layer12.cpp

00001 /*
00002  * libmad - MPEG audio decoder library
00003  * Copyright (C) 2000-2004 Underbit Technologies, Inc.
00004  *
00005  * This program is free software; you can redistribute it and/or modify
00006  * it under the terms of the GNU General Public License as published by
00007  * the Free Software Foundation; either version 2 of the License, or
00008  * (at your option) any later version.
00009  *
00010  * This program is distributed in the hope that it will be useful,
00011  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00012  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00013  * GNU General Public License for more details.
00014  *
00015  * You should have received a copy of the GNU General Public License
00016  * along with this program; if not, write to the Free Software
00017  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
00018  *
00019  * $Id: layer12.c,v 1.1 2010/11/23 20:12:57 andy Exp $
00020  */
00021 
00022 #  include "config.h"
00023 
00024 # include "global.h"
00025 
00026 # ifdef HAVE_LIMITS_H
00027 #  include <limits.h>
00028 # else
00029 #  define CHAR_BIT  8
00030 # endif
00031 
00032 # include "fixed.h"
00033 # include "bit.h"
00034 # include "stream.h"
00035 # include "frame.h"
00036 # include "layer12.h"
00037 
00038 /*
00039  * scalefactor table
00040  * used in both Layer I and Layer II decoding
00041  */
00042 # include "sf_table.h"
00043 
00044 /* --- Layer I ------------------------------------------------------------- */
00045 
00046 /* linear scaling table */
00047 static
00048 mad_fixed_t const linear_table[14] = {
00049   MAD_F(0x15555555),  /* 2^2  / (2^2  - 1) == 1.33333333333333 */
00050   MAD_F(0x12492492),  /* 2^3  / (2^3  - 1) == 1.14285714285714 */
00051   MAD_F(0x11111111),  /* 2^4  / (2^4  - 1) == 1.06666666666667 */
00052   MAD_F(0x10842108),  /* 2^5  / (2^5  - 1) == 1.03225806451613 */
00053   MAD_F(0x10410410),  /* 2^6  / (2^6  - 1) == 1.01587301587302 */
00054   MAD_F(0x10204081),  /* 2^7  / (2^7  - 1) == 1.00787401574803 */
00055   MAD_F(0x10101010),  /* 2^8  / (2^8  - 1) == 1.00392156862745 */
00056   MAD_F(0x10080402),  /* 2^9  / (2^9  - 1) == 1.00195694716243 */
00057   MAD_F(0x10040100),  /* 2^10 / (2^10 - 1) == 1.00097751710655 */
00058   MAD_F(0x10020040),  /* 2^11 / (2^11 - 1) == 1.00048851978505 */
00059   MAD_F(0x10010010),  /* 2^12 / (2^12 - 1) == 1.00024420024420 */
00060   MAD_F(0x10008004),  /* 2^13 / (2^13 - 1) == 1.00012208521548 */
00061   MAD_F(0x10004001),  /* 2^14 / (2^14 - 1) == 1.00006103888177 */
00062   MAD_F(0x10002000)   /* 2^15 / (2^15 - 1) == 1.00003051850948 */
00063 };
00064 
00065 /*
00066  * NAME:    I_sample()
00067  * DESCRIPTION:    decode one requantized Layer I sample from a bitstream
00068  */
00069 static
00070 mad_fixed_t I_sample(struct mad_bitptr *ptr, unsigned int nb)
00071 {
00072   mad_fixed_t sample;
00073 
00074   sample = mad_bit_read(ptr, nb);
00075 
00076   /* invert most significant bit, extend sign, then scale to fixed format */
00077 
00078   sample ^= 1 << (nb - 1);
