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e3faad811e
This commit improves the TNS implementation to the point where it's actually usable and very rarely results in nastyness (in all bitrates except extremely low bitrates it's increasing the quality and prevents some distortions from the coder being audiable). Also adds a double filter support which is only used if the energy difference between the top and bottom of the SFBs is above the thresholds defined in the header file. Looking at the bitstream that fdk_aac generates it sometimes used a double filter despite the specs stating that a single filter should be enough for almost all cases and purposes. Unlike FAAC or fdk_aac we sometimes use a reverse filter in case the energy difference isn't enought to use a double filter. This actually works better. Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>
195 lines
7.3 KiB
C
195 lines
7.3 KiB
C
/*
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* AAC encoder TNS
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* Copyright (C) 2015 Rostislav Pehlivanov
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg 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 GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* AAC encoder temporal noise shaping
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* @author Rostislav Pehlivanov ( atomnuker gmail com )
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*/
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#include "aacenc.h"
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#include "aacenc_tns.h"
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#include "aactab.h"
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#include "aacenc_utils.h"
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#include "aacenc_quantization.h"
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/**
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* Encode TNS data.
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* Coefficient compression saves a single bit per coefficient.
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*/
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void ff_aac_encode_tns_info(AACEncContext *s, SingleChannelElement *sce)
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{
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uint8_t u_coef;
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const uint8_t coef_res = TNS_Q_BITS == 4;
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int i, w, filt, coef_len, coef_compress = 0;
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const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE;
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TemporalNoiseShaping *tns = &sce->tns;
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if (!sce->tns.present)
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return;
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for (i = 0; i < sce->ics.num_windows; i++) {
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put_bits(&s->pb, 2 - is8, sce->tns.n_filt[i]);
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if (tns->n_filt[i]) {
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put_bits(&s->pb, 1, coef_res);
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for (filt = 0; filt < tns->n_filt[i]; filt++) {
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put_bits(&s->pb, 6 - 2 * is8, tns->length[i][filt]);
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put_bits(&s->pb, 5 - 2 * is8, tns->order[i][filt]);
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if (tns->order[i][filt]) {
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put_bits(&s->pb, 1, !!tns->direction[i][filt]);
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put_bits(&s->pb, 1, !!coef_compress);
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coef_len = coef_res + 3 - coef_compress;
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for (w = 0; w < tns->order[i][filt]; w++) {
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u_coef = (tns->coef_idx[i][filt][w])&(~(~0<<coef_len));
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put_bits(&s->pb, coef_len, u_coef);
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}
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}
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}
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}
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}
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}
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static inline void quantize_coefs(double *coef, int *idx, float *lpc, int order)
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{
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int i;
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uint8_t u_coef;
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const float *quant_arr = tns_tmp2_map[TNS_Q_BITS == 4];
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const double iqfac_p = ((1 << (TNS_Q_BITS-1)) - 0.5)/(M_PI/2.0);
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const double iqfac_m = ((1 << (TNS_Q_BITS-1)) + 0.5)/(M_PI/2.0);
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for (i = 0; i < order; i++) {
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idx[i] = ceilf(asin(coef[i])*((coef[i] >= 0) ? iqfac_p : iqfac_m));
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u_coef = (idx[i])&(~(~0<<TNS_Q_BITS));
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lpc[i] = quant_arr[u_coef];
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}
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}
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/* Apply TNS filter */
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void ff_aac_apply_tns(AACEncContext *s, SingleChannelElement *sce)
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{
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TemporalNoiseShaping *tns = &sce->tns;
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IndividualChannelStream *ics = &sce->ics;
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int w, filt, m, i, top, order, bottom, start, end, size, inc;
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const int mmm = FFMIN(ics->tns_max_bands, ics->max_sfb);
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float lpc[TNS_MAX_ORDER];
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for (w = 0; w < ics->num_windows; w++) {
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bottom = ics->num_swb;
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for (filt = 0; filt < tns->n_filt[w]; filt++) {
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top = bottom;
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bottom = FFMAX(0, top - tns->length[w][filt]);
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order = tns->order[w][filt];
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if (order == 0)
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continue;
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// tns_decode_coef
