266 lines
8.2 KiB
C
266 lines
8.2 KiB
C
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/*
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** FAAD2 - Freeware Advanced Audio (AAC) Decoder including SBR decoding
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** Copyright (C) 2003-2004 M. Bakker, Ahead Software AG, http://www.nero.com
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**
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** This program is free software; you can redistribute it and/or modify
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** it under the terms of the GNU General Public License as published by
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** the Free Software Foundation; either version 2 of the License, or
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** (at your option) any later version.
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**
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** This program is distributed in the hope that it will be useful,
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** but WITHOUT ANY WARRANTY; without even the implied warranty of
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** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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** GNU General Public License for more details.
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**
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** You should have received a copy of the GNU General Public License
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** along with this program; if not, write to the Free Software
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** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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**
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** Any non-GPL usage of this software or parts of this software is strictly
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** forbidden.
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**
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** Commercial non-GPL licensing of this software is possible.
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** For more info contact Ahead Software through Mpeg4AAClicense@nero.com.
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**
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** $Id$
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**/
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#include "common.h"
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#include "structs.h"
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#include "pns.h"
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/* static function declarations */
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static void gen_rand_vector(real_t *spec, int16_t scale_factor, uint16_t size,
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uint8_t sub);
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#ifdef FIXED_POINT
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#define DIV(A, B) (((int64_t)A << REAL_BITS)/B)
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#define step(shift) \
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if ((0x40000000l >> shift) + root <= value) \
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{ \
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value -= (0x40000000l >> shift) + root; \
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root = (root >> 1) | (0x40000000l >> shift); \
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} else { \
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root = root >> 1; \
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}
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/* fixed point square root approximation */
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/* !!!! ONLY WORKS FOR EVEN %REAL_BITS% !!!! */
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real_t fp_sqrt(real_t value)
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{
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real_t root = 0;
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step( 0); step( 2); step( 4); step( 6);
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step( 8); step(10); step(12); step(14);
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step(16); step(18); step(20); step(22);
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step(24); step(26); step(28); step(30);
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if (root < value)
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++root;
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root <<= (REAL_BITS/2);
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return root;
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}
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static real_t pow2_table[] =
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{
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COEF_CONST(1.0),
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COEF_CONST(1.18920711500272),
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COEF_CONST(1.41421356237310),
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COEF_CONST(1.68179283050743)
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};
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#endif
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/* The function gen_rand_vector(addr, size) generates a vector of length
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<size> with signed random values of average energy MEAN_NRG per random
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value. A suitable random number generator can be realized using one
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multiplication/accumulation per random value.
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*/
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static INLINE void gen_rand_vector(real_t *spec, int16_t scale_factor, uint16_t size,
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uint8_t sub)
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{
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#ifndef FIXED_POINT
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uint16_t i;
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real_t energy = 0.0;
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real_t scale = (real_t)1.0/(real_t)size;
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for (i = 0; i < size; i++)
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{
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real_t tmp = scale*(real_t)(int32_t)random_int();
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spec[i] = tmp;
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energy += tmp*tmp;
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}
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scale = (real_t)1.0/(real_t)sqrt(energy);
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scale *= (real_t)pow(2.0, 0.25 * scale_factor);
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for (i = 0; i < size; i++)
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{
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spec[i] *= scale;
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}
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#else
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uint16_t i;
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real_t energy = 0, scale;
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int32_t exp, frac;
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for (i = 0; i < size; i++)
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{
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/* this can be replaced by a 16 bit random generator!!!! */
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real_t tmp = (int32_t)random_int();
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if (tmp < 0)
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tmp = -(tmp & ((1<<(REAL_BITS-1))-1));
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else
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tmp = (tmp & ((1<<(REAL_BITS-1))-1));
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energy += MUL_R(tmp,tmp);
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spec[i] = tmp;
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}
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energy = fp_sqrt(energy);
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if (energy > 0)
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{
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scale = DIV(REAL_CONST(1),energy);
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exp = scale_factor >> 2;
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frac = scale_factor & 3;
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/* IMDCT pre-scaling */
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exp -= sub;
