aboutsummaryrefslogtreecommitdiffstats
path: root/libavcodec/twinvq.c
blob: 7c449f3299068a14228a5242c77a79c0d6927011 (plain) (blame)
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
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
/*
 * TwinVQ decoder
 * Copyright (c) 2009 Vitor Sessak
 *
 * 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
 */

#include <math.h>
#include <stdint.h>

#include "libavutil/channel_layout.h"
#include "libavutil/float_dsp.h"
#include "avcodec.h"
#include "get_bits.h"
#include "fft.h"
#include "internal.h"
#include "lsp.h"
#include "sinewin.h"
#include "twinvq_data.h"

enum FrameType {
    FT_SHORT = 0,  ///< Short frame  (divided in n   sub-blocks)
    FT_MEDIUM,     ///< Medium frame (divided in m<n sub-blocks)
    FT_LONG,       ///< Long frame   (single sub-block + PPC)
    FT_PPC,        ///< Periodic Peak Component (part of the long frame)
};

/**
 * Parameters and tables that are different for each frame type
 */
struct FrameMode {
    uint8_t         sub;      ///< Number subblocks in each frame
    const uint16_t *bark_tab;

    /** number of distinct bark scale envelope values */
    uint8_t         bark_env_size;

    const int16_t  *bark_cb;    ///< codebook for the bark scale envelope (BSE)
    uint8_t         bark_n_coef;///< number of BSE CB coefficients to read
    uint8_t         bark_n_bit; ///< number of bits of the BSE coefs

    //@{
    /** main codebooks for spectrum data */
    const int16_t    *cb0;
    const int16_t    *cb1;
    //@}

    uint8_t         cb_len_read; ///< number of spectrum coefficients to read
};

/**
 * Parameters and tables that are different for every combination of
 * bitrate/sample rate
 */
typedef struct {
    struct FrameMode fmode[3]; ///< frame type-dependant parameters

    uint16_t     size;        ///< frame size in samples
    uint8_t      n_lsp;       ///< number of lsp coefficients
    const float *lspcodebook;

    /* number of bits of the different LSP CB coefficients */
    uint8_t      lsp_bit0;
    uint8_t      lsp_bit1;
    uint8_t      lsp_bit2;

    uint8_t      lsp_split;      ///< number of CB entries for the LSP decoding
    const int16_t *ppc_shape_cb; ///< PPC shape CB

    /** number of the bits for the PPC period value */
    uint8_t      ppc_period_bit;

    uint8_t      ppc_shape_bit;  ///< number of bits of the PPC shape CB coeffs
    uint8_t      ppc_shape_len;  ///< size of PPC shape CB
    uint8_t      pgain_bit;      ///< bits for PPC gain

    /** constant for peak period to peak width conversion */
    uint16_t     peak_per2wid;
} ModeTab;

static const ModeTab mode_08_08 = {
    {
        { 8, bark_tab_s08_64,  10, tab.fcb08s, 1, 5, tab.cb0808s0, tab.cb0808s1, 18 },
        { 2, bark_tab_m08_256, 20, tab.fcb08m, 2, 5, tab.cb0808m0, tab.cb0808m1, 16 },
        { 1, bark_tab_l08_512, 30, tab.fcb08l, 3, 6, tab.cb0808l0, tab.cb0808l1, 17 }
    },
    512, 12, tab.lsp08, 1, 5, 3, 3, tab.shape08, 8, 28, 20, 6, 40
};

static const ModeTab mode_11_08 = {
    {
        { 8, bark_tab_s11_64,  10, tab.fcb11s, 1, 5, tab.cb1108s0, tab.cb1108s1, 29 },
        { 2, bark_tab_m11_256, 20, tab.fcb11m, 2, 5, tab.cb1108m0, tab.cb1108m1, 24 },
        { 1, bark_tab_l11_512, 30, tab.fcb11l, 3, 6, tab.cb1108l0, tab.cb1108l1, 27 }
    },
    512, 16, tab.lsp11, 1, 6, 4, 3, tab.shape11, 9, 36, 30, 7, 90
};

static const ModeTab mode_11_10 = {
    {
        { 8, bark_tab_s11_64,  10, tab.fcb11s, 1, 5, tab.cb1110s0, tab.cb1110s1, 21 },
        { 2, bark_tab_m11_256, 20, tab.fcb11m, 2, 5, tab.cb1110m0, tab.cb1110m1, 18 },
        { 1, bark_tab_l11_512, 30, tab.fcb11l, 3, 6, tab.cb1110l0, tab.cb1110l1, 20 }
    },
    512, 16, tab.lsp11, 1, 6, 4, 3, tab.shape11, 9, 36, 30, 7, 90
};

static const ModeTab mode_16_16 = {
    {
        { 8, bark_tab_s16_128,  10, tab.fcb16s, 1, 5, tab.cb1616s0, tab.cb1616s1, 16 },
        { 2, bark_tab_m16_512,  20, tab.fcb16m, 2, 5, tab.cb1616m0, tab.cb1616m1, 15 },
        { 1, bark_tab_l16_1024, 30, tab.fcb16l, 3, 6, tab.cb1616l0, tab.cb1616l1, 16 }
    },
    1024, 16, tab.lsp16, 1, 6, 4, 3, tab.shape16, 9, 56, 60, 7, 180
};

static const ModeTab mode_22_20 = {
    {
        { 8, bark_tab_s22_128,  10, tab.fcb22s_1, 1, 6, tab.cb2220s0, tab.cb2220s1, 18 },
        { 2, bark_tab_m22_512,  20, tab.fcb22m_1, 2, 6, tab.cb2220m0, tab.cb2220m1, 17 },
        { 1, bark_tab_l22_1024, 32, tab.fcb22l_1, 4, 6, tab.cb2220l0, tab.cb2220l1, 18 }
    },
    1024, 16, tab.lsp22_1, 1, 6, 4, 3, tab.shape22_1, 9, 56, 36, 7, 144
};

