Repository navigation
Expand file tree
/
Copy pathlib.rs
More file actions
1055 lines (1012 loc) · 35 KB
/
Copy pathlib.rs
File metadata and controls
1055 lines (1012 loc) · 35 KB
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
//! Clean-room AC-3 (Dolby Digital) audio decoder, written from ATSC A/52:2012 ("Digital Audio
//! Compression Standard", §5 bit stream syntax, §6-7 decoding).
//!
//! - All audio coding modes (1+1, 1/0 … 3/2) with or without LFE, 32 / 44.1 / 48 kHz, every
//! frame size (Table 5.18).
//! - Exponents (D15 / D25 / D45, reuse across blocks), the parametric bit allocation exactly as
//! specified (§7.2, fixed-point integer steps and Tables 7.6-7.16) including delta bit allocation,
//! grouped and asymmetric mantissas, dither for zero-bit mantissas (§7.3.4), channel coupling
//! with phase flags, rematrixing, dynamic range control (dynrng / dynrng2), block switching
//! (512- and 256-sample IMDCTs, §7.9.4) with the Kaiser-Bessel derived window.
//! - Output: planar f32 at full scale ±1, channels in WAV / SMPTE order (L R C LFE Ls Rs); no
//! downmix.
//!
//! E-AC-3 (bsid 11-16) is recognised and refused.
#![cfg_attr(not(test), deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable))]
mod tables;
use std::sync::OnceLock;
#[derive(Debug, thiserror::Error, PartialEq, Eq)]
pub enum Error {
#[error("not an AC-3 frame")]
NoSync,
#[error("unsupported AC-3: {0}")]
Unsupported(String),
#[error("invalid AC-3 frame: {0}")]
Invalid(&'static str),
}
pub type Result<T> = std::result::Result<T, Error>;
/// Data rate in kb/s by frmsizecod / 2 (Table 5.18).
const BITRATES: [u32; 19] = [32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 448, 512, 576, 640];
/// Full-bandwidth channels per acmod (Table 5.8).
const NFCHANS: [usize; 8] = [2, 1, 2, 3, 3, 4, 4, 5];
/// syncinfo and the start of bsi.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Header {
pub sample_rate: u32,
pub bitrate_kbps: u32,
/// Bytes in the syncframe.
pub frame_bytes: usize,
pub bsid: u8,
pub acmod: u8,
pub lfeon: bool,
}
impl Header {
/// Output channels (full bandwidth + LFE).
pub fn channels(&self) -> usize {
NFCHANS[self.acmod as usize] + self.lfeon as usize
}
}
/// Parse the frame header at the start of `b`.
pub fn parse_header(b: &[u8]) -> Result<Header> {
if b.len() < 7 || b[0] != 0x0B || b[1] != 0x77 {
return Err(Error::NoSync);
}
let fscod = b[4] >> 6;
let frmsizecod = b[4] & 0x3F;
let bsid = b[5] >> 3;
if bsid > 10 {
return Err(Error::Unsupported(format!("bsid {bsid} (E-AC-3)")));
}
if fscod == 3 || frmsizecod >= 38 {
return Err(Error::Invalid("reserved fscod / frmsizecod"));
}
let kbps = BITRATES[(frmsizecod / 2) as usize];
let words = match fscod {
0 => kbps * 2,
1 => kbps * 96_000 / 44_100 + (frmsizecod & 1) as u32,
_ => kbps * 3,
};
// bsid 9 / 10: half / quarter sample rate (A/52 Annex note on "bsid 9 and 10")
let shift = bsid.saturating_sub(8) as u32;
let sample_rate = [48_000, 44_100, 32_000][fscod as usize] >> shift;
let mut r = Bits::new(&b[6..]);
let acmod = r.read(3) as u8;
if acmod & 1 != 0 && acmod != 1 {
r.skip(2);
}
if acmod & 4 != 0 {
r.skip(2);
}
if acmod == 2 {
r.skip(2);
}
let lfeon = r.read(1) == 1;
Ok(Header { sample_rate, bitrate_kbps: kbps >> shift, frame_bytes: words as usize * 2, bsid, acmod, lfeon })
}
/// MSB-first bit reader; reads past the end give zeros.
struct Bits<'a> {
d: &'a [u8],
pos: usize,
}
impl<'a> Bits<'a> {
fn new(d: &'a [u8]) -> Self {
Self { d, pos: 0 }
}
fn read(&mut self, n: u32) -> u32 {
let mut v = 0u32;
for _ in 0..n {
let byte = self.d.get(self.pos >> 3).copied().unwrap_or(0);
v = (v << 1) | ((byte >> (7 - (self.pos & 7))) & 1) as u32;
self.pos += 1;
}
v
}
fn bit(&mut self) -> bool {
self.read(1) == 1
}
fn skip(&mut self, n: usize) {
self.pos += n;
}
fn overrun(&self) -> bool {
self.pos > self.d.len() * 8
}
}
/// Index of the LFE and coupling channels in the per-channel arrays.
