ref: 36ac51109224df99ad0e96609d37d126864f51ff
dir: /libfaad/specrec.c/
/*
** 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 1.1 2002/01/14 19:15:57 menno Exp $
**/
/*
Spectral reconstruction:
- grouping/sectioning
- inverse quantization
- applying scalefactors
*/
#ifdef __ICL
#include <mathf.h>
#else
#include <math.h>
#endif
#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().
*/
int window_grouping_info(ic_stream *ics, int fs_index)
{
int 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;
ics->num_swb = num_swb_long_window[fs_index];
/* preparation of sect_sfb_offset for long blocks */
/* also copy the last value! */
for (i = 0; i < ics->num_swb + 1; i++)
{
ics->sect_sfb_offset[0][i] = swb_offset_long_window[fs_index][i];
ics->swb_offset[i] = swb_offset_long_window[fs_index][i];
}
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_short_window[fs_index];
for (i = 0; i < ics->num_swb + 1; i++)
ics->swb_offset[i] = swb_offset_short_window[fs_index][i];
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++)
{
int width;
int sect_sfb = 0;
int offset = 0;
for (i = 0; i < ics->num_swb; i++)
{
width = swb_offset_short_window[fs_index][i+1] -
swb_offset_short_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, float *spec_data)
{
int g, width, sfb, win, bin;
float *start_inptr, *start_win_ptr, *win_ptr;
float tmp_spec[1024];
float *tmp_spec_ptr, *spec_ptr;
tmp_spec_ptr = tmp_spec;
for (g = 1024/16-1; g >= 0; --g)
{
*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++)
{
int j = 0;
int 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++)
*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 (g = 1024/16 - 1; g >= 0; --g)
{
*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(float *iq_table, float *pow2_table)
{
int i;
/* build pow() table for inverse quantization */
for(i = 0; i < IQ_TABLE_SIZE; i++)
{
#ifdef __ICL
iq_table[i] = powf(i, 4.0f/3.0f);
#else
iq_table[i] = (float)pow(i, 4.0/3.0);
#endif
}
/* build pow(2, 0.25) table for scalefactors */
for(i = 0; i < POW_TABLE_SIZE; i++)
{
#ifdef __ICL
pow2_table[i] = powf(2.0f, 0.25f * (i-100));
#else
pow2_table[i] = (float)pow(2.0, 0.25 * (i-100));
#endif
}
}
void inverse_quantization(float *x_invquant, short *x_quant, float *iq_table)
{
int i;
for(i = 0; i < 1024; i++)
{
short q = x_quant[i];
if (q > 0)
{
if (q < IQ_TABLE_SIZE)
x_invquant[i] = iq_table[q];
else
#ifdef __ICL
x_invquant[i] = powf(q, 4.0f/3.0f);
#else
x_invquant[i] = (float)pow(q, 4.0/3.0);
#endif
} else if (q < 0) {
q = -q;
if (q < IQ_TABLE_SIZE)
x_invquant[i] = -iq_table[q];
else
#ifdef __ICL
x_invquant[i] = -powf(q, 4.0f/3.0f);
#else
x_invquant[i] = -(float)pow(q, 4.0/3.0);
#endif
} else {
x_invquant[i] = 0.0f;
}
}
}
static __inline float get_scale_factor_gain(int scale_factor, float *pow2_table)
{
if ((scale_factor >= 0) && (scale_factor < POW_TABLE_SIZE))
return pow2_table[scale_factor];
else
#ifdef __ICL
return powf(2.0f, 0.25f * (scale_factor - 100));
#else
return (float)pow(2.0, 0.25 * (scale_factor - 100));
#endif
}
void apply_scalefactors(ic_stream *ics, float *x_invquant, float *pow2_table)
{
int g, sfb, top;
float *fp, scale;
int groups = 0;
for (g = 0; g < ics->num_window_groups; g++)
{
int 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*128);
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);
for ( ; k < top; k++)
*fp++ *= scale;
}
groups += ics->window_group_length[g];
}
}