Diff: layer12.cpp

Revision:

0:7627c79db971

Child:

1:7c923cbe9f1d

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layer12.cpp	Fri Nov 26 12:18:30 2010 +0000
@@ -0,0 +1,529 @@
+/*
+ * libmad - MPEG audio decoder library
+ * Copyright (C) 2000-2004 Underbit Technologies, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * $Id: layer12.c,v 1.1 2010/11/23 20:12:57 andy Exp $
+ */
+
+#  include "config.h"
+
+# include "global.h"
+
+# ifdef HAVE_LIMITS_H
+#  include <limits.h>
+# else
+#  define CHAR_BIT  8
+# endif
+
+# include "fixed.h"
+# include "bit.h"
+# include "stream.h"
+# include "frame.h"
+# include "layer12.h"
+
+/*
+ * scalefactor table
+ * used in both Layer I and Layer II decoding
+ */
+# include "sf_table.h"
+
+/* --- Layer I ------------------------------------------------------------- */
+
+/* linear scaling table */
+static
+mad_fixed_t const linear_table[14] = {
+  MAD_F(0x15555555),  /* 2^2  / (2^2  - 1) == 1.33333333333333 */
+  MAD_F(0x12492492),  /* 2^3  / (2^3  - 1) == 1.14285714285714 */
+  MAD_F(0x11111111),  /* 2^4  / (2^4  - 1) == 1.06666666666667 */
+  MAD_F(0x10842108),  /* 2^5  / (2^5  - 1) == 1.03225806451613 */
+  MAD_F(0x10410410),  /* 2^6  / (2^6  - 1) == 1.01587301587302 */
+  MAD_F(0x10204081),  /* 2^7  / (2^7  - 1) == 1.00787401574803 */
+  MAD_F(0x10101010),  /* 2^8  / (2^8  - 1) == 1.00392156862745 */
+  MAD_F(0x10080402),  /* 2^9  / (2^9  - 1) == 1.00195694716243 */
+  MAD_F(0x10040100),  /* 2^10 / (2^10 - 1) == 1.00097751710655 */
+  MAD_F(0x10020040),  /* 2^11 / (2^11 - 1) == 1.00048851978505 */
+  MAD_F(0x10010010),  /* 2^12 / (2^12 - 1) == 1.00024420024420 */
+  MAD_F(0x10008004),  /* 2^13 / (2^13 - 1) == 1.00012208521548 */
+  MAD_F(0x10004001),  /* 2^14 / (2^14 - 1) == 1.00006103888177 */
+  MAD_F(0x10002000)   /* 2^15 / (2^15 - 1) == 1.00003051850948 */
+};
+
+/*
+ * NAME:    I_sample()
+ * DESCRIPTION:    decode one requantized Layer I sample from a bitstream
+ */
+static
+mad_fixed_t I_sample(struct mad_bitptr *ptr, unsigned int nb)
+{
+  mad_fixed_t sample;
+
+  sample = mad_bit_read(ptr, nb);
+
+  /* invert most significant bit, extend sign, then scale to fixed format */
+
+  sample ^= 1 << (nb - 1);
+  sample |= -(sample & (1 << (nb - 1)));
+
+  sample <<= MAD_F_FRACBITS - (nb - 1);
+
+  /* requantize the sample */
+
+  /* s'' = (2^nb / (2^nb - 1)) * (s''' + 2^(-nb + 1)) */
+
+  sample += MAD_F_ONE >> (nb - 1);
+
+  return mad_f_mul(sample, linear_table[nb - 2]);
+
+  /* s' = factor * s'' */
+  /* (to be performed by caller) */
+}
+
+/*
+ * NAME:    layer->I()
+ * DESCRIPTION:    decode a single Layer I frame
+ */
+int mad_layer_I(struct mad_stream *stream, struct mad_frame *frame)
+{
+  struct mad_header *header = &frame->header;
+  unsigned int nch, bound, ch, s, sb, nb;
+  unsigned char allocation[2][32], scalefactor[2][32];
+
+  nch = MAD_NCHANNELS(header);
+
+  bound = 32;
+  if (header->mode == MAD_MODE_JOINT_STEREO) {
+    header->flags |= MAD_FLAG_I_STEREO;
+    bound = 4 + header->mode_extension * 4;
+  }
+
+  /* check CRC word */
+
+  if (header->flags & MAD_FLAG_PROTECTION) {
+    header->crc_check =
+      mad_bit_crc(stream->ptr, 4 * (bound * nch + (32 - bound)),
+          header->crc_check);
+
+    if (header->crc_check != header->crc_target &&
+    !(frame->options & MAD_OPTION_IGNORECRC)) {