static const ModeTab mode_22_24 = {
    {
        { 8, bark_tab_s22_128,  10, tab.fcb22s_1, 1, 6, tab.cb2224s0, tab.cb2224s1, 15 },
        { 2, bark_tab_m22_512,  20, tab.fcb22m_1, 2, 6, tab.cb2224m0, tab.cb2224m1, 14 },
        { 1, bark_tab_l22_1024, 32, tab.fcb22l_1, 4, 6, tab.cb2224l0, tab.cb2224l1, 15 }
    },
    1024, 16, tab.lsp22_1, 1, 6, 4, 3, tab.shape22_1, 9, 56, 36, 7, 144
};

static const ModeTab mode_22_32 = {
    {
        { 4, bark_tab_s22_128, 10, tab.fcb22s_2, 1, 6, tab.cb2232s0, tab.cb2232s1, 11 },
        { 2, bark_tab_m22_256, 20, tab.fcb22m_2, 2, 6, tab.cb2232m0, tab.cb2232m1, 11 },
        { 1, bark_tab_l22_512, 32, tab.fcb22l_2, 4, 6, tab.cb2232l0, tab.cb2232l1, 12 }
    },
    512, 16, tab.lsp22_2, 1, 6, 4, 4, tab.shape22_2, 9, 56, 36, 7, 72
};

static const ModeTab mode_44_40 = {
    {
        { 16, bark_tab_s44_128,  10, tab.fcb44s, 1, 6, tab.cb4440s0, tab.cb4440s1, 18 },
        { 4,  bark_tab_m44_512,  20, tab.fcb44m, 2, 6, tab.cb4440m0, tab.cb4440m1, 17 },
        { 1,  bark_tab_l44_2048, 40, tab.fcb44l, 4, 6, tab.cb4440l0, tab.cb4440l1, 17 }
    },
    2048, 20, tab.lsp44, 1, 6, 4, 4, tab.shape44, 9, 84, 54, 7, 432
};

static const ModeTab mode_44_48 = {
    {
        { 16, bark_tab_s44_128,  10, tab.fcb44s, 1, 6, tab.cb4448s0, tab.cb4448s1, 15 },
        { 4,  bark_tab_m44_512,  20, tab.fcb44m, 2, 6, tab.cb4448m0, tab.cb4448m1, 14 },
        { 1,  bark_tab_l44_2048, 40, tab.fcb44l, 4, 6, tab.cb4448l0, tab.cb4448l1, 14 }
    },
    2048, 20, tab.lsp44, 1, 6, 4, 4, tab.shape44, 9, 84, 54, 7, 432
};

typedef struct TwinContext {
    AVCodecContext *avctx;
    AVFloatDSPContext fdsp;
    FFTContext mdct_ctx[3];

    const ModeTab *mtab;

    // history
    float lsp_hist[2][20];           ///< LSP coefficients of the last frame
    float bark_hist[3][2][40];       ///< BSE coefficients of last frame

    // bitstream parameters
    int16_t permut[4][4096];
    uint8_t length[4][2];            ///< main codebook stride
    uint8_t length_change[4];
    uint8_t bits_main_spec[2][4][2]; ///< bits for the main codebook
    int bits_main_spec_change[4];
    int n_div[4];

    float *spectrum;
    float *curr_frame;               ///< non-interleaved output
    float *prev_frame;               ///< non-interleaved previous frame
    int last_block_pos[2];
    int discarded_packets;

    float *cos_tabs[3];

    // scratch buffers
    float *tmp_buf;
} TwinContext;

#define PPC_SHAPE_CB_SIZE 64
#define PPC_SHAPE_LEN_MAX 60
#define SUB_AMP_MAX       4500.0
#define MULAW_MU          100.0
#define GAIN_BITS         8
#define AMP_MAX           13000.0
#define SUB_GAIN_BITS     5
#define WINDOW_TYPE_BITS  4
#define PGAIN_MU          200
#define LSP_COEFS_MAX     20
#define LSP_SPLIT_MAX     4
#define CHANNELS_MAX      2
#define SUBBLOCKS_MAX     16
#define BARK_N_COEF_MAX   4

/** @note not speed critical, hence not optimized */
static void memset_float(float *buf, float val, int size)
{
    while (size--)
        *buf++ = val;
}

/**
 * Evaluate a single LPC amplitude spectrum envelope coefficient from the line
 * spectrum pairs.
 *
 * @param lsp a vector of the cosine of the LSP values
 * @param cos_val cos(PI*i/N) where i is the index of the LPC amplitude
 * @param order the order of the LSP (and the size of the *lsp buffer). Must
 *        be a multiple of four.
 * @return the LPC value
 *
 * @todo reuse code from Vorbis decoder: vorbis_floor0_decode
 */
static float eval_lpc_spectrum(const float *lsp, float cos_val, int order)
{
    int j;
    float p         = 0.5f;
    float q         = 0.5f;
    float two_cos_w = 2.0f * cos_val;

    for (j = 0; j + 1 < order; j += 2 * 2) {
        // Unroll the loop once since order is a multiple of four
        q *= lsp[j]     - two_cos_w;
        p *= lsp[j + 1] - two_cos_w;

        q *= lsp[j + 2] - two_cos_w;
        p *= lsp[j + 3] - two_cos_w;
    }

    p *= p * (2.0f - two_cos_w);
    q *= q * (2.0f + two_cos_w);

    return 0.5 / (p + q);
}

/**
 * Evaluate the LPC amplitude spectrum envelope from the line spectrum pairs.
 */
static void eval_lpcenv(TwinContext *tctx, const float *cos_vals, float *lpc)
{
    int i;
    const ModeTab *mtab = tctx->mtab;
    int size_s          = mtab->size / mtab->fmode[FT_SHORT].sub;

    for (i = 0; i < size_s / 2; i++) {
        float cos_i = tctx->cos_tabs[0][i];
        lpc[i]              = eval_lpc_spectrum(cos_vals,  cos_i, mtab->n_lsp);
        lpc[size_s - i - 1] = eval_lpc_spectrum(cos_vals, -cos_i, mtab->n_lsp);
    }
}

static void interpolate(float *out, float v1, float v2, int size)
{
    int i;
    float step = (v1 - v2) / (size + 1);

    for (i = 0; i < size; i++) {
        v2    += step;
        out[i] = v2;
    }
}

static inline float get_cos(int idx, int part, const float *cos_tab, int size)
{
    return part ? -cos_tab[size - idx - 1]
                :  cos_tab[idx];
}

