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/*

 * 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 1.17 2004/02/05 09:02:39 rob Exp $

 */

# ifdef HAVE_CONFIG_H

#  include "config.h"

# endif

# 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

 */

static

mad_fixed_t const sf_table[64] = {

# include "sf_table.dat"

};

/* --- 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])) {

	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.dat"

};

/*

 * 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)) {

    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])) {

	  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])) {

	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;

}