const LFE: usize = 5;
const CPL: usize = 6;
/// Bit allocation parameter tables (Tables 7.6-7.11).
const SLOWDEC: [i32; 4] = [0x0f, 0x11, 0x13, 0x15];
const FASTDEC: [i32; 4] = [0x3f, 0x53, 0x67, 0x7b];
const SLOWGAIN: [i32; 4] = [0x540, 0x4d8, 0x478, 0x410];
const DBPBTAB: [i32; 4] = [0x000, 0x700, 0x900, 0xb00];
const FLOORTAB: [i32; 8] = [0x2f0, 0x2b0, 0x270, 0x230, 0x1f0, 0x170, 0x0f0, -0x800];
const FASTGAIN: [i32; 8] = [0x080, 0x100, 0x180, 0x200, 0x280, 0x300, 0x380, 0x400];
/// Mantissa bits of the asymmetric quantizers by bap (Table 7.18).
const QNTZTAB: [u32; 16] = [0, 0, 0, 3, 0, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16];
/// The Kaiser-Bessel derived window of §7.9.4 (α = 5, 512 points), whose first half Table 7.33
/// lists to five decimals.
fn window() -> &'static [f32; 256] {
static W: OnceLock<[f32; 256]> = OnceLock::new();
W.get_or_init(|| {
let i0 = |x: f64| {
let (mut s, mut t) = (1.0f64, 1.0f64);
for k in 1..50 {
t *= (x / 2.0) / k as f64;
s += t * t;
}
s
};
let alpha = 5.0 * std::f64::consts::PI;
let k: Vec<f64> = (0..=256).map(|j| i0(alpha * (1.0 - ((j as f64 - 128.0) / 128.0).powi(2)).max(0.0).sqrt())).collect();
let total: f64 = k.iter().sum();
let mut acc = 0.0;
let mut w = [0f32; 256];
for n in 0..256 {
acc += k[n];
w[n] = (acc / total).sqrt() as f32;
}
w
})
}
/// Twiddles for the IMDCTs: (xcos1, xsin1) for N = 512 and (xcos2, xsin2) for the 256-sample
/// transforms, and the IFFT kernels.
struct Twiddles {
c1: [f32; 128],
s1: [f32; 128],
c2: [f32; 64],
s2: [f32; 64],
/// e^{j 2π m / 128}, m = 0..128.
e: [(f32, f32); 128],
}
fn twiddles() -> &'static Twiddles {
static T: OnceLock<Twiddles> = OnceLock::new();
T.get_or_init(|| {
use std::f64::consts::PI;
let n = 512.0;
let mut t = Twiddles { c1: [0.0; 128], s1: [0.0; 128], c2: [0.0; 64], s2: [0.0; 64], e: [(0.0, 0.0); 128] };
for k in 0..128 {
let a = 2.0 * PI * (8 * k + 1) as f64 / (8.0 * n);
t.c1[k] = -a.cos() as f32;
t.s1[k] = -a.sin() as f32;
let m = 2.0 * PI * k as f64 / 128.0;
t.e[k] = (m.cos() as f32, m.sin() as f32);
}
for k in 0..64 {
let a = 2.0 * PI * (8 * k + 1) as f64 / (4.0 * n);
t.c2[k] = -a.cos() as f32;
t.s2[k] = -a.sin() as f32;
}
t
})
}
/// In-place complex inverse DFT of size `n` (128 or 64) by radix-2 decimation in time:
/// z[n] = Σ Z[k] e^{+j 2π k n / size}.
fn ifft(re: &mut [f32], im: &mut [f32]) {
let n = re.len();
let e = &twiddles().e;
// bit reversal
let bits = n.trailing_zeros();
for i in 0..n {
let j = i.reverse_bits() >> (usize::BITS - bits);
if j > i {
re.swap(i, j);
im.swap(i, j);
}
}
let mut len =
8000
2;
while len <= n {
let step = 128 / len;
for s in (0..n).step_by(len) {
for k in 0..len / 2 {
let (wr, wi) = e[k * step];
let (a, b) = (s + k, s + k + len / 2);
let tr = re[b] * wr - im[b] * wi;
let ti = re[b] * wi + im[b] * wr;
re[b] = re[a] - tr;
im[b] = im[a] - ti;
re[a] += tr;
im[a] += ti;
}
}
len *= 2;
}
}
/// Inverse transform of one block of 256 coefficients into 512 windowed samples (§7.9.4).
fn imdct(x: &[f32; 256], short: bool, out: &mut [f32; 512]) {
let w = window();
let t = twiddles();
const N: usize = 512;
if !short {
let (mut zr, mut zi) = ([0f32; 128], [0f32; 128]);
for k in 0..N / 4 {
let (a, b) = (x[N / 2 - 2 * k - 1], x[2 * k]);
zr[k] = a * t.c1[k] - b * t.s1[k];
zi[k] = b * t.c1[k] + a * t.s1[k];
}
ifft(&mut zr, &mut zi);
let (mut yr, mut yi) = ([0f32; 128], [0f32; 128]);
for n in 0..N / 4 {
yr[n] = zr[n] * t.c1[n] - zi[n] * t.s1[n];
yi[n] = zi[n] * t.c1[n] + zr[n] * t.s1[n];
}
for n in 0..N / 8 {
out[2 * n] = -yi[N / 8 + n] * w[2 * n];
out[2 * n + 1] = yr[N / 8 - n - 1] * w[2 * n + 1];
out[N / 4 + 2 * n] = -yr[n] * w[N / 4 + 2 * n];
out[N / 4 + 2 * n + 1] = yi[N / 4 - n - 1] * w[N / 4 + 2 * n + 1];
out[N / 2 + 2 * n] = -yr[N / 8 + n] * w[N / 2 - 2 * n - 1];
out[N / 2 + 2 * n + 1] = yi[N / 8 - n - 1] * w[N / 2 - 2 * n - 2];
out[3 * N / 4 + 2 * n] = yi[n] * w[N / 4 - 2 * n - 1];
out[3 * N / 4 + 2 * n + 1] = -yr[N / 4 - n - 1] * w[N / 4 - 2 * n - 2];
}
return;
}
let mut y = [([0f32; 64], [0f32; 64]); 2];
for (h, yh) in y.iter_mut().enumerate() {
let (mut zr, mut zi) = ([0f32; 64], [0f32; 64]);
for k in 0..N / 8 {
let (a, b) = (x[2 * (N / 4 - 2 * k - 1) + h], x[2 * (2 * k) + h]);
zr[k] = a * t.c2[k] - b * t.s2[k];
zi[k] = b * t.c2[k] + a * t.s2[k];
}
ifft(&mut zr, &mut zi);
for n in 0..N / 8 {
yh.0[n] = zr[n] * t.c2[n] - zi[n] * t.s2[n];
yh.1[n] = zi[n] * t.c2[n] + zr[n] * t.s2[n];
}
}
let ((yr1, yi1), (yr2, yi2)) = (y[0], y[1]);
for n in 0..N / 8 {
out[2 * n] = -yi1[n] * w[2 * n];
out[2 * n + 1] = yr1[N / 8 - n - 1] * w[2 * n + 1];
out[N / 4 + 2 * n] = -yr1[n] * w[N / 4 + 2 * n];
out[N / 4 + 2 * n + 1] = yi1[N / 8 - n - 1] * w[N / 4 + 2 * n + 1];
out[N / 2 + 2 * n] = -yr2[n] * w[N / 2 - 2 * n - 1];
out[N / 2 + 2 * n + 1] = yi2[N / 8 - n - 1] * w[N / 2 - 2 * n - 2];
out[3 * N / 4 + 2 * n] = yi2[n] * w[N / 4 - 2 * n - 1];
out[3 * N / 4 + 2 * n + 1] = -yr2[N / 8 - n - 1] * w[N / 4 - 2 * n - 2];
}
}
fn logadd(a: i32, b: i32) -> i32 {
let c = a - b;
let addr = ((c.abs() >> 1) as usize).min(255);
if c >= 0 { a + tables::LATAB[addr] as i32 } else { b + tables::LATAB[addr] as i32 }
}
fn calc_lowcomp(a: i32, b0: i32, b1: i32, bin: usize) -> i32 {
if bin < 7 {
if b0 + 256 == b1 {
384
} else if b0 > b1 {
(a - 64).max(0)
} else {
a
}
} else if bin < 20 {
if b0 + 256 == b1 {
320
} else if b0 > b1 {
(a - 64).max(0)
} else {
a
}
} else {
(a - 128).max(0)
}
}
/// Inputs to the bit allocation of one channel.
struct AllocParams {
start: usize,
end: usize,
fgain: i32,
snroffset: i32,
/// Coupling channel leak initialisation.
leak: Option<(i32, i32)>,
/// Delta bit allocation segments (offset, length, ba) when in use.
dba: Option<Vec<(u8, u8, u8)>>,
}
/// The parametric bit allocation of §7.2.2 for one exponent set.
