ac3enc: use dsputil functions in apply_window()
[libav.git] / libavcodec / ac3enc.c
1 /*
2 * The simplest AC-3 encoder
3 * Copyright (c) 2000 Fabrice Bellard
4 * Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
5 * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
6 *
7 * This file is part of FFmpeg.
8 *
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
13 *
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24 /**
25 * @file
26 * The simplest AC-3 encoder.
27 */
28
29 //#define DEBUG
30
31 #include "libavcore/audioconvert.h"
32 #include "libavutil/crc.h"
33 #include "avcodec.h"
34 #include "put_bits.h"
35 #include "dsputil.h"
36 #include "ac3.h"
37 #include "audioconvert.h"
38
39
40 #ifndef CONFIG_AC3ENC_FLOAT
41 #define CONFIG_AC3ENC_FLOAT 0
42 #endif
43
44
45 /** Maximum number of exponent groups. +1 for separate DC exponent. */
46 #define AC3_MAX_EXP_GROUPS 85
47
48 /* stereo rematrixing algorithms */
49 #define AC3_REMATRIXING_IS_STATIC 0x1
50 #define AC3_REMATRIXING_SUMS 0
51 #define AC3_REMATRIXING_NONE 1
52 #define AC3_REMATRIXING_ALWAYS 3
53
54 /** Scale a float value by 2^bits and convert to an integer. */
55 #define SCALE_FLOAT(a, bits) lrintf((a) * (float)(1 << (bits)))
56
57
58 #if CONFIG_AC3ENC_FLOAT
59 #include "ac3enc_float.h"
60 #else
61 #include "ac3enc_fixed.h"
62 #endif
63
64
65 /**
66 * Data for a single audio block.
67 */
68 typedef struct AC3Block {
69 uint8_t **bap; ///< bit allocation pointers (bap)
70 CoefType **mdct_coef; ///< MDCT coefficients
71 int32_t **fixed_coef; ///< fixed-point MDCT coefficients
72 uint8_t **exp; ///< original exponents
73 uint8_t **grouped_exp; ///< grouped exponents
74 int16_t **psd; ///< psd per frequency bin
75 int16_t **band_psd; ///< psd per critical band
76 int16_t **mask; ///< masking curve
77 uint16_t **qmant; ///< quantized mantissas
78 int8_t exp_shift[AC3_MAX_CHANNELS]; ///< exponent shift values
79 uint8_t new_rematrixing_strategy; ///< send new rematrixing flags in this block
80 uint8_t rematrixing_flags[4]; ///< rematrixing flags
81 } AC3Block;
82
83 /**
84 * AC-3 encoder private context.
85 */
86 typedef struct AC3EncodeContext {
87 PutBitContext pb; ///< bitstream writer context
88 DSPContext dsp;
89 AC3MDCTContext mdct; ///< MDCT context
90
91 AC3Block blocks[AC3_MAX_BLOCKS]; ///< per-block info
92
93 int bitstream_id; ///< bitstream id (bsid)
94 int bitstream_mode; ///< bitstream mode (bsmod)
95
96 int bit_rate; ///< target bit rate, in bits-per-second
97 int sample_rate; ///< sampling frequency, in Hz
98
99 int frame_size_min; ///< minimum frame size in case rounding is necessary
100 int frame_size; ///< current frame size in bytes
101 int frame_size_code; ///< frame size code (frmsizecod)
102 uint16_t crc_inv[2];
103 int bits_written; ///< bit count (used to avg. bitrate)
104 int samples_written; ///< sample count (used to avg. bitrate)
105
106 int fbw_channels; ///< number of full-bandwidth channels (nfchans)
107 int channels; ///< total number of channels (nchans)
108 int lfe_on; ///< indicates if there is an LFE channel (lfeon)
109 int lfe_channel; ///< channel index of the LFE channel
110 int channel_mode; ///< channel mode (acmod)
111 const uint8_t *channel_map; ///< channel map used to reorder channels
112
113 int cutoff; ///< user-specified cutoff frequency, in Hz
114 int bandwidth_code[AC3_MAX_CHANNELS]; ///< bandwidth code (0 to 60) (chbwcod)
115 int nb_coefs[AC3_MAX_CHANNELS];
116
117 int rematrixing; ///< determines how rematrixing strategy is calculated
118
119 /* bitrate allocation control */
120 int slow_gain_code; ///< slow gain code (sgaincod)
121 int slow_decay_code; ///< slow decay code (sdcycod)
122 int fast_decay_code; ///< fast decay code (fdcycod)
123 int db_per_bit_code; ///< dB/bit code (dbpbcod)
124 int floor_code; ///< floor code (floorcod)
125 AC3BitAllocParameters bit_alloc; ///< bit allocation parameters
126 int coarse_snr_offset; ///< coarse SNR offsets (csnroffst)
127 int fast_gain_code[AC3_MAX_CHANNELS]; ///< fast gain codes (signal-to-mask ratio) (fgaincod)
128 int fine_snr_offset[AC3_MAX_CHANNELS]; ///< fine SNR offsets (fsnroffst)
129 int frame_bits_fixed; ///< number of non-coefficient bits for fixed parameters
130 int frame_bits; ///< all frame bits except exponents and mantissas
131 int exponent_bits; ///< number of bits used for exponents
132
133 /* mantissa encoding */
134 int mant1_cnt, mant2_cnt, mant4_cnt; ///< mantissa counts for bap=1,2,4
135 uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; ///< mantissa pointers for bap=1,2,4
136
137 SampleType **planar_samples;
138 uint8_t *bap_buffer;
139 uint8_t *bap1_buffer;
140 CoefType *mdct_coef_buffer;
141 int32_t *fixed_coef_buffer;
142 uint8_t *exp_buffer;
143 uint8_t *grouped_exp_buffer;
144 int16_t *psd_buffer;
145 int16_t *band_psd_buffer;
146 int16_t *mask_buffer;
147 uint16_t *qmant_buffer;
148
149 uint8_t exp_strategy[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS]; ///< exponent strategies
150
151 DECLARE_ALIGNED(16, SampleType, windowed_samples)[AC3_WINDOW_SIZE];
152 } AC3EncodeContext;
153
154
155 /* prototypes for functions in ac3enc_fixed.c and ac3enc_float.c */
156
157 static av_cold void mdct_end(AC3MDCTContext *mdct);
158
159 static av_cold int mdct_init(AVCodecContext *avctx, AC3MDCTContext *mdct,
160 int nbits);
161
162 static void mdct512(AC3MDCTContext *mdct, CoefType *out, SampleType *in);
163
164 static void apply_window(DSPContext *dsp, SampleType *output, const SampleType *input,
165 const SampleType *window, int n);
166
167 static int normalize_samples(AC3EncodeContext *s);
168
169 static void scale_coefficients(AC3EncodeContext *s);
170
171
172 /**
173 * LUT for number of exponent groups.
174 * exponent_group_tab[exponent strategy-1][number of coefficients]
175 */
176 static uint8_t exponent_group_tab[3][256];
177
178
179 /**
180 * List of supported channel layouts.
181 */
182 static const int64_t ac3_channel_layouts[] = {
183 AV_CH_LAYOUT_MONO,
184 AV_CH_LAYOUT_STEREO,
185 AV_CH_LAYOUT_2_1,
186 AV_CH_LAYOUT_SURROUND,
187 AV_CH_LAYOUT_2_2,
188 AV_CH_LAYOUT_QUAD,
189 AV_CH_LAYOUT_4POINT0,
190 AV_CH_LAYOUT_5POINT0,
191 AV_CH_LAYOUT_5POINT0_BACK,
192 (AV_CH_LAYOUT_MONO | AV_CH_LOW_FREQUENCY),
193 (AV_CH_LAYOUT_STEREO | AV_CH_LOW_FREQUENCY),
194 (AV_CH_LAYOUT_2_1 | AV_CH_LOW_FREQUENCY),
195 (AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY),
196 (AV_CH_LAYOUT_2_2 | AV_CH_LOW_FREQUENCY),
197 (AV_CH_LAYOUT_QUAD | AV_CH_LOW_FREQUENCY),
198 (AV_CH_LAYOUT_4POINT0 | AV_CH_LOW_FREQUENCY),
199 AV_CH_LAYOUT_5POINT1,
200 AV_CH_LAYOUT_5POINT1_BACK,
201 0
202 };
203
204
205 /**
206 * Adjust the frame size to make the average bit rate match the target bit rate.
207 * This is only needed for 11025, 22050, and 44100 sample rates.
