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14 roytam 1 /*
2  * libmad - MPEG audio decoder library
26 roytam 3  * Copyright (C) 2000-2004 Underbit Technologies, Inc.
14 roytam 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  *
26 roytam 19  * $Id: layer12.c,v 1.17 2004/02/05 09:02:39 rob Exp $
14 roytam 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
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  */
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  
138       if (nb == 15) {
139         stream->error = MAD_ERROR_BADBITALLOC;
140         return -1;
141       }
142  
143       allocation[ch][sb] = nb ? nb + 1 : 0;
144     }
145   }
146  
147   for (sb = bound; sb < 32; ++sb) {
148     nb = mad_bit_read(&stream->ptr, 4);
149  
150     if (nb == 15) {
151       stream->error = MAD_ERROR_BADBITALLOC;
152       return -1;
153     }
154  
155     allocation[0][sb] =
156     allocation[1][sb] = nb ? nb + 1 : 0;
157   }
158  
159   /* decode scalefactors */
160  
161   for (sb = 0; sb < 32; ++sb) {
162     for (ch = 0; ch < nch; ++ch) {
163       if (allocation[ch][sb]) {
164         scalefactor[ch][sb] = mad_bit_read(&stream->ptr, 6);
165  
166 # if defined(OPT_STRICT)
167         /*
168          * Scalefactor index 63 does not appear in Table B.1 of
169          * ISO/IEC 11172-3. Nonetheless, other implementations accept it,
170          * so we only reject it if OPT_STRICT is defined.
171          */
172         if (scalefactor[ch][sb] == 63) {
173           stream->error = MAD_ERROR_BADSCALEFACTOR;
174           return -1;
175         }
176 # endif
177       }
178     }
179   }
180  
181   /* decode samples */
182  
183   for (s = 0; s < 12; ++s) {
184     for (sb = 0; sb < bound; ++sb) {
185       for (ch = 0; ch < nch; ++ch) {
186         nb = allocation[ch][sb];
187         frame->sbsample[ch][s][sb] = nb ?
188           mad_f_mul(I_sample(&stream->ptr, nb),
189                     sf_table[scalefactor[ch][sb]]) : 0;
190       }
191     }
192  
193     for (sb = bound; sb < 32; ++sb) {
194       if ((nb = allocation[0][sb])) {
195         mad_fixed_t sample;
196  
197         sample = I_sample(&stream->ptr, nb);
198  
199         for (ch = 0; ch < nch; ++ch) {
200           frame->sbsample[ch][s][sb] =
201             mad_f_mul(sample, sf_table[scalefactor[ch][sb]]);
202         }
203       }
204       else {
205         for (ch = 0; ch < nch; ++ch)
206           frame->sbsample[ch][s][sb] = 0;
207       }
208     }
209   }
210  
211   return 0;
212 }
213  
214 /* --- Layer II ------------------------------------------------------------ */
215  
216 /* possible quantization per subband table */
217 static
218 struct {
219   unsigned int sblimit;
220   unsigned char const offsets[30];
221 } const sbquant_table[5] = {
222   /* ISO/IEC 11172-3 Table B.2a */
223   { 27, { 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 3, 3, 3, 3, 3,       /* 0 */
224           3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0 } },
225   /* ISO/IEC 11172-3 Table B.2b */
226   { 30, { 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 3, 3, 3, 3, 3,       /* 1 */
227           3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0 } },
228   /* ISO/IEC 11172-3 Table B.2c */
229   {  8, { 5, 5, 2, 2, 2, 2, 2, 2 } },                           /* 2 */
230   /* ISO/IEC 11172-3 Table B.2d */
231   { 12, { 5, 5, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2 } },               /* 3 */
232   /* ISO/IEC 13818-3 Table B.1 */
233   { 30, { 4, 4, 4, 4, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1,       /* 4 */
234           1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 } }
235 };
236  
237 /* bit allocation table */
238 static
239 struct {
240   unsigned short nbal;
241   unsigned short offset;
242 } const bitalloc_table[8] = {
243   { 2, 0 },  /* 0 */
244   { 2, 3 },  /* 1 */
