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 # include "global.h"
23
24 #ifndef CHAR_BIT
25 #define CHAR_BIT 8
26 #endif
27
28 # include "fixed.h"
29 # include "bit.h"
30 # include "stream.h"
31 # include "frame.h"
32 # include "layer12.h"
33
34 /*
35 * scalefactor table
36 * used in both Layer I and Layer II decoding
37 */
38 static
39 mad_fixed_t const sf_table[64] = {
40 # include "sf_table.dat"
41 };
42
43 /* --- Layer I ------------------------------------------------------------- */
44
45 /* linear scaling table */
46 static
47 mad_fixed_t const linear_table[14] = {
48 MAD_F(0x15555555), /* 2^2 / (2^2 - 1) == 1.33333333333333 */
49 MAD_F(0x12492492), /* 2^3 / (2^3 - 1) == 1.14285714285714 */
50 MAD_F(0x11111111), /* 2^4 / (2^4 - 1) == 1.06666666666667 */
51 MAD_F(0x10842108), /* 2^5 / (2^5 - 1) == 1.03225806451613 */
52 MAD_F(0x10410410), /* 2^6 / (2^6 - 1) == 1.01587301587302 */
53 MAD_F(0x10204081), /* 2^7 / (2^7 - 1) == 1.00787401574803 */
54 MAD_F(0x10101010), /* 2^8 / (2^8 - 1) == 1.00392156862745 */
55 MAD_F(0x10080402), /* 2^9 / (2^9 - 1) == 1.00195694716243 */
56 MAD_F(0x10040100), /* 2^10 / (2^10 - 1) == 1.00097751710655 */
57 MAD_F(0x10020040), /* 2^11 / (2^11 - 1) == 1.00048851978505 */
58 MAD_F(0x10010010), /* 2^12 / (2^12 - 1) == 1.00024420024420 */
59 MAD_F(0x10008004), /* 2^13 / (2^13 - 1) == 1.00012208521548 */
60 MAD_F(0x10004001), /* 2^14 / (2^14 - 1) == 1.00006103888177 */
61 MAD_F(0x10002000) /* 2^15 / (2^15 - 1) == 1.00003051850948 */
62 };
63
64 /*
65 * NAME: I_sample()
66 * DESCRIPTION: decode one requantized Layer I sample from a bitstream
67 */
68 static
I_sample(struct mad_bitptr * ptr,unsigned int nb)69 mad_fixed_t I_sample(struct mad_bitptr *ptr, unsigned int nb)
70 {
71 mad_fixed_t sample;
72
73 sample = mad_bit_read(ptr, nb);
74
75 /* invert most significant bit, extend sign, then scale to fixed format */
76
77 sample ^= 1 << (nb - 1);
78 sample |= -(sample & (1 << (nb - 1)));
79
80 sample <<= MAD_F_FRACBITS - (nb - 1);
81
82 /* requantize the sample */
83
84 /* s'' = (2^nb / (2^nb - 1)) * (s''' + 2^(-nb + 1)) */
85
86 sample += MAD_F_ONE >> (nb - 1);
87
88 return mad_f_mul(sample, linear_table[nb - 2]);
89
90 /* s' = factor * s'' */
91 /* (to be performed by caller) */
92 }
93
94 /*
95 * NAME: layer->I()
96 * DESCRIPTION: decode a single Layer I frame
97 */
mad_layer_I(struct mad_stream * stream,struct mad_frame * frame)98 int mad_layer_I(struct mad_stream *stream, struct mad_frame *frame)
99 {
100 struct mad_header *header = &frame->header;
101 unsigned int nch, bound, ch, s, sb, nb;
102 unsigned char allocation[2][32], scalefactor[2][32];
103
104 nch = MAD_NCHANNELS(header);
105
106 bound = 32;
107 if (header->mode == MAD_MODE_JOINT_STEREO) {
108 header->flags |= MAD_FLAG_I_STEREO;
109 bound = 4 + header->mode_extension * 4;
110 }
111
112 /* check CRC word */
113
114 if (header->flags & MAD_FLAG_PROTECTION) {
115 header->crc_check =
116 mad_bit_crc(stream->ptr, 4 * (bound * nch + (32 - bound)),
117 header->crc_check);