/**
 * Evaluate the LPC amplitude spectrum envelope from the line spectrum pairs.
 * Probably for speed reasons, the coefficients are evaluated as
 * siiiibiiiisiiiibiiiisiiiibiiiisiiiibiiiis ...
 * where s is an evaluated value, i is a value interpolated from the others
 * and b might be either calculated or interpolated, depending on an
 * unexplained condition.
 *
 * @param step the size of a block "siiiibiiii"
 * @param in the cosine of the LSP data
 * @param part is 0 for 0...PI (positive cosine values) and 1 for PI...2PI
 *        (negative cosine values)
 * @param size the size of the whole output
 */
static inline void eval_lpcenv_or_interp(TwinContext *tctx,
                                         enum FrameType ftype,
                                         float *out, const float *in,
                                         int size, int step, int part)
{
    int i;
    const ModeTab *mtab  = tctx->mtab;
    const float *cos_tab = tctx->cos_tabs[ftype];

    // Fill the 's'
    for (i = 0; i < size; i += step)
        out[i] =
            eval_lpc_spectrum(in,
                              get_cos(i, part, cos_tab, size),
                              mtab->n_lsp);

    // Fill the 'iiiibiiii'
    for (i = step; i <= size - 2 * step; i += step) {
        if (out[i + step] + out[i - step] > 1.95 * out[i] ||
            out[i + step]                 >= out[i - step]) {
            interpolate(out + i - step + 1, out[i], out[i - step], step - 1);
        } else {
            out[i - step / 2] =
                eval_lpc_spectrum(in,
                                  get_cos(i - step / 2, part, cos_tab, size),
                                  mtab->n_lsp);
            interpolate(out + i - step + 1, out[i - step / 2],
                        out[i - step], step / 2 - 1);
            interpolate(out + i - step / 2 + 1, out[i],
                        out[i - step / 2], step / 2 - 1);
        }
    }

    interpolate(out + size - 2 * step + 1, out[size - step],
                out[size - 2 * step], step - 1);
}

static void eval_lpcenv_2parts(TwinContext *tctx, enum FrameType ftype,
                               const float *buf, float *lpc,
                               int size, int step)
{
    eval_lpcenv_or_interp(tctx, ftype, lpc, buf, size / 2, step, 0);
    eval_lpcenv_or_interp(tctx, ftype, lpc + size / 2, buf, size / 2,
                          2 * step, 1);

    interpolate(lpc + size / 2 - step + 1, lpc[size / 2],
                lpc[size / 2 - step], step);

    memset_float(lpc + size - 2 * step + 1, lpc[size - 2 * step], 2 * step - 1);
}

/**
 * Inverse quantization. Read CB coefficients for cb1 and cb2 from the
 * bitstream, sum the corresponding vectors and write the result to *out
 * after permutation.
 */
static void dequant(TwinContext *tctx, GetBitContext *gb, float *out,
                    enum FrameType ftype,
                    const int16_t *cb0, const int16_t *cb1, int cb_len)
{
    int pos = 0;
    int i, j;

    for (i = 0; i < tctx->n_div[ftype]; i++) {
        int tmp0, tmp1;
        int sign0 = 1;
        int sign1 = 1;
        const int16_t *tab0, *tab1;
        int length = tctx->length[ftype][i >= tctx->length_change[ftype]];
        int bitstream_second_part = (i >= tctx->bits_main_spec_change[ftype]);

        int bits = tctx->bits_main_spec[0][ftype][bitstream_second_part];
        if (bits == 7) {
            if (get_bits1(gb))
                sign0 = -1;
            bits = 6;
        }
        tmp0 = get_bits(gb, bits);

        bits = tctx->bits_main_spec[1][ftype][bitstream_second_part];

        if (bits == 7) {
            if (get_bits1(gb))
                sign1 = -1;

            bits = 6;
        }
        tmp1 = get_bits(gb, bits);

        tab0 = cb0 + tmp0 * cb_len;
        tab1 = cb1 + tmp1 * cb_len;

        for (j = 0; j < length; j++)
            out[tctx->permut[ftype][pos + j]] = sign0 * tab0[j] +
                                                sign1 * tab1[j];

        pos += length;
    }
}

static inline float mulawinv(float y, float clip, float mu)
{
    y = av_clipf(y / clip, -1, 1);
    return clip * FFSIGN(y) * (exp(log(1 + mu) * fabs(y)) - 1) / mu;
}

/**
 * Evaluate a * b / 400 rounded to the nearest integer. When, for example,
 * a * b == 200 and the nearest integer is ill-defined, use a table to emulate
 * the following broken float-based implementation used by the binary decoder:
 *
 * @code
 * static int very_broken_op(int a, int b)
 * {
 *    static float test; // Ugh, force gcc to do the division first...
 *
 *    test = a / 400.0;
 *    return b * test + 0.5;
 * }
 * @endcode
 *
 * @note if this function is replaced by just ROUNDED_DIV(a * b, 400.0), the
 * stddev between the original file (before encoding with Yamaha encoder) and
 * the decoded output increases, which leads one to believe that the encoder
 * expects exactly this broken calculation.
 */
static int very_broken_op(int a, int b)
{
    int x = a * b + 200;
    int size;
    const uint8_t *rtab;

    if (x % 400 || b % 5)
        return x / 400;

    x /= 400;

    size = tabs[b / 5].size;
    rtab = tabs[b / 5].tab;
    return x - rtab[size * av_log2(2 * (x - 1) / size) + (x - 1) % size];
}

/**
 * Sum to data a periodic peak of a given period, width and shape.
 *
 * @param period the period of the peak divised by 400.0
 */
static void add_peak(int period, int width, const float *shape,
                     float ppc_gain, float *speech, int len)
{
    int i, j;

    const float *shape_end = shape + len;
    int center;

