/*
  * AAC encoder TNS
  * Copyright (C) 2015 Rostislav Pehlivanov
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg 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
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**
  * @file
  * AAC encoder temporal noise shaping
  * @author Rostislav Pehlivanov ( atomnuker gmail com )
  */
 
 #include "aacenc.h"
 #include "aacenc_tns.h"
 #include "aactab.h"
 #include "aacenc_utils.h"
 #include "aacenc_quantization.h"
 
 /**
  * Encode TNS data.

  * Coefficient compression saves a single bit per coefficient.

  */

 void ff_aac_encode_tns_info(AACEncContext *s, SingleChannelElement *sce)

 {

     uint8_t u_coef;
     const uint8_t coef_res = TNS_Q_BITS == 4;
     int i, w, filt, coef_len, coef_compress = 0;

     const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE;

     TemporalNoiseShaping *tns = &sce->tns;

 
     if (!sce->tns.present)
         return;
 
     for (i = 0; i < sce->ics.num_windows; i++) {
         put_bits(&s->pb, 2 - is8, sce->tns.n_filt[i]);

         if (tns->n_filt[i]) {
             put_bits(&s->pb, 1, coef_res);
             for (filt = 0; filt < tns->n_filt[i]; filt++) {
                 put_bits(&s->pb, 6 - 2 * is8, tns->length[i][filt]);
                 put_bits(&s->pb, 5 - 2 * is8, tns->order[i][filt]);
                 if (tns->order[i][filt]) {
                     put_bits(&s->pb, 1, !!tns->direction[i][filt]);

                     put_bits(&s->pb, 1, !!coef_compress);

                     coef_len = coef_res + 3 - coef_compress;
                     for (w = 0; w < tns->order[i][filt]; w++) {
                         u_coef = (tns->coef_idx[i][filt][w])&(~(~0<<coef_len));
                         put_bits(&s->pb, coef_len, u_coef);
                     }

                 }
             }
         }
     }
 }
 

 static inline void quantize_coefs(double *coef, int *idx, float *lpc, int order)

 {

     int i;
     uint8_t u_coef;
     const float *quant_arr = tns_tmp2_map[TNS_Q_BITS == 4];
     const double iqfac_p = ((1 << (TNS_Q_BITS-1)) - 0.5)/(M_PI/2.0);
     const double iqfac_m = ((1 << (TNS_Q_BITS-1)) + 0.5)/(M_PI/2.0);

     for (i = 0; i < order; i++) {

         idx[i] = ceilf(asin(coef[i])*((coef[i] >= 0) ? iqfac_p : iqfac_m));
         u_coef = (idx[i])&(~(~0<<TNS_Q_BITS));
         lpc[i] = quant_arr[u_coef];

     }
 }
 

 /* Apply TNS filter */

 void ff_aac_apply_tns(AACEncContext *s, SingleChannelElement *sce)

 {

     TemporalNoiseShaping *tns = &sce->tns;

     IndividualChannelStream *ics = &sce->ics;
     int w, filt, m, i, top, order, bottom, start, end, size, inc;
     const int mmm = FFMIN(ics->tns_max_bands, ics->max_sfb);
     float lpc[TNS_MAX_ORDER];

     for (w = 0; w < ics->num_windows; w++) {
         bottom = ics->num_swb;

         for (filt = 0; filt < tns->n_filt[w]; filt++) {
             top    = bottom;
             bottom = FFMAX(0, top - tns->length[w][filt]);
             order  = tns->order[w][filt];

             if (order == 0)

                 continue;
 

             // tns_decode_coef
             compute_lpc_coefs(tns->coef[w][filt], order, lpc, 0, 0, 0);
 
             start = ics->swb_offset[FFMIN(bottom, mmm)];
             end   = ics->swb_offset[FFMIN(   top, mmm)];

             if ((size = end - start) <= 0)
                 continue;
             if (tns->direction[w][filt]) {
                 inc = -1;
                 start = end - 1;
             } else {
                 inc = 1;
             }
             start += w * 128;
 

             // ar filter
             for (m = 0; m < size; m++, start += inc)
                 for (i = 1; