forked from FFmpeg/FFmpeg
-
Notifications
You must be signed in to change notification settings - Fork 2
/
Copy pathac3enc.c
2502 lines (2192 loc) · 85 KB
/
ac3enc.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/*
* The simplest AC-3 encoder
* Copyright (c) 2000 Fabrice Bellard
* Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
* Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* The simplest AC-3 encoder.
*/
//#define ASSERT_LEVEL 2
#include <stdint.h>
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
#include "libavutil/channel_layout.h"
#include "libavutil/crc.h"
#include "libavutil/internal.h"
#include "libavutil/opt.h"
#include "avcodec.h"
#include "put_bits.h"
#include "ac3dsp.h"
#include "ac3.h"
#include "fft.h"
#include "ac3enc.h"
#include "eac3enc.h"
typedef struct AC3Mant {
int16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; ///< mantissa pointers for bap=1,2,4
int mant1_cnt, mant2_cnt, mant4_cnt; ///< mantissa counts for bap=1,2,4
} AC3Mant;
#define CMIXLEV_NUM_OPTIONS 3
static const float cmixlev_options[CMIXLEV_NUM_OPTIONS] = {
LEVEL_MINUS_3DB, LEVEL_MINUS_4POINT5DB, LEVEL_MINUS_6DB
};
#define SURMIXLEV_NUM_OPTIONS 3
static const float surmixlev_options[SURMIXLEV_NUM_OPTIONS] = {
LEVEL_MINUS_3DB, LEVEL_MINUS_6DB, LEVEL_ZERO
};
#define EXTMIXLEV_NUM_OPTIONS 8
static const float extmixlev_options[EXTMIXLEV_NUM_OPTIONS] = {
LEVEL_PLUS_3DB, LEVEL_PLUS_1POINT5DB, LEVEL_ONE, LEVEL_MINUS_4POINT5DB,
LEVEL_MINUS_3DB, LEVEL_MINUS_4POINT5DB, LEVEL_MINUS_6DB, LEVEL_ZERO
};
/**
* LUT for number of exponent groups.
* exponent_group_tab[coupling][exponent strategy-1][number of coefficients]
*/
static uint8_t exponent_group_tab[2][3][256];
/**
* List of supported channel layouts.
*/
const uint64_t ff_ac3_channel_layouts[19] = {
AV_CH_LAYOUT_MONO,
AV_CH_LAYOUT_STEREO,
AV_CH_LAYOUT_2_1,
AV_CH_LAYOUT_SURROUND,
AV_CH_LAYOUT_2_2,
AV_CH_LAYOUT_QUAD,
AV_CH_LAYOUT_4POINT0,
AV_CH_LAYOUT_5POINT0,
AV_CH_LAYOUT_5POINT0_BACK,
(AV_CH_LAYOUT_MONO | AV_CH_LOW_FREQUENCY),
(AV_CH_LAYOUT_STEREO | AV_CH_LOW_FREQUENCY),
(AV_CH_LAYOUT_2_1 | AV_CH_LOW_FREQUENCY),
(AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY),
(AV_CH_LAYOUT_2_2 | AV_CH_LOW_FREQUENCY),
(AV_CH_LAYOUT_QUAD | AV_CH_LOW_FREQUENCY),
(AV_CH_LAYOUT_4POINT0 | AV_CH_LOW_FREQUENCY),
AV_CH_LAYOUT_5POINT1,
AV_CH_LAYOUT_5POINT1_BACK,
0
};
/**
* LUT to select the bandwidth code based on the bit rate, sample rate, and
* number of full-bandwidth channels.