118
119 if (header->crc_check != header->crc_target &&
120 !(frame->options & MAD_OPTION_IGNORECRC)) {
121 stream->error = MAD_ERROR_BADCRC;
122 return -1;
123 }
124 }
125
126 /* decode bit allocations */
127
128 for (sb = 0; sb < bound; ++sb) {
129 for (ch = 0; ch < nch; ++ch) {
130 nb = mad_bit_read(&stream->ptr, 4);
131
132 if (nb == 15) {
133 stream->error = MAD_ERROR_BADBITALLOC;
134 return -1;
135 }
136
137 allocation[ch][sb] = nb ? nb + 1 : 0;
138 }
139 }
140
141 for (sb = bound; sb < 32; ++sb) {
142 nb = mad_bit_read(&stream->ptr, 4);
143
144 if (nb == 15) {
145 stream->error = MAD_ERROR_BADBITALLOC;
146 return -1;
147 }
148
149 allocation[0][sb] =
150 allocation[1][sb] = nb ? nb + 1 : 0;
151 }
152
153 /* decode scalefactors */
154
155 for (sb = 0; sb < 32; ++sb) {
156 for (ch = 0; ch < nch; ++ch) {
157 if (allocation[ch][sb]) {
158 scalefactor[ch][sb] = mad_bit_read(&stream->ptr, 6);
159 }
160 }
161 }
162
163 /* decode samples */
164
165 for (s = 0; s < 12; ++s) {
166 for (sb = 0; sb < bound; ++sb) {
167 for (ch = 0; ch < nch; ++ch) {
168 nb = allocation[ch][sb];
169 frame->sbsample[ch][s][sb] = nb ?
170 mad_f_mul(I_sample(&stream->ptr, nb),
171 sf_table[scalefactor[ch][sb]]) : 0;
172 }
173 }
174
175 for (sb = bound; sb < 32; ++sb) {
176 if ((nb = allocation[0][sb])) {
177 mad_fixed_t sample;
178
179 sample = I_sample(&stream->ptr, nb);
180
181 for (ch = 0; ch < nch; ++ch) {
182 frame->sbsample[ch][s][sb] =
183 mad_f_mul(sample, sf_table[scalefactor[ch][sb]]);
184 }
185 }
186 else {
187 for (ch = 0; ch < nch; ++ch)
188 frame->sbsample[ch][s][sb] = 0;
189 }
190 }
191 }
192
193 return 0;
194 }
195
196 /* --- Layer II ------------------------------------------------------------ */
197
198 /* possible quantization per subband table */
199 static
200 struct {
201 unsigned int sblimit;
202 unsigned char const offsets[30];
203 } const sbquant_table[5] = {
204 /* ISO/IEC 11172-3 Table B.2a */
205 { 27, { 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 3, 3, 3, 3, 3, /* 0 */
206 3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0 } },
207 /* ISO/IEC 11172-3 Table B.2b */
208 { 30, { 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 3, 3, 3, 3, 3, /* 1 */
209 3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0 } },
210 /* ISO/IEC 11172-3 Table B.2c */
211 { 8, { 5, 5, 2, 2, 2, 2, 2, 2 } }, /* 2 */
212 /* ISO/IEC 11172-3 Table B.2d */
213 { 12, { 5, 5, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2 } }, /* 3 */
214 /* ISO/IEC 13818-3 Table B.1 */
215 { 30, { 4, 4, 4, 4, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, /* 4 */
216 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 } }
217 };
218
219 /* bit allocation table */
220 static
221 struct {
222 unsigned short nbal;
223 unsigned short offset;
224 } const bitalloc_table[8] = {
225 { 2, 0 }, /* 0 */
226 { 2, 3 }, /* 1 */
227 { 3, 3 }, /* 2 */
228 { 3, 1 }, /* 3 */
229 { 4, 2 }, /* 4 */
230 { 4, 3 }, /* 5 */
231 { 4, 4 }, /* 6 */
232 { 4, 5 } /* 7 */
233 };
234