00079   sample |= -(sample & (1 << (nb - 1)));
00080 
00081   sample <<= MAD_F_FRACBITS - (nb - 1);
00082 
00083   /* requantize the sample */
00084 
00085   /* s'' = (2^nb / (2^nb - 1)) * (s''' + 2^(-nb + 1)) */
00086 
00087   sample += MAD_F_ONE >> (nb - 1);
00088 
00089   return mad_f_mul(sample, linear_table[nb - 2]);
00090 
00091   /* s' = factor * s'' */
00092   /* (to be performed by caller) */
00093 }
00094 
00095 /*
00096  * NAME:    layer->I()
00097  * DESCRIPTION:    decode a single Layer I frame
00098  */
00099 int mad_layer_I(struct mad_stream *stream, struct mad_frame *frame)
00100 {
00101   struct mad_header *header = &frame->header;
00102   unsigned int nch, bound, ch, s, sb, nb;
00103   unsigned char allocation[2][32], scalefactor[2][32];
00104 
00105   nch = MAD_NCHANNELS(header);
00106 
00107   bound = 32;
00108   if (header->mode == MAD_MODE_JOINT_STEREO) {
00109     header->flags |= MAD_FLAG_I_STEREO;
00110     bound = 4 + header->mode_extension * 4;
00111   }
00112 
00113   /* check CRC word */
00114 
00115   if (header->flags & MAD_FLAG_PROTECTION) {
00116     header->crc_check =
00117       mad_bit_crc(stream->ptr, 4 * (bound * nch + (32 - bound)),
00118           header->crc_check);
00119 
00120     if (header->crc_check != header->crc_target &&
00121     !(frame->options & MAD_OPTION_IGNORECRC)) {
00122       stream->error = MAD_ERROR_BADCRC;
00123       return -1;
00124     }
00125   }
00126 
00127   /* decode bit allocations */
00128 
00129   for (sb = 0; sb < bound; ++sb) {
00130     for (ch = 0; ch < nch; ++ch) {
00131       nb = mad_bit_read(&stream->ptr, 4);
00132 
00133       if (nb == 15) {
00134     stream->error = MAD_ERROR_BADBITALLOC;
00135     return -1;
00136       }
00137 
00138       allocation[ch][sb] = nb ? nb + 1 : 0;
00139     }
00140   }
00141 
00142   for (sb = bound; sb < 32; ++sb) {
00143     nb = mad_bit_read(&stream->ptr, 4);
00144 
00145     if (nb == 15) {
00146       stream->error = MAD_ERROR_BADBITALLOC;
00147       return -1;
00148     }
00149 
00150     allocation[0][sb] =
00151     allocation[1][sb] = nb ? nb + 1 : 0;
00152   }
00153 
00154   /* decode scalefactors */
00155 
00156   for (sb = 0; sb < 32; ++sb) {
00157     for (ch = 0; ch < nch; ++ch) {
00158       if (allocation[ch][sb]) {
00159     scalefactor[ch][sb] = mad_bit_read(&stream->ptr, 6);
00160 
00161 # if defined(OPT_STRICT)
00162     /*
00163      * Scalefactor index 63 does not appear in Table B.1 of
00164      * ISO/IEC 11172-3. Nonetheless, other implementations accept it,
00165      * so we only reject it if OPT_STRICT is defined.
00166      */
00167     if (scalefactor[ch][sb] == 63) {
00168       stream->error = MAD_ERROR_BADSCALEFACTOR;
00169       return -1;
00170     }
00171 # endif
00172       }
00173     }
00174   }
00175 
00176   /* decode samples */
00177 
00178   for (s = 0; s < 12; ++s) {
00179     for (sb = 0; sb < bound; ++sb) {
00180       for (ch = 0; ch < nch; ++ch) {
00181     nb = allocation[ch][sb];
00182     frame->sbsample[ch][s][sb] = nb ?