* bandwidth_tab[fbw_channels-1][sample rate code][bit rate code]
*/
static const uint8_t ac3_bandwidth_tab[5][3][19] = {
// 32 40 48 56 64 80 96 112 128 160 192 224 256 320 384 448 512 576 640
{ { 0, 0, 0, 12, 16, 32, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48 },
{ 0, 0, 0, 16, 20, 36, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56 },
{ 0, 0, 0, 32, 40, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60 } },
{ { 0, 0, 0, 0, 0, 0, 0, 20, 24, 32, 48, 48, 48, 48, 48, 48, 48, 48, 48 },
{ 0, 0, 0, 0, 0, 0, 4, 24, 28, 36, 56, 56, 56, 56, 56, 56, 56, 56, 56 },
{ 0, 0, 0, 0, 0, 0, 20, 44, 52, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60 } },
{ { 0, 0, 0, 0, 0, 0, 0, 0, 0, 16, 24, 32, 40, 48, 48, 48, 48, 48, 48 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 4, 20, 28, 36, 44, 56, 56, 56, 56, 56, 56 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 20, 40, 48, 60, 60, 60, 60, 60, 60, 60, 60 } },
{ { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 12, 24, 32, 48, 48, 48, 48, 48, 48 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 16, 28, 36, 56, 56, 56, 56, 56, 56 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 48, 60, 60, 60, 60, 60, 60, 60 } },
{ { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8, 20, 32, 40, 48, 48, 48, 48 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 12, 24, 36, 44, 56, 56, 56, 56 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 28, 44, 60, 60, 60, 60, 60, 60 } }
};
/**
* LUT to select the coupling start band based on the bit rate, sample rate, and
* number of full-bandwidth channels. -1 = coupling off
* ac3_coupling_start_tab[channel_mode-2][sample rate code][bit rate code]
*
* TODO: more testing for optimal parameters.
* multi-channel tests at 44.1kHz and 32kHz.
*/
static const int8_t ac3_coupling_start_tab[6][3][19] = {
// 32 40 48 56 64 80 96 112 128 160 192 224 256 320 384 448 512 576 640
// 2/0
{ { 0, 0, 0, 0, 0, 0, 0, 1, 1, 7, 8, 11, 12, -1, -1, -1, -1, -1, -1 },
{ 0, 0, 0, 0, 0, 0, 1, 3, 5, 7, 10, 12, 13, -1, -1, -1, -1, -1, -1 },
{ 0, 0, 0, 0, 1, 2, 2, 9, 13, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1 } },
// 3/0
{ { 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 6, 9, 11, 12, 13, -1, -1, -1, -1 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 6, 9, 11, 12, 13, -1, -1, -1, -1 },
{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 } },
// 2/1 - untested
{ { 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 6, 9, 11, 12, 13, -1, -1, -1, -1 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 6, 9, 11, 12, 13, -1, -1, -1, -1 },
{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 } },
// 3/1
{ { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 2, 10, 11, 11, 12, 12, 14, -1 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 2, 10, 11, 11, 12, 12, 14, -1 },
{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 } },
// 2/2 - untested
{ { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 2, 10, 11, 11, 12, 12, 14, -1 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 2, 10, 11, 11, 12, 12, 14, -1 },
{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 } },
// 3/2
{ { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 6, 8, 11, 12, 12, -1, -1 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 6, 8, 11, 12, 12, -1, -1 },
{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 } },
};
/**
* Adjust the frame size to make the average bit rate match the target bit rate.
* This is only needed for 11025, 22050, and 44100 sample rates or any E-AC-3.
*
* @param s AC-3 encoder private context
*/
void ff_ac3_adjust_frame_size(AC3EncodeContext *s)
{
while (s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
s->bits_written -= s->bit_rate;
s->samples_written -= s->sample_rate;
}
s->frame_size = s->frame_size_min +
2 * (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
s->bits_written += s->frame_size * 8;
s->samples_written += AC3_BLOCK_SIZE * s->num_blocks;
}
/**
* Set the initial coupling strategy parameters prior to coupling analysis.