fn bit_allocation(exp: &[u8; 256], p: &AllocParams, g: &Globals, bap: &mut [u8; 256]) {
let (start, end) = (p.start, p.end);
if start >= end {
return;
}
let (sdecay, fdecay, sgain, dbknee, floor) = (SLOWDEC[g.sdcycod], FASTDEC[g.fdcycod], SLOWGAIN[g.sgaincod], DBPBTAB[g.dbpbcod], FLOORTAB[g.floorcod]);
let mut psd = [0i32; 256];
for bin in start..end {
psd[bin] = 3072 - ((exp[bin] as i32) << 7);
8BD0
}
// PSD integration
let mut bndpsd = [0i32; 50];
let mut j = start;
let mut k = tables::MASKTAB[start] as usize;
loop {
let lastbin = (tables::BNDTAB[k] as usize + tables::BNDSZ[k] as usize).min(end);
bndpsd[k] = psd[j];
j += 1;
while j < lastbin {
bndpsd[k] = logadd(bndpsd[k], psd[j]);
j += 1;
}
k += 1;
if end <= lastbin || k >= 50 {
break;
}
}
// excitation
let bndstrt = tables::MASKTAB[start] as usize;
let bndend = tables::MASKTAB[end - 1] as usize + 1;
let mut excite = [0i32; 50];
let (mut fastleak, mut slowleak) = p.leak.unwrap_or((0, 0));
let begin = if bndstrt == 0 {
// the last band of the LFE channel (bndend 7) has no band above it
let lfe_last = |bin: usize| !(bndend == 7 && bin == 6);
let mut lowcomp = 0;
lowcomp = calc_lowcomp(lowcomp, bndpsd[0], bndpsd[1], 0);
excite[0] = bndpsd[0] - p.fgain - lowcomp;
lowcomp = calc_lowcomp(lowcomp, bndpsd[1], bndpsd[2], 1);
excite[1] = bndpsd[1] - p.fgain - lowcomp;
let mut b = 7;
for bin in 2..7 {
if lfe_last(bin) {
lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin + 1], bin);
}
fastleak = bndpsd[bin] - p.fgain;
slowleak = bndpsd[bin] - sgain;
excite[bin] = fastleak - lowcomp;
if lfe_last(bin) && bndpsd[bin] <= bndpsd[bin + 1] {
b = bin + 1;
break;
}
}
for bin in b..bndend.min(22) {
if lfe_last(bin) {
lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin + 1], bin);
}
fastleak -= fdecay;
fastleak = fastleak.max(bndpsd[bin] - p.fgain);
slowleak -= sdecay;
slowleak = slowleak.max(bndpsd[bin] - sgain);
excite[bin] = (fastleak - lowcomp).max(slowleak);
}
22
} else {
bndstrt
};
for bin in begin..bndend {
fastleak -= fdecay;
fastleak = fastleak.max(bndpsd[bin] - p.fgain);
slowleak -= sdecay;
slowleak = slowleak.max(bndpsd[bin] - sgain);
excite[bin] = fastleak.max(slowleak);
}
// masking curve
let mut mask = [0i32; 50];
for bin in bndstrt..bndend {
if bndpsd[bin] < dbknee {
excite[bin] += (dbknee - bndpsd[bin]) >> 2;
}
mask[bin] = excite[bin].max(tables::HTH[g.fscod][bin] as i32);
}
// delta bit allocation
if let Some(segs) = &p.dba {
let mut band = 0usize;
for &(off, len, ba) in segs {
band += off as usize;
let delta = if ba >= 4 { (ba as i32 - 3) << 7 } else { (ba as i32 - 4) << 7 };
for _ in 0..len {
if band < 50 {
mask[band] += delta;
}
band += 1;
}
}
}
// bit allocation pointers
let mut i = start;
let mut j = tables::MASKTAB[start] as usize;
loop {
let lastbin = (tables::BNDTAB[j] as usize + tables::BNDSZ[j] as usize).min(end);
let mut m = mask[j] - p.snroffset - floor;
if m < 0 {
m = 0;
}
m &= 0x1fe0;
m += floor;
while i < lastbin {
let addr = ((psd[i] - m) >> 5).clamp(0, 63) as usize;
bap[i] = tables::BAPTAB[addr];
i += 1;
}
j += 1;
if end <= lastbin || j >= 50 {
break;
}
}
}
/// Bit allocation parameters common to all channels of a block.
