ps_syntax.c

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    { /*5*/ -26, 10 },           /* index 9: 10 bits: 111111111x */
    { /*-5*/ -36, 11 },          /* index 10: 11 bits: 1111111111x */
    { /*6*/ -25, 12 },           /* index 11: 12 bits: 11111111111x */
    { /*-6*/ -37, 13 },          /* index 12: 13 bits: 111111111111x */
    { /*-7*/ -38, /*7*/ -24 }    /* index 13: 14 bits: 1111111111111x */
};

static const int8_t f_huff_ipd[][2] = {
    { 1, /*0*/ -31 },         /* index 0: 1 bits: x */
    { 2, 3 },                 /* index 1: 2 bits: 0x */
    { /*1*/ -30, 4 },         /* index 2: 3 bits: 00x */
    { 5, 6 },                 /* index 3: 3 bits: 01x */
    { /*4*/ -27, /*5*/ -26 }, /* index 4: 4 bits: 001x */
    { /*3*/ -28, /*6*/ -25 }, /* index 5: 4 bits: 010x */
    { /*2*/ -29, /*7*/ -24 }  /* index 6: 4 bits: 011x */
};

static const int8_t t_huff_ipd[][2] = {
    { 1, /*0*/ -31 },         /* index 0: 1 bits: x */
    { 2, 3 },                 /* index 1: 2 bits: 0x */
    { 4, 5 },                 /* index 2: 3 bits: 00x */
    { /*1*/ -30, /*7*/ -24 }, /* index 3: 3 bits: 01x */
    { /*5*/ -26, 6 },         /* index 4: 4 bits: 000x */
    { /*2*/ -29, /*6*/ -25 }, /* index 5: 4 bits: 001x */
    { /*4*/ -27, /*3*/ -28 }  /* index 6: 5 bits: 0001x */
};

static const int8_t f_huff_opd[][2] = {
    { 1, /*0*/ -31 },         /* index 0: 1 bits: x */
    { 2, 3 },                 /* index 1: 2 bits: 0x */
    { /*7*/ -24, /*1*/ -30 }, /* index 2: 3 bits: 00x */
    { 4, 5 },                 /* index 3: 3 bits: 01x */
    { /*3*/ -28, /*6*/ -25 }, /* index 4: 4 bits: 010x */
    { /*2*/ -29, 6 },         /* index 5: 4 bits: 011x */
    { /*5*/ -26, /*4*/ -27 }  /* index 6: 5 bits: 0111x */
};

static const int8_t t_huff_opd[][2] = {
    { 1, /*0*/ -31 },         /* index 0: 1 bits: x */
    { 2, 3 },                 /* index 1: 2 bits: 0x */
    { 4, 5 },                 /* index 2: 3 bits: 00x */
    { /*1*/ -30, /*7*/ -24 }, /* index 3: 3 bits: 01x */
    { /*5*/ -26, 6 },         /* index 4: 4 bits: 000x */
    { /*2*/ -29, /*6*/ -25 }, /* index 5: 4 bits: 001x */
    { /*4*/ -27, /*3*/ -28 }  /* index 6: 5 bits: 0001x */
};

/* static function declarations */
static uint16_t ps_extension(ps_info *ps, bitfile *ld,
                             const uint8_t ps_extension_id,
                             const uint16_t num_bits_left);
static void huff_data(bitfile *ld, const uint8_t dt, const uint8_t nr_par,
                      ps_huff_tab t_huff, ps_huff_tab f_huff, int8_t *par);
static INLINE int8_t ps_huff_dec(bitfile *ld, ps_huff_tab t_huff);


uint16_t ps_data(ps_info *ps, bitfile *ld)
{
    uint8_t tmp, n;
    uint16_t bits = (uint16_t)faad_get_processed_bits(ld);

    /* check for new PS header */
    if (faad_get1bit(ld
        DEBUGVAR(1,1000,"ps_data(): enable_ps_header")))
    {
        ps->use34hybrid_bands = 0;

        /* Inter-channel Intensity Difference (IID) parameters enabled */
        ps->enable_iid = (uint8_t)faad_get1bit(ld
            DEBUGVAR(1,1001,"ps_data(): enable_iid"));

        if (ps->enable_iid)
        {
            ps->iid_mode = (uint8_t)faad_getbits(ld, 3
                DEBUGVAR(1,1002,"ps_data(): iid_mode"));

            ps->nr_iid_par = nr_iid_par_tab[ps->iid_mode];
            ps->nr_ipdopd_par = nr_ipdopd_par_tab[ps->iid_mode];

            if (ps->iid_mode == 2 || ps->iid_mode == 5)
                ps->use34hybrid_bands = 1;

            /* IPD freq res equal to IID freq res */
            ps->ipd_mode = ps->iid_mode;
        }

        /* Inter-channel Coherence (ICC) parameters enabled */
        ps->enable_icc = (uint8_t)faad_get1bit(ld
            DEBUGVAR(1,1003,"ps_data(): enable_icc"));

        if (ps->enable_icc)
        {
            ps->icc_mode = (uint8_t)faad_getbits(ld, 3
                DEBUGVAR(1,1004,"ps_data(): icc_mode"));

            ps->nr_icc_par = nr_icc_par_tab[ps->icc_mode];

            if (ps->icc_mode == 2 || ps->icc_mode == 5)
                ps->use34hybrid_bands = 1;
        }