208 */
209 static void adjust_frame_size(AC3EncodeContext *s)
210 {
211 while (s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
212 s->bits_written -= s->bit_rate;
213 s->samples_written -= s->sample_rate;
214 }
215 s->frame_size = s->frame_size_min +
216 2 * (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
217 s->bits_written += s->frame_size * 8;
218 s->samples_written += AC3_FRAME_SIZE;
219 }
220
221
222 /**
223 * Deinterleave input samples.
224 * Channels are reordered from FFmpeg's default order to AC-3 order.
225 */
226 static void deinterleave_input_samples(AC3EncodeContext *s,
227 const SampleType *samples)
228 {
229 int ch, i;
230
231 /* deinterleave and remap input samples */
232 for (ch = 0; ch < s->channels; ch++) {
233 const SampleType *sptr;
234 int sinc;
235
236 /* copy last 256 samples of previous frame to the start of the current frame */
237 memcpy(&s->planar_samples[ch][0], &s->planar_samples[ch][AC3_FRAME_SIZE],
238 AC3_BLOCK_SIZE * sizeof(s->planar_samples[0][0]));
239
240 /* deinterleave */
241 sinc = s->channels;
242 sptr = samples + s->channel_map[ch];
243 for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) {
244 s->planar_samples[ch][i] = *sptr;
245 sptr += sinc;
246 }
247 }
248 }
249
250
251 /**
252 * Apply the MDCT to input samples to generate frequency coefficients.
253 * This applies the KBD window and normalizes the input to reduce precision
254 * loss due to fixed-point calculations.
255 */
256 static void apply_mdct(AC3EncodeContext *s)
257 {
258 int blk, ch;
259
260 for (ch = 0; ch < s->channels; ch++) {
261 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
262 AC3Block *block = &s->blocks[blk];
263 const SampleType *input_samples = &s->planar_samples[ch][blk * AC3_BLOCK_SIZE];
264
265 apply_window(&s->dsp, s->windowed_samples, input_samples, s->mdct.window, AC3_WINDOW_SIZE);
266
267 block->exp_shift[ch] = normalize_samples(s);
268
269 mdct512(&s->mdct, block->mdct_coef[ch], s->windowed_samples);
270 }
271 }
272 }
273
274
275 /**
276 * Initialize stereo rematrixing.
277 * If the strategy does not change for each frame, set the rematrixing flags.
278 */
279 static void rematrixing_init(AC3EncodeContext *s)
280 {
281 if (s->channel_mode == AC3_CHMODE_STEREO)
282 s->rematrixing = AC3_REMATRIXING_SUMS;
283 else
284 s->rematrixing = AC3_REMATRIXING_NONE;
285 /* NOTE: AC3_REMATRIXING_ALWAYS might be used in
286 the future in conjunction with channel coupling. */
287
288 if (s->rematrixing & AC3_REMATRIXING_IS_STATIC) {
289 int flag = (s->rematrixing == AC3_REMATRIXING_ALWAYS);
290 s->blocks[0].new_rematrixing_strategy = 1;
291 memset(s->blocks[0].rematrixing_flags, flag,
292 sizeof(s->blocks[0].rematrixing_flags));
293 }
294 }
295
296
297 /**
298 * Determine rematrixing flags for each block and band.
299 */
300 static void compute_rematrixing_strategy(AC3EncodeContext *s)
301 {
302 int nb_coefs;
303 int blk, bnd, i;
304 AC3Block *block, *block0;
305
306 if (s->rematrixing & AC3_REMATRIXING_IS_STATIC)
307 return;
308
309 nb_coefs = FFMIN(s->nb_coefs[0], s->nb_coefs[1]);
310
311 s->blocks[0].new_rematrixing_strategy = 1;
312 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
313 block = &s->blocks[blk];
314 for (bnd = 0; bnd < 4; bnd++) {
315 /* calculate calculate sum of squared coeffs for one band in one block */
316 int start = ff_ac3_rematrix_band_tab[bnd];
317 int end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
318 CoefSumType sum[4] = {0,};
319 for (i = start; i < end; i++) {
320 CoefType lt = block->mdct_coef[0][i];
321 CoefType rt = block->mdct_coef[1][i];
322 CoefType md = lt + rt;
323 CoefType sd = lt - rt;
324 sum[0] += lt * lt;
325 sum[1] += rt * rt;
326 sum[2] += md * md;
327 sum[3] += sd * sd;
328 }
329
330 /* compare sums to determine if rematrixing will be used for this band */
331 if (FFMIN(sum[2], sum[3]) < FFMIN(sum[0], sum[1]))
332 block->rematrixing_flags[bnd] = 1;
333 else
334 block->rematrixing_flags[bnd] = 0;
335
336 /* determine if new rematrixing flags will be sent */
337 if (blk &&
338 !block->new_rematrixing_strategy &&
339 block->rematrixing_flags[bnd] != block0->rematrixing_flags[bnd]) {
340 block->new_rematrixing_strategy = 1;
341 }
342 }
343 block0 = block;
344 }
345 }
346
347
348 /**
349 * Apply stereo rematrixing to coefficients based on rematrixing flags.
350 */
351 static void apply_rematrixing(AC3EncodeContext *s)
352 {
353 int nb_coefs;
354 int blk, bnd, i;
355 int start, end;
356 uint8_t *flags;
357
358 if (s->rematrixing == AC3_REMATRIXING_NONE)
359 return;
360
361 nb_coefs = FFMIN(s->nb_coefs[0], s->nb_coefs[1]);
362
363 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
364 AC3Block *block = &s->blocks[blk];
365 if (block->new_rematrixing_strategy)
366 flags = block->rematrixing_flags;
367 for (bnd = 0; bnd < 4; bnd++) {
368 if (flags[bnd]) {
369 start = ff_ac3_rematrix_band_tab[bnd];
370 end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
371 for (i = start; i < end; i++) {
372 int32_t lt = block->fixed_coef[0][i];
373 int32_t rt = block->fixed_coef[1][i];
374 block->fixed_coef[0][i] = (lt + rt) >> 1;
375 block->fixed_coef[1][i] = (lt - rt) >> 1;
376 }
377 }
378 }
379 }
380 }
381
382
383 /**
384 * Initialize exponent tables.
385 */
386 static av_cold void exponent_init(AC3EncodeContext *s)
387 {
388 int i;
389 for (i = 73; i < 256; i++) {
390 exponent_group_tab[0][i] = (i - 1) / 3;
391 exponent_group_tab[1][i] = (i + 2) / 6;
392 exponent_group_tab[2][i] = (i + 8) / 12;
393 }
394 /* LFE */
395 exponent_group_tab[0][7] = 2;
396 }
397
398
399 /**
400 * Extract exponents from the MDCT coefficients.
401 * This takes into account the normalization that was done to the input samples
402 * by adjusting the exponents by the exponent shift values.
403 */
404 static void extract_exponents(AC3EncodeContext *s)
405 {
406 int blk, ch, i;
407
408 for (ch = 0; ch < s->channels; ch++) {
409 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
410 AC3Block *block = &s->blocks[blk];
411 uint8_t *exp = block->exp[ch];
412 int32_t *coef = block->fixed_coef[ch];
413 int exp_shift = block->exp_shift[ch];
414 for (i = 0; i < AC3_MAX_COEFS; i++) {
415 int e;
416 int v = abs(coef[i]);
417 if (v == 0)
418 e = 24;
419 else {
420 e = 23 - av_log2(v) + exp_shift;
421 if (e >= 24) {
422 e = 24;
423 coef[i] = 0;
424 }
425 }
426 exp[i] = e;
427 }
428 }
429 }
430 }
431
432
433 /**
434 * Exponent Difference Threshold.
435 * New exponents are sent if their SAD exceed this number.
436 */
437 #define EXP_DIFF_THRESHOLD 1000
438
439
440 /**
441 * Calculate exponent strategies for all blocks in a single channel.
442 */
443 static void compute_exp_strategy_ch(AC3EncodeContext *s, uint8_t *exp_strategy,
444 uint8_t *exp)
445 {
446 int blk, blk1;
447 int exp_diff;
448
449 /* estimate if the exponent variation & decide if they should be
450 reused in the next frame */
451 exp_strategy[0] = EXP_NEW;
452 exp += AC3_MAX_COEFS;
453 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) {
454 exp_diff = s->dsp.sad[0](NULL, exp, exp - AC3_MAX_COEFS, 16, 16);
455 if (exp_diff > EXP_DIFF_THRESHOLD)
456 exp_strategy[blk] = EXP_NEW;
457 else
458 exp_strategy[blk] = EXP_REUSE;
459 exp += AC3_MAX_COEFS;
460 }
461 emms_c();
462
463 /* now select the encoding strategy type : if exponents are often
464 recoded, we use a coarse encoding */
465 blk = 0;
466 while (blk < AC3_MAX_BLOCKS) {
467 blk1 = blk + 1;
468 while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
469 blk1++;
470 switch (blk1 - blk) {
471 case 1: exp_strategy[blk] = EXP_D45; break;
472 case 2:
473 case 3: exp_strategy[blk] = EXP_D25; break;
474 default: exp_strategy[blk] = EXP_D15; break;
475 }
476 blk = blk1;
477 }
478 }
479
480
481 /**
482 * Calculate exponent strategies for all channels.