#[derive(Clone, Copy, Default)]
struct Globals {
fscod: usize,
sdcycod: usize,
fdcycod: usize,
sgaincod: usize,
dbpbcod: usize,
floorcod: usize,
}
/// State carried from block to block within a syncframe.
struct Frame {
nfchans: usize,
blksw: [bool; 5],
dithflag: [bool; 5],
dynrng: [f32; 2],
cplinu: bool,
chincpl: [bool; 5],
phsflginu: bool,
cplbegf: usize,
cplendf: usize,
/// Coupling band of each coupling sub-band (relative to cplbegf).
sub_to_band: [usize; 18],
ncplbnd: usize,
cplco: [[f32; 18]; 5],
phsflg: [bool; 18],
rematflg: [bool; 4],
expstr: [u8; 7],
endmant: [usize; 5],
exps: [[u8; 256]; 7],
g: Globals,
csnroffst: i32,
fsnroffst: [i32; 7],
fgaincod: [usize; 7],
cplleak: (i32, i32),
deltbae: [u8; 7],
deltsegs: [Vec<(u8, u8, u8)>; 7],
bap: [[u8; 256]; 7],
}
impl Frame {
fn new(nfchans: usize, fscod: usize) -> Frame {
Frame {
nfchans,
blksw: [false; 5],
dithflag: [false; 5],
dynrng: [1.0; 2],
cplinu: false,
chincpl: [false; 5],
phsflginu: false,
cplbegf: 0,
cplendf: 0,
sub_to_band: [0; 18],
ncplbnd: 0,
cplco: [[0.0; 18]; 5],
phsflg: [false; 18],
rematflg: [false; 4],
expstr: [0; 7],
endmant: [0; 5],
exps: [[0; 256]; 7],
g: Globals { fscod, ..Default::default() },
csnroffst: 0,
fsnroffst: [0; 7],
fgaincod: [0; 7],
cplleak: (0, 0),
deltbae: [2; 7],
deltsegs: Default::default(),
bap: [[0; 256]; 7],
}
}
fn cplstrtmant(&self) -> usize {
37 + 12 * self.cplbegf
}
fn cplendmant(&self) -> usize {
37 + 12 * (self.cplendf + 3)
}
}
/// dynrng gain (§7.7.1.2): X (3-bit signed) gives 6.02 dB steps, Y a linear factor in [1/2, 1).
fn dynrng_gain(v: u32) -> f32 {
let x = ((v as i32) << 24) >> 29;
let y = (v & 0x1F) as f32;
2f32.powi(x + 1) * (32.0 + y) / 64.0
}
/// Decode exponents of one set (§7.1.3) into `exp[first..]`; `ngrps` groups of 3 mapped values,
/// each expanded to `grpsize` bins after the absolute exponent.
fn decode_exponents(r: &mut Bits, absexp: i32, ngrps: usize, grpsize: usize, exp: &mut [u8; 256], first: usize, skip_abs: bool) -> Result<()> {
let mut prev = absexp;
let mut at = first;
if !skip_abs {
exp[at] = absexp.clamp(0, 24) as u8;
at += 1;
}
for _ in 0..ngrps {
let g = r.read(7) as i32;
if g > 124 {
return Err(Error::Invalid("exponent group out of range"));
}
for d in [g / 25, (g % 25) / 5, g % 5] {
prev += d - 2;
if !(0..=24).contains(&prev) {
return Err(Error::Invalid("exponent out of range"));
}
for _ in 0..grpsize {
if at < 256 {
exp[at] = prev as u8;
}
at += 1;
}
}
}
Ok(())
}
/// Grouped-mantissa buffers shared by all exponent sets of a block (§7.3.5).
#[derive(Default)]
struct Groups {
b1: ([f32; 3], usize),
b2: ([f32; 3], usize),
b4: ([f32; 2], usize),
}
const fn sym(levels: i32, code: i32) -> f32 {
(2 * code - (levels - 1)) as f32 / levels as f32
}
/// The mantissa value (before the exponent shift) of a bin with allocation `bap`.
fn mantissa(r: &mut Bits, bap: u8, gr: &mut Groups) -> f32 {
match bap {
1 => {
if gr.b1.1 == 0 {
let g = r.read(5) as i32;
gr.b1.0 = [sym(3, g / 9), sym(3, (g % 9) / 3), sym(3, g % 3)];
gr.b1.1 = 3;
}
gr.b1.1 -= 1;
gr.b1.0[2 - gr.b1.1]
}
2 => {
if gr.b2.1 == 0 {
let g = r.read(7) as i32;
gr.b2.0 = [sym(5, g / 25), sym(5, (g % 25) / 5), sym(5, g % 5)];
gr.b2.1 = 3;
}
gr.b2.1 -= 1;
gr.b2.0[2 - gr.b2.1]
}
3 => sym(7, r.read(3) as i32),
4 => {
if gr.b4.1 == 0 {
let g = r.read(7) as i32;
gr.b4.0 = [sym(11, g / 11), sym(11, g % 11)];
gr.b4.1 = 2;
}
gr.b4.1 -= 1;
gr.b4.0[1 - gr.b4.1]
}
5 => sym(15, r.read(4) as i32),
_ => {
let bits = QNTZTAB[bap as usize & 15];
let v = r.read(bits) as i32;
let v = (v << (32 - bits)) >> (32 - bits);
v as f32 / (1u32 << (bits - 1)) as f32
}
}
}
/// A decoder: keeps the overlap of each channel between frames.
pub struct Decoder {
delay: [[f32; 256]; 6],
dither: u32,
seed: u32,
}
impl Default for Decoder {
fn default() -> Self {
Self::new()
}
}
/// A decoded syncframe: 1536 samples per channel, WAV channel order.