    // First peak centered around zero
    for (i = 0; i < width / 2; i++)
        speech[i] += ppc_gain * *shape++;

    for (i = 1; i < ROUNDED_DIV(len, width); i++) {
        center = very_broken_op(period, i);
        for (j = -width / 2; j < (width + 1) / 2; j++)
            speech[j + center] += ppc_gain * *shape++;
    }

    // For the last block, be careful not to go beyond the end of the buffer
    center = very_broken_op(period, i);
    for (j = -width / 2; j < (width + 1) / 2 && shape < shape_end; j++)
        speech[j + center] += ppc_gain * *shape++;
}

static void decode_ppc(TwinContext *tctx, int period_coef, const float *shape,
                       float ppc_gain, float *speech)
{
    const ModeTab *mtab = tctx->mtab;
    int isampf          = tctx->avctx->sample_rate / 1000;
    int ibps            = tctx->avctx->bit_rate / (1000 * tctx->avctx->channels);
    int min_period      = ROUNDED_DIV(40 * 2 * mtab->size, isampf);
    int max_period      = ROUNDED_DIV(40 * 2 * mtab->size * 6, isampf);
    int period_range    = max_period - min_period;

    // This is actually the period multiplied by 400. It is just linearly coded
    // between its maximum and minimum value.
    int period = min_period +
                 ROUNDED_DIV(period_coef * period_range,
                             (1 << mtab->ppc_period_bit) - 1);
    int width;

    if (isampf == 22 && ibps == 32) {
        // For some unknown reason, NTT decided to code this case differently...
        width = ROUNDED_DIV((period + 800) * mtab->peak_per2wid,
                            400 * mtab->size);
    } else
        width = period * mtab->peak_per2wid / (400 * mtab->size);

    add_peak(period, width, shape, ppc_gain, speech, mtab->ppc_shape_len);
}

static void dec_gain(TwinContext *tctx, GetBitContext *gb, enum FrameType ftype,
                     float *out)
{
    const ModeTab *mtab = tctx->mtab;
    int i, j;
    int sub        = mtab->fmode[ftype].sub;
    float step     = AMP_MAX / ((1 << GAIN_BITS) - 1);
    float sub_step = SUB_AMP_MAX / ((1 << SUB_GAIN_BITS) - 1);

    if (ftype == FT_LONG) {
        for (i = 0; i < tctx->avctx->channels; i++)
            out[i] = (1.0 / (1 << 13)) *
                     mulawinv(step * 0.5 + step * get_bits(gb, GAIN_BITS),
                              AMP_MAX, MULAW_MU);
    } else {
        for (i = 0; i < tctx->avctx->channels; i++) {
            float val = (1.0 / (1 << 23)) *
                        mulawinv(step * 0.5 + step * get_bits(gb, GAIN_BITS),
                                 AMP_MAX, MULAW_MU);

            for (j = 0; j < sub; j++)
                out[i * sub + j] =
                    val * mulawinv(sub_step * 0.5 +
                                   sub_step * get_bits(gb, SUB_GAIN_BITS),
                                   SUB_AMP_MAX, MULAW_MU);
        }
    }
}

/**
 * Rearrange the LSP coefficients so that they have a minimum distance of
 * min_dist. This function does it exactly as described in section of 3.2.4
 * of the G.729 specification (but interestingly is different from what the
 * reference decoder actually does).
 */
static void rearrange_lsp(int order, float *lsp, float min_dist)
{
    int i;
    float min_dist2 = min_dist * 0.5;
    for (i = 1; i < order; i++)
        if (lsp[i] - lsp[i - 1] < min_dist) {
            float avg = (lsp[i] + lsp[i - 1]) * 0.5;

            lsp[i - 1] = avg - min_dist2;
            lsp[i]     = avg + min_dist2;
        }
}

static void decode_lsp(TwinContext *tctx, int lpc_idx1, uint8_t *lpc_idx2,
                       int lpc_hist_idx, float *lsp, float *hist)
{
    const ModeTab *mtab = tctx->mtab;
    int i, j;

    const float *cb  = mtab->lspcodebook;
    const float *cb2 = cb  + (1 << mtab->lsp_bit1) * mtab->n_lsp;
    const float *cb3 = cb2 + (1 << mtab->lsp_bit2) * mtab->n_lsp;

    const int8_t funny_rounding[4] = {
        -2,
        mtab->lsp_split == 4 ? -2 : 1,
        mtab->lsp_split == 4 ? -2 : 1,
        0
    };

    j = 0;
    for (i = 0; i < mtab->lsp_split; i++) {
        int chunk_end = ((i + 1) * mtab->n_lsp + funny_rounding[i]) /
                        mtab->lsp_split;
        for (; j < chunk_end; j++)
            lsp[j] = cb[lpc_idx1     * mtab->n_lsp + j] +
                     cb2[lpc_idx2[i] * mtab->n_lsp + j];
    }

    rearrange_lsp(mtab->n_lsp, lsp, 0.0001);

    for (i = 0; i < mtab->n_lsp; i++) {
        float tmp1 = 1.0     - cb3[lpc_hist_idx * mtab->n_lsp + i];
        float tmp2 = hist[i] * cb3[lpc_hist_idx * mtab->n_lsp + i];
        hist[i] = lsp[i];
        lsp[i]  = lsp[i] * tmp1 + tmp2;
    }

    rearrange_lsp(mtab->n_lsp, lsp, 0.0001);
    rearrange_lsp(mtab->n_lsp, lsp, 0.000095);
    ff_sort_nearly_sorted_floats(lsp, mtab->n_lsp);
}

static void dec_lpc_spectrum_inv(TwinContext *tctx, float *lsp,
                                 enum FrameType ftype, float *lpc)
{
    int i;
    int size = tctx->mtab->size / tctx->mtab->fmode[ftype].sub;

    for (i = 0; i < tctx->mtab->n_lsp; i++)
        lsp[i] = 2 * cos(lsp[i]);

