shithub: aacdec

ref: 1a8846b50eb297b9faa06e1273b1589a7ee833ca
dir: /libfaad/specrec.c/

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/*
** FAAD - Freeware Advanced Audio Decoder
** Copyright (C) 2002 M. Bakker
**  
** 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: specrec.c,v 1.8 2002/06/13 11:03:28 menno Exp $
**/

/*
  Spectral reconstruction:
   - grouping/sectioning
   - inverse quantization
   - applying scalefactors
*/

#include "common.h"

#include "specrec.h"
#include "syntax.h"
#include "data.h"


#define bit_set(A, B) ((A) & (1<<(B)))

/* 4.5.2.3.4 */
/*
  - determine the number of windows in a window_sequence named num_windows
  - determine the number of window_groups named num_window_groups
  - determine the number of windows in each group named window_group_length[g]
  - determine the total number of scalefactor window bands named num_swb for
    the actual window type
  - determine swb_offset[swb], the offset of the first coefficient in
    scalefactor window band named swb of the window actually used
  - determine sect_sfb_offset[g][section],the offset of the first coefficient
    in section named section. This offset depends on window_sequence and
    scale_factor_grouping and is needed to decode the spectral_data().
*/
uint8_t window_grouping_info(ic_stream *ics, uint8_t fs_index,
                             uint8_t object_type, uint16_t frame_len)
{
    uint8_t i, g;

    switch (ics->window_sequence) {
    case ONLY_LONG_SEQUENCE:
    case LONG_START_SEQUENCE:
    case LONG_STOP_SEQUENCE:
        ics->num_windows = 1;
        ics->num_window_groups = 1;
        ics->window_group_length[ics->num_window_groups-1] = 1;
#ifdef LD_DEC
        if (object_type == LD)
        {
            ics->num_swb = num_swb_512_window[fs_index];
        } else {
#endif
            ics->num_swb = num_swb_1024_window[fs_index];
#ifdef LD_DEC
        }
#endif

        /* preparation of sect_sfb_offset for long blocks */
        /* also copy the last value! */
#ifdef LD_DEC
        if (object_type == LD)
        {
            for (i = 0; i < ics->num_swb; i++)
            {
                ics->sect_sfb_offset[0][i] = swb_offset_512_window[fs_index][i];
                ics->swb_offset[i] = swb_offset_512_window[fs_index][i];
            }
            ics->sect_sfb_offset[0][ics->num_swb] = frame_len;
            ics->swb_offset[ics->num_swb] = frame_len;
        } else {
#endif
            for (i = 0; i < ics->num_swb; i++)
            {
                ics->sect_sfb_offset[0][i] = swb_offset_1024_window[fs_index][i];
                ics->swb_offset[i] = swb_offset_1024_window[fs_index][i];
            }
            ics->sect_sfb_offset[0][ics->num_swb] = frame_len;
            ics->swb_offset[ics->num_swb] = frame_len;
#ifdef LD_DEC
        }
#endif
        return 0;
    case EIGHT_SHORT_SEQUENCE:
        ics->num_windows = 8;
        ics->num_window_groups = 1;
        ics->window_group_length[ics->num_window_groups-1] = 1;
        ics->num_swb = num_swb_128_window[fs_index];

        for (i = 0; i < ics->num_swb; i++)
            ics->swb_offset[i] = swb_offset_128_window[fs_index][i];
        ics->swb_offset[ics->num_swb] = frame_len/8;

        for (i = 0; i < ics->num_windows-1; i++) {
            if (bit_set(ics->scale_factor_grouping, 6-i) == 0)
            {
                ics->num_window_groups += 1;
                ics->window_group_length[ics->num_window_groups-1] = 1;
            } else {
                ics->window_group_length[ics->num_window_groups-1] += 1;
            }
        }