483 * Array arrangement is reversed to simplify the per-channel calculation.
484 */
485 static void compute_exp_strategy(AC3EncodeContext *s)
486 {
487 int ch, blk;
488
489 for (ch = 0; ch < s->fbw_channels; ch++) {
490 compute_exp_strategy_ch(s, s->exp_strategy[ch], s->blocks[0].exp[ch]);
491 }
492 if (s->lfe_on) {
493 ch = s->lfe_channel;
494 s->exp_strategy[ch][0] = EXP_D15;
495 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++)
496 s->exp_strategy[ch][blk] = EXP_REUSE;
497 }
498 }
499
500
501 /**
502 * Set each encoded exponent in a block to the minimum of itself and the
503 * exponents in the same frequency bin of up to 5 following blocks.
504 */
505 static void exponent_min(uint8_t *exp, int num_reuse_blocks, int nb_coefs)
506 {
507 int blk, i;
508
509 if (!num_reuse_blocks)
510 return;
511
512 for (i = 0; i < nb_coefs; i++) {
513 uint8_t min_exp = *exp;
514 uint8_t *exp1 = exp + AC3_MAX_COEFS;
515 for (blk = 0; blk < num_reuse_blocks; blk++) {
516 uint8_t next_exp = *exp1;
517 if (next_exp < min_exp)
518 min_exp = next_exp;
519 exp1 += AC3_MAX_COEFS;
520 }
521 *exp++ = min_exp;
522 }
523 }
524
525
526 /**
527 * Update the exponents so that they are the ones the decoder will decode.
528 */
529 static void encode_exponents_blk_ch(uint8_t *exp, int nb_exps, int exp_strategy)
530 {
531 int nb_groups, i, k;
532
533 nb_groups = exponent_group_tab[exp_strategy-1][nb_exps] * 3;
534
535 /* for each group, compute the minimum exponent */
536 switch(exp_strategy) {
537 case EXP_D25:
538 for (i = 1, k = 1; i <= nb_groups; i++) {
539 uint8_t exp_min = exp[k];
540 if (exp[k+1] < exp_min)
541 exp_min = exp[k+1];
542 exp[i] = exp_min;
543 k += 2;
544 }
545 break;
546 case EXP_D45:
547 for (i = 1, k = 1; i <= nb_groups; i++) {
548 uint8_t exp_min = exp[k];
549 if (exp[k+1] < exp_min)
550 exp_min = exp[k+1];
551 if (exp[k+2] < exp_min)
552 exp_min = exp[k+2];
553 if (exp[k+3] < exp_min)
554 exp_min = exp[k+3];
555 exp[i] = exp_min;
556 k += 4;
557 }
558 break;
559 }
560
561 /* constraint for DC exponent */
562 if (exp[0] > 15)
563 exp[0] = 15;
564
565 /* decrease the delta between each groups to within 2 so that they can be
566 differentially encoded */
567 for (i = 1; i <= nb_groups; i++)
568 exp[i] = FFMIN(exp[i], exp[i-1] + 2);
569 i--;
570 while (--i >= 0)
571 exp[i] = FFMIN(exp[i], exp[i+1] + 2);
572
573 /* now we have the exponent values the decoder will see */
574 switch (exp_strategy) {
575 case EXP_D25:
576 for (i = nb_groups, k = nb_groups * 2; i > 0; i--) {
577 uint8_t exp1 = exp[i];
578 exp[k--] = exp1;
579 exp[k--] = exp1;
580 }
581 break;
582 case EXP_D45:
583 for (i = nb_groups, k = nb_groups * 4; i > 0; i--) {
584 exp[k] = exp[k-1] = exp[k-2] = exp[k-3] = exp[i];
585 k -= 4;
586 }
587 break;
588 }
589 }
590
591
592 /**
593 * Encode exponents from original extracted form to what the decoder will see.
594 * This copies and groups exponents based on exponent strategy and reduces
595 * deltas between adjacent exponent groups so that they can be differentially
596 * encoded.
597 */
598 static void encode_exponents(AC3EncodeContext *s)
599 {
600 int blk, blk1, ch;
601 uint8_t *exp, *exp1, *exp_strategy;
602 int nb_coefs, num_reuse_blocks;
603
604 for (ch = 0; ch < s->channels; ch++) {
605 exp = s->blocks[0].exp[ch];
606 exp_strategy = s->exp_strategy[ch];
607 nb_coefs = s->nb_coefs[ch];
608
609 blk = 0;
610 while (blk < AC3_MAX_BLOCKS) {
611 blk1 = blk + 1;
612
613 /* count the number of EXP_REUSE blocks after the current block */
614 while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
615 blk1++;
616 num_reuse_blocks = blk1 - blk - 1;
617
618 /* for the EXP_REUSE case we select the min of the exponents */
619 exponent_min(exp, num_reuse_blocks, nb_coefs);
620
621 encode_exponents_blk_ch(exp, nb_coefs, exp_strategy[blk]);
622
623 /* copy encoded exponents for reuse case */
624 exp1 = exp + AC3_MAX_COEFS;
625 while (blk < blk1-1) {
626 memcpy(exp1, exp, nb_coefs * sizeof(*exp));
627 exp1 += AC3_MAX_COEFS;
628 blk++;
629 }
630 blk = blk1;
631 exp = exp1;
632 }
633 }
634 }
635
636
637 /**
638 * Group exponents.
639 * 3 delta-encoded exponents are in each 7-bit group. The number of groups
640 * varies depending on exponent strategy and bandwidth.
641 */
642 static void group_exponents(AC3EncodeContext *s)
643 {
644 int blk, ch, i;
645 int group_size, nb_groups, bit_count;
646 uint8_t *p;
647 int delta0, delta1, delta2;
648 int exp0, exp1;
649
650 bit_count = 0;
651 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
652 AC3Block *block = &s->blocks[blk];
653 for (ch = 0; ch < s->channels; ch++) {
654 int exp_strategy = s->exp_strategy[ch][blk];
655 if (exp_strategy == EXP_REUSE)
656 continue;
657 group_size = exp_strategy + (exp_strategy == EXP_D45);
658 nb_groups = exponent_group_tab[exp_strategy-1][s->nb_coefs[ch]];
659 bit_count += 4 + (nb_groups * 7);
660 p = block->exp[ch];
661
662 /* DC exponent */
663 exp1 = *p++;
664 block->grouped_exp[ch][0] = exp1;
665
666 /* remaining exponents are delta encoded */
667 for (i = 1; i <= nb_groups; i++) {
668 /* merge three delta in one code */
669 exp0 = exp1;
670 exp1 = p[0];
671 p += group_size;
672 delta0 = exp1 - exp0 + 2;
673
674 exp0 = exp1;
675 exp1 = p[0];
676 p += group_size;
677 delta1 = exp1 - exp0 + 2;
678
679 exp0 = exp1;
680 exp1 = p[0];
681 p += group_size;
682 delta2 = exp1 - exp0 + 2;
683
684 block->grouped_exp[ch][i] = ((delta0 * 5 + delta1) * 5) + delta2;
685 }
686 }
687 }
688
689 s->exponent_bits = bit_count;
690 }
691
692
693 /**
694 * Calculate final exponents from the supplied MDCT coefficients and exponent shift.
695 * Extract exponents from MDCT coefficients, calculate exponent strategies,
696 * and encode final exponents.
697 */
698 static void process_exponents(AC3EncodeContext *s)
699 {
700 extract_exponents(s);
701
702 compute_exp_strategy(s);
703
704 encode_exponents(s);
705
706 group_exponents(s);
707 }
708
709
710 /**
711 * Count frame bits that are based solely on fixed parameters.
712 * This only has to be run once when the encoder is initialized.