    switch (ftype) {
    case FT_LONG:
        eval_lpcenv_2parts(tctx, ftype, lsp, lpc, size, 8);
        break;
    case FT_MEDIUM:
        eval_lpcenv_2parts(tctx, ftype, lsp, lpc, size, 2);
        break;
    case FT_SHORT:
        eval_lpcenv(tctx, lsp, lpc);
        break;
    }
}

static const uint8_t wtype_to_wsize[] = { 0, 0, 2, 2, 2, 1, 0, 1, 1 };

static void imdct_and_window(TwinContext *tctx, enum FrameType ftype, int wtype,
                             float *in, float *prev, int ch)
{
    FFTContext *mdct    = &tctx->mdct_ctx[ftype];
    const ModeTab *mtab = tctx->mtab;
    int bsize           = mtab->size / mtab->fmode[ftype].sub;
    int size            = mtab->size;
    float *buf1         = tctx->tmp_buf;
    int j, first_wsize, wsize; // Window size
    float *out  = tctx->curr_frame + 2 * ch * mtab->size;
    float *out2 = out;
    float *prev_buf;
    int types_sizes[] = {
        mtab->size /  mtab->fmode[FT_LONG].sub,
        mtab->size /  mtab->fmode[FT_MEDIUM].sub,
        mtab->size / (mtab->fmode[FT_SHORT].sub * 2),
    };

    wsize       = types_sizes[wtype_to_wsize[wtype]];
    first_wsize = wsize;
    prev_buf    = prev + (size - bsize) / 2;

    for (j = 0; j < mtab->fmode[ftype].sub; j++) {
        int sub_wtype = ftype == FT_MEDIUM ? 8 : wtype;

        if (!j && wtype == 4)
            sub_wtype = 4;
        else if (j == mtab->fmode[ftype].sub - 1 && wtype == 7)
            sub_wtype = 7;

        wsize = types_sizes[wtype_to_wsize[sub_wtype]];

        mdct->imdct_half(mdct, buf1 + bsize * j, in + bsize * j);

        tctx->fdsp.vector_fmul_window(out2, prev_buf + (bsize - wsize) / 2,
                                      buf1 + bsize * j,
                                      ff_sine_windows[av_log2(wsize)],
                                      wsize / 2);
        out2 += wsize;

        memcpy(out2, buf1 + bsize * j + wsize / 2,
               (bsize - wsize / 2) * sizeof(float));

        out2 += ftype == FT_MEDIUM ? (bsize - wsize) / 2 : bsize - wsize;

        prev_buf = buf1 + bsize * j + bsize / 2;
    }

    tctx->last_block_pos[ch] = (size + first_wsize) / 2;
}

static void imdct_output(TwinContext *tctx, enum FrameType ftype, int wtype,
                         float **out)
{
    const ModeTab *mtab = tctx->mtab;
    float *prev_buf     = tctx->prev_frame + tctx->last_block_pos[0];
    int size1, size2, i;

    for (i = 0; i < tctx->avctx->channels; i++)
        imdct_and_window(tctx, ftype, wtype,
                         tctx->spectrum + i * mtab->size,
                         prev_buf + 2 * i * mtab->size,
                         i);

    if (!out)
        return;

    size2 = tctx->last_block_pos[0];
    size1 = mtab->size - size2;

    memcpy(&out[0][0],     prev_buf,         size1 * sizeof(out[0][0]));
    memcpy(&out[0][size1], tctx->curr_frame, size2 * sizeof(out[0][0]));

    if (tctx->avctx->channels == 2) {
        memcpy(&out[1][0], &prev_buf[2 * mtab->size],
               size1 * sizeof(out[1][0]));
        memcpy(&out[1][size1], &tctx->curr_frame[2 * mtab->size],
               size2 * sizeof(out[1][0]));
        tctx->fdsp.butterflies_float(out[0], out[1], mtab->size);
    }
}

static void dec_bark_env(TwinContext *tctx, const uint8_t *in, int use_hist,
                         int ch, float *out, float gain, enum FrameType ftype)
{
    const ModeTab *mtab = tctx->mtab;
    int i, j;
    float *hist     = tctx->bark_hist[ftype][ch];
    float val       = ((const float []) { 0.4, 0.35, 0.28 })[ftype];
    int bark_n_coef = mtab->fmode[ftype].bark_n_coef;
    int fw_cb_len   = mtab->fmode[ftype].bark_env_size / bark_n_coef;
    int idx         = 0;

    for (i = 0; i < fw_cb_len; i++)
        for (j = 0; j < bark_n_coef; j++, idx++) {
            float tmp2 = mtab->fmode[ftype].bark_cb[fw_cb_len * in[j] + i] *
                         (1.0 / 4096);
            float st   = use_hist ? (1.0 - val) * tmp2 + val * hist[idx] + 1.0
                                  : tmp2 + 1.0;

            hist[idx] = tmp2;
            if (st < -1.0)
                st = 1.0;

            memset_float(out, st * gain, mtab->fmode[ftype].bark_tab[idx]);
            out += mtab->fmode[ftype].bark_tab[idx];
        }
}

static void read_and_decode_spectrum(TwinContext *tctx, GetBitContext *gb,
                                     float *out, enum FrameType ftype)
{
    const ModeTab *mtab = tctx->mtab;
    int channels        = tctx->avctx->channels;
    int sub             = mtab->fmode[ftype].sub;
    int block_size      = mtab->size / sub;
    float gain[CHANNELS_MAX * SUBBLOCKS_MAX];
    float ppc_shape[PPC_SHAPE_LEN_MAX * CHANNELS_MAX * 4];
    uint8_t bark1[CHANNELS_MAX][SUBBLOCKS_MAX][BARK_N_COEF_MAX];
    uint8_t bark_use_hist[CHANNELS_MAX][SUBBLOCKS_MAX];

    uint8_t lpc_idx1[CHANNELS_MAX];
    uint8_t lpc_idx2[CHANNELS_MAX][LSP_SPLIT_MAX];
    uint8_t lpc_hist_idx[CHANNELS_MAX];

    int i, j, k;

    dequant(tctx, gb, out, ftype,
            mtab->fmode[ftype].cb0, mtab->fmode[ftype].cb1,
            mtab->fmode[ftype].cb_len_read);