235 /* offsets into quantization class table */
236 static
237 unsigned char const offset_table[6][15] = {
238 { 0, 1, 16 }, /* 0 */
239 { 0, 1, 2, 3, 4, 5, 16 }, /* 1 */
240 { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 }, /* 2 */
241 { 0, 1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 }, /* 3 */
242 { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 16 }, /* 4 */
243 { 0, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 } /* 5 */
244 };
245
246 /* quantization class table */
247 static
248 struct quantclass {
249 unsigned short nlevels;
250 unsigned char group;
251 unsigned char bits;
252 mad_fixed_t C;
253 mad_fixed_t D;
254 } const qc_table[17] = {
255 # include "qc_table.dat"
256 };
257
258 /*
259 * NAME: II_samples()
260 * DESCRIPTION: decode three requantized Layer II samples from a bitstream
261 */
262 static
II_samples(struct mad_bitptr * ptr,struct quantclass const * quantclass,mad_fixed_t output[3])263 void II_samples(struct mad_bitptr *ptr,
264 struct quantclass const *quantclass,
265 mad_fixed_t output[3])
266 {
267 unsigned int nb, s, sample[3];
268
269 if ((nb = quantclass->group)) {
270 unsigned int c, nlevels;
271
272 /* degrouping */
273 c = mad_bit_read(ptr, quantclass->bits);
274 nlevels = quantclass->nlevels;
275
276 for (s = 0; s < 3; ++s) {
277 sample[s] = c % nlevels;
278 c /= nlevels;
279 }
280 }
281 else {
282 nb = quantclass->bits;
283
284 for (s = 0; s < 3; ++s)
285 sample[s] = mad_bit_read(ptr, nb);
286 }
287
288 for (s = 0; s < 3; ++s) {
289 mad_fixed_t requantized;
290
291 /* invert most significant bit, extend sign, then scale to fixed format */
292
293 requantized = sample[s] ^ (1 << (nb - 1));
294 requantized |= -(requantized & (1 << (nb - 1)));
295
296 requantized <<= MAD_F_FRACBITS - (nb - 1);
297
298 /* requantize the sample */
299
300 /* s'' = C * (s''' + D) */
301
302 output[s] = mad_f_mul(requantized + quantclass->D, quantclass->C);
303
304 /* s' = factor * s'' */
305 /* (to be performed by caller) */
306 }
307 }
308
309 /*
310 * NAME: layer->II()
311 * DESCRIPTION: decode a single Layer II frame
312 */
mad_layer_II(struct mad_stream * stream,struct mad_frame * frame)313 int mad_layer_II(struct mad_stream *stream, struct mad_frame *frame)
314 {
315 struct mad_header *header = &frame->header;
316 struct mad_bitptr start;
317 unsigned int index, sblimit, nbal, nch, bound, gr, ch, s, sb;
318 unsigned char const *offsets;
319 unsigned char allocation[2][32], scfsi[2][32], scalefactor[2][32][3];
320 mad_fixed_t samples[3];
321
322 nch = MAD_NCHANNELS(header);
323
324 if (header->flags & MAD_FLAG_LSF_EXT)
325 index = 4;
326 else if (header->flags & MAD_FLAG_FREEFORMAT)
327 goto freeformat;
328 else {
329 unsigned long bitrate_per_channel;
330
331 bitrate_per_channel = header->bitrate;
332 if (nch == 2) {
333 bitrate_per_channel /= 2;
334 }
335 else { /* nch == 1 */
336 if (bitrate_per_channel > 192000) {
337 /*
338 * ISO/IEC 11172-3 does not allow single channel mode for 224, 256,
339 * 320, or 384 kbps bitrates in Layer II.