00183       mad_f_mul(I_sample(&stream->ptr, nb),
00184             sf_table[scalefactor[ch][sb]]) : 0;
00185       }
00186     }
00187 
00188     for (sb = bound; sb < 32; ++sb) {
00189       if ((nb = allocation[0][sb]) != 0) {
00190     mad_fixed_t sample;
00191 
00192     sample = I_sample(&stream->ptr, nb);
00193 
00194     for (ch = 0; ch < nch; ++ch) {
00195       frame->sbsample[ch][s][sb] =
00196         mad_f_mul(sample, sf_table[scalefactor[ch][sb]]);
00197     }
00198       }
00199       else {
00200     for (ch = 0; ch < nch; ++ch)
00201       frame->sbsample[ch][s][sb] = 0;
00202       }
00203     }
00204   }
00205 
00206   return 0;
00207 }
00208 
00209 /* --- Layer II ------------------------------------------------------------ */
00210 
00211 /* possible quantization per subband table */
00212 static
00213 const struct {
00214   unsigned int sblimit;
00215   unsigned char offsets[30];
00216 } sbquant_table[5] = {
00217   /* ISO/IEC 11172-3 Table B.2a */
00218   { 27, { 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 3, 3, 3, 3, 3,    /* 0 */
00219       3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0 } },
00220   /* ISO/IEC 11172-3 Table B.2b */
00221   { 30, { 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 3, 3, 3, 3, 3,    /* 1 */
00222       3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0 } },
00223   /* ISO/IEC 11172-3 Table B.2c */
00224   {  8, { 5, 5, 2, 2, 2, 2, 2, 2 } },                /* 2 */
00225   /* ISO/IEC 11172-3 Table B.2d */
00226   { 12, { 5, 5, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2 } },        /* 3 */
00227   /* ISO/IEC 13818-3 Table B.1 */
00228   { 30, { 4, 4, 4, 4, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1,    /* 4 */
00229       1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 } }
00230 };
00231 
00232 /* bit allocation table */
00233 static
00234 struct {
00235   unsigned short nbal;
00236   unsigned short offset;
00237 } const bitalloc_table[8] = {
00238   { 2, 0 },  /* 0 */
00239   { 2, 3 },  /* 1 */
00240   { 3, 3 },  /* 2 */
00241   { 3, 1 },  /* 3 */
00242   { 4, 2 },  /* 4 */
00243   { 4, 3 },  /* 5 */
00244   { 4, 4 },  /* 6 */
00245   { 4, 5 }   /* 7 */
00246 };
00247 
00248 /* offsets into quantization class table */
00249 static
00250 unsigned char const offset_table[6][15] = {
00251   { 0, 1, 16                                             },  /* 0 */
00252   { 0, 1,  2, 3, 4, 5, 16                                },  /* 1 */
00253   { 0, 1,  2, 3, 4, 5,  6, 7,  8,  9, 10, 11, 12, 13, 14 },  /* 2 */
00254   { 0, 1,  3, 4, 5, 6,  7, 8,  9, 10, 11, 12, 13, 14, 15 },  /* 3 */
00255   { 0, 1,  2, 3, 4, 5,  6, 7,  8,  9, 10, 11, 12, 13, 16 },  /* 4 */
00256   { 0, 2,  4, 5, 6, 7,  8, 9, 10, 11, 12, 13, 14, 15, 16 }   /* 5 */
00257 };
00258 
00259 /* quantization class table */
00260 static
00261 struct quantclass {
00262   unsigned short nlevels;
00263   unsigned char group;
00264   unsigned char bits;
00265   mad_fixed_t C;
00266   mad_fixed_t D;
00267 } const qc_table[17] = {
00268 # include "qc_table.h"
00269 };
00270 
00271 /*
00272  * NAME:    II_samples()
00273  * DESCRIPTION:    decode three requantized Layer II samples from a bitstream
00274  */
00275 static
00276 void II_samples(struct mad_bitptr *ptr,
00277         struct quantclass const *quantclass,
00278         mad_fixed_t output[3])
00279 {
00280   unsigned int nb, s, sample[3];
00281 
00282   if ((nb = quantclass->group) != 0) {
00283     unsigned int c, nlevels;
00284 
00285     /* degrouping */
00286     c = mad_bit_read(ptr, quantclass->bits);
00287     nlevels = quantclass->nlevels;
00288 
00289     for (s = 0; s < 3; ++s) {