#[derive(Clone, Debug)]
pub struct Decoded {
pub header: Header,
pub channels: Vec<Vec<f32>>,
}
impl Decoder {
pub fn new() -> Decoder {
Decoder { delay: [[0.0; 256]; 6], dither: 0, seed: 0x1234_5678 }
}
/// Seed the dither generator (dither is decoder-specific noise; tests compare two seeds).
pub fn set_dither_seed(&mut self, seed: u32) {
self.seed = seed;
}
/// Forget the overlap (before decoding from another position).
pub fn reset(&mut self) {
self.delay = [[0.0; 256]; 6];
}
fn dither(&mut self) -> f32 {
// uniform in [-0.707, 0.707] (§7.3.4; any reasonably random sequence)
self.dither = self.dither.wrapping_mul(1_664_525).wrapping_add(1_013_904_223);
((self.dither >> 8) as f32 / (1u32 << 24) as f32 * 2.0 - 1.0) * 0.707
}
/// Decode one syncframe.
pub fn decode(&mut self, frame: &[u8]) -> Result<Decoded> {
let h = parse_header(frame)?;
if frame.len() < h.frame_bytes {
return Err(Error::Invalid("truncated syncframe"));
}
let fscod = (frame[4] >> 6) as usize;
// Dither is reseeded per syncframe from its CRC words (plus the configured seed), so a
// frame decodes to the same samples however it was reached (seeking, render caches).
let crcs = u32::from_be_bytes([frame[2], frame[3], frame[h.frame_bytes - 2], frame[h.frame_bytes - 1]]);
self.dither = self.seed ^ crcs.wrapping_mul(0x9E37_79B9);
let mut r = Bits::new(&frame[..h.frame_bytes]);
r.skip(40); // syncinfo
// bsi
r.skip(8); // bsid, bsmod
let acmod = r.read(3) as usize;
if acmod & 1 != 0 && acmod != 1 {
r.skip(2);
}
if acmod & 4 != 0 {
r.skip(2);
}
if acmod == 2 {
r.skip(2);
}
let lfeon = r.bit();
for k in 0..if acmod == 0 { 2 } else { 1 } {
let _ = k;
r.skip(5); // dialnorm
if r.bit() {
r.skip(8); // compr
}
if r.bit() {
r.skip(8); // langcod
}
if r.bit() {
r.skip(7); // mixlevel, roomtyp
}
}
r.skip(2); // copyrightb, origbs
if r.bit() {
r.skip(14);
}
if r.bit() {
r.skip(14);
}
if r.bit() {
let l = r.read(6) as usize;
r.skip((l + 1) * 8);
}
let nfchans = NFCHANS[acmod];
let mut f = Frame::new(nfchans, fscod);
let nout = nfchans + lfeon as usize;
let mut pcm: Vec<Vec<f32>> = vec![Vec::with_capacity(1536); nout];
for blk in 0..6 {
let mut coefs = [[0f32; 256]; 6];
self.audio_block(&mut r, &mut f, acmod, lfeon, blk, &mut coefs)?;
if r.overrun() {
return Err(Error::Invalid("audio block runs past the frame"));
}
// inverse transform, overlap-add
let mut buf = [0f32; 512];
for ch in 0..nout {
let src = if ch < nfchans { ch } else { LFE };
let short = ch < nfchans && f.blksw[ch];
imdct(&coefs[src], short, &mut buf);
let d = &mut self.delay[src];
for n in 0..256 {
pcm[ch].push(2.0 * (buf[n] + d[n]));
d[n] = buf[256 + n];
}
}
}
Ok(Decoded { header: h, channels: wav_order(pcm, acmod, lfeon) })
}
fn audio_block(&mut self, r: &mut Bits, f: &mut Frame, acmod: usize, lfeon: bool, blk: usize, coefs: &mut [[f32; 256]; 6]) -> Result<()> {
let nf = f.nfchans;
for ch in 0..nf {
f.blksw[ch] = r.bit();
}
for ch in 0..nf {
f.dithflag[ch] = r.bit();
}
for k in 0..if acmod == 0 { 2 } else { 1 } {
if r.bit() {
f.dynrng[k] = dynrng_gain(r.read(8));
} else if blk == 0 {
f.dynrng[k] = 1.0;
}
}