713 */
714 static void count_frame_bits_fixed(AC3EncodeContext *s)
715 {
716 static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
717 int blk;
718 int frame_bits;
719
720 /* assumptions:
721 * no dynamic range codes
722 * no channel coupling
723 * bit allocation parameters do not change between blocks
724 * SNR offsets do not change between blocks
725 * no delta bit allocation
726 * no skipped data
727 * no auxilliary data
728 */
729
730 /* header size */
731 frame_bits = 65;
732 frame_bits += frame_bits_inc[s->channel_mode];
733
734 /* audio blocks */
735 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
736 frame_bits += s->fbw_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
737 if (s->channel_mode == AC3_CHMODE_STEREO) {
738 frame_bits++; /* rematstr */
739 }
740 frame_bits += 2 * s->fbw_channels; /* chexpstr[2] * c */
741 if (s->lfe_on)
742 frame_bits++; /* lfeexpstr */
743 frame_bits++; /* baie */
744 frame_bits++; /* snr */
745 frame_bits += 2; /* delta / skip */
746 }
747 frame_bits++; /* cplinu for block 0 */
748 /* bit alloc info */
749 /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
750 /* csnroffset[6] */
751 /* (fsnoffset[4] + fgaincod[4]) * c */
752 frame_bits += 2*4 + 3 + 6 + s->channels * (4 + 3);
753
754 /* auxdatae, crcrsv */
755 frame_bits += 2;
756
757 /* CRC */
758 frame_bits += 16;
759
760 s->frame_bits_fixed = frame_bits;
761 }
762
763
764 /**
765 * Initialize bit allocation.
766 * Set default parameter codes and calculate parameter values.
767 */
768 static void bit_alloc_init(AC3EncodeContext *s)
769 {
770 int ch;
771
772 /* init default parameters */
773 s->slow_decay_code = 2;
774 s->fast_decay_code = 1;
775 s->slow_gain_code = 1;
776 s->db_per_bit_code = 3;
777 s->floor_code = 4;
778 for (ch = 0; ch < s->channels; ch++)
779 s->fast_gain_code[ch] = 4;
780
781 /* initial snr offset */
782 s->coarse_snr_offset = 40;
783
784 /* compute real values */
785 /* currently none of these values change during encoding, so we can just
786 set them once at initialization */
787 s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
788 s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
789 s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
790 s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
791 s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
792
793 count_frame_bits_fixed(s);
794 }
795
796
797 /**
798 * Count the bits used to encode the frame, minus exponents and mantissas.
799 * Bits based on fixed parameters have already been counted, so now we just
800 * have to add the bits based on parameters that change during encoding.
801 */
802 static void count_frame_bits(AC3EncodeContext *s)
803 {
804 int blk, ch;
805 int frame_bits = 0;
806
807 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
808 /* stereo rematrixing */
809 if (s->channel_mode == AC3_CHMODE_STEREO &&
810 s->blocks[blk].new_rematrixing_strategy) {
811 frame_bits += 4;
812 }
813
814 for (ch = 0; ch < s->fbw_channels; ch++) {
815 if (s->exp_strategy[ch][blk] != EXP_REUSE)
816 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
817 }
818 }
819 s->frame_bits = s->frame_bits_fixed + frame_bits;
820 }
821
822
823 /**
824 * Calculate the number of bits needed to encode a set of mantissas.
825 */
826 static int compute_mantissa_size(int mant_cnt[5], uint8_t *bap, int nb_coefs)
827 {
828 int bits, b, i;
829
830 bits = 0;
831 for (i = 0; i < nb_coefs; i++) {
832 b = bap[i];
833 if (b <= 4) {
834 // bap=1 to bap=4 will be counted in compute_mantissa_size_final
835 mant_cnt[b]++;
836 } else if (b <= 13) {
837 // bap=5 to bap=13 use (bap-1) bits
838 bits += b - 1;
839 } else {
840 // bap=14 uses 14 bits and bap=15 uses 16 bits
841 bits += (b == 14) ? 14 : 16;
842 }
843 }
844 return bits;
845 }
846
847
848 /**
849 * Finalize the mantissa bit count by adding in the grouped mantissas.
850 */
851 static int compute_mantissa_size_final(int mant_cnt[5])
852 {
853 // bap=1 : 3 mantissas in 5 bits
854 int bits = (mant_cnt[1] / 3) * 5;
855 // bap=2 : 3 mantissas in 7 bits
856 // bap=4 : 2 mantissas in 7 bits
857 bits += ((mant_cnt[2] / 3) + (mant_cnt[4] >> 1)) * 7;
858 // bap=3 : each mantissa is 3 bits
859 bits += mant_cnt[3] * 3;
860 return bits;
861 }
862
863
864 /**
865 * Calculate masking curve based on the final exponents.
866 * Also calculate the power spectral densities to use in future calculations.
867 */
868 static void bit_alloc_masking(AC3EncodeContext *s)
869 {
870 int blk, ch;
871
872 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
873 AC3Block *block = &s->blocks[blk];
874 for (ch = 0; ch < s->channels; ch++) {
875 /* We only need psd and mask for calculating bap.
876 Since we currently do not calculate bap when exponent
877 strategy is EXP_REUSE we do not need to calculate psd or mask. */
878 if (s->exp_strategy[ch][blk] != EXP_REUSE) {
879 ff_ac3_bit_alloc_calc_psd(block->exp[ch], 0,
880 s->nb_coefs[ch],
881 block->psd[ch], block->band_psd[ch]);
882 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, block->band_psd[ch],
883 0, s->nb_coefs[ch],
884 ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
885 ch == s->lfe_channel,
886 DBA_NONE, 0, NULL, NULL, NULL,
887 block->mask[ch]);
888 }
889 }
890 }
891 }
892
893
894 /**
895 * Ensure that bap for each block and channel point to the current bap_buffer.
896 * They may have been switched during the bit allocation search.
897 */
898 static void reset_block_bap(AC3EncodeContext *s)
899 {
900 int blk, ch;
901 if (s->blocks[0].bap[0] == s->bap_buffer)
902 return;
903 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
904 for (ch = 0; ch < s->channels; ch++) {
905 s->blocks[blk].bap[ch] = &s->bap_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
906 }
907 }
908 }
909
910
911 /**
912 * Run the bit allocation with a given SNR offset.
913 * This calculates the bit allocation pointers that will be used to determine
914 * the quantization of each mantissa.
915 * @return the number of bits needed for mantissas if the given SNR offset is
916 * is used.
917 */
918 static int bit_alloc(AC3EncodeContext *s, int snr_offset)
919 {
920 int blk, ch;
921 int mantissa_bits;
922 int mant_cnt[5];
923
924 snr_offset = (snr_offset - 240) << 2;
925
926 reset_block_bap(s);
927 mantissa_bits = 0;
928 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
929 AC3Block *block = &s->blocks[blk];
930 // initialize grouped mantissa counts. these are set so that they are
931 // padded to the next whole group size when bits are counted in
932 // compute_mantissa_size_final
933 mant_cnt[0] = mant_cnt[3] = 0;
934 mant_cnt[1] = mant_cnt[2] = 2;
935 mant_cnt[4] = 1;
936 for (ch = 0; ch < s->channels; ch++) {
937 /* Currently the only bit allocation parameters which vary across
938 blocks within a frame are the exponent values. We can take
939 advantage of that by reusing the bit allocation pointers
940 whenever we reuse exponents. */
941 if (s->exp_strategy[ch][blk] == EXP_REUSE) {
942 memcpy(block->bap[ch], s->blocks[blk-1].bap[ch], AC3_MAX_COEFS);
943 } else {
944 ff_ac3_bit_alloc_calc_bap(block->mask[ch], block->psd[ch], 0,
945 s->nb_coefs[ch], snr_offset,
946 s->bit_alloc.floor, ff_ac3_bap_tab,
947 block->bap[ch]);
948 }
949 mantissa_bits += compute_mantissa_size(mant_cnt, block->bap[ch], s->nb_coefs[ch]);
950 }
951 mantissa_bits += compute_mantissa_size_final(mant_cnt);
952 }
953 return mantissa_bits;
954 }
955
956
957 /**
958 * Constant bitrate bit allocation search.
959 * Find the largest SNR offset that will allow data to fit in the frame.