*
* @param s AC-3 encoder private context
*/
void ff_ac3_compute_coupling_strategy(AC3EncodeContext *s)
{
int blk, ch;
int got_cpl_snr;
int num_cpl_blocks;
/* set coupling use flags for each block/channel */
/* TODO: turn coupling on/off and adjust start band based on bit usage */
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
for (ch = 1; ch <= s->fbw_channels; ch++)
block->channel_in_cpl[ch] = s->cpl_on;
}
/* enable coupling for each block if at least 2 channels have coupling
enabled for that block */
got_cpl_snr = 0;
num_cpl_blocks = 0;
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
block->num_cpl_channels = 0;
for (ch = 1; ch <= s->fbw_channels; ch++)
block->num_cpl_channels += block->channel_in_cpl[ch];
block->cpl_in_use = block->num_cpl_channels > 1;
num_cpl_blocks += block->cpl_in_use;
if (!block->cpl_in_use) {
block->num_cpl_channels = 0;
for (ch = 1; ch <= s->fbw_channels; ch++)
block->channel_in_cpl[ch] = 0;
}
block->new_cpl_strategy = !blk;
if (blk) {
for (ch = 1; ch <= s->fbw_channels; ch++) {
if (block->channel_in_cpl[ch] != s->blocks[blk-1].channel_in_cpl[ch]) {
block->new_cpl_strategy = 1;
break;
}
}
}
block->new_cpl_leak = block->new_cpl_strategy;
if (!blk || (block->cpl_in_use && !got_cpl_snr)) {
block->new_snr_offsets = 1;
if (block->cpl_in_use)
got_cpl_snr = 1;
} else {
block->new_snr_offsets = 0;
}
}
if (!num_cpl_blocks)
s->cpl_on = 0;
/* set bandwidth for each channel */
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
for (ch = 1; ch <= s->fbw_channels; ch++) {
if (block->channel_in_cpl[ch])
block->end_freq[ch] = s->start_freq[CPL_CH];
else
block->end_freq[ch] = s->bandwidth_code * 3 + 73;
}
}
}
/**
* Apply stereo rematrixing to coefficients based on rematrixing flags.
*
* @param s AC-3 encoder private context
*/
void ff_ac3_apply_rematrixing(AC3EncodeContext *s)
{
int nb_coefs;
int blk, bnd, i;
int start, end;
uint8_t *flags = NULL;
if (!s->rematrixing_enabled)
return;
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
if (block->new_rematrixing_strategy)
flags = block->rematrixing_flags;
nb_coefs = FFMIN(block->end_freq[1], block->end_freq[2]);
for (bnd = 0; bnd < block->num_rematrixing_bands; bnd++) {
if (flags[bnd]) {
start = ff_ac3_rematrix_band_tab[bnd];
end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
for (i = start; i < end; i++) {
int32_t lt = block->fixed_coef[1][i];
int32_t rt = block->fixed_coef[2][i];
block->fixed_coef[1][i] = (lt + rt) >> 1;
block->fixed_coef[2][i] = (lt - rt) >> 1;
}
}
}
}
}
/*
* Initialize exponent tables.
*/
static av_cold void exponent_init(AC3EncodeContext *s)
{
int expstr, i, grpsize;
for (expstr = EXP_D15-1; expstr <= EXP_D45-1; expstr++) {
grpsize = 3 << expstr;
for (i = 12; i < 256; i++) {
exponent_group_tab[0][expstr][i] = (i + grpsize - 4) / grpsize;
exponent_group_tab[1][expstr][i] = (i ) / grpsize;
}
}
/* LFE */
exponent_group_tab[0][0][7] = 2;
if (CONFIG_EAC3_ENCODER && s->eac3)
ff_eac3_exponent_init();
}
/*
* Extract exponents from the MDCT coefficients.
*/
static void extract_exponents(AC3EncodeContext *s)
{
int ch = !s->cpl_on;
int chan_size = AC3_MAX_COEFS * s->num_blocks * (s->channels - ch + 1);
AC3Block *block = &s->blocks[0];
s->ac3dsp.extract_exponents(block->exp[ch], block->fixed_coef[ch], chan_size);
}
/**
* Exponent Difference Threshold.
* New exponents are sent if their SAD exceed this number.
*/
#define EXP_DIFF_THRESHOLD 500
/**
* Table used to select exponent strategy based on exponent reuse block interval.
