_4POINT0  AV_CH_LOW_FREQUENCY), 
1734 
AV_CH_LAYOUT_5POINT1, 
1735 
AV_CH_LAYOUT_5POINT1_BACK, 
1736 
0 },

1737 
}; 