+      stream->error = MAD_ERROR_BADCRC;
+      return -1;
+    }
+  }
+
+  /* decode bit allocations */
+
+  for (sb = 0; sb < bound; ++sb) {
+    for (ch = 0; ch < nch; ++ch) {
+      nb = mad_bit_read(&stream->ptr, 4);
+
+      if (nb == 15) {
+    stream->error = MAD_ERROR_BADBITALLOC;
+    return -1;
+      }
+
+      allocation[ch][sb] = nb ? nb + 1 : 0;
+    }
+  }
+
+  for (sb = bound; sb < 32; ++sb) {
+    nb = mad_bit_read(&stream->ptr, 4);
+
+    if (nb == 15) {
+      stream->error = MAD_ERROR_BADBITALLOC;
+      return -1;
+    }
+
+    allocation[0][sb] =
+    allocation[1][sb] = nb ? nb + 1 : 0;
+  }
+
+  /* decode scalefactors */
+
+  for (sb = 0; sb < 32; ++sb) {
+    for (ch = 0; ch < nch; ++ch) {
+      if (allocation[ch][sb]) {
+    scalefactor[ch][sb] = mad_bit_read(&stream->ptr, 6);
+
+# if defined(OPT_STRICT)
+    /*
+     * Scalefactor index 63 does not appear in Table B.1 of
+     * ISO/IEC 11172-3. Nonetheless, other implementations accept it,
+     * so we only reject it if OPT_STRICT is defined.
+     */
+    if (scalefactor[ch][sb] == 63) {
+      stream->error = MAD_ERROR_BADSCALEFACTOR;
+      return -1;
+    }
+# endif
+      }
+    }
+  }
+
+  /* decode samples */
+
+  for (s = 0; s < 12; ++s) {
+    for (sb = 0; sb < bound; ++sb) {
+      for (ch = 0; ch < nch; ++ch) {
+    nb = allocation[ch][sb];
+    frame->sbsample[ch][s][sb] = nb ?
+      mad_f_mul(I_sample(&stream->ptr, nb),
+            sf_table[scalefactor[ch][sb]]) : 0;
+      }
+    }
+
+    for (sb = bound; sb < 32; ++sb) {
+      if ((nb = allocation[0][sb]) != 0) {
+    mad_fixed_t sample;
+
+    sample = I_sample(&stream->ptr, nb);
+
+    for (ch = 0; ch < nch; ++ch) {
+      frame->sbsample[ch][s][sb] =
+        mad_f_mul(sample, sf_table[scalefactor[ch][sb]]);
+    }
+      }
+      else {
+    for (ch = 0; ch < nch; ++ch)
+      frame->sbsample[ch][s][sb] = 0;
+      }
+    }
+  }
+
+  return 0;
+}
+
+/* --- Layer II ------------------------------------------------------------ */
+
+/* possible quantization per subband table */
+static
+struct {
+  unsigned int sblimit;
+  unsigned char const offsets[30];
+} const sbquant_table[5] = {
+  /* ISO/IEC 11172-3 Table B.2a */
+  { 27, { 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 3, 3, 3, 3, 3,    /* 0 */
+      3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0 } },
+  /* ISO/IEC 11172-3 Table B.2b */
+  { 30, { 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 3, 3, 3, 3, 3,    /* 1 */
+      3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0 } },
+  /* ISO/IEC 11172-3 Table B.2c */
+  {  8, { 5, 5, 2, 2, 2, 2, 2, 2 } },                /* 2 */
+  /* ISO/IEC 11172-3 Table B.2d */
+  { 12, { 5, 5, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2 } },        /* 3 */
+  /* ISO/IEC 13818-3 Table B.1 */
+  { 30, { 4, 4, 4, 4, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1,    /* 4 */
+      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 } }
+};
+
+/* bit allocation table */
+static
+struct {
+  unsigned short nbal;
+  unsigned short offset;
+} const bitalloc_table[8] = {
+  { 2, 0 },  /* 0 */
+  { 2, 3 },  /* 1 */
+  { 3, 3 },  /* 2 */
+  { 3, 1 },  /* 3 */
+  { 4, 2 },  /* 4 */
+  { 4, 3 },  /* 5 */
+  { 4, 4 },  /* 6 */
+  { 4, 5 }   /* 7 */
