1 /*
2 * libmad - MPEG audio decoder library
3 * Copyright (C) 2000-2004 Underbit Technologies, Inc.
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 *
19 * $Id: layer12.c,v 1.17 2004/02/05 09:02:39 rob Exp $
20 */
21
22 # ifdef HAVE_CONFIG_H
23 # include "config.h"
24 # endif
25
26 # include "global.h"
27
28 # ifdef HAVE_LIMITS_H
29 # include <limits.h>
30 # else
31 # define CHAR_BIT 8
32 # endif
33
34 # include "fixed.h"
35 # include "bit.h"
36 # include "stream.h"
37 # include "frame.h"
38 # include "layer12.h"
39
40 /*
41 * scalefactor table
42 * used in both Layer I and Layer II decoding
43 */
44 static
45 mad_fixed_t const sf_table[64] = {
46 # include "sf_table.dat"
47 };
48
49 /* --- Layer I ------------------------------------------------------------- */
50
51 /* linear scaling table */
52 static
53 mad_fixed_t const linear_table[14] = {
54 MAD_F(0x15555555), /* 2^2 / (2^2 - 1) == 1.33333333333333 */
55 MAD_F(0x12492492), /* 2^3 / (2^3 - 1) == 1.14285714285714 */
56 MAD_F(0x11111111), /* 2^4 / (2^4 - 1) == 1.06666666666667 */
57 MAD_F(0x10842108), /* 2^5 / (2^5 - 1) == 1.03225806451613 */
58 MAD_F(0x10410410), /* 2^6 / (2^6 - 1) == 1.01587301587302 */
59 MAD_F(0x10204081), /* 2^7 / (2^7 - 1) == 1.00787401574803 */
60 MAD_F(0x10101010), /* 2^8 / (2^8 - 1) == 1.00392156862745 */
61 MAD_F(0x10080402), /* 2^9 / (2^9 - 1) == 1.00195694716243 */
62 MAD_F(0x10040100), /* 2^10 / (2^10 - 1) == 1.00097751710655 */
63 MAD_F(0x10020040), /* 2^11 / (2^11 - 1) == 1.00048851978505 */
64 MAD_F(0x10010010), /* 2^12 / (2^12 - 1) == 1.00024420024420 */
65 MAD_F(0x10008004), /* 2^13 / (2^13 - 1) == 1.00012208521548 */
66 MAD_F(0x10004001), /* 2^14 / (2^14 - 1) == 1.00006103888177 */
67 MAD_F(0x10002000) /* 2^15 / (2^15 - 1) == 1.00003051850948 */
68 };
69
70 /*
71 * NAME: I_sample()
72 * DESCRIPTION: decode one requantized Layer I sample from a bitstream
73 */
74 static
I_sample(struct mad_bitptr * ptr,unsigned int nb)75 mad_fixed_t I_sample(struct mad_bitptr *ptr, unsigned int nb)
76 {
77 mad_fixed_t sample;
78
79 sample = mad_bit_read(ptr, nb);
80
81 /* invert most significant bit, extend sign, then scale to fixed format */
82
83 sample ^= 1 << (nb - 1);
84 sample |= -(sample & (1 << (nb - 1)));
85
86 sample <<= MAD_F_FRACBITS - (nb - 1);
87
88 /* requantize the sample */
89
90 /* s'' = (2^nb / (2^nb - 1)) * (s''' + 2^(-nb + 1)) */
91
92 sample += MAD_F_ONE >> (nb - 1);
93
94 return mad_f_mul(sample, linear_table[nb - 2]);
95
96 /* s' = factor * s'' */
97 /* (to be performed by caller) */
98 }
99
100 /*
101 * NAME: layer->I()
102 * DESCRIPTION: decode a single Layer I frame