*/
static const uint8_t exp_strategy_reuse_tab[4][6] = {
{ EXP_D15, EXP_D15, EXP_D15, EXP_D15, EXP_D15, EXP_D15 },
{ EXP_D15, EXP_D15, EXP_D15, EXP_D15, EXP_D15, EXP_D15 },
{ EXP_D25, EXP_D25, EXP_D15, EXP_D15, EXP_D15, EXP_D15 },
{ EXP_D45, EXP_D25, EXP_D25, EXP_D15, EXP_D15, EXP_D15 }
};
/*
* Calculate exponent strategies for all channels.
* Array arrangement is reversed to simplify the per-channel calculation.
*/
static void compute_exp_strategy(AC3EncodeContext *s)
{
int ch, blk, blk1;
for (ch = !s->cpl_on; ch <= s->fbw_channels; ch++) {
uint8_t *exp_strategy = s->exp_strategy[ch];
uint8_t *exp = s->blocks[0].exp[ch];
int exp_diff;
/* estimate if the exponent variation & decide if they should be
reused in the next frame */
exp_strategy[0] = EXP_NEW;
exp += AC3_MAX_COEFS;
for (blk = 1; blk < s->num_blocks; blk++, exp += AC3_MAX_COEFS) {
if (ch == CPL_CH) {
if (!s->blocks[blk-1].cpl_in_use) {
exp_strategy[blk] = EXP_NEW;
continue;
} else if (!s->blocks[blk].cpl_in_use) {
exp_strategy[blk] = EXP_REUSE;
continue;
}
} else if (s->blocks[blk].channel_in_cpl[ch] != s->blocks[blk-1].channel_in_cpl[ch]) {
exp_strategy[blk] = EXP_NEW;
continue;
}
exp_diff = s->dsp.sad[0](NULL, exp, exp - AC3_MAX_COEFS, 16, 16);
exp_strategy[blk] = EXP_REUSE;
if (ch == CPL_CH && exp_diff > (EXP_DIFF_THRESHOLD * (s->blocks[blk].end_freq[ch] - s->start_freq[ch]) / AC3_MAX_COEFS))
exp_strategy[blk] = EXP_NEW;
else if (ch > CPL_CH && exp_diff > EXP_DIFF_THRESHOLD)
exp_strategy[blk] = EXP_NEW;
}
/* now select the encoding strategy type : if exponents are often
recoded, we use a coarse encoding */
blk = 0;
while (blk < s->num_blocks) {
blk1 = blk + 1;
while (blk1 < s->num_blocks && exp_strategy[blk1] == EXP_REUSE)
blk1++;
exp_strategy[blk] = exp_strategy_reuse_tab[s->num_blks_code][blk1-blk-1];
blk = blk1;
}
}
if (s->lfe_on) {
ch = s->lfe_channel;
s->exp_strategy[ch][0] = EXP_D15;
for (blk = 1; blk < s->num_blocks; blk++)
s->exp_strategy[ch][blk] = EXP_REUSE;
}
/* for E-AC-3, determine frame exponent strategy */
if (CONFIG_EAC3_ENCODER && s->eac3)
ff_eac3_get_frame_exp_strategy(s);
}
/**
* Update the exponents so that they are the ones the decoder will decode.