+};
+
+/* offsets into quantization class table */
+static
+unsigned char const offset_table[6][15] = {
+  { 0, 1, 16                                             },  /* 0 */
+  { 0, 1,  2, 3, 4, 5, 16                                },  /* 1 */
+  { 0, 1,  2, 3, 4, 5,  6, 7,  8,  9, 10, 11, 12, 13, 14 },  /* 2 */
+  { 0, 1,  3, 4, 5, 6,  7, 8,  9, 10, 11, 12, 13, 14, 15 },  /* 3 */
+  { 0, 1,  2, 3, 4, 5,  6, 7,  8,  9, 10, 11, 12, 13, 16 },  /* 4 */
+  { 0, 2,  4, 5, 6, 7,  8, 9, 10, 11, 12, 13, 14, 15, 16 }   /* 5 */
+};
+
+/* quantization class table */
+static
+struct quantclass {
+  unsigned short nlevels;
+  unsigned char group;
+  unsigned char bits;
+  mad_fixed_t C;
+  mad_fixed_t D;
+} const qc_table[17] = {
+# include "qc_table.h"
+};
+
+/*
+ * NAME:    II_samples()
+ * DESCRIPTION:    decode three requantized Layer II samples from a bitstream
+ */
+static
+void II_samples(struct mad_bitptr *ptr,
+        struct quantclass const *quantclass,
+        mad_fixed_t output[3])
+{
+  unsigned int nb, s, sample[3];
+
+  if ((nb = quantclass->group) != 0) {
+    unsigned int c, nlevels;
+
+    /* degrouping */
+    c = mad_bit_read(ptr, quantclass->bits);
+    nlevels = quantclass->nlevels;
+
+    for (s = 0; s < 3; ++s) {
+      sample[s] = c % nlevels;
+      c /= nlevels;
+    }
+  }
+  else {
+    nb = quantclass->bits;
+
+    for (s = 0; s < 3; ++s)
+      sample[s] = mad_bit_read(ptr, nb);
+  }
+
+  for (s = 0; s < 3; ++s) {
+    mad_fixed_t requantized;
+
+    /* invert most significant bit, extend sign, then scale to fixed format */
+
+    requantized  = sample[s] ^ (1 << (nb - 1));
+    requantized |= -(requantized & (1 << (nb - 1)));
+
+    requantized <<= MAD_F_FRACBITS - (nb - 1);
+
+    /* requantize the sample */
+
+    /* s'' = C * (s''' + D) */
+
+    output[s] = mad_f_mul(requantized + quantclass->D, quantclass->C);
+
+    /* s' = factor * s'' */
+    /* (to be performed by caller) */
+  }
+}
+
+/*
+ * NAME:    layer->II()
+ * DESCRIPTION:    decode a single Layer II frame
+ */
+int mad_layer_II(struct mad_stream *stream, struct mad_frame *frame)
+{
+  struct mad_header *header = &frame->header;
+  struct mad_bitptr start;
+  unsigned int index, sblimit, nbal, nch, bound, gr, ch, s, sb;
+  unsigned char const *offsets;
+  unsigned char allocation[2][32], scfsi[2][32], scalefactor[2][32][3];
+  mad_fixed_t samples[3];
+
+  nch = MAD_NCHANNELS(header);
+
+  if (header->flags & MAD_FLAG_LSF_EXT)
+    index = 4;
+  else if (header->flags & MAD_FLAG_FREEFORMAT)
+    goto freeformat;
+  else {
+    unsigned long bitrate_per_channel;
+
+    bitrate_per_channel = header->bitrate;
+    if (nch == 2) {
+      bitrate_per_channel /= 2;
+
+# if defined(OPT_STRICT)
+      /*
+       * ISO/IEC 11172-3 allows only single channel mode for 32, 48, 56, and
+       * 80 kbps bitrates in Layer II, but some encoders ignore this
+       * restriction. We enforce it if OPT_STRICT is defined.
+       */
+      if (bitrate_per_channel <= 28000 || bitrate_per_channel == 40000) {
+    stream->error = MAD_ERROR_BADMODE;
+    return -1;
+      }
+# endif
+    }
+    else {  /* nch == 1 */
+      if (bitrate_per_channel > 192000) {
+    /*
+     * ISO/IEC 11172-3 does not allow single channel mode for 224, 256,
+     * 320, or 384 kbps bitrates in Layer II.