00290       sample[s] = c % nlevels;
00291       c /= nlevels;
00292     }
00293   }
00294   else {
00295     nb = quantclass->bits;
00296 
00297     for (s = 0; s < 3; ++s)
00298       sample[s] = mad_bit_read(ptr, nb);
00299   }
00300 
00301   for (s = 0; s < 3; ++s) {
00302     mad_fixed_t requantized;
00303 
00304     /* invert most significant bit, extend sign, then scale to fixed format */
00305 
00306     requantized  = sample[s] ^ (1 << (nb - 1));
00307     requantized |= -(requantized & (1 << (nb - 1)));
00308 
00309     requantized <<= MAD_F_FRACBITS - (nb - 1);
00310 
00311     /* requantize the sample */
00312 
00313     /* s'' = C * (s''' + D) */
00314 
00315     output[s] = mad_f_mul(requantized + quantclass->D, quantclass->C);
00316 
00317     /* s' = factor * s'' */
00318     /* (to be performed by caller) */
00319   }
00320 }
00321 
00322 /*
00323  * NAME:    layer->II()
00324  * DESCRIPTION:    decode a single Layer II frame
00325  */
00326 int mad_layer_II(struct mad_stream *stream, struct mad_frame *frame)
00327 {
00328   struct mad_header *header = &frame->header;
00329   struct mad_bitptr start;
00330   unsigned int index, sblimit, nbal, nch, bound, gr, ch, s, sb;
00331   unsigned char const *offsets;
00332   unsigned char allocation[2][32], scfsi[2][32], scalefactor[2][32][3];
00333   mad_fixed_t samples[3];
00334 
00335   nch = MAD_NCHANNELS(header);
00336 
00337   if (header->flags & MAD_FLAG_LSF_EXT)
00338     index = 4;
00339   else if (header->flags & MAD_FLAG_FREEFORMAT)
00340     goto freeformat;
00341   else {
00342     unsigned long bitrate_per_channel;
00343 
00344     bitrate_per_channel = header->bitrate;
00345     if (nch == 2) {
00346       bitrate_per_channel /= 2;
00347 
00348 # if defined(OPT_STRICT)
00349       /*
00350        * ISO/IEC 11172-3 allows only single channel mode for 32, 48, 56, and
00351        * 80 kbps bitrates in Layer II, but some encoders ignore this
00352        * restriction. We enforce it if OPT_STRICT is defined.
00353        */
00354       if (bitrate_per_channel <= 28000 || bitrate_per_channel == 40000) {
00355     stream->error = MAD_ERROR_BADMODE;
00356     return -1;
00357       }
00358 # endif
00359     }
00360     else {  /* nch == 1 */
00361       if (bitrate_per_channel > 192000) {
00362     /*
00363      * ISO/IEC 11172-3 does not allow single channel mode for 224, 256,
00364      * 320, or 384 kbps bitrates in Layer II.
00365      */
00366     stream->error = MAD_ERROR_BADMODE;
00367     return -1;
00368       }
00369     }
00370 
00371     if (bitrate_per_channel <= 48000)
00372       index = (header->samplerate == 32000) ? 3 : 2;
00373     else if (bitrate_per_channel <= 80000)
00374       index = 0;
00375     else {
00376     freeformat:
00377       index = (header->samplerate == 48000) ? 0 : 1;
00378     }
00379   }
00380 
00381   sblimit = sbquant_table[index].sblimit;
00382   offsets = sbquant_table[index].offsets;
00383 
00384   bound = 32;
00385   if (header->mode == MAD_MODE_JOINT_STEREO) {
00386     header->flags |= MAD_FLAG_I_STEREO;
00387     bound = 4 + header->mode_extension * 4;
00388   }
00389 
00390   if (bound > sblimit)
00391     bound = sblimit;
00392 
00393   start = stream->ptr;
00394 
00395   /* decode bit allocations */
00396 
00397   for (sb = 0; sb < bound; ++sb) {
00398     nbal = bitalloc_table[offsets[sb]].nbal;
00399 
00400     for (ch = 0; ch < nch; ++ch)
00401       allocation[ch][sb] = mad_bit_read(&stream->ptr, nbal);
00402   }
00403 
00404   for (sb = bound; sb < sblimit; ++sb) {
00405     nbal = bitalloc_table[offsets[sb]].nbal;
00406 
00407     allocation[0][sb] =
00408     allocation[1][sb] = mad_bit_read(&stream->ptr, nbal);