*
* @param[in,out] exp array of exponents for 1 block in 1 channel
* @param nb_exps number of exponents in active bandwidth
* @param exp_strategy exponent strategy for the block
* @param cpl indicates if the block is in the coupling channel
*/
static void encode_exponents_blk_ch(uint8_t *exp, int nb_exps, int exp_strategy,
int cpl)
{
int nb_groups, i, k;
nb_groups = exponent_group_tab[cpl][exp_strategy-1][nb_exps] * 3;
/* for each group, compute the minimum exponent */
switch(exp_strategy) {
case EXP_D25:
for (i = 1, k = 1-cpl; i <= nb_groups; i++) {
uint8_t exp_min = exp[k];
if (exp[k+1] < exp_min)
exp_min = exp[k+1];
exp[i-cpl] = exp_min;
k += 2;
}
break;
case EXP_D45:
for (i = 1, k = 1-cpl; i <= nb_groups; i++) {
uint8_t exp_min = exp[k];
if (exp[k+1] < exp_min)
exp_min = exp[k+1];
if (exp[k+2] < exp_min)
exp_min = exp[k+2];
if (exp[k+3] < exp_min)
exp_min = exp[k+3];
exp[i-cpl] = exp_min;
k += 4;
}
break;
}
/* constraint for DC exponent */
if (!cpl && exp[0] > 15)
exp[0] = 15;
/* decrease the delta between each groups to within 2 so that they can be
differentially encoded */
for (i = 1; i <= nb_groups; i++)
exp[i] = FFMIN(exp[i], exp[i-1] + 2);
i--;
while (--i >= 0)
exp[i] = FFMIN(exp[i], exp[i+1] + 2);
if (cpl)
exp[-1] = exp[0] & ~1;
/* now we have the exponent values the decoder will see */
switch (exp_strategy) {
case EXP_D25:
for (i = nb_groups, k = (nb_groups * 2)-cpl; i > 0; i--) {
uint8_t exp1 = exp[i-cpl];
exp[k--] = exp1;
exp[k--] = exp1;
}
break;
case EXP_D45:
for (i = nb_groups, k = (nb_groups * 4)-cpl; i > 0; i--) {
exp[k] = exp[k-1] = exp[k-2] = exp[k-3] = exp[i-cpl];
k -= 4;
}
break;
}
}
/*
* Encode exponents from original extracted form to what the decoder will see.
* This copies and groups exponents based on exponent strategy and reduces
* deltas between adjacent exponent groups so that they can be differentially
* encoded.
*/
static void encode_exponents(AC3EncodeContext *s)
{
int blk, blk1, ch, cpl;
uint8_t *exp, *exp_strategy;
int nb_coefs, num_reuse_blocks;
for (ch = !s->cpl_on; ch <= s->channels; ch++) {
exp = s->blocks[0].exp[ch] + s->start_freq[ch];
exp_strategy = s->exp_strategy[ch];
cpl = (ch == CPL_CH);
blk = 0;
while (blk < s->num_blocks) {
AC3Block *block = &s->blocks[blk];
if (cpl && !block->cpl_in_use) {
exp += AC3_MAX_COEFS;
blk++;
continue;
}
nb_coefs = block->end_freq[ch] - s->start_freq[ch];
blk1 = blk + 1;
/* count the number of EXP_REUSE blocks after the current block
and set exponent reference block numbers */
s->exp_ref_block[ch][blk] = blk;
while (blk1 < s->num_blocks && exp_strategy[blk1] == EXP_REUSE) {
s->exp_ref_block[ch][blk1] = blk;
blk1++;
}
num_reuse_blocks = blk1 - blk - 1;
/* for the EXP_REUSE case we select the min of the exponents */
s->ac3dsp.ac3_exponent_min(exp-s->start_freq[ch], num_reuse_blocks,
AC3_MAX_COEFS);
encode_exponents_blk_ch(exp, nb_coefs, exp_strategy[blk], cpl);
exp += AC3_MAX_COEFS * (num_reuse_blocks + 1);
blk = blk1;
}
}
/* reference block numbers have been changed, so reset ref_bap_set */
s->ref_bap_set = 0;
}
/*
* Count exponent bits based on bandwidth, coupling, and exponent strategies.
*/
static int count_exponent_bits(AC3EncodeContext *s)
{
int blk, ch;
int nb_groups, bit_count;
bit_count = 0;
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
for (ch = !block->cpl_in_use; ch <= s->channels; ch++) {
int exp_strategy = s->exp_strategy[ch][blk];
int cpl = (ch == CPL_CH);
int nb_coefs = block->end_freq[ch] - s->start_freq[ch];
if (exp_strategy == EXP_REUSE)
continue;
nb_groups = exponent_group_tab[cpl][exp_strategy-1][nb_coefs];
bit_count += 4 + (nb_groups * 7);
}
}
return bit_count;
}
/**
* Group exponents.