    for (i = 0; i < channels; i++)
        for (j = 0; j < sub; j++)
            for (k = 0; k < mtab->fmode[ftype].bark_n_coef; k++)
                bark1[i][j][k] =
                    get_bits(gb, mtab->fmode[ftype].bark_n_bit);

    for (i = 0; i < channels; i++)
        for (j = 0; j < sub; j++)
            bark_use_hist[i][j] = get_bits1(gb);

    dec_gain(tctx, gb, ftype, gain);

    for (i = 0; i < channels; i++) {
        lpc_hist_idx[i] = get_bits(gb, tctx->mtab->lsp_bit0);
        lpc_idx1[i]     = get_bits(gb, tctx->mtab->lsp_bit1);

        for (j = 0; j < tctx->mtab->lsp_split; j++)
            lpc_idx2[i][j] = get_bits(gb, tctx->mtab->lsp_bit2);
    }

    if (ftype == FT_LONG) {
        int cb_len_p = (tctx->n_div[3] + mtab->ppc_shape_len * channels - 1) /
                       tctx->n_div[3];
        dequant(tctx, gb, ppc_shape, FT_PPC, mtab->ppc_shape_cb,
                mtab->ppc_shape_cb + cb_len_p * PPC_SHAPE_CB_SIZE, cb_len_p);
    }

    for (i = 0; i < channels; i++) {
        float *chunk = out + mtab->size * i;
        float lsp[LSP_COEFS_MAX];

        for (j = 0; j < sub; j++) {
            dec_bark_env(tctx, bark1[i][j], bark_use_hist[i][j], i,
                         tctx->tmp_buf, gain[sub * i + j], ftype);

            tctx->fdsp.vector_fmul(chunk + block_size * j,
                                   chunk + block_size * j,
                                   tctx->tmp_buf, block_size);
        }

        if (ftype == FT_LONG) {
            float pgain_step = 25000.0 / ((1 << mtab->pgain_bit) - 1);
            int p_coef       = get_bits(gb, tctx->mtab->ppc_period_bit);
            int g_coef       = get_bits(gb, tctx->mtab->pgain_bit);
            float v          = 1.0 / 8192 *
                               mulawinv(pgain_step * g_coef + pgain_step / 2,
                                        25000.0, PGAIN_MU);

            decode_ppc(tctx, p_coef, ppc_shape + i * mtab->ppc_shape_len, v,
                       chunk);
        }

        decode_lsp(tctx, lpc_idx1[i], lpc_idx2[i], lpc_hist_idx[i], lsp,
                   tctx->lsp_hist[i]);

        dec_lpc_spectrum_inv(tctx, lsp, ftype, tctx->tmp_buf);

        for (j = 0; j < mtab->fmode[ftype].sub; j++) {
            tctx->fdsp.vector_fmul(chunk, chunk, tctx->tmp_buf, block_size);
            chunk += block_size;
        }
    }
}

static int twin_decode_frame(AVCodecContext *avctx, void *data,
                             int *got_frame_ptr, AVPacket *avpkt)
{
    AVFrame *frame     = data;
    const uint8_t *buf = avpkt->data;
    int buf_size       = avpkt->size;
    TwinContext *tctx  = avctx->priv_data;
    GetBitContext gb;
    const ModeTab *mtab = tctx->mtab;
    float **out         = NULL;
    enum FrameType ftype;
    int window_type, ret;
    static const enum FrameType wtype_to_ftype_table[] = {
        FT_LONG,   FT_LONG, FT_SHORT, FT_LONG,
        FT_MEDIUM, FT_LONG, FT_LONG,  FT_MEDIUM, FT_MEDIUM
    };

    if (buf_size * 8 < avctx->bit_rate * mtab->size / avctx->sample_rate + 8) {
        av_log(avctx, AV_LOG_ERROR,
               "Frame too small (%d bytes). Truncated file?\n", buf_size);
        return AVERROR(EINVAL);
    }

    /* get output buffer */
    if (tctx->discarded_packets >= 2) {
        frame->nb_samples = mtab->size;
        if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
            return ret;
        out = (float **)frame->extended_data;
    }

    init_get_bits(&gb, buf, buf_size * 8);
    skip_bits(&gb, get_bits(&gb, 8));
    window_type = get_bits(&gb, WINDOW_TYPE_BITS);

    if (window_type > 8) {
        av_log(avctx, AV_LOG_ERROR, "Invalid window type, broken sample?\n");
        return -1;
    }

    ftype = wtype_to_ftype_table[window_type];

    read_and_decode_spectrum(tctx, &gb, tctx->spectrum, ftype);

    imdct_output(tctx, ftype, window_type, out);

    FFSWAP(float *, tctx->curr_frame, tctx->prev_frame);

    if (tctx->discarded_packets < 2) {
        tctx->discarded_packets++;
        *got_frame_ptr = 0;
        return buf_size;
    }

    *got_frame_ptr = 1;

    return buf_size;
}

/**
 * Init IMDCT and windowing tables
 */
static av_cold int init_mdct_win(TwinContext *tctx)
{
    int i, j, ret;
    const ModeTab *mtab = tctx->mtab;
    int size_s          = mtab->size / mtab->fmode[FT_SHORT].sub;
    int size_m          = mtab->size / mtab->fmode[FT_MEDIUM].sub;
    int channels        = tctx->avctx->channels;
    float norm          = channels == 1 ? 2.0 : 1.0;

    for (i = 0; i < 3; i++) {
        int bsize = tctx->mtab->size / tctx->mtab->fmode[i].sub;
        if ((ret = ff_mdct_init(&tctx->mdct_ctx[i], av_log2(bsize) + 1, 1,
                                -sqrt(norm / bsize) / (1 << 15))))
            return ret;
    }

    FF_ALLOC_OR_GOTO(tctx->avctx, tctx->tmp_buf,
                     mtab->size * sizeof(*tctx->tmp_buf), alloc_fail);