00409   }
00410 
00411   /* decode scalefactor selection info */
00412 
00413   for (sb = 0; sb < sblimit; ++sb) {
00414     for (ch = 0; ch < nch; ++ch) {
00415       if (allocation[ch][sb])
00416     scfsi[ch][sb] = mad_bit_read(&stream->ptr, 2);
00417     }
00418   }
00419 
00420   /* check CRC word */
00421 
00422   if (header->flags & MAD_FLAG_PROTECTION) {
00423     header->crc_check =
00424       mad_bit_crc(start, mad_bit_length(&start, &stream->ptr),
00425           header->crc_check);
00426 
00427     if (header->crc_check != header->crc_target &&
00428     !(frame->options & MAD_OPTION_IGNORECRC)) {
00429       stream->error = MAD_ERROR_BADCRC;
00430       return -1;
00431     }
00432   }
00433 
00434   /* decode scalefactors */
00435 
00436   for (sb = 0; sb < sblimit; ++sb) {
00437     for (ch = 0; ch < nch; ++ch) {
00438       if (allocation[ch][sb]) {
00439     scalefactor[ch][sb][0] = mad_bit_read(&stream->ptr, 6);
00440 
00441     switch (scfsi[ch][sb]) {
00442     case 2:
00443       scalefactor[ch][sb][2] =
00444       scalefactor[ch][sb][1] =
00445       scalefactor[ch][sb][0];
00446       break;
00447 
00448     case 0:
00449       scalefactor[ch][sb][1] = mad_bit_read(&stream->ptr, 6);
00450       /* fall through */
00451 
00452     case 1:
00453     case 3:
00454       scalefactor[ch][sb][2] = mad_bit_read(&stream->ptr, 6);
00455     }
00456 
00457     if (scfsi[ch][sb] & 1)
00458       scalefactor[ch][sb][1] = scalefactor[ch][sb][scfsi[ch][sb] - 1];
00459 
00460 # if defined(OPT_STRICT)
00461     /*
00462      * Scalefactor index 63 does not appear in Table B.1 of
00463      * ISO/IEC 11172-3. Nonetheless, other implementations accept it,
00464      * so we only reject it if OPT_STRICT is defined.
00465      */
00466     if (scalefactor[ch][sb][0] == 63 ||
00467         scalefactor[ch][sb][1] == 63 ||
00468         scalefactor[ch][sb][2] == 63) {
00469       stream->error = MAD_ERROR_BADSCALEFACTOR;
00470       return -1;
00471     }
00472 # endif
00473       }
00474     }
00475   }
00476 
00477   /* decode samples */
00478 
00479   for (gr = 0; gr < 12; ++gr) {
00480     for (sb = 0; sb < bound; ++sb) {
00481       for (ch = 0; ch < nch; ++ch) {
00482     if ((index = allocation[ch][sb]) != 0) {
00483       index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
00484 
00485       II_samples(&stream->ptr, &qc_table[index], samples);
00486 
00487       for (s = 0; s < 3; ++s) {
00488         frame->sbsample[ch][3 * gr + s][sb] =
00489           mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
00490       }
00491     }
00492     else {
00493       for (s = 0; s < 3; ++s)
00494         frame->sbsample[ch][3 * gr + s][sb] = 0;
00495     }
00496       }
00497     }
00498 
00499     for (sb = bound; sb < sblimit; ++sb) {
00500       if ((index = allocation[0][sb])!= 0) {
00501     index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
00502 
00503     II_samples(&stream->ptr, &qc_table[index], samples);
00504 
00505     for (ch = 0; ch < nch; ++ch) {
00506       for (s = 0; s < 3; ++s) {
00507         frame->sbsample[ch][3 * gr + s][sb] =
00508           mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
00509       }
00510     }
00511       }
00512       else {
00513     for (ch = 0; ch < nch; ++ch) {
00514       for (s = 0; s < 3; ++s)
00515         frame->sbsample[ch][3 * gr + s][sb] = 0;
00516     }
00517       }
00518     }
00519 
00520     for (ch = 0; ch < nch; ++ch) {
00521       for (s = 0; s < 3; ++s) {
00522     for (sb = sblimit; sb < 32; ++sb)
00523       frame->sbsample[ch][3 * gr + s][sb] = 0;
00524       }
00525     }
00526   }
00527 
00528   return 0;
00529 }