960 */
961 static int cbr_bit_allocation(AC3EncodeContext *s)
962 {
963 int ch;
964 int bits_left;
965 int snr_offset, snr_incr;
966
967 bits_left = 8 * s->frame_size - (s->frame_bits + s->exponent_bits);
968
969 snr_offset = s->coarse_snr_offset << 4;
970
971 /* if previous frame SNR offset was 1023, check if current frame can also
972 use SNR offset of 1023. if so, skip the search. */
973 if ((snr_offset | s->fine_snr_offset[0]) == 1023) {
974 if (bit_alloc(s, 1023) <= bits_left)
975 return 0;
976 }
977
978 while (snr_offset >= 0 &&
979 bit_alloc(s, snr_offset) > bits_left) {
980 snr_offset -= 64;
981 }
982 if (snr_offset < 0)
983 return AVERROR(EINVAL);
984
985 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
986 for (snr_incr = 64; snr_incr > 0; snr_incr >>= 2) {
987 while (snr_offset + snr_incr <= 1023 &&
988 bit_alloc(s, snr_offset + snr_incr) <= bits_left) {
989 snr_offset += snr_incr;
990 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
991 }
992 }
993 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
994 reset_block_bap(s);
995
996 s->coarse_snr_offset = snr_offset >> 4;
997 for (ch = 0; ch < s->channels; ch++)
998 s->fine_snr_offset[ch] = snr_offset & 0xF;
999
1000 return 0;
1001 }
1002
1003
1004 /**
1005 * Downgrade exponent strategies to reduce the bits used by the exponents.
1006 * This is a fallback for when bit allocation fails with the normal exponent
1007 * strategies. Each time this function is run it only downgrades the
1008 * strategy in 1 channel of 1 block.
1009 * @return non-zero if downgrade was unsuccessful
1010 */
1011 static int downgrade_exponents(AC3EncodeContext *s)
1012 {
1013 int ch, blk;
1014
1015 for (ch = 0; ch < s->fbw_channels; ch++) {
1016 for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
1017 if (s->exp_strategy[ch][blk] == EXP_D15) {
1018 s->exp_strategy[ch][blk] = EXP_D25;
1019 return 0;
1020 }
1021 }
1022 }
1023 for (ch = 0; ch < s->fbw_channels; ch++) {
1024 for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
1025 if (s->exp_strategy[ch][blk] == EXP_D25) {
1026 s->exp_strategy[ch][blk] = EXP_D45;
1027 return 0;
1028 }
1029 }
1030 }
1031 for (ch = 0; ch < s->fbw_channels; ch++) {
1032 /* block 0 cannot reuse exponents, so only downgrade D45 to REUSE if
1033 the block number > 0 */
1034 for (blk = AC3_MAX_BLOCKS-1; blk > 0; blk--) {
1035 if (s->exp_strategy[ch][blk] > EXP_REUSE) {
1036 s->exp_strategy[ch][blk] = EXP_REUSE;
1037 return 0;
1038 }
1039 }
1040 }
1041 return -1;
1042 }
1043
1044
1045 /**
1046 * Reduce the bandwidth to reduce the number of bits used for a given SNR offset.
1047 * This is a second fallback for when bit allocation still fails after exponents
1048 * have been downgraded.
1049 * @return non-zero if bandwidth reduction was unsuccessful
1050 */
1051 static int reduce_bandwidth(AC3EncodeContext *s, int min_bw_code)
1052 {
1053 int ch;
1054
1055 if (s->bandwidth_code[0] > min_bw_code) {
1056 for (ch = 0; ch < s->fbw_channels; ch++) {
1057 s->bandwidth_code[ch]--;
1058 s->nb_coefs[ch] = s->bandwidth_code[ch] * 3 + 73;
1059 }
1060 return 0;
1061 }
1062 return -1;
1063 }
1064
1065
1066 /**
1067 * Perform bit allocation search.
1068 * Finds the SNR offset value that maximizes quality and fits in the specified
1069 * frame size. Output is the SNR offset and a set of bit allocation pointers
1070 * used to quantize the mantissas.
1071 */
1072 static int compute_bit_allocation(AC3EncodeContext *s)
1073 {
1074 int ret;
1075
1076 count_frame_bits(s);
1077
1078 bit_alloc_masking(s);
1079
1080 ret = cbr_bit_allocation(s);
1081 while (ret) {
1082 /* fallback 1: downgrade exponents */
1083 if (!downgrade_exponents(s)) {
1084 extract_exponents(s);
1085 encode_exponents(s);
1086 group_exponents(s);
1087 ret = compute_bit_allocation(s);
1088 continue;
1089 }
1090
1091 /* fallback 2: reduce bandwidth */
1092 /* only do this if the user has not specified a specific cutoff
1093 frequency */
1094 if (!s->cutoff && !reduce_bandwidth(s, 0)) {
1095 process_exponents(s);
1096 ret = compute_bit_allocation(s);
1097 continue;
1098 }
1099
1100 /* fallbacks were not enough... */
1101 break;
1102 }
1103
1104 return ret;
1105 }
1106
1107
1108 /**
1109 * Symmetric quantization on 'levels' levels.
1110 */
1111 static inline int sym_quant(int c, int e, int levels)
1112 {
1113 int v;
1114
1115 if (c >= 0) {
1116 v = (levels * (c << e)) >> 24;
1117 v = (v + 1) >> 1;
1118 v = (levels >> 1) + v;
1119 } else {
1120 v = (levels * ((-c) << e)) >> 24;
1121 v = (v + 1) >> 1;
1122 v = (levels >> 1) - v;
1123 }
1124 assert(v >= 0 && v < levels);
1125 return v;
1126 }
1127
1128
1129 /**
1130 * Asymmetric quantization on 2^qbits levels.
1131 */
1132 static inline int asym_quant(int c, int e, int qbits)
1133 {
1134 int lshift, m, v;
1135
1136 lshift = e + qbits - 24;
1137 if (lshift >= 0)
1138 v = c << lshift;
1139 else
1140 v = c >> (-lshift);
1141 /* rounding */
1142 v = (v + 1) >> 1;
1143 m = (1 << (qbits-1));
1144 if (v >= m)
1145 v = m - 1;
1146 assert(v >= -m);
1147 return v & ((1 << qbits)-1);
1148 }
1149
1150
1151 /**
1152 * Quantize a set of mantissas for a single channel in a single block.
1153 */
1154 static void quantize_mantissas_blk_ch(AC3EncodeContext *s, int32_t *fixed_coef,
1155 int8_t exp_shift, uint8_t *exp,
1156 uint8_t *bap, uint16_t *qmant, int n)
1157 {
1158 int i;
1159
1160 for (i = 0; i < n; i++) {
1161 int v;
1162 int c = fixed_coef[i];
1163 int e = exp[i] - exp_shift;
1164 int b = bap[i];
1165 switch (b) {
1166 case 0:
1167 v = 0;
1168 break;
1169 case 1:
1170 v = sym_quant(c, e, 3);
1171 switch (s->mant1_cnt) {
1172 case 0:
1173 s->qmant1_ptr = &qmant[i];
1174 v = 9 * v;
1175 s->mant1_cnt = 1;
1176 break;
1177 case 1:
1178 *s->qmant1_ptr += 3 * v;
1179 s->mant1_cnt = 2;
1180 v = 128;
1181 break;
1182 default:
1183 *s->qmant1_ptr += v;
1184 s->mant1_cnt = 0;
1185 v = 128;
1186 break;
1187 }
1188 break;
1189 case 2:
1190 v = sym_quant(c, e, 5);
1191 switch (s->mant2_cnt) {
1192 case 0:
1193 s->qmant2_ptr = &qmant[i];
1194 v = 25 * v;
1195 s->mant2_cnt = 1;
1196 break;
1197 case 1:
1198 *s->qmant2_ptr += 5 * v;
1199 s->mant2_cnt = 2;
1200 v = 128;
1201 break;
1202 default:
1203 *s->qmant2_ptr += v;
1204 s->mant2_cnt = 0;
1205 v = 128;
1206 break;
1207 }
1208 break;
1209 case 3:
1210 v = sym_quant(c, e, 7);
1211 break;
1212 case 4:
1213 v = sym_quant(c, e, 11);
1214 switch (s->mant4_cnt) {
1215 case 0:
1216 s->qmant4_ptr = &qmant[i];
1217 v = 11 * v;
1218 s->mant4_cnt = 1;
1219 break;
1220 default:
1221 *s->qmant4_ptr += v;
1222 s->mant4_cnt = 0;
1223 v = 128;
1224 break;
1225 }
1226 break;
1227 case 5:
1228 v = sym_quant(c, e, 15);
1229 break;
1230 case 14:
1231 v = asym_quant(c, e, 14);
1232 break;
1233 case 15:
1234 v = asym_quant(c, e, 16);
1235 break;
1236 default:
1237 v = asym_quant(c, e, b - 1);
1238 break;
1239 }
1240 qmant[i] = v;
1241 }
1242 }
1243
1244
1245 /**
1246 * Quantize mantissas using coefficients, exponents, and bit allocation pointers.