    FF_ALLOC_OR_GOTO(tctx->avctx, tctx->spectrum,
                     2 * mtab->size * channels * sizeof(*tctx->spectrum),
                     alloc_fail);
    FF_ALLOC_OR_GOTO(tctx->avctx, tctx->curr_frame,
                     2 * mtab->size * channels * sizeof(*tctx->curr_frame),
                     alloc_fail);
    FF_ALLOC_OR_GOTO(tctx->avctx, tctx->prev_frame,
                     2 * mtab->size * channels * sizeof(*tctx->prev_frame),
                     alloc_fail);

    for (i = 0; i < 3; i++) {
        int m       = 4 * mtab->size / mtab->fmode[i].sub;
        double freq = 2 * M_PI / m;
        FF_ALLOC_OR_GOTO(tctx->avctx, tctx->cos_tabs[i],
                         (m / 4) * sizeof(*tctx->cos_tabs[i]), alloc_fail);

        for (j = 0; j <= m / 8; j++)
            tctx->cos_tabs[i][j] = cos((2 * j + 1) * freq);
        for (j = 1; j < m / 8; j++)
            tctx->cos_tabs[i][m / 4 - j] = tctx->cos_tabs[i][j];
    }

    ff_init_ff_sine_windows(av_log2(size_m));
    ff_init_ff_sine_windows(av_log2(size_s / 2));
    ff_init_ff_sine_windows(av_log2(mtab->size));

    return 0;

alloc_fail:
    return AVERROR(ENOMEM);
}

/**
 * Interpret the data as if it were a num_blocks x line_len[0] matrix and for
 * each line do a cyclic permutation, i.e.
 * abcdefghijklm -> defghijklmabc
 * where the amount to be shifted is evaluated depending on the column.
 */
static void permutate_in_line(int16_t *tab, int num_vect, int num_blocks,
                              int block_size,
                              const uint8_t line_len[2], int length_div,
                              enum FrameType ftype)
{
    int i, j;

    for (i = 0; i < line_len[0]; i++) {
        int shift;

        if (num_blocks == 1                             ||
            (ftype == FT_LONG && num_vect % num_blocks) ||
            (ftype != FT_LONG && num_vect & 1)          ||
            i == line_len[1]) {
            shift = 0;
        } else if (ftype == FT_LONG) {
            shift = i;
        } else
            shift = i * i;

        for (j = 0; j < num_vect && (j + num_vect * i < block_size * num_blocks); j++)
            tab[i * num_vect + j] = i * num_vect + (j + shift) % num_vect;
    }
}

/**
 * Interpret the input data as in the following table:
 *
 * @verbatim
 *
 * abcdefgh
 * ijklmnop
 * qrstuvw
 * x123456
 *
 * @endverbatim
 *
 * and transpose it, giving the output
 * aiqxbjr1cks2dlt3emu4fvn5gow6hp
 */
static void transpose_perm(int16_t *out, int16_t *in, int num_vect,
                           const uint8_t line_len[2], int length_div)
{
    int i, j;
    int cont = 0;

    for (i = 0; i < num_vect; i++)
        for (j = 0; j < line_len[i >= length_div]; j++)
            out[cont++] = in[j * num_vect + i];
}

static void linear_perm(int16_t *out, int16_t *in, int n_blocks, int size)
{
    int block_size = size / n_blocks;
    int i;

    for (i = 0; i < size; i++)
        out[i] = block_size * (in[i] % n_blocks) + in[i] / n_blocks;
}

static av_cold void construct_perm_table(TwinContext *tctx,
                                         enum FrameType ftype)
{
    int block_size, size;
    const ModeTab *mtab = tctx->mtab;
    int16_t *tmp_perm = (int16_t *)tctx->tmp_buf;

    if (ftype == FT_PPC) {
        size       = tctx->avctx->channels;
        block_size = mtab->ppc_shape_len;
    } else {
        size       = tctx->avctx->channels * mtab->fmode[ftype].sub;
        block_size = mtab->size / mtab->fmode[ftype].sub;
    }

    permutate_in_line(tmp_perm, tctx->n_div[ftype], size,
                      block_size, tctx->length[ftype],
                      tctx->length_change[ftype], ftype);

    transpose_perm(tctx->permut[ftype], tmp_perm, tctx->n_div[ftype],
                   tctx->length[ftype], tctx->length_change[ftype]);

    linear_perm(tctx->permut[ftype], tctx->permut[ftype], size,
                size * block_size);
}

static av_cold void init_bitstream_params(TwinContext *tctx)
{
    const ModeTab *mtab = tctx->mtab;
    int n_ch            = tctx->avctx->channels;
    int total_fr_bits   = tctx->avctx->bit_rate * mtab->size /
                          tctx->avctx->sample_rate;

    int lsp_bits_per_block = n_ch * (mtab->lsp_bit0 + mtab->lsp_bit1 +
                                     mtab->lsp_split * mtab->lsp_bit2);

    int ppc_bits = n_ch * (mtab->pgain_bit + mtab->ppc_shape_bit +
                           mtab->ppc_period_bit);

    int bsize_no_main_cb[3], bse_bits[3], i;
    enum FrameType frametype;

    for (i = 0; i < 3; i++)
        // +1 for history usage switch
        bse_bits[i] = n_ch *
                      (mtab->fmode[i].bark_n_coef *
                       mtab->fmode[i].bark_n_bit + 1);

    bsize_no_main_cb[2] = bse_bits[2] + lsp_bits_per_block + ppc_bits +
                          WINDOW_TYPE_BITS + n_ch * GAIN_BITS;

    for (i = 0; i < 2; i++)
        bsize_no_main_cb[i] =
            lsp_bits_per_block + n_ch * GAIN_BITS + WINDOW_TYPE_BITS +
            mtab->fmode[i].sub * (bse_bits[i] + n_ch * SUB_GAIN_BITS);

