libmad/layer12.c

/*
 * 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"
#include <string.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];
    memset(allocation, 0, sizeof(allocation));
    memset(scalefactor, 0, sizeof(scalefactor));

    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;
}