103 */
mad_layer_I(struct mad_stream * stream,struct mad_frame * frame)104 int mad_layer_I(struct mad_stream *stream, struct mad_frame *frame)
105 {
106 struct mad_header *header = &frame->header;
107 unsigned int nch, bound, ch, s, sb, nb;
108 unsigned char allocation[2][32], scalefactor[2][32];
109
110 nch = MAD_NCHANNELS(header);
111
112 bound = 32;
113 if (header->mode == MAD_MODE_JOINT_STEREO) {
114 header->flags |= MAD_FLAG_I_STEREO;
115 bound = 4 + header->mode_extension * 4;
116 }
117
118 /* check CRC word */
119
120 if (header->flags & MAD_FLAG_PROTECTION) {
121 header->crc_check =
122 mad_bit_crc(stream->ptr, 4 * (bound * nch + (32 - bound)),
123 header->crc_check);
124
125 if (header->crc_check != header->crc_target &&
126 !(frame->options & MAD_OPTION_IGNORECRC)) {
127 stream->error = MAD_ERROR_BADCRC;
128 return -1;
129 }
130 }
131
132 /* decode bit allocations */
133
134 for (sb = 0; sb < bound; ++sb) {
135 for (ch = 0; ch < nch; ++ch) {
136 nb = mad_bit_read(&stream->ptr, 4);
137 if (mad_bit_nextbyte(&stream->ptr) > stream->next_frame)
138 {
139 stream->error = MAD_ERROR_LOSTSYNC;
140 stream->sync = 0;
141 return -1;
142 }
143
144 if (nb == 15) {
145 stream->error = MAD_ERROR_BADBITALLOC;
146 return -1;
147 }
148
149 allocation[ch][sb] = nb ? nb + 1 : 0;
150 }
151 }
152
153 for (sb = bound; sb < 32; ++sb) {
154 nb = mad_bit_read(&stream->ptr, 4);
155 if (mad_bit_nextbyte(&stream->ptr) > stream->next_frame)
156 {
157 stream->error = MAD_ERROR_LOSTSYNC;
158 stream->sync = 0;
159 return -1;
160 }
161
162 if (nb == 15) {
163 stream->error = MAD_ERROR_BADBITALLOC;
164 return -1;
165 }
166
167 allocation[0][sb] =
168 allocation[1][sb] = nb ? nb + 1 : 0;
169 }
170
171 /* decode scalefactors */
172
173 for (sb = 0; sb < 32; ++sb) {
174 for (ch = 0; ch < nch; ++ch) {
175 if (allocation[ch][sb]) {
176 scalefactor[ch][sb] = mad_bit_read(&stream->ptr, 6);
177 if (mad_bit_nextbyte(&stream->ptr) > stream->next_frame)
178 {
179 stream->error = MAD_ERROR_LOSTSYNC;
180 stream->sync = 0;
181 return -1;
182 }
183
184 # if defined(OPT_STRICT)
185 /*
186 * Scalefactor index 63 does not appear in Table B.1 of
187 * ISO/IEC 11172-3. Nonetheless, other implementations accept it,
188 * so we only reject it if OPT_STRICT is defined.
189 */
190 if (scalefactor[ch][sb] == 63) {
191 stream->error = MAD_ERROR_BADSCALEFACTOR;
192 return -1;
193 }
194 # endif
195 }
196 }
197 }
198
199 /* decode samples */
200
201 for (s = 0; s < 12; ++s) {
202 for (sb = 0; sb < bound; ++sb) {
203 for (ch = 0; ch < nch; ++ch) {
204 nb = allocation[ch][sb];
205 frame->sbsample[ch][s][sb] = nb ?