    // The remaining bits are all used for the main spectrum coefficients
    for (i = 0; i < 4; i++) {
        int bit_size, vect_size;
        int rounded_up, rounded_down, num_rounded_down, num_rounded_up;
        if (i == 3) {
            bit_size  = n_ch * mtab->ppc_shape_bit;
            vect_size = n_ch * mtab->ppc_shape_len;
        } else {
            bit_size  = total_fr_bits - bsize_no_main_cb[i];
            vect_size = n_ch * mtab->size;
        }

        tctx->n_div[i] = (bit_size + 13) / 14;

        rounded_up                     = (bit_size + tctx->n_div[i] - 1) /
                                         tctx->n_div[i];
        rounded_down                   = (bit_size) / tctx->n_div[i];
        num_rounded_down               = rounded_up * tctx->n_div[i] - bit_size;
        num_rounded_up                 = tctx->n_div[i] - num_rounded_down;
        tctx->bits_main_spec[0][i][0]  = (rounded_up + 1)   / 2;
        tctx->bits_main_spec[1][i][0]  =  rounded_up        / 2;
        tctx->bits_main_spec[0][i][1]  = (rounded_down + 1) / 2;
        tctx->bits_main_spec[1][i][1]  =  rounded_down      / 2;
        tctx->bits_main_spec_change[i] = num_rounded_up;

        rounded_up             = (vect_size + tctx->n_div[i] - 1) /
                                 tctx->n_div[i];
        rounded_down           = (vect_size) / tctx->n_div[i];
        num_rounded_down       = rounded_up * tctx->n_div[i] - vect_size;
        num_rounded_up         = tctx->n_div[i] - num_rounded_down;
        tctx->length[i][0]     = rounded_up;
        tctx->length[i][1]     = rounded_down;
        tctx->length_change[i] = num_rounded_up;
    }

    for (frametype = FT_SHORT; frametype <= FT_PPC; frametype++)
        construct_perm_table(tctx, frametype);
}

static av_cold int twin_decode_close(AVCodecContext *avctx)
{
    TwinContext *tctx = avctx->priv_data;
    int i;

    for (i = 0; i < 3; i++) {
        ff_mdct_end(&tctx->mdct_ctx[i]);
        av_free(tctx->cos_tabs[i]);
    }

    av_free(tctx->curr_frame);
    av_free(tctx->spectrum);
    av_free(tctx->prev_frame);
    av_free(tctx->tmp_buf);

    return 0;
}

static av_cold int twin_decode_init(AVCodecContext *avctx)
{
    int ret, isampf, ibps;
    TwinContext *tctx = avctx->priv_data;

    tctx->avctx       = avctx;
    avctx->sample_fmt = AV_SAMPLE_FMT_FLTP;

    if (!avctx->extradata || avctx->extradata_size < 12) {
        av_log(avctx, AV_LOG_ERROR, "Missing or incomplete extradata\n");
        return AVERROR_INVALIDDATA;
    }
    avctx->channels = AV_RB32(avctx->extradata)     + 1;
    avctx->bit_rate = AV_RB32(avctx->extradata + 4) * 1000;
    isampf          = AV_RB32(avctx->extradata + 8);

    if (isampf < 8 || isampf > 44) {
        av_log(avctx, AV_LOG_ERROR, "Unsupported sample rate\n");
        return AVERROR_INVALIDDATA;
    }
    switch (isampf) {
    case 44:
        avctx->sample_rate = 44100;
        break;
    case 22:
        avctx->sample_rate = 22050;
        break;
    case 11:
        avctx->sample_rate = 11025;
        break;
    default:
        avctx->sample_rate = isampf * 1000;
        break;
    }

    if (avctx->channels <= 0 || avctx->channels > CHANNELS_MAX) {
        av_log(avctx, AV_LOG_ERROR, "Unsupported number of channels: %i\n",
               avctx->channels);
        return -1;
    }
    avctx->channel_layout = avctx->channels == 1 ? AV_CH_LAYOUT_MONO
                                                 : AV_CH_LAYOUT_STEREO;

    ibps = avctx->bit_rate / (1000 * avctx->channels);

    if (ibps > 255U) {
        av_log(avctx, AV_LOG_ERROR, "unsupported per channel bitrate %dkbps\n", ibps);
        return AVERROR_INVALIDDATA;
    }

    switch ((isampf << 8) + ibps) {
    case (8 << 8) + 8:
        tctx->mtab = &mode_08_08;
        break;
    case (11 << 8) + 8:
        tctx->mtab = &mode_11_08;
        break;
    case (11 << 8) + 10:
        tctx->mtab = &mode_11_10;
        break;
    case (16 << 8) + 16:
        tctx->mtab = &mode_16_16;
        break;
    case (22 << 8) + 20:
        tctx->mtab = &mode_22_20;
        break;
    case (22 << 8) + 24:
        tctx->mtab = &mode_22_24;
        break;
    case (22 << 8) + 32:
        tctx->mtab = &mode_22_32;
        break;
    case (44 << 8) + 40:
        tctx->mtab = &mode_44_40;
        break;
    case (44 << 8) + 48:
        tctx->mtab = &mode_44_48;
        break;
    default:
        av_log(avctx, AV_LOG_ERROR,
               "This version does not support %d kHz - %d kbit/s/ch mode.\n",
               isampf, isampf);
        return -1;
    }

    avpriv_float_dsp_init(&tctx->fdsp, avctx->flags & CODEC_FLAG_BITEXACT);
    if ((ret = init_mdct_win(tctx))) {
        av_log(avctx, AV_LOG_ERROR, "Error initializing MDCT\n");
        twin_decode_close(avctx);
        return ret;
    }
    init_bitstream_params(tctx);

    memset_float(tctx->bark_hist[0][0], 0.1, FF_ARRAY_ELEMS(tctx->bark_hist));

    return 0;
}

AVCodec ff_twinvq_decoder = {
    .name           = "twinvq",
    .type           = AVMEDIA_TYPE_AUDIO,
    .id             = AV_CODEC_ID_TWINVQ,
    .priv_data_size = sizeof(TwinContext),
    .init           = twin_decode_init,
    .close          = twin_decode_close,
    .decode         = twin_decode_frame,
    .capabilities   = CODEC_CAP_DR1,
    .long_name      = NULL_IF_CONFIG_SMALL("VQF TwinVQ"),
    .sample_fmts    = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_FLTP,
                                                      AV_SAMPLE_FMT_NONE },
};