        /* preparation of sect_sfb_offset for short blocks */
        for (g = 0; g < ics->num_window_groups; g++)
        {
            uint16_t width;
            uint8_t sect_sfb = 0;
            uint16_t offset = 0;

            for (i = 0; i < ics->num_swb; i++)
            {
                if (i+1 == ics->num_swb)
                {
                    width = (frame_len/8) - swb_offset_128_window[fs_index][i];
                } else {
                    width = swb_offset_128_window[fs_index][i+1] -
                        swb_offset_128_window[fs_index][i];
                }
                width *= ics->window_group_length[g];
                ics->sect_sfb_offset[g][sect_sfb++] = offset;
                offset += width;
            }
            ics->sect_sfb_offset[g][sect_sfb] = offset;
        }
        return 0;
    default:
        return 1;
    }
}

/*
  For ONLY_LONG_SEQUENCE windows (num_window_groups = 1,
  window_group_length[0] = 1) the spectral data is in ascending spectral
  order.
  For the EIGHT_SHORT_SEQUENCE window, the spectral order depends on the
  grouping in the following manner:
  - Groups are ordered sequentially
  - Within a group, a scalefactor band consists of the spectral data of all
    grouped SHORT_WINDOWs for the associated scalefactor window band. To
    clarify via example, the length of a group is in the range of one to eight
    SHORT_WINDOWs.
  - If there are eight groups each with length one (num_window_groups = 8,
    window_group_length[0..7] = 1), the result is a sequence of eight spectra,
    each in ascending spectral order.
  - If there is only one group with length eight (num_window_groups = 1,
    window_group_length[0] = 8), the result is that spectral data of all eight
    SHORT_WINDOWs is interleaved by scalefactor window bands.
  - Within a scalefactor window band, the coefficients are in ascending
    spectral order.
*/
void quant_to_spec(ic_stream *ics, real_t *spec_data, uint16_t frame_len)
{
    int8_t i;
    uint8_t g, sfb, win;
    uint16_t width, bin;
    real_t *start_inptr, *start_win_ptr, *win_ptr;

    real_t tmp_spec[1024];
    real_t *tmp_spec_ptr, *spec_ptr;

    tmp_spec_ptr = tmp_spec;
    for (i = frame_len/16-1; i >= 0; --i)
    {
        *tmp_spec_ptr++ = 0; *tmp_spec_ptr++ = 0;
        *tmp_spec_ptr++ = 0; *tmp_spec_ptr++ = 0;
        *tmp_spec_ptr++ = 0; *tmp_spec_ptr++ = 0;
        *tmp_spec_ptr++ = 0; *tmp_spec_ptr++ = 0;
        *tmp_spec_ptr++ = 0; *tmp_spec_ptr++ = 0;
        *tmp_spec_ptr++ = 0; *tmp_spec_ptr++ = 0;
        *tmp_spec_ptr++ = 0; *tmp_spec_ptr++ = 0;
        *tmp_spec_ptr++ = 0; *tmp_spec_ptr++ = 0;
    }

    spec_ptr = spec_data;
    tmp_spec_ptr = tmp_spec;
    start_win_ptr = tmp_spec_ptr;

    for (g = 0; g < ics->num_window_groups; g++)
    {
        uint16_t j = 0;
        uint16_t win_inc = 0;

        start_inptr = spec_ptr;

        win_inc = ics->swb_offset[ics->num_swb];

        for (sfb = 0; sfb < ics->num_swb; sfb++)
        {
            width = ics->swb_offset[sfb+1] - ics->swb_offset[sfb];

            win_ptr = start_win_ptr;

            for (win = 0; win < ics->window_group_length[g]; win++)
            {
                tmp_spec_ptr = win_ptr + j;

                for (bin = 0; bin < width; bin += 4)
                {
                    *tmp_spec_ptr++ = *spec_ptr++;
                    *tmp_spec_ptr++ = *spec_ptr++;
                    *tmp_spec_ptr++ = *spec_ptr++;
                    *tmp_spec_ptr++ = *spec_ptr++;
                }

                win_ptr += win_inc;
            }
            j += width;
        }
        start_win_ptr += (spec_ptr - start_inptr);
    }

    spec_ptr = spec_data;
    tmp_spec_ptr = tmp_spec;

