ref: 3def44dfa46085e1d8ccaf9688a6817853bfcee9
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]; } }