1247 */
1248 static void quantize_mantissas(AC3EncodeContext *s)
1249 {
1250 int blk, ch;
1251
1252
1253 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1254 AC3Block *block = &s->blocks[blk];
1255 s->mant1_cnt = s->mant2_cnt = s->mant4_cnt = 0;
1256 s->qmant1_ptr = s->qmant2_ptr = s->qmant4_ptr = NULL;
1257
1258 for (ch = 0; ch < s->channels; ch++) {
1259 quantize_mantissas_blk_ch(s, block->fixed_coef[ch], block->exp_shift[ch],
1260 block->exp[ch], block->bap[ch],
1261 block->qmant[ch], s->nb_coefs[ch]);
1262 }
1263 }
1264 }
1265
1266
1267 /**
1268 * Write the AC-3 frame header to the output bitstream.
1269 */
1270 static void output_frame_header(AC3EncodeContext *s)
1271 {
1272 put_bits(&s->pb, 16, 0x0b77); /* frame header */
1273 put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
1274 put_bits(&s->pb, 2, s->bit_alloc.sr_code);
1275 put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min) / 2);
1276 put_bits(&s->pb, 5, s->bitstream_id);
1277 put_bits(&s->pb, 3, s->bitstream_mode);
1278 put_bits(&s->pb, 3, s->channel_mode);
1279 if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
1280 put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
1281 if (s->channel_mode & 0x04)
1282 put_bits(&s->pb, 2, 1); /* XXX -6 dB */
1283 if (s->channel_mode == AC3_CHMODE_STEREO)
1284 put_bits(&s->pb, 2, 0); /* surround not indicated */
1285 put_bits(&s->pb, 1, s->lfe_on); /* LFE */
1286 put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
1287 put_bits(&s->pb, 1, 0); /* no compression control word */
1288 put_bits(&s->pb, 1, 0); /* no lang code */
1289 put_bits(&s->pb, 1, 0); /* no audio production info */
1290 put_bits(&s->pb, 1, 0); /* no copyright */
1291 put_bits(&s->pb, 1, 1); /* original bitstream */
1292 put_bits(&s->pb, 1, 0); /* no time code 1 */
1293 put_bits(&s->pb, 1, 0); /* no time code 2 */
1294 put_bits(&s->pb, 1, 0); /* no additional bit stream info */
1295 }
1296
1297
1298 /**
1299 * Write one audio block to the output bitstream.
1300 */
1301 static void output_audio_block(AC3EncodeContext *s, int blk)
1302 {
1303 int ch, i, baie, rbnd;
1304 AC3Block *block = &s->blocks[blk];
1305
1306 /* block switching */
1307 for (ch = 0; ch < s->fbw_channels; ch++)
1308 put_bits(&s->pb, 1, 0);
1309
1310 /* dither flags */
1311 for (ch = 0; ch < s->fbw_channels; ch++)
1312 put_bits(&s->pb, 1, 1);
1313
1314 /* dynamic range codes */
1315 put_bits(&s->pb, 1, 0);
1316
1317 /* channel coupling */
1318 if (!blk) {
1319 put_bits(&s->pb, 1, 1); /* coupling strategy present */
1320 put_bits(&s->pb, 1, 0); /* no coupling strategy */
1321 } else {
1322 put_bits(&s->pb, 1, 0); /* no new coupling strategy */
1323 }
1324
1325 /* stereo rematrixing */
1326 if (s->channel_mode == AC3_CHMODE_STEREO) {
1327 put_bits(&s->pb, 1, block->new_rematrixing_strategy);
1328 if (block->new_rematrixing_strategy) {
1329 /* rematrixing flags */
1330 for (rbnd = 0; rbnd < 4; rbnd++)
1331 put_bits(&s->pb, 1, block->rematrixing_flags[rbnd]);
1332 }
1333 }
1334
1335 /* exponent strategy */
1336 for (ch = 0; ch < s->fbw_channels; ch++)
1337 put_bits(&s->pb, 2, s->exp_strategy[ch][blk]);
1338 if (s->lfe_on)
1339 put_bits(&s->pb, 1, s->exp_strategy[s->lfe_channel][blk]);
1340
1341 /* bandwidth */
1342 for (ch = 0; ch < s->fbw_channels; ch++) {
1343 if (s->exp_strategy[ch][blk] != EXP_REUSE)
1344 put_bits(&s->pb, 6, s->bandwidth_code[ch]);
1345 }
1346
1347 /* exponents */
1348 for (ch = 0; ch < s->channels; ch++) {
1349 int nb_groups;
1350
1351 if (s->exp_strategy[ch][blk] == EXP_REUSE)
1352 continue;
1353
1354 /* DC exponent */
1355 put_bits(&s->pb, 4, block->grouped_exp[ch][0]);
1356
1357 /* exponent groups */
1358 nb_groups = exponent_group_tab[s->exp_strategy[ch][blk]-1][s->nb_coefs[ch]];
1359 for (i = 1; i <= nb_groups; i++)
1360 put_bits(&s->pb, 7, block->grouped_exp[ch][i]);
1361
1362 /* gain range info */
1363 if (ch != s->lfe_channel)
1364 put_bits(&s->pb, 2, 0);
1365 }
1366
1367 /* bit allocation info */
1368 baie = (blk == 0);
1369 put_bits(&s->pb, 1, baie);
1370 if (baie) {
1371 put_bits(&s->pb, 2, s->slow_decay_code);
1372 put_bits(&s->pb, 2, s->fast_decay_code);
1373 put_bits(&s->pb, 2, s->slow_gain_code);
1374 put_bits(&s->pb, 2, s->db_per_bit_code);
1375 put_bits(&s->pb, 3, s->floor_code);
1376 }
1377
1378 /* snr offset */
1379 put_bits(&s->pb, 1, baie);
1380 if (baie) {
1381 put_bits(&s->pb, 6, s->coarse_snr_offset);
1382 for (ch = 0; ch < s->channels; ch++) {
1383 put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
1384 put_bits(&s->pb, 3, s->fast_gain_code[ch]);
1385 }
1386 }
1387
1388 put_bits(&s->pb, 1, 0); /* no delta bit allocation */
1389 put_bits(&s->pb, 1, 0); /* no data to skip */
1390
1391 /* mantissas */
1392 for (ch = 0; ch < s->channels; ch++) {
1393 int b, q;
1394 for (i = 0; i < s->nb_coefs[ch]; i++) {
1395 q = block->qmant[ch][i];
1396 b = block->bap[ch][i];
1397 switch (b) {
1398 case 0: break;
1399 case 1: if (q != 128) put_bits(&s->pb, 5, q); break;
1400 case 2: if (q != 128) put_bits(&s->pb, 7, q); break;
1401 case 3: put_bits(&s->pb, 3, q); break;
1402 case 4: if (q != 128) put_bits(&s->pb, 7, q); break;
1403 case 14: put_bits(&s->pb, 14, q); break;
1404 case 15: put_bits(&s->pb, 16, q); break;
1405 default: put_bits(&s->pb, b-1, q); break;
1406 }
1407 }
1408 }
1409 }
1410
1411
1412 /** CRC-16 Polynomial */
1413 #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1414
1415
1416 static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1417 {
1418 unsigned int c;
1419
1420 c = 0;
1421 while (a) {
1422 if (a & 1)
1423 c ^= b;
1424 a = a >> 1;
1425 b = b << 1;
1426 if (b & (1 << 16))
1427 b ^= poly;
1428 }
1429 return c;
1430 }
1431
1432
1433 static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1434 {
1435 unsigned int r;
1436 r = 1;
1437 while (n) {
1438 if (n & 1)
1439 r = mul_poly(r, a, poly);
1440 a = mul_poly(a, a, poly);
1441 n >>= 1;
1442 }
1443 return r;
1444 }
1445
1446
1447 /**
1448 * Fill the end of the frame with 0's and compute the two CRCs.
1449 */
1450 static void output_frame_end(AC3EncodeContext *s)
1451 {
1452 const AVCRC *crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);
1453 int frame_size_58, pad_bytes, crc1, crc2_partial, crc2, crc_inv;
1454 uint8_t *frame;
1455
1456 frame_size_58 = ((s->frame_size >> 2) + (s->frame_size >> 4)) << 1;
1457
1458 /* pad the remainder of the frame with zeros */
1459 flush_put_bits(&s->pb);
1460 frame = s->pb.buf;
1461 pad_bytes = s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
1462 assert(pad_bytes >= 0);
1463 if (pad_bytes > 0)
1464 memset(put_bits_ptr(&s->pb), 0, pad_bytes);
1465
1466 /* compute crc1 */
1467 /* this is not so easy because it is at the beginning of the data... */
1468 crc1 = av_bswap16(av_crc(crc_ctx, 0, frame + 4, frame_size_58 - 4));
1469 crc_inv = s->crc_inv[s->frame_size > s->frame_size_min];
1470 crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
1471 AV_WB16(frame + 2, crc1);
1472
1473 /* compute crc2 */
1474 crc2_partial = av_crc(crc_ctx, 0, frame + frame_size_58,
1475 s->frame_size - frame_size_58 - 3);
1476 crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
1477 /* ensure crc2 does not match sync word by flipping crcrsv bit if needed */
1478 if (crc2 == 0x770B) {
1479 frame[s->frame_size - 3] ^= 0x1;
1480 crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
1481 }
1482 crc2 = av_bswap16(crc2);
1483 AV_WB16(frame + s->frame_size - 2, crc2);
1484 }
1485
1486
1487 /**
1488 * Write the frame to the output bitstream.