206 mad_f_mul(I_sample(&stream->ptr, nb),
207 sf_table[scalefactor[ch][sb]]) : 0;
208 if (mad_bit_nextbyte(&stream->ptr) > stream->next_frame)
209 {
210 stream->error = MAD_ERROR_LOSTSYNC;
211 stream->sync = 0;
212 return -1;
213 }
214 }
215 }
216
217 for (sb = bound; sb < 32; ++sb) {
218 if ((nb = allocation[0][sb])) {
219 mad_fixed_t sample;
220
221 sample = I_sample(&stream->ptr, nb);
222 if (mad_bit_nextbyte(&stream->ptr) > stream->next_frame)
223 {
224 stream->error = MAD_ERROR_LOSTSYNC;
225 stream->sync = 0;
226 return -1;
227 }
228
229 for (ch = 0; ch < nch; ++ch) {
230 frame->sbsample[ch][s][sb] =
231 mad_f_mul(sample, sf_table[scalefactor[ch][sb]]);
232 }
233 }
234 else {
235 for (ch = 0; ch < nch; ++ch)
236 frame->sbsample[ch][s][sb] = 0;
237 }
238 }
239 }
240
241 return 0;
242 }
243
244 /* --- Layer II ------------------------------------------------------------ */
245
246 /* possible quantization per subband table */
247 static
248 struct {
249 unsigned int sblimit;
250 unsigned char const offsets[30];
251 } const sbquant_table[5] = {
252 /* ISO/IEC 11172-3 Table B.2a */
253 { 27, { 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 3, 3, 3, 3, 3, /* 0 */
254 3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0 } },
255 /* ISO/IEC 11172-3 Table B.2b */
256 { 30, { 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 3, 3, 3, 3, 3, /* 1 */
257 3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0 } },
258 /* ISO/IEC 11172-3 Table B.2c */
259 { 8, { 5, 5, 2, 2, 2, 2, 2, 2 } }, /* 2 */
260 /* ISO/IEC 11172-3 Table B.2d */
261 { 12, { 5, 5, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2 } }, /* 3 */
262 /* ISO/IEC 13818-3 Table B.1 */
263 { 30, { 4, 4, 4, 4, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, /* 4 */
264 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 } }
265 };
266
267 /* bit allocation table */
268 static
269 struct {
270 unsigned short nbal;
271 unsigned short offset;
272 } const bitalloc_table[8] = {
273 { 2, 0 }, /* 0 */
274 { 2, 3 }, /* 1 */
275 { 3, 3 }, /* 2 */
276 { 3, 1 }, /* 3 */
277 { 4, 2 }, /* 4 */
278 { 4, 3 }, /* 5 */
279 { 4, 4 }, /* 6 */
280 { 4, 5 } /* 7 */
281 };
282
283 /* offsets into quantization class table */
284 static
285 unsigned char const offset_table[6][15] = {
286 { 0, 1, 16 }, /* 0 */
287 { 0, 1, 2, 3, 4, 5, 16 }, /* 1 */
288 { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 }, /* 2 */
289 { 0, 1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 }, /* 3 */
290 { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 16 }, /* 4 */
291 { 0, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 } /* 5 */
292 };
293
294 /* quantization class table */
295 static
296 struct quantclass {
297 unsigned short nlevels;
298 unsigned char group;
299 unsigned char bits;
300 mad_fixed_t C;
301 mad_fixed_t D;
302 } const qc_table[17] = {
303 # include "qc_table.dat"
304 };
305
306 /*
307 * NAME: II_samples()
308 * DESCRIPTION: decode three requantized Layer II samples from a bitstream
309 */
310 static
II_samples(struct mad_bitptr * ptr,struct quantclass const * quantclass,mad_fixed_t output[3])311 void II_samples(struct mad_bitptr *ptr,
312 struct quantclass const *quantclass,
313 mad_fixed_t output[3])
314 {
315 unsigned int nb, s, sample[3];
316
317 if ((nb = quantclass->group)) {
318 unsigned int c, nlevels;
319
320 /* degrouping */
321 c = mad_bit_read(ptr, quantclass->bits);
322 nlevels = quantclass->nlevels;
323
324 for (s = 0; s < 3; ++s) {
325 sample[s] = c % nlevels;
326 c /= nlevels;
327 }
328 }
329 else {
330 nb = quantclass->bits;
331
332 for (s = 0; s < 3; ++s)
333 sample[s] = mad_bit_read(ptr, nb);
334 }
335
336 for (s = 0; s < 3; ++s) {
337 mad_fixed_t requantized;
338
339 /* invert most significant bit, extend sign, then scale to fixed format */
340
341 requantized = sample[s] ^ (1 << (nb - 1));
342 requantized |= -(requantized & (1 << (nb - 1)));
343
344 requantized <<= MAD_F_FRACBITS - (nb - 1);
345
346 /* requantize the sample */
347
348 /* s'' = C * (s''' + D) */
349
350 output[s] = mad_f_mul(requantized + quantclass->D, quantclass->C);
351
352 /* s' = factor * s'' */
353 /* (to be performed by caller) */
354 }
355 }
356
357 /*
358 * NAME: layer->II()
359 * DESCRIPTION: decode a single Layer II frame
360 */
mad_layer_II(struct mad_stream * stream,struct mad_frame * frame)361 int mad_layer_II(struct mad_stream *stream, struct mad_frame *frame)
362 {
363 struct mad_header *header = &frame->header;
364 struct mad_bitptr start;
365 unsigned int index, sblimit, nbal, nch, bound, gr, ch, s, sb;
366 unsigned char const *offsets;
367 unsigned char allocation[2][32], scfsi[2][32], scalefactor[2][32][3];
368 mad_fixed_t samples[3];
369
370 nch = MAD_NCHANNELS(header);
371
372 if (header->flags & MAD_FLAG_LSF_EXT)
373 index = 4;
374 else if (header->flags & MAD_FLAG_FREEFORMAT)
375 goto freeformat;
376 else {
377 unsigned long bitrate_per_channel;
378
379 bitrate_per_channel = header->bitrate;
380 if (nch == 2) {
381 bitrate_per_channel /= 2;
382
383 # if defined(OPT_STRICT)
384 /*
385 * ISO/IEC 11172-3 allows only single channel mode for 32, 48, 56, and
386 * 80 kbps bitrates in Layer II, but some encoders ignore this
387 * restriction. We enforce it if OPT_STRICT is defined.