* 3 delta-encoded exponents are in each 7-bit group. The number of groups
* varies depending on exponent strategy and bandwidth.
*
* @param s AC-3 encoder private context
*/
void ff_ac3_group_exponents(AC3EncodeContext *s)
{
int blk, ch, i, cpl;
int group_size, nb_groups;
uint8_t *p;
int delta0, delta1, delta2;
int exp0, exp1;
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
for (ch = !block->cpl_in_use; ch <= s->channels; ch++) {
int exp_strategy = s->exp_strategy[ch][blk];
if (exp_strategy == EXP_REUSE)
continue;
cpl = (ch == CPL_CH);
group_size = exp_strategy + (exp_strategy == EXP_D45);
nb_groups = exponent_group_tab[cpl][exp_strategy-1][block->end_freq[ch]-s->start_freq[ch]];
p = block->exp[ch] + s->start_freq[ch] - cpl;
/* DC exponent */
exp1 = *p++;
block->grouped_exp[ch][0] = exp1;
/* remaining exponents are delta encoded */
for (i = 1; i <= nb_groups; i++) {
/* merge three delta in one code */
exp0 = exp1;
exp1 = p[0];
p += group_size;
delta0 = exp1 - exp0 + 2;
av_assert2(delta0 >= 0 && delta0 <= 4);
exp0 = exp1;
exp1 = p[0];
p += group_size;
delta1 = exp1 - exp0 + 2;
av_assert2(delta1 >= 0 && delta1 <= 4);
exp0 = exp1;
exp1 = p[0];
p += group_size;
delta2 = exp1 - exp0 + 2;
av_assert2(delta2 >= 0 && delta2 <= 4);
block->grouped_exp[ch][i] = ((delta0 * 5 + delta1) * 5) + delta2;
}
}
}
}
/**
* Calculate final exponents from the supplied MDCT coefficients and exponent shift.
* Extract exponents from MDCT coefficients, calculate exponent strategies,
* and encode final exponents.
*
* @param s AC-3 encoder private context
*/
void ff_ac3_process_exponents(AC3EncodeContext *s)
{
extract_exponents(s);
compute_exp_strategy(s);
encode_exponents(s);
emms_c();
}
/*
* Count frame bits that are based solely on fixed parameters.
* This only has to be run once when the encoder is initialized.
*/
static void count_frame_bits_fixed(AC3EncodeContext *s)
{
static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
int blk;
int frame_bits;
/* assumptions:
* no dynamic range codes
* bit allocation parameters do not change between blocks
* no delta bit allocation
* no skipped data
* no auxiliary data
* no E-AC-3 metadata
*/
/* header */
frame_bits = 16; /* sync info */
if (s->eac3) {
/* bitstream info header */
frame_bits += 35;
frame_bits += 1 + 1;
if (s->num_blocks != 0x6)
frame_bits++;
frame_bits++;
/* audio frame header */
if (s->num_blocks == 6)
frame_bits += 2;
frame_bits += 10;
/* exponent strategy */
if (s->use_frame_exp_strategy)
frame_bits += 5 * s->fbw_channels;
else
frame_bits += s->num_blocks * 2 * s->fbw_channels;
if (s->lfe_on)
frame_bits += s->num_blocks;
/* converter exponent strategy */
if (s->num_blks_code != 0x3)
frame_bits++;
else
frame_bits += s->fbw_channels * 5;
/* snr offsets */
frame_bits += 10;
/* block start info */
if (s->num_blocks != 1)
frame_bits++;
} else {
frame_bits += 49;
frame_bits += frame_bits_inc[s->channel_mode];
}
/* audio blocks */
for (blk = 0; blk < s->num_blocks; blk++) {
if (!s->eac3) {
/* block switch flags */
frame_bits += s->fbw_channels;
/* dither flags */
frame_bits += s->fbw_channels;
}
/* dynamic range */
frame_bits++;
/* spectral extension */
if (s->eac3)
frame_bits++;
if (!s->eac3) {
/* exponent strategy */
frame_bits += 2 * s->fbw_channels;
if (s->lfe_on)
frame_bits++;
/* bit allocation params */
frame_bits++;
if (!blk)
frame_bits += 2 + 2 + 2 + 2 + 3;
}
/* converter snr offset */
if (s->eac3)
frame_bits++;
if (!s->eac3) {
/* delta bit allocation */
frame_bits++;
/* skipped data */
frame_bits++;
}
}
/* auxiliary data */
frame_bits++;
/* CRC */
frame_bits += 1 + 16;
s->frame_bits_fixed = frame_bits;
}
/*
* Initialize bit allocation.