1489 */
1490 static void output_frame(AC3EncodeContext *s, unsigned char *frame)
1491 {
1492 int blk;
1493
1494 init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
1495
1496 output_frame_header(s);
1497
1498 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
1499 output_audio_block(s, blk);
1500
1501 output_frame_end(s);
1502 }
1503
1504
1505 /**
1506 * Encode a single AC-3 frame.
1507 */
1508 static int ac3_encode_frame(AVCodecContext *avctx, unsigned char *frame,
1509 int buf_size, void *data)
1510 {
1511 AC3EncodeContext *s = avctx->priv_data;
1512 const SampleType *samples = data;
1513 int ret;
1514
1515 if (s->bit_alloc.sr_code == 1)
1516 adjust_frame_size(s);
1517
1518 deinterleave_input_samples(s, samples);
1519
1520 apply_mdct(s);
1521
1522 compute_rematrixing_strategy(s);
1523
1524 scale_coefficients(s);
1525
1526 apply_rematrixing(s);
1527
1528 process_exponents(s);
1529
1530 ret = compute_bit_allocation(s);
1531 if (ret) {
1532 av_log(avctx, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
1533 return ret;
1534 }
1535
1536 quantize_mantissas(s);
1537
1538 output_frame(s, frame);
1539
1540 return s->frame_size;
1541 }
1542
1543
1544 /**
1545 * Finalize encoding and free any memory allocated by the encoder.
1546 */
1547 static av_cold int ac3_encode_close(AVCodecContext *avctx)
1548 {
1549 int blk, ch;
1550 AC3EncodeContext *s = avctx->priv_data;
1551
1552 for (ch = 0; ch < s->channels; ch++)
1553 av_freep(&s->planar_samples[ch]);
1554 av_freep(&s->planar_samples);
1555 av_freep(&s->bap_buffer);
1556 av_freep(&s->bap1_buffer);
1557 av_freep(&s->mdct_coef_buffer);
1558 av_freep(&s->fixed_coef_buffer);
1559 av_freep(&s->exp_buffer);
1560 av_freep(&s->grouped_exp_buffer);
1561 av_freep(&s->psd_buffer);
1562 av_freep(&s->band_psd_buffer);
1563 av_freep(&s->mask_buffer);
1564 av_freep(&s->qmant_buffer);
1565 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1566 AC3Block *block = &s->blocks[blk];
1567 av_freep(&block->bap);
1568 av_freep(&block->mdct_coef);
1569 av_freep(&block->fixed_coef);
1570 av_freep(&block->exp);
1571 av_freep(&block->grouped_exp);
1572 av_freep(&block->psd);
1573 av_freep(&block->band_psd);
1574 av_freep(&block->mask);
1575 av_freep(&block->qmant);
1576 }
1577
1578 mdct_end(&s->mdct);
1579
1580 av_freep(&avctx->coded_frame);
1581 return 0;
1582 }
1583
1584
1585 /**
1586 * Set channel information during initialization.
1587 */
1588 static av_cold int set_channel_info(AC3EncodeContext *s, int channels,
1589 int64_t *channel_layout)
1590 {
1591 int ch_layout;
1592
1593 if (channels < 1 || channels > AC3_MAX_CHANNELS)
1594 return AVERROR(EINVAL);
1595 if ((uint64_t)*channel_layout > 0x7FF)
1596 return AVERROR(EINVAL);
1597 ch_layout = *channel_layout;
1598 if (!ch_layout)
1599 ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);
1600 if (av_get_channel_layout_nb_channels(ch_layout) != channels)
1601 return AVERROR(EINVAL);
1602
1603 s->lfe_on = !!(ch_layout & AV_CH_LOW_FREQUENCY);
1604 s->channels = channels;
1605 s->fbw_channels = channels - s->lfe_on;
1606 s->lfe_channel = s->lfe_on ? s->fbw_channels : -1;
1607 if (s->lfe_on)
1608 ch_layout -= AV_CH_LOW_FREQUENCY;
1609
1610 switch (ch_layout) {
1611 case AV_CH_LAYOUT_MONO: s->channel_mode = AC3_CHMODE_MONO; break;
1612 case AV_CH_LAYOUT_STEREO: s->channel_mode = AC3_CHMODE_STEREO; break;
1613 case AV_CH_LAYOUT_SURROUND: s->channel_mode = AC3_CHMODE_3F; break;
1614 case AV_CH_LAYOUT_2_1: s->channel_mode = AC3_CHMODE_2F1R; break;
1615 case AV_CH_LAYOUT_4POINT0: s->channel_mode = AC3_CHMODE_3F1R; break;
1616 case AV_CH_LAYOUT_QUAD:
1617 case AV_CH_LAYOUT_2_2: s->channel_mode = AC3_CHMODE_2F2R; break;
1618 case AV_CH_LAYOUT_5POINT0:
1619 case AV_CH_LAYOUT_5POINT0_BACK: s->channel_mode = AC3_CHMODE_3F2R; break;
1620 default:
1621 return AVERROR(EINVAL);
1622 }
1623
1624 s->channel_map = ff_ac3_enc_channel_map[s->channel_mode][s->lfe_on];
1625 *channel_layout = ch_layout;
1626 if (s->lfe_on)
1627 *channel_layout |= AV_CH_LOW_FREQUENCY;
1628
1629 return 0;
1630 }
1631
1632
1633 static av_cold int validate_options(AVCodecContext *avctx, AC3EncodeContext *s)
1634 {
1635 int i, ret;
1636
1637 /* validate channel layout */
1638 if (!avctx->channel_layout) {
1639 av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
1640 "encoder will guess the layout, but it "
1641 "might be incorrect.\n");
1642 }
1643 ret = set_channel_info(s, avctx->channels, &avctx->channel_layout);
1644 if (ret) {
1645 av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");
1646 return ret;
1647 }
1648
1649 /* validate sample rate */
1650 for (i = 0; i < 9; i++) {
1651 if ((ff_ac3_sample_rate_tab[i / 3] >> (i % 3)) == avctx->sample_rate)
1652 break;
1653 }
1654 if (i == 9) {
1655 av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1656 return AVERROR(EINVAL);
1657 }
1658 s->sample_rate = avctx->sample_rate;
1659 s->bit_alloc.sr_shift = i % 3;
1660 s->bit_alloc.sr_code = i / 3;
1661
1662 /* validate bit rate */
1663 for (i = 0; i < 19; i++) {
1664 if ((ff_ac3_bitrate_tab[i] >> s->bit_alloc.sr_shift)*1000 == avctx->bit_rate)
1665 break;
1666 }
1667 if (i == 19) {
1668 av_log(avctx, AV_LOG_ERROR, "invalid bit rate\n");
1669 return AVERROR(EINVAL);
1670 }
1671 s->bit_rate = avctx->bit_rate;
1672 s->frame_size_code = i << 1;
1673
1674 /* validate cutoff */
1675 if (avctx->cutoff < 0) {
1676 av_log(avctx, AV_LOG_ERROR, "invalid cutoff frequency\n");
1677 return AVERROR(EINVAL);
1678 }
1679 s->cutoff = avctx->cutoff;
1680 if (s->cutoff > (s->sample_rate >> 1))
1681 s->cutoff = s->sample_rate >> 1;
1682
1683 return 0;
1684 }
1685
1686
1687 /**
1688 * Set bandwidth for all channels.
1689 * The user can optionally supply a cutoff frequency. Otherwise an appropriate
1690 * default value will be used.