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compute_lpc_coefs(tns->coef[w][filt], order, lpc, 0, 0, 0);
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start = ics->swb_offset[FFMIN(bottom, mmm)];
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end = ics->swb_offset[FFMIN( top, mmm)];
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if ((size = end - start) <= 0)
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continue;
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if (tns->direction[w][filt]) {
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inc = -1;
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start = end - 1;
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} else {
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inc = 1;
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}
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start += w * 128;
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// ar filter
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for (m = 0; m < size; m++, start += inc)
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for (i = 1; i <= FFMIN(m, order); i++)
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sce->coeffs[start] += lpc[i-1]*sce->pcoeffs[start - i*inc];
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}
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}
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}
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void ff_aac_search_for_tns(AACEncContext *s, SingleChannelElement *sce)
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{
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TemporalNoiseShaping *tns = &sce->tns;
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int w, w2, g, count = 0;
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const int mmm = FFMIN(sce->ics.tns_max_bands, sce->ics.max_sfb);
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const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE;
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const int order = is8 ? 7 : s->profile == FF_PROFILE_AAC_LOW ? 12 : TNS_MAX_ORDER;
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int sfb_start = av_clip(tns_min_sfb[is8][s->samplerate_index], 0, mmm);
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int sfb_end = av_clip(sce->ics.num_swb, 0, mmm);
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for (w = 0; w < sce->ics.num_windows; w++) {
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float e_ratio = 0.0f, threshold = 0.0f, spread = 0.0f, en[2] = {0.0, 0.0f};
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double gain = 0.0f, coefs[MAX_LPC_ORDER] = {0};
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int coef_start = w*sce->ics.num_swb + sce->ics.swb_offset[sfb_start];
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int coef_len = sce->ics.swb_offset[sfb_end] - sce->ics.swb_offset[sfb_start];
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for (g = 0; g < sce->ics.num_swb; g++) {
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if (w*16+g < sfb_start || w*16+g > sfb_end)
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continue;
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for (w2 = 0; w2 < sce->ics.group_len[w]; w2++) {
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FFPsyBand *band = &s->psy.ch[s->cur_channel].psy_bands[(w+w2)*16+g];
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if ((w+w2)*16+g > sfb_start + ((sfb_end - sfb_start)/2))
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en[1] += band->energy;
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else
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en[0] += band->energy;
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threshold += band->threshold;
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spread += band->spread;
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}
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}
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if (coef_len <= 0 || (sfb_end - sfb_start) <= 0)
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continue;
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else
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e_ratio = en[0]/en[1];
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/* LPC */
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gain = ff_lpc_calc_ref_coefs_f(&s->lpc, &sce->coeffs[coef_start],
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coef_len, order, coefs);
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if (gain > TNS_GAIN_THRESHOLD_LOW && gain < TNS_GAIN_THRESHOLD_HIGH &&
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(en[0]+en[1]) > TNS_GAIN_THRESHOLD_LOW*threshold &&
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spread < TNS_SPREAD_THRESHOLD && order) {
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if (is8 || order < 2 || (e_ratio > TNS_E_RATIO_LOW && e_ratio < TNS_E_RATIO_HIGH)) {
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tns->n_filt[w] = 1;
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for (g = 0; g < tns->n_filt[w]; g++) {
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tns->length[w][g] = sfb_end - sfb_start;
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tns->direction[w][g] = en[0] < en[1];
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tns->order[w][g] = order;
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quantize_coefs(coefs, tns->coef_idx[w][g], tns->coef[w][g],
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order);
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}
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} else { /* 2 filters due to energy disbalance */
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tns->n_filt[w] = 2;
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for (g = 0; g < tns->n_filt[w]; g++) {
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tns->direction[w][g] = en[g] < en[!g];
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tns->order[w][g] = !g ? order/2 : order - tns->order[w][g-1];
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tns->length[w][g] = !g ? (sfb_end - sfb_start)/2 : \
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(sfb_end - sfb_start) - tns->length[w][g-1];
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quantize_coefs(&coefs[!g ? 0 : order - tns->order[w][g-1]],
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tns->coef_idx[w][g], tns->coef[w][g],
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tns->order[w][g]);
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}
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}
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count++;
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}
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}
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sce->tns.present = !!count;
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}
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