// coupling strategy
if r.bit() {
f.cplinu = r.bit();
if f.cplinu {
for ch in 0..nf {
f.chincpl[ch] = r.bit();
}
if acmod == 2 {
f.phsflginu = r.bit();
}
f.cplbegf = r.read(4) as usize;
f.cplendf = r.read(4) as usize;
if f.cplendf + 3 <= f.cplbegf {
return Err(Error::Invalid("coupling end below start"));
}
let nsub = 3 + f.cplendf - f.cplbegf;
let mut band = 0;
f.sub_to_band[0] = 0;
for s in 1..nsub {
if !r.bit() {
band += 1;
}
f.sub_to_band[s] = band;
}
f.ncplbnd = band + 1;
} else {
f.chincpl = [false; 5];
}
} else if blk == 0 {
return Err(Error::Invalid("no coupling strategy in block 0"));
}
// coupling coordinates
if f.cplinu {
let mut any = false;
for ch in 0..nf {
if f.chincpl[ch] && r.bit() {
any = true;
let mstr = r.read(2) as i32;
for bnd in 0..f.ncplbnd {
let e = r.read(4) as i32;
let m = r.read(4) as f32;
let v = if e == 15 { m / 16.0 } else { (m + 16.0) / 32.0 };
let co = v * 2f32.powi(-(e + 3 * mstr));
for s in 0..(3 + f.cplendf - f.cplbegf) {
if f.sub_to_band[s] == bnd {
f.cplco[ch][s] = co;
}
}
}
}
}
if acmod == 2 && f.phsflginu && any {
for bnd in 0..f.ncplbnd {
let flag = r.bit();
for s in 0..(3 + f.cplendf - f.cplbegf) {
if f.sub_to_band[s] == bnd {
f.phsflg[s] = flag;
}
}
}
}
}
// rematrixing
if acmod == 2 && r.bit() {
let n = if !f.cplinu || f.cplbegf > 2 {
4
} else if f.cplbegf > 0 {
3
} else {
2
};
f.rematflg = [false; 4];
for k in 0..n {
f.rematflg[k] = r.bit();
}
}
// exponent strategies
if f.cplinu {
f.expstr[CPL] = r.read(2) as u8;
}
for ch in 0..nf {
f.expstr[ch] = r.read(2) as u8;
}
if lfeon {
f.expstr[LFE] = r.read(1) as u8;
}
for ch in 0..nf {
if f.expstr[ch] != 0 {
if f.chincpl[ch] && f.cplinu {
f.endmant[ch] = f.cplstrtmant();
} else {
let bw = r.read(6) as usize;
if bw > 60 {
return Err(Error::Invalid("chbwcod > 60"));
}
f.endmant[ch] = (bw + 12) * 3 + 37;
}
}
}
// exponents
if f.cplinu && f.expstr[CPL] != 0 {
let abs = (r.read(4) as i32) << 1;
let grpsize = 1 << (f.expstr[CPL] - 1);
let ngrps = (f.cplendmant() - f.cplstrtmant()) / (3 * grpsize);
let first = f.cplstrtmant();
decode_exponents(r, abs, ngrps, grpsize, &mut f.exps[CPL], first, true)?;
}
for ch in 0..nf {
if f.expstr[ch] != 0 {
let abs = r.read(4) as i32;
let grpsize = 1usize << (f.expstr[ch] - 1);
let ngrps = (f.endmant[ch] - 1 + 3 * grpsize - 3) / (3 * grpsize);
decode_exponents(r, abs, ngrps, grpsize, &mut f.exps[ch], 0, false)?;
r.skip(2); // gainrng
}
}
if lfeon && f.expstr[LFE] != 0 {
let abs = r.read(4) as i32;
decode_exponents(r, abs, 2, 1, &mut f.exps[LFE], 0, false)?;
}
// bit allocation parametric information
if r.bit() {
f.g.sdcycod = r.read(2) as usize;
f.g.fdcycod = r.read(2) as usize;
f.g.sgaincod = r.read(2) as usize;
f.g.dbpbcod = r.read(2) as usize;
f.g.floorcod = r.read(3) as usize;
} else if blk == 0 {
return Err(Error::Invalid("no bit allocation information in block 0"));
}
if r.bit() {
f.csnroffst = r.read(6) as i32;
if f.cplinu {
f.fsnroffst[CPL] = r.read(4) as i32;
f.fgaincod[CPL] = r.read(3) as usize;
}
for ch in 0..nf {
f.fsnroffst[ch] = r.read(4) as i32;
f.fgaincod[ch] = r.read(3) as usize;
}
if lfeon {