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if (exp < 0)
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scale >>= -exp;
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else
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scale <<= exp;
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if (frac)
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scale = MUL_C(scale, pow2_table[frac]);
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for (i = 0; i < size; i++)
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{
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spec[i] = MUL_R(spec[i], scale);
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}
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}
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#endif
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}
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void pns_decode(ic_stream *ics_left, ic_stream *ics_right,
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real_t *spec_left, real_t *spec_right, uint16_t frame_len,
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uint8_t channel_pair, uint8_t object_type)
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{
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uint8_t g, sfb, b;
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uint16_t size, offs;
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uint8_t group = 0;
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uint16_t nshort = frame_len >> 3;
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uint8_t sub = 0;
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#ifdef FIXED_POINT
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/* IMDCT scaling */
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if (object_type == LD)
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{
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sub = 9 /*9*/;
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} else {
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if (ics_left->window_sequence == EIGHT_SHORT_SEQUENCE)
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sub = 7 /*7*/;
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else
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sub = 10 /*10*/;
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}
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#endif
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for (g = 0; g < ics_left->num_window_groups; g++)
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{
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/* Do perceptual noise substitution decoding */
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for (b = 0; b < ics_left->window_group_length[g]; b++)
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{
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for (sfb = 0; sfb < ics_left->max_sfb; sfb++)
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{
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if (is_noise(ics_left, g, sfb))
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{
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#ifdef LTP_DEC
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/* Simultaneous use of LTP and PNS is not prevented in the
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syntax. If both LTP, and PNS are enabled on the same
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scalefactor band, PNS takes precedence, and no prediction
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is applied to this band.
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*/
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ics_left->ltp.long_used[sfb] = 0;
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ics_left->ltp2.long_used[sfb] = 0;
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#endif
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#ifdef MAIN_DEC
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/* For scalefactor bands coded using PNS the corresponding
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predictors are switched to "off".
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*/
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ics_left->pred.prediction_used[sfb] = 0;
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#endif
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offs = ics_left->swb_offset[sfb];
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size = ics_left->swb_offset[sfb+1] - offs;
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/* Generate random vector */
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gen_rand_vector(&spec_left[(group*nshort)+offs],
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ics_left->scale_factors[g][sfb], size, sub);
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}
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/* From the spec:
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If the same scalefactor band and group is coded by perceptual noise
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substitution in both channels of a channel pair, the correlation of
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the noise signal can be controlled by means of the ms_used field: While
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the default noise generation process works independently for each channel
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(separate generation of random vectors), the same random vector is used
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for both channels if ms_used[] is set for a particular scalefactor band
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and group. In this case, no M/S stereo coding is carried out (because M/S
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stereo coding and noise substitution coding are mutually exclusive).
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If the same scalefactor band and group is coded by perceptual noise
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substitution in only one channel of a channel pair the setting of ms_used[]
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is not evaluated.
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*/
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if (channel_pair)
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{
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if (is_noise(ics_right, g, sfb))
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{
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if (((ics_left->ms_mask_present == 1) &&
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(ics_left->ms_used[g][sfb])) ||
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(ics_left->ms_mask_present == 2))
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{
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uint16_t c;
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offs = ics_right->swb_offset[sfb];
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size = ics_right->swb_offset[sfb+1] - offs;
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for (c = 0; c < size; c++)
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{
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spec_right[(group*nshort) + offs + c] =
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spec_left[(group*nshort) + offs + c];
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}
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} else /*if (ics_left->ms_mask_present == 0)*/ {
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#ifdef LTP_DEC
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ics_right->ltp.long_used[sfb] = 0;
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ics_right->ltp2.long_used[sfb] = 0;
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#endif
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#ifdef MAIN_DEC
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ics_right->pred.prediction_used[sfb] = 0;
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#endif
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offs = ics_right->swb_offset[sfb];
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size = ics_right->swb_offset[sfb+1] - offs;
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/* Generate random vector */
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gen_rand_vector(&spec_right[(group*nshort)+offs],
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ics_right->scale_factors[g][sfb], size, sub);
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}
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}
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}
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} /* sfb */
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group++;
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} /* b */
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} /* g */
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}
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