388 */
389 if (bitrate_per_channel <= 28000 || bitrate_per_channel == 40000) {
390 stream->error = MAD_ERROR_BADMODE;
391 return -1;
392 }
393 # endif
394 }
395 else { /* nch == 1 */
396 if (bitrate_per_channel > 192000) {
397 /*
398 * ISO/IEC 11172-3 does not allow single channel mode for 224, 256,
399 * 320, or 384 kbps bitrates in Layer II.
400 */
401 stream->error = MAD_ERROR_BADMODE;
402 return -1;
403 }
404 }
405
406 if (bitrate_per_channel <= 48000)
407 index = (header->samplerate == 32000) ? 3 : 2;
408 else if (bitrate_per_channel <= 80000)
409 index = 0;
410 else {
411 freeformat:
412 index = (header->samplerate == 48000) ? 0 : 1;
413 }
414 }
415
416 sblimit = sbquant_table[index].sblimit;
417 offsets = sbquant_table[index].offsets;
418
419 bound = 32;
420 if (header->mode == MAD_MODE_JOINT_STEREO) {
421 header->flags |= MAD_FLAG_I_STEREO;
422 bound = 4 + header->mode_extension * 4;
423 }
424
425 if (bound > sblimit)
426 bound = sblimit;
427
428 start = stream->ptr;
429
430 /* decode bit allocations */
431
432 for (sb = 0; sb < bound; ++sb) {
433 nbal = bitalloc_table[offsets[sb]].nbal;
434
435 for (ch = 0; ch < nch; ++ch)
436 {
437 allocation[ch][sb] = mad_bit_read(&stream->ptr, nbal);
438 if (mad_bit_nextbyte(&stream->ptr) > stream->next_frame)
439 {
440 stream->error = MAD_ERROR_LOSTSYNC;
441 stream->sync = 0;
442 return -1;
443 }
444 }
445 }
446
447 for (sb = bound; sb < sblimit; ++sb) {
448 nbal = bitalloc_table[offsets[sb]].nbal;
449
450 allocation[0][sb] =
451 allocation[1][sb] = mad_bit_read(&stream->ptr, nbal);
452
453 if (mad_bit_nextbyte(&stream->ptr) > stream->next_frame)
454 {
455 stream->error = MAD_ERROR_LOSTSYNC;
456 stream->sync = 0;
457 return -1;
458 }
459 }
460
461 /* decode scalefactor selection info */
462
463 for (sb = 0; sb < sblimit; ++sb) {
464 for (ch = 0; ch < nch; ++ch) {
465 if (allocation[ch][sb])
466 scfsi[ch][sb] = mad_bit_read(&stream->ptr, 2);
467 if (mad_bit_nextbyte(&stream->ptr) > stream->next_frame)
468 {
469 stream->error = MAD_ERROR_LOSTSYNC;
470 stream->sync = 0;
471 return -1;
472 }
473 }
474 }
475
476 /* check CRC word */
477
478 if (header->flags & MAD_FLAG_PROTECTION) {
479 header->crc_check =
480 mad_bit_crc(start, mad_bit_length(&start, &stream->ptr),
481 header->crc_check);
482
483 if (header->crc_check != header->crc_target &&
484 !(frame->options & MAD_OPTION_IGNORECRC)) {
485 stream->error = MAD_ERROR_BADCRC;
486 return -1;
487 }
488 }
489
490 /* decode scalefactors */
491
492 for (sb = 0; sb < sblimit; ++sb) {
493 for (ch = 0; ch < nch; ++ch) {
494 if (allocation[ch][sb]) {
495 scalefactor[ch][sb][0] = mad_bit_read(&stream->ptr, 6);
496 if (mad_bit_nextbyte(&stream->ptr) > stream->next_frame)
497 {
498 stream->error = MAD_ERROR_LOSTSYNC;
499 stream->sync = 0;