        /* PS extension layer enabled */
        ps->enable_ext = (uint8_t)faad_get1bit(ld
            DEBUGVAR(1,1005,"ps_data(): enable_ext"));
    }

    ps->frame_class = (uint8_t)faad_get1bit(ld
        DEBUGVAR(1,1006,"ps_data(): frame_class"));
    tmp = (uint8_t)faad_getbits(ld, 2
        DEBUGVAR(1,1007,"ps_data(): num_env_idx"));

    ps->num_env = num_env_tab[ps->frame_class][tmp];

    if (ps->frame_class)
    {
        for (n = 1; n < ps->num_env+1; n++)
        {
            ps->border_position[n] = (uint8_t)faad_getbits(ld, 5
                DEBUGVAR(1,1008,"ps_data(): border_position"));
        }
    }

    if (ps->enable_iid)
    {
        for (n = 0; n < ps->num_env; n++)
        {
            ps->iid_dt[n] = (uint8_t)faad_get1bit(ld
                DEBUGVAR(1,1009,"ps_data(): iid_dt"));

            /* iid_data */
            if (ps->iid_mode < 3)
            {
                huff_data(ld, ps->iid_dt[n], ps->nr_iid_par, t_huff_iid_def,
                    f_huff_iid_def, ps->iid_index[n]);
            } else {
                huff_data(ld, ps->iid_dt[n], ps->nr_iid_par, t_huff_iid_fine,
                    f_huff_iid_fine, ps->iid_index[n]);
            }
        }
    }

    if (ps->enable_icc)
    {
        for (n = 0; n < ps->num_env; n++)
        {
            ps->icc_dt[n] = (uint8_t)faad_get1bit(ld
                DEBUGVAR(1,1010,"ps_data(): icc_dt"));

            /* icc_data */
            huff_data(ld, ps->icc_dt[n], ps->nr_icc_par, t_huff_icc,
                f_huff_icc, ps->icc_index[n]);
        }
    }

    if (ps->enable_ext)
    {
        uint16_t num_bits_left;
        uint16_t cnt = (uint16_t)faad_getbits(ld, 4
            DEBUGVAR(1,1011,"ps_data(): ps_extension_size"));
        if (cnt == 15)
        {
            cnt += (uint16_t)faad_getbits(ld, 8
                DEBUGVAR(1,1012,"ps_data(): esc_count"));
        }

        num_bits_left = 8 * cnt;
        while (num_bits_left > 7)
        {
            uint8_t ps_extension_id = (uint8_t)faad_getbits(ld, 2
                DEBUGVAR(1,1013,"ps_data(): ps_extension_size"));

            num_bits_left -= 2;
            num_bits_left -= ps_extension(ps, ld, ps_extension_id, num_bits_left);
        }

        faad_getbits(ld, num_bits_left
            DEBUGVAR(1,1014,"ps_data(): fill_bits"));
    }

    bits = (uint16_t)faad_get_processed_bits(ld) - bits;

    ps->ps_data_available = 1;

    return bits;
}

static uint16_t ps_extension(ps_info *ps, bitfile *ld,
                             const uint8_t ps_extension_id,
                             const uint16_t num_bits_left)
{
    uint8_t n;
    uint16_t bits = (uint16_t)faad_get_processed_bits(ld);

    if (ps_extension_id == 0)
    {
        ps->enable_ipdopd = (uint8_t)faad_get1bit(ld
            DEBUGVAR(1,1015,"ps_extension(): enable_ipdopd"));

        if (ps->enable_ipdopd)
        {
            for (n = 0; n < ps->num_env; n++)
            {
                ps->ipd_dt[n] = (uint8_t)faad_get1bit(ld
                    DEBUGVAR(1,1016,"ps_extension(): ipd_dt"));

                /* ipd_data */
                huff_data(ld, ps->ipd_dt[n], ps->nr_ipdopd_par, t_huff_ipd,
                    f_huff_ipd, ps->ipd_index[n]);

                ps->opd_dt[n] = (uint8_t)faad_get1bit(ld
                    DEBUGVAR(1,1017,"ps_extension(): opd_dt"));

                /* opd_data */
                huff_data(ld, ps->opd_dt[n], ps->nr_ipdopd_par, t_huff_opd,
                    f_huff_opd, ps->opd_index[n]);
            }
        }
        faad_get1bit(ld
            DEBUGVAR(1,1018,"ps_extension(): reserved_ps"));
    }

    /* return number of bits read */
    bits = (uint16_t)faad_get_processed_bits(ld) - bits;

    return bits;
}

/* read huffman data coded in either the frequency or the time direction */
static void huff_data(bitfile *ld, const uint8_t dt, const uint8_t nr_par,
                      ps_huff_tab t_huff, ps_huff_tab f_huff, int8_t *par)
{
    uint8_t n;

    if (dt)
    {
        /* coded in time direction */
        for (n = 0; n < nr_par; n++)
        {
            par[n] = ps_huff_dec(ld, t_huff);
        }
    } else {
        /* coded in frequency direction */
        par[0] = ps_huff_dec(ld, f_huff);

        for (n = 1; n < nr_par; n++)
        {
            par[n] = ps_huff_dec(ld, f_huff);
        }
    }
}

/* binary search huffman decoding */
static INLINE int8_t ps_huff_dec(bitfile *ld, ps_huff_tab t_huff)
{
    uint8_t bit;
    int16_t index = 0;

    while (index >= 0)
    {
        bit = (uint8_t)faad_get1bit(ld);
        index = t_huff[index][bit];
    }

    return index + 31;
}

#endif