    for (i = frame_len/16 - 1; i >= 0; --i)
    {
        *spec_ptr++ = *tmp_spec_ptr++; *spec_ptr++ = *tmp_spec_ptr++;
        *spec_ptr++ = *tmp_spec_ptr++; *spec_ptr++ = *tmp_spec_ptr++;
        *spec_ptr++ = *tmp_spec_ptr++; *spec_ptr++ = *tmp_spec_ptr++;
        *spec_ptr++ = *tmp_spec_ptr++; *spec_ptr++ = *tmp_spec_ptr++;
        *spec_ptr++ = *tmp_spec_ptr++; *spec_ptr++ = *tmp_spec_ptr++;
        *spec_ptr++ = *tmp_spec_ptr++; *spec_ptr++ = *tmp_spec_ptr++;
        *spec_ptr++ = *tmp_spec_ptr++; *spec_ptr++ = *tmp_spec_ptr++;
        *spec_ptr++ = *tmp_spec_ptr++; *spec_ptr++ = *tmp_spec_ptr++;
    }
}

void build_tables(real_t *iq_table, real_t *pow2_table)
{
    uint16_t i;

    /* build pow(x, 4/3) table for inverse quantization */
    for(i = 0; i < IQ_TABLE_SIZE; i++)
    {
        iq_table[i] = (real_t)exp(log(i) * 4.0/3.0);
    }

    /* build pow(2, 0.25*x) table for scalefactors */
    for(i = 0; i < POW_TABLE_SIZE; i++)
    {
        pow2_table[i] = (real_t)exp(LN2 * 0.25 * (i-100));
    }
}

static INLINE real_t iquant(int16_t q, real_t *iq_table)
{
    if (q > 0)
    {
        if (q < IQ_TABLE_SIZE)
            return iq_table[q];
        else
            return MUL(iq_table[q>>3], 16);
    } else if (q < 0) {
        q = -q;
        if (q < IQ_TABLE_SIZE)
            return -iq_table[q];
        else
          return -MUL(iq_table[q>>3], 16);
    } else {
        return 0.0f;
    }
}

void inverse_quantization(real_t *x_invquant, int16_t *x_quant, real_t *iq_table,
                          uint16_t frame_len)
{
    int8_t i;
    int16_t *in_ptr = x_quant;
    real_t *out_ptr = x_invquant;

    for(i = frame_len/8-1; i >= 0; --i)
    {
        *out_ptr++ = iquant(*in_ptr++, iq_table);
        *out_ptr++ = iquant(*in_ptr++, iq_table);
        *out_ptr++ = iquant(*in_ptr++, iq_table);
        *out_ptr++ = iquant(*in_ptr++, iq_table);
        *out_ptr++ = iquant(*in_ptr++, iq_table);
        *out_ptr++ = iquant(*in_ptr++, iq_table);
        *out_ptr++ = iquant(*in_ptr++, iq_table);
        *out_ptr++ = iquant(*in_ptr++, iq_table);
    }
}

static INLINE real_t get_scale_factor_gain(uint16_t scale_factor, real_t *pow2_table)
{
    if (scale_factor < POW_TABLE_SIZE)
        return pow2_table[scale_factor];
    else
        return (real_t)exp(LN2 * 0.25 * (scale_factor - 100));
}

void apply_scalefactors(ic_stream *ics, real_t *x_invquant, real_t *pow2_table,
                        uint16_t frame_len)
{
    uint8_t g, sfb;
    uint16_t top;
    real_t *fp, scale;
    uint8_t groups = 0;
    uint16_t nshort = frame_len/8;

    for (g = 0; g < ics->num_window_groups; g++)
    {
        uint16_t k = 0;

        /* using this 128*groups doesn't hurt long blocks, because
           long blocks only have 1 group, so that means 'groups' is
           always 0 for long blocks
        */
        fp = x_invquant + (groups*nshort);

        for (sfb = 0; sfb < ics->max_sfb; sfb++)
        {
            top = ics->sect_sfb_offset[g][sfb+1];

            scale = get_scale_factor_gain(ics->scale_factors[g][sfb], pow2_table);

            /* minimum size of a sf band is 4 and always a multiple of 4 */
            for ( ; k < top; k+=4)
            {
                *fp = MUL(*fp, scale); fp++;
                *fp = MUL(*fp, scale); fp++;
                *fp = MUL(*fp, scale); fp++;
                *fp = MUL(*fp, scale); fp++;
            }
        }
        groups += ics->window_group_length[g];
    }
}