* Set default parameter codes and calculate parameter values.
*/
static void bit_alloc_init(AC3EncodeContext *s)
{
int ch;
/* init default parameters */
s->slow_decay_code = 2;
s->fast_decay_code = 1;
s->slow_gain_code = 1;
s->db_per_bit_code = s->eac3 ? 2 : 3;
s->floor_code = 7;
for (ch = 0; ch <= s->channels; ch++)
s->fast_gain_code[ch] = 4;
/* initial snr offset */
s->coarse_snr_offset = 40;
/* compute real values */
/* currently none of these values change during encoding, so we can just
set them once at initialization */
s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
s->bit_alloc.cpl_fast_leak = 0;
s->bit_alloc.cpl_slow_leak = 0;
count_frame_bits_fixed(s);
}
/*
* Count the bits used to encode the frame, minus exponents and mantissas.
* Bits based on fixed parameters have already been counted, so now we just
* have to add the bits based on parameters that change during encoding.
*/
static void count_frame_bits(AC3EncodeContext *s)
{
AC3EncOptions *opt = &s->options;
int blk, ch;
int frame_bits = 0;
/* header */
if (s->eac3) {
if (opt->eac3_mixing_metadata) {
if (s->channel_mode > AC3_CHMODE_STEREO)
frame_bits += 2;
if (s->has_center)
frame_bits += 6;
if (s->has_surround)
frame_bits += 6;
frame_bits += s->lfe_on;
frame_bits += 1 + 1 + 2;
if (s->channel_mode < AC3_CHMODE_STEREO)
frame_bits++;
frame_bits++;
}
if (opt->eac3_info_metadata) {
frame_bits += 3 + 1 + 1;
if (s->channel_mode == AC3_CHMODE_STEREO)
frame_bits += 2 + 2;
if (s->channel_mode >= AC3_CHMODE_2F2R)
frame_bits += 2;
frame_bits++;
if (opt->audio_production_info)
frame_bits += 5 + 2 + 1;
frame_bits++;
}
/* coupling */
if (s->channel_mode > AC3_CHMODE_MONO) {
frame_bits++;
for (blk = 1; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
frame_bits++;
if (block->new_cpl_strategy)
frame_bits++;
}
}
/* coupling exponent strategy */
if (s->cpl_on) {
if (s->use_frame_exp_strategy) {
frame_bits += 5 * s->cpl_on;
} else {
for (blk = 0; blk < s->num_blocks; blk++)
frame_bits += 2 * s->blocks[blk].cpl_in_use;
}
}
} else {
if (opt->audio_production_info)
frame_bits += 7;
if (s->bitstream_id == 6) {
if (opt->extended_bsi_1)
frame_bits += 14;
if (opt->extended_bsi_2)
frame_bits += 14;
}
}
/* audio blocks */
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
/* coupling strategy */
if (!s->eac3)
frame_bits++;
if (block->new_cpl_strategy) {
if (!s->eac3)
frame_bits++;
if (block->cpl_in_use) {
if (s->eac3)
frame_bits++;
if (!s->eac3 || s->channel_mode != AC3_CHMODE_STEREO)
frame_bits += s->fbw_channels;
if (s->channel_mode == AC3_CHMODE_STEREO)
frame_bits++;
frame_bits += 4 + 4;
if (s->eac3)
frame_bits++;
else
frame_bits += s->num_cpl_subbands - 1;
}
}
/* coupling coordinates */
if (block->cpl_in_use) {
for (ch = 1; ch <= s->fbw_channels; ch++) {
if (block->channel_in_cpl[ch]) {
if (!s->eac3 || block->new_cpl_coords[ch] != 2)
frame_bits++;