+     */
+    stream->error = MAD_ERROR_BADMODE;
+    return -1;
+      }
+    }
+
+    if (bitrate_per_channel <= 48000)
+      index = (header->samplerate == 32000) ? 3 : 2;
+    else if (bitrate_per_channel <= 80000)
+      index = 0;
+    else {
+    freeformat:
+      index = (header->samplerate == 48000) ? 0 : 1;
+    }
+  }
+
+  sblimit = sbquant_table[index].sblimit;
+  offsets = sbquant_table[index].offsets;
+
+  bound = 32;
+  if (header->mode == MAD_MODE_JOINT_STEREO) {
+    header->flags |= MAD_FLAG_I_STEREO;
+    bound = 4 + header->mode_extension * 4;
+  }
+
+  if (bound > sblimit)
+    bound = sblimit;
+
+  start = stream->ptr;
+
+  /* decode bit allocations */
+
+  for (sb = 0; sb < bound; ++sb) {
+    nbal = bitalloc_table[offsets[sb]].nbal;
+
+    for (ch = 0; ch < nch; ++ch)
+      allocation[ch][sb] = mad_bit_read(&stream->ptr, nbal);
+  }
+
+  for (sb = bound; sb < sblimit; ++sb) {
+    nbal = bitalloc_table[offsets[sb]].nbal;
+
+    allocation[0][sb] =
+    allocation[1][sb] = mad_bit_read(&stream->ptr, nbal);
+  }
+
+  /* decode scalefactor selection info */
+
+  for (sb = 0; sb < sblimit; ++sb) {
+    for (ch = 0; ch < nch; ++ch) {
+      if (allocation[ch][sb])
+    scfsi[ch][sb] = mad_bit_read(&stream->ptr, 2);
+    }
+  }
+
+  /* check CRC word */
+
+  if (header->flags & MAD_FLAG_PROTECTION) {
+    header->crc_check =
+      mad_bit_crc(start, mad_bit_length(&start, &stream->ptr),
+          header->crc_check);
+
+    if (header->crc_check != header->crc_target &&
+    !(frame->options & MAD_OPTION_IGNORECRC)) {
+      stream->error = MAD_ERROR_BADCRC;
+      return -1;
+    }
+  }
+
+  /* decode scalefactors */
+
+  for (sb = 0; sb < sblimit; ++sb) {
+    for (ch = 0; ch < nch; ++ch) {
+      if (allocation[ch][sb]) {
+    scalefactor[ch][sb][0] = mad_bit_read(&stream->ptr, 6);
+
+    switch (scfsi[ch][sb]) {
+    case 2:
+      scalefactor[ch][sb][2] =
+      scalefactor[ch][sb][1] =
+      scalefactor[ch][sb][0];
+      break;
+
+    case 0:
+      scalefactor[ch][sb][1] = mad_bit_read(&stream->ptr, 6);
+      /* fall through */
+
+    case 1:
+    case 3:
+      scalefactor[ch][sb][2] = mad_bit_read(&stream->ptr, 6);
+    }
+
+    if (scfsi[ch][sb] & 1)
+      scalefactor[ch][sb][1] = scalefactor[ch][sb][scfsi[ch][sb] - 1];
+
+# if defined(OPT_STRICT)
+    /*
+     * Scalefactor index 63 does not appear in Table B.1 of
+     * ISO/IEC 11172-3. Nonetheless, other implementations accept it,
+     * so we only reject it if OPT_STRICT is defined.
+     */
+    if (scalefactor[ch][sb][0] == 63 ||
+        scalefactor[ch][sb][1] == 63 ||
+        scalefactor[ch][sb][2] == 63) {
+      stream->error = MAD_ERROR_BADSCALEFACTOR;
+      return -1;
+    }
+# endif
+      }
+    }
+  }
+
+  /* decode samples */
+
+  for (gr = 0; gr < 12; ++gr) {
+    for (sb = 0; sb < bound; ++sb) {
+      for (ch = 0; ch < nch; ++ch) {
+    if ((index = allocation[ch][sb]) != 0) {
+      index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
+
+      II_samples(&stream->ptr, &qc_table[index], samples);
+
+      for (s = 0; s < 3; ++s) {
+        frame->sbsample[ch][3 * gr + s][sb] =
+          mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
+      }
+    }
+    else {
+      for (s = 0; s < 3; ++s)
+        frame->sbsample[ch][3 * gr + s][sb] = 0;
+    }
+      }
+    }
+
+    for (sb = bound; sb < sblimit; ++sb) {
+      if ((index = allocation[0][sb])!= 0) {
+    index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
+
+    II_samples(&stream->ptr, &qc_table[index], samples);
+
+    for (ch = 0; ch < nch; ++ch) {
+      for (s = 0; s < 3; ++s) {
+        frame->sbsample[ch][3 * gr + s][sb] =
+          mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
+      }
+    }
+      }
+      else {
+    for (ch = 0; ch < nch; ++ch) {
+      for (s = 0; s < 3; ++s)
+        frame->sbsample[ch][3 * gr + s][sb] = 0;
+    }
+      }
+    }
+
+    for (ch = 0; ch < nch; ++ch) {
+      for (s = 0; s < 3; ++s) {
+    for (sb = sblimit; sb < 32; ++sb)
+      frame->sbsample[ch][3 * gr + s][sb] = 0;
+      }
+    }
+  }
+
+  return 0;
+}