340 */
341 stream->error = MAD_ERROR_BADMODE;
342 return -1;
343 }
344 }
345
346 if (bitrate_per_channel <= 48000)
347 index = (header->samplerate == 32000) ? 3 : 2;
348 else if (bitrate_per_channel <= 80000)
349 index = 0;
350 else {
351 freeformat:
352 index = (header->samplerate == 48000) ? 0 : 1;
353 }
354 }
355
356 sblimit = sbquant_table[index].sblimit;
357 offsets = sbquant_table[index].offsets;
358
359 bound = 32;
360 if (header->mode == MAD_MODE_JOINT_STEREO) {
361 header->flags |= MAD_FLAG_I_STEREO;
362 bound = 4 + header->mode_extension * 4;
363 }
364
365 if (bound > sblimit)
366 bound = sblimit;
367
368 start = stream->ptr;
369
370 /* decode bit allocations */
371
372 for (sb = 0; sb < bound; ++sb) {
373 nbal = bitalloc_table[offsets[sb]].nbal;
374
375 for (ch = 0; ch < nch; ++ch)
376 allocation[ch][sb] = mad_bit_read(&stream->ptr, nbal);
377 }
378
379 for (sb = bound; sb < sblimit; ++sb) {
380 nbal = bitalloc_table[offsets[sb]].nbal;
381
382 allocation[0][sb] =
383 allocation[1][sb] = mad_bit_read(&stream->ptr, nbal);
384 }
385
386 /* decode scalefactor selection info */
387
388 for (sb = 0; sb < sblimit; ++sb) {
389 for (ch = 0; ch < nch; ++ch) {
390 if (allocation[ch][sb])
391 scfsi[ch][sb] = mad_bit_read(&stream->ptr, 2);
392 }
393 }
394
395 /* check CRC word */
396
397 if (header->flags & MAD_FLAG_PROTECTION) {
398 header->crc_check =
399 mad_bit_crc(start, mad_bit_length(&start, &stream->ptr),
400 header->crc_check);
401
402 if (header->crc_check != header->crc_target &&
403 !(frame->options & MAD_OPTION_IGNORECRC)) {
404 stream->error = MAD_ERROR_BADCRC;
405 return -1;
406 }
407 }
408
409 /* decode scalefactors */
410
411 for (sb = 0; sb < sblimit; ++sb) {
412 for (ch = 0; ch < nch; ++ch) {
413 if (allocation[ch][sb]) {
414 scalefactor[ch][sb][0] = mad_bit_read(&stream->ptr, 6);
415
416 switch (scfsi[ch][sb]) {
417 case 2:
418 scalefactor[ch][sb][2] =
419 scalefactor[ch][sb][1] =
420 scalefactor[ch][sb][0];
421 break;
422
423 case 0:
424 scalefactor[ch][sb][1] = mad_bit_read(&stream->ptr, 6);
425 /* fall through */
426
427 case 1:
428 case 3:
429 scalefactor[ch][sb][2] = mad_bit_read(&stream->ptr, 6);
430 }
431
432 if (scfsi[ch][sb] & 1)
433 scalefactor[ch][sb][1] = scalefactor[ch][sb][scfsi[ch][sb] - 1];
434 }
435 }
436 }
437
438 /* decode samples */
439
440 for (gr = 0; gr < 12; ++gr) {
441 for (sb = 0; sb < bound; ++sb) {
442 for (ch = 0; ch < nch; ++ch) {
443 if ((index = allocation[ch][sb])) {
444 index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
445
446 II_samples(&stream->ptr, &qc_table[index], samples);
447
448 for (s = 0; s < 3; ++s) {
449 frame->sbsample[ch][3 * gr + s][sb] =
450 mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
451 }
452 }
453 else {
454 for (s = 0; s < 3; ++s)
455 frame->sbsample[ch][3 * gr + s][sb] = 0;
456 }
457 }
458 }
459
460 for (sb = bound; sb < sblimit; ++sb) {
461 if ((index = allocation[0][sb])) {
462 index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
463
464 II_samples(&stream->ptr, &qc_table[index], samples);
465
466 for (ch = 0; ch < nch; ++ch) {
467 for (s = 0; s < 3; ++s) {
468 frame->sbsample[ch][3 * gr + s][sb] =
469 mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
470 }
471 }
472 }
473 else {
474 for (ch = 0; ch < nch; ++ch) {
475 for (s = 0; s < 3; ++s)
476 frame->sbsample[ch][3 * gr + s][sb] = 0;
477 }
478 }
479 }
480
481 for (ch = 0; ch < nch; ++ch) {
482 for (s = 0; s < 3; ++s) {
483 for (sb = sblimit; sb < 32; ++sb)
484 frame->sbsample[ch][3 * gr + s][sb] = 0;
485 }
486 }
487 }
488
489 return 0;
490 }
491