if (block->new_cpl_coords[ch]) {
frame_bits += 2;
frame_bits += (4 + 4) * s->num_cpl_bands;
}
}
}
}
/* stereo rematrixing */
if (s->channel_mode == AC3_CHMODE_STEREO) {
if (!s->eac3 || blk > 0)
frame_bits++;
if (s->blocks[blk].new_rematrixing_strategy)
frame_bits += block->num_rematrixing_bands;
}
/* bandwidth codes & gain range */
for (ch = 1; ch <= s->fbw_channels; ch++) {
if (s->exp_strategy[ch][blk] != EXP_REUSE) {
if (!block->channel_in_cpl[ch])
frame_bits += 6;
frame_bits += 2;
}
}
/* coupling exponent strategy */
if (!s->eac3 && block->cpl_in_use)
frame_bits += 2;
/* snr offsets and fast gain codes */
if (!s->eac3) {
frame_bits++;
if (block->new_snr_offsets)
frame_bits += 6 + (s->channels + block->cpl_in_use) * (4 + 3);
}
/* coupling leak info */
if (block->cpl_in_use) {
if (!s->eac3 || block->new_cpl_leak != 2)
frame_bits++;
if (block->new_cpl_leak)
frame_bits += 3 + 3;
}
}
s->frame_bits = s->frame_bits_fixed + frame_bits;
}
/*
* Calculate masking curve based on the final exponents.
* Also calculate the power spectral densities to use in future calculations.
*/
static void bit_alloc_masking(AC3EncodeContext *s)
{
int blk, ch;
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
for (ch = !block->cpl_in_use; ch <= s->channels; ch++) {
/* We only need psd and mask for calculating bap.
Since we currently do not calculate bap when exponent
strategy is EXP_REUSE we do not need to calculate psd or mask. */
if (s->exp_strategy[ch][blk] != EXP_REUSE) {
ff_ac3_bit_alloc_calc_psd(block->exp[ch], s->start_freq[ch],
block->end_freq[ch], block->psd[ch],
block->band_psd[ch]);
ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, block->band_psd[ch],
s->start_freq[ch], block->end_freq[ch],
ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
ch == s->lfe_channel,
DBA_NONE, 0, NULL, NULL, NULL,
block->mask[ch]);
}
}
}
}
/*
* Ensure that bap for each block and channel point to the current bap_buffer.
* They may have been switched during the bit allocation search.
*/
static void reset_block_bap(AC3EncodeContext *s)
{
int blk, ch;
uint8_t *ref_bap;
if (s->ref_bap[0][0] == s->bap_buffer && s->ref_bap_set)
return;
ref_bap = s->bap_buffer;
for (ch = 0; ch <= s->channels; ch++) {
for (blk = 0; blk < s->num_blocks; blk++)
s->ref_bap[ch][blk] = ref_bap + AC3_MAX_COEFS * s->exp_ref_block[ch][blk];
ref_bap += AC3_MAX_COEFS * s->num_blocks;
}
s->ref_bap_set = 1;
}
/**
* Initialize mantissa counts.
* These are set so that they are padded to the next whole group size when bits
* are counted in compute_mantissa_size.
*
* @param[in,out] mant_cnt running counts for each bap value for each block
*/
static void count_mantissa_bits_init(uint16_t mant_cnt[AC3_MAX_BLOCKS][16])
{
int blk;
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
memset(mant_cnt[blk], 0, sizeof(mant_cnt[blk]));
mant_cnt[blk][1] = mant_cnt[blk][2] = 2;