1691 */
1692 static av_cold void set_bandwidth(AC3EncodeContext *s)
1693 {
1694 int ch, bw_code;
1695
1696 if (s->cutoff) {
1697 /* calculate bandwidth based on user-specified cutoff frequency */
1698 int fbw_coeffs;
1699 fbw_coeffs = s->cutoff * 2 * AC3_MAX_COEFS / s->sample_rate;
1700 bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
1701 } else {
1702 /* use default bandwidth setting */
1703 /* XXX: should compute the bandwidth according to the frame
1704 size, so that we avoid annoying high frequency artifacts */
1705 bw_code = 50;
1706 }
1707
1708 /* set number of coefficients for each channel */
1709 for (ch = 0; ch < s->fbw_channels; ch++) {
1710 s->bandwidth_code[ch] = bw_code;
1711 s->nb_coefs[ch] = bw_code * 3 + 73;
1712 }
1713 if (s->lfe_on)
1714 s->nb_coefs[s->lfe_channel] = 7; /* LFE channel always has 7 coefs */
1715 }
1716
1717
1718 static av_cold int allocate_buffers(AVCodecContext *avctx)
1719 {
1720 int blk, ch;
1721 AC3EncodeContext *s = avctx->priv_data;
1722
1723 FF_ALLOC_OR_GOTO(avctx, s->planar_samples, s->channels * sizeof(*s->planar_samples),
1724 alloc_fail);
1725 for (ch = 0; ch < s->channels; ch++) {
1726 FF_ALLOCZ_OR_GOTO(avctx, s->planar_samples[ch],
1727 (AC3_FRAME_SIZE+AC3_BLOCK_SIZE) * sizeof(**s->planar_samples),
1728 alloc_fail);
1729 }
1730 FF_ALLOC_OR_GOTO(avctx, s->bap_buffer, AC3_MAX_BLOCKS * s->channels *
1731 AC3_MAX_COEFS * sizeof(*s->bap_buffer), alloc_fail);
1732 FF_ALLOC_OR_GOTO(avctx, s->bap1_buffer, AC3_MAX_BLOCKS * s->channels *
1733 AC3_MAX_COEFS * sizeof(*s->bap1_buffer), alloc_fail);
1734 FF_ALLOC_OR_GOTO(avctx, s->mdct_coef_buffer, AC3_MAX_BLOCKS * s->channels *
1735 AC3_MAX_COEFS * sizeof(*s->mdct_coef_buffer), alloc_fail);
1736 FF_ALLOC_OR_GOTO(avctx, s->exp_buffer, AC3_MAX_BLOCKS * s->channels *
1737 AC3_MAX_COEFS * sizeof(*s->exp_buffer), alloc_fail);
1738 FF_ALLOC_OR_GOTO(avctx, s->grouped_exp_buffer, AC3_MAX_BLOCKS * s->channels *
1739 128 * sizeof(*s->grouped_exp_buffer), alloc_fail);
1740 FF_ALLOC_OR_GOTO(avctx, s->psd_buffer, AC3_MAX_BLOCKS * s->channels *
1741 AC3_MAX_COEFS * sizeof(*s->psd_buffer), alloc_fail);
1742 FF_ALLOC_OR_GOTO(avctx, s->band_psd_buffer, AC3_MAX_BLOCKS * s->channels *
1743 64 * sizeof(*s->band_psd_buffer), alloc_fail);
1744 FF_ALLOC_OR_GOTO(avctx, s->mask_buffer, AC3_MAX_BLOCKS * s->channels *
1745 64 * sizeof(*s->mask_buffer), alloc_fail);
1746 FF_ALLOC_OR_GOTO(avctx, s->qmant_buffer, AC3_MAX_BLOCKS * s->channels *
1747 AC3_MAX_COEFS * sizeof(*s->qmant_buffer), alloc_fail);
1748 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1749 AC3Block *block = &s->blocks[blk];
1750 FF_ALLOC_OR_GOTO(avctx, block->bap, s->channels * sizeof(*block->bap),
1751 alloc_fail);
1752 FF_ALLOCZ_OR_GOTO(avctx, block->mdct_coef, s->channels * sizeof(*block->mdct_coef),
1753 alloc_fail);
1754 FF_ALLOCZ_OR_GOTO(avctx, block->exp, s->channels * sizeof(*block->exp),
1755 alloc_fail);
1756 FF_ALLOCZ_OR_GOTO(avctx, block->grouped_exp, s->channels * sizeof(*block->grouped_exp),
1757 alloc_fail);
1758 FF_ALLOCZ_OR_GOTO(avctx, block->psd, s->channels * sizeof(*block->psd),
1759 alloc_fail);
1760 FF_ALLOCZ_OR_GOTO(avctx, block->band_psd, s->channels * sizeof(*block->band_psd),
1761 alloc_fail);
1762 FF_ALLOCZ_OR_GOTO(avctx, block->mask, s->channels * sizeof(*block->mask),
1763 alloc_fail);
1764 FF_ALLOCZ_OR_GOTO(avctx, block->qmant, s->channels * sizeof(*block->qmant),
1765 alloc_fail);
1766
1767 for (ch = 0; ch < s->channels; ch++) {
1768 /* arrangement: block, channel, coeff */
1769 block->bap[ch] = &s->bap_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1770 block->mdct_coef[ch] = &s->mdct_coef_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1771 block->grouped_exp[ch] = &s->grouped_exp_buffer[128 * (blk * s->channels + ch)];
1772 block->psd[ch] = &s->psd_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1773 block->band_psd[ch] = &s->band_psd_buffer [64 * (blk * s->channels + ch)];
1774 block->mask[ch] = &s->mask_buffer [64 * (blk * s->channels + ch)];
1775 block->qmant[ch] = &s->qmant_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1776
1777 /* arrangement: channel, block, coeff */
1778 block->exp[ch] = &s->exp_buffer [AC3_MAX_COEFS * (AC3_MAX_BLOCKS * ch + blk)];
1779 }
1780 }
1781
1782 if (CONFIG_AC3ENC_FLOAT) {
1783 FF_ALLOC_OR_GOTO(avctx, s->fixed_coef_buffer, AC3_MAX_BLOCKS * s->channels *
1784 AC3_MAX_COEFS * sizeof(*s->fixed_coef_buffer), alloc_fail);
1785 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1786 AC3Block *block = &s->blocks[blk];
1787 FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, s->channels *
1788 sizeof(*block->fixed_coef), alloc_fail);
1789 for (ch = 0; ch < s->channels; ch++)
1790 block->fixed_coef[ch] = &s->fixed_coef_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
1791 }
1792 } else {
1793 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1794 AC3Block *block = &s->blocks[blk];
1795 FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, s->channels *
1796 sizeof(*block->fixed_coef), alloc_fail);
1797 for (ch = 0; ch < s->channels; ch++)
1798 block->fixed_coef[ch] = (int32_t *)block->mdct_coef[ch];
1799 }
1800 }
1801
1802 return 0;
1803 alloc_fail:
1804 return AVERROR(ENOMEM);
1805 }
1806
1807
1808 /**
1809 * Initialize the encoder.
1810 */
1811 static av_cold int ac3_encode_init(AVCodecContext *avctx)
1812 {
1813 AC3EncodeContext *s = avctx->priv_data;
1814 int ret, frame_size_58;
1815
1816 avctx->frame_size = AC3_FRAME_SIZE;
1817
1818 ac3_common_init();
1819
1820 ret = validate_options(avctx, s);
1821 if (ret)
1822 return ret;
1823
1824 s->bitstream_id = 8 + s->bit_alloc.sr_shift;
1825 s->bitstream_mode = 0; /* complete main audio service */
1826
1827 s->frame_size_min = 2 * ff_ac3_frame_size_tab[s->frame_size_code][s->bit_alloc.sr_code];
1828 s->bits_written = 0;
1829 s->samples_written = 0;
1830 s->frame_size = s->frame_size_min;
1831
1832 /* calculate crc_inv for both possible frame sizes */
1833 frame_size_58 = (( s->frame_size >> 2) + ( s->frame_size >> 4)) << 1;
1834 s->crc_inv[0] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1835 if (s->bit_alloc.sr_code == 1) {
1836 frame_size_58 = (((s->frame_size+2) >> 2) + ((s->frame_size+2) >> 4)) << 1;
1837 s->crc_inv[1] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1838 }
1839
1840 set_bandwidth(s);
1841
1842 rematrixing_init(s);
1843
1844 exponent_init(s);
1845
1846 bit_alloc_init(s);
1847
1848 ret = mdct_init(avctx, &s->mdct, 9);
1849 if (ret)
1850 goto init_fail;
1851
1852 ret = allocate_buffers(avctx);
1853 if (ret)
1854 goto init_fail;
1855
1856 avctx->coded_frame= avcodec_alloc_frame();
1857
1858 dsputil_init(&s->dsp, avctx);
1859
1860 return 0;
1861 init_fail:
1862 ac3_encode_close(avctx);
1863 return ret;
1864 }