245   { 3, 3 },  /* 2 */
246   { 3, 1 },  /* 3 */
247   { 4, 2 },  /* 4 */
248   { 4, 3 },  /* 5 */
249   { 4, 4 },  /* 6 */
250   { 4, 5 }   /* 7 */
251 };
252  
253 /* offsets into quantization class table */
254 static
255 unsigned char const offset_table[6][15] = {
256   { 0, 1, 16                                             },  /* 0 */
257   { 0, 1,  2, 3, 4, 5, 16                                },  /* 1 */
258   { 0, 1,  2, 3, 4, 5,  6, 7,  8,  9, 10, 11, 12, 13, 14 },  /* 2 */
259   { 0, 1,  3, 4, 5, 6,  7, 8,  9, 10, 11, 12, 13, 14, 15 },  /* 3 */
260   { 0, 1,  2, 3, 4, 5,  6, 7,  8,  9, 10, 11, 12, 13, 16 },  /* 4 */
261   { 0, 2,  4, 5, 6, 7,  8, 9, 10, 11, 12, 13, 14, 15, 16 }   /* 5 */
262 };
263  
264 /* quantization class table */
265 static
266 struct quantclass {
267   unsigned short nlevels;
268   unsigned char group;
269   unsigned char bits;
270   mad_fixed_t C;
271   mad_fixed_t D;
272 } const qc_table[17] = {
273 # include "qc_table.dat"
274 };
275  
276 /*
277  * NAME:        II_samples()
278  * DESCRIPTION: decode three requantized Layer II samples from a bitstream
279  */
280 static
281 void II_samples(struct mad_bitptr *ptr,
282                 struct quantclass const *quantclass,
283                 mad_fixed_t output[3])
284 {
285   unsigned int nb, s, sample[3];
286  
287   if ((nb = quantclass->group)) {
288     unsigned int c, nlevels;
289  
290     /* degrouping */
291     c = mad_bit_read(ptr, quantclass->bits);
292     nlevels = quantclass->nlevels;
293  
294     for (s = 0; s < 3; ++s) {
295       sample[s] = c % nlevels;
296       c /= nlevels;
297     }
298   }
299   else {
300     nb = quantclass->bits;
301  
302     for (s = 0; s < 3; ++s)
303       sample[s] = mad_bit_read(ptr, nb);
304   }
305  
306   for (s = 0; s < 3; ++s) {
307     mad_fixed_t requantized;
308  
309     /* invert most significant bit, extend sign, then scale to fixed format */
310  
311     requantized  = sample[s] ^ (1 << (nb - 1));
312     requantized |= -(requantized & (1 << (nb - 1)));
313  
314     requantized <<= MAD_F_FRACBITS - (nb - 1);
315  
316     /* requantize the sample */
317  
318     /* s'' = C * (s''' + D) */
319  
320     output[s] = mad_f_mul(requantized + quantclass->D, quantclass->C);
321  
322     /* s' = factor * s'' */
323     /* (to be performed by caller) */
324   }
325 }
326  
327 /*
328  * NAME:        layer->II()
329  * DESCRIPTION: decode a single Layer II frame
330  */
331 int mad_layer_II(struct mad_stream *stream, struct mad_frame *frame)
332 {
333   struct mad_header *header = &frame->header;
334   struct mad_bitptr start;
335   unsigned int index, sblimit, nbal, nch, bound, gr, ch, s, sb;
336   unsigned char const *offsets;
337   unsigned char allocation[2][32], scfsi[2][32], scalefactor[2][32][3];
338   mad_fixed_t samples[3];
339  
340   nch = MAD_NCHANNELS(header);
341  
342   if (header->flags & MAD_FLAG_LSF_EXT)
343     index = 4;
26 roytam 344   else if (header->flags & MAD_FLAG_FREEFORMAT)
345     goto freeformat;
14 roytam 346   else {
26 roytam 347     unsigned long bitrate_per_channel;
348  
349     bitrate_per_channel = header->bitrate;
350     if (nch == 2) {
351       bitrate_per_channel /= 2;
352  
353 # if defined(OPT_STRICT)
354       /*
355        * ISO/IEC 11172-3 allows only single channel mode for 32, 48, 56, and
356        * 80 kbps bitrates in Layer II, but some encoders ignore this
357        * restriction. We enforce it if OPT_STRICT is defined.
358        */
359       if (bitrate_per_channel <= 28000 || bitrate_per_channel == 40000) {
360         stream->error = MAD_ERROR_BADMODE;
361         return -1;
362       }
363 # endif
364     }
365     else {  /* nch == 1 */
366       if (bitrate_per_channel > 192000) {
367         /*
368          * ISO/IEC 11172-3 does not allow single channel mode for 224, 256,
369          * 320, or 384 kbps bitrates in Layer II.