f.fsnroffst[LFE] = r.read(4) as i32;
f.fgaincod[LFE] = r.read(3) as usize;
}
} else if blk == 0 {
return Err(Error::Invalid("no SNR offsets in block 0"));
}
if f.cplinu && r.bit() {
f.cplleak = (((r.read(3) as i32) << 8) + 768, ((r.read(3) as i32) << 8) + 768);
}
// delta bit allocation
if blk == 0 {
f.deltbae = [2; 7];
}
if r.bit() {
if f.cplinu {
f.deltbae[CPL] = r.read(2) as u8;
}
for ch in 0..nf {
f.deltbae[ch] = r.read(2) as u8;
}
let order: Vec<usize> = f.cplinu.then_some(CPL).into_iter().chain(0..nf).collect();
for ch in order {
if f.deltbae[ch] == 1 {
let n = r.read(3) as usize + 1;
f.deltsegs[ch] = (0..n).map(|_| (r.read(5) as u8, r.read(4) as u8, r.read(3) as u8)).collect();
} else if f.deltbae[ch] == 3 {
return Err(Error::Invalid("reserved delta bit allocation state"));
}
}
}
// skip field
if r.bit() {
let l = r.read(9) as usize;
r.skip(l * 8);
}
// bit allocation for every exponent set
let all_zero = f.csnroffst == 0 && (0..7).all(|c| f.fsnroffst[c] == 0);
let snr = |fine: i32| (((f.csnroffst - 15) << 4) + fine) << 2;
let mut sets: Vec<(usize, AllocParams)> = Vec::new();
for ch in 0..nf {
let dba = (f.deltbae[ch] <= 1).then(|| f.deltsegs[ch].clone());
sets.push((ch, AllocParams { start: 0, end: f.endmant[ch], fgain: FASTGAIN[f.fgaincod[ch]], snroffset: snr(f.fsnroffst[ch]), leak: None, dba }));
}
if f.cplinu {
let dba = (f.deltbae[CPL] <= 1).then(|| f.deltsegs[CPL].clone());
sets.push((
CPL,
AllocParams {
start: f.cplstrtmant(),
end: f.cplendmant(),
fgain: FASTGAIN[f.fgaincod[CPL]],
snroffset: snr(f.fsnroffst[CPL]),
leak: Some(f.cplleak),
dba,
},
));
}
if lfeon {
sets.push((LFE, AllocParams { start: 0, end: 7, fgain: FASTGAIN[f.fgaincod[LFE]], snroffset: snr(f.fsnroffst[LFE]), leak: None, dba: None }));
}
for (ch, p) in &sets {
f.bap[*ch] = [0; 256];
if !all_zero {
let exps = f.exps[*ch];
bit_allocation(&exps, p, &f.g, &mut f.bap[*ch]);
}
}
// mantissas
let mut gr = Groups::default();
let mut cpl = [0f32; 256];
let mut got_cpl = false;
for ch in 0..nf {
for bin in 0..f.endmant[ch] {
let b = f.bap[ch][bin];
let m = if b == 0 { if f.dithflag[ch] { self.dither() } else { 0.0 } } else { mantissa(r, b, &mut gr) };
coefs[ch][bin] = m * 2f32.powi(-(f.exps[ch][bin] as i32));
}
if f.cplinu && f.chincpl[ch] && !got_cpl {
got_cpl = true;
for bin in f.cplstrtmant()..f.cplendmant() {
let b = f.bap[CPL][bin];
// zero-bit coupling mantissas are dithered per channel when decoupling
cpl[bin] = if b == 0 { f32::NAN } else { mantissa(r, b, &mut gr) };
}
}
}
if lfeon {
for bin in 0..7 {
let b = f.bap[LFE][bin];
let m = if b == 0 { 0.0 } else { mantissa(r, b, &mut gr) };
coefs[LFE][bin] = m * 2f32.powi(-(f.exps[LFE][bin] as i32));
}
}
// decoupling
if f.cplinu {
for ch in 0..nf {
if !f.chincpl[ch] {
continue;
}
for bin in f.cplstrtmant()..f.cplendmant() {
let s = (bin - 37) / 12 - f.cplbegf;
let m = if cpl[bin].is_nan() { if f.dithflag[ch] { self.dither() } else { 0.0 } } else { cpl[bin] };
let mut v = m * 2f32.powi(-(f.exps[CPL][bin] as i32)) * f.cplco[ch][s] * 8.0;
if acmod == 2 && ch == 1 && f.phsflginu && f.phsflg[s] {
v = -v;
}
coefs[ch][bin] = v;
}