500 return -1;
501 }
502
503 switch (scfsi[ch][sb]) {
504 case 2:
505 scalefactor[ch][sb][2] =
506 scalefactor[ch][sb][1] =
507 scalefactor[ch][sb][0];
508 break;
509
510 case 0:
511 scalefactor[ch][sb][1] = mad_bit_read(&stream->ptr, 6);
512 if (mad_bit_nextbyte(&stream->ptr) > stream->next_frame)
513 {
514 stream->error = MAD_ERROR_LOSTSYNC;
515 stream->sync = 0;
516 return -1;
517 }
518 /* fall through */
519
520 case 1:
521 case 3:
522 scalefactor[ch][sb][2] = mad_bit_read(&stream->ptr, 6);
523 if (mad_bit_nextbyte(&stream->ptr) > stream->next_frame)
524 {
525 stream->error = MAD_ERROR_LOSTSYNC;
526 stream->sync = 0;
527 return -1;
528 }
529 }
530
531 if (scfsi[ch][sb] & 1)
532 scalefactor[ch][sb][1] = scalefactor[ch][sb][scfsi[ch][sb] - 1];
533
534 # if defined(OPT_STRICT)
535 /*
536 * Scalefactor index 63 does not appear in Table B.1 of
537 * ISO/IEC 11172-3. Nonetheless, other implementations accept it,
538 * so we only reject it if OPT_STRICT is defined.
539 */
540 if (scalefactor[ch][sb][0] == 63 ||
541 scalefactor[ch][sb][1] == 63 ||
542 scalefactor[ch][sb][2] == 63) {
543 stream->error = MAD_ERROR_BADSCALEFACTOR;
544 return -1;
545 }
546 # endif
547 }
548 }
549 }
550
551 /* decode samples */
552
553 for (gr = 0; gr < 12; ++gr) {
554 for (sb = 0; sb < bound; ++sb) {
555 for (ch = 0; ch < nch; ++ch) {
556 if ((index = allocation[ch][sb])) {
557 index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
558
559 II_samples(&stream->ptr, &qc_table[index], samples);
560 if (mad_bit_nextbyte(&stream->ptr) > stream->next_frame)
561 {
562 stream->error = MAD_ERROR_LOSTSYNC;
563 stream->sync = 0;
564 return -1;
565 }
566
567 for (s = 0; s < 3; ++s) {
568 frame->sbsample[ch][3 * gr + s][sb] =
569 mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
570 }
571 }
572 else {
573 for (s = 0; s < 3; ++s)
574 frame->sbsample[ch][3 * gr + s][sb] = 0;
575 }
576 }
577 }
578
579 for (sb = bound; sb < sblimit; ++sb) {
580 if ((index = allocation[0][sb])) {
581 index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
582
583 II_samples(&stream->ptr, &qc_table[index], samples);
584 if (mad_bit_nextbyte(&stream->ptr) > stream->next_frame)
585 {
586 stream->error = MAD_ERROR_LOSTSYNC;
587 stream->sync = 0;
588 return -1;
589 }
590
591 for (ch = 0; ch < nch; ++ch) {
592 for (s = 0; s < 3; ++s) {
593 frame->sbsample[ch][3 * gr + s][sb] =
594 mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
595 }
596 }
597 }
598 else {
599 for (ch = 0; ch < nch; ++ch) {
600 for (s = 0; s < 3; ++s)
601 frame->sbsample[ch][3 * gr + s][sb] = 0;
602 }
603 }
604 }
605
606 for (ch = 0; ch < nch; ++ch) {
607 for (s = 0; s < 3; ++s) {
608 for (sb = sblimit; sb < 32; ++sb)
609 frame->sbsample[ch][3 * gr + s][sb] = 0;
610 }
611 }
612 }
613
614 return 0;
615 }
616