370          */
371         stream->error = MAD_ERROR_BADMODE;
372         return -1;
373       }
374     }
375  
376     if (bitrate_per_channel <= 48000)
14 roytam 377       index = (header->samplerate == 32000) ? 3 : 2;
26 roytam 378     else if (bitrate_per_channel <= 80000)
14 roytam 379       index = 0;
26 roytam 380     else {
381     freeformat:
14 roytam 382       index = (header->samplerate == 48000) ? 0 : 1;
383     }
384   }
385  
386   sblimit = sbquant_table[index].sblimit;
387   offsets = sbquant_table[index].offsets;
388  
389   bound = 32;
390   if (header->mode == MAD_MODE_JOINT_STEREO) {
391     header->flags |= MAD_FLAG_I_STEREO;
392     bound = 4 + header->mode_extension * 4;
393   }
394  
395   if (bound > sblimit)
396     bound = sblimit;
397  
398   start = stream->ptr;
399  
400   /* decode bit allocations */
401  
402   for (sb = 0; sb < bound; ++sb) {
403     nbal = bitalloc_table[offsets[sb]].nbal;
404  
405     for (ch = 0; ch < nch; ++ch)
406       allocation[ch][sb] = mad_bit_read(&stream->ptr, nbal);
407   }
408  
409   for (sb = bound; sb < sblimit; ++sb) {
410     nbal = bitalloc_table[offsets[sb]].nbal;
411  
412     allocation[0][sb] =
413     allocation[1][sb] = mad_bit_read(&stream->ptr, nbal);
414   }
415  
416   /* decode scalefactor selection info */
417  
418   for (sb = 0; sb < sblimit; ++sb) {
419     for (ch = 0; ch < nch; ++ch) {
420       if (allocation[ch][sb])
421         scfsi[ch][sb] = mad_bit_read(&stream->ptr, 2);
422     }
423   }
424  
425   /* check CRC word */
426  
427   if (header->flags & MAD_FLAG_PROTECTION) {
428     header->crc_check =
429       mad_bit_crc(start, mad_bit_length(&start, &stream->ptr),
430                   header->crc_check);
431  
432     if (header->crc_check != header->crc_target &&
433         !(frame->options & MAD_OPTION_IGNORECRC)) {
434       stream->error = MAD_ERROR_BADCRC;
435       return -1;
436     }
437   }
438  
439   /* decode scalefactors */
440  
441   for (sb = 0; sb < sblimit; ++sb) {
442     for (ch = 0; ch < nch; ++ch) {
443       if (allocation[ch][sb]) {
444         scalefactor[ch][sb][0] = mad_bit_read(&stream->ptr, 6);
445  
446         switch (scfsi[ch][sb]) {
447         case 2:
448           scalefactor[ch][sb][2] =
449           scalefactor[ch][sb][1] =
450           scalefactor[ch][sb][0];
451           break;
452  
453         case 0:
454           scalefactor[ch][sb][1] = mad_bit_read(&stream->ptr, 6);
455           /* fall through */
456  
457         case 1:
458         case 3:
459           scalefactor[ch][sb][2] = mad_bit_read(&stream->ptr, 6);
460         }
461  
462         if (scfsi[ch][sb] & 1)
463           scalefactor[ch][sb][1] = scalefactor[ch][sb][scfsi[ch][sb] - 1];
464  
465 # if defined(OPT_STRICT)
466         /*
467          * Scalefactor index 63 does not appear in Table B.1 of
468          * ISO/IEC 11172-3. Nonetheless, other implementations accept it,
469          * so we only reject it if OPT_STRICT is defined.
470          */
471         if (scalefactor[ch][sb][0] == 63 ||
472             scalefactor[ch][sb][1] == 63 ||
473             scalefactor[ch][sb][2] == 63) {
474           stream->error = MAD_ERROR_BADSCALEFACTOR;
475           return -1;
476         }
477 # endif
478       }
479     }
480   }
481  
482   /* decode samples */
483  
484   for (gr = 0; gr < 12; ++gr) {
485     for (sb = 0; sb < bound; ++sb) {
486       for (ch = 0; ch < nch; ++ch) {
487         if ((index = allocation[ch][sb])) {
488           index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
489  
490           II_samples(&stream->ptr, &qc_table[index], samples);
491  
492           for (s = 0; s < 3; ++s) {
493             frame->sbsample[ch][3 * gr + s][sb] =
494               mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
495           }
496         }
497         else {
498           for (s = 0; s < 3; ++s)
499             frame->sbsample[ch][3 * gr + s][sb] = 0;
500         }
501       }
502     }
503  
504     for (sb = bound; sb < sblimit; ++sb) {
505       if ((index = allocation[0][sb])) {
506         index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
507  
508         II_samples(&stream->ptr, &qc_table[index], samples);
509  
510         for (ch = 0; ch < nch; ++ch) {
511           for (s = 0; s < 3; ++s) {
512             frame->sbsample[ch][3 * gr + s][sb] =
513               mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
514           }
515         }
516       }
517       else {
518         for (ch = 0; ch < nch; ++ch) {
519           for (s = 0; s < 3; ++s)
520             frame->sbsample[ch][3 * gr + s][sb] = 0;
521         }
522       }
523     }
524  
525     for (ch = 0; ch < nch; ++ch) {
526       for (s = 0; s < 3; ++s) {
527         for (sb = sblimit; sb < 32; ++sb)
528           frame->sbsample[ch][3 * gr + s][sb] = 0;
529       }
530     }
531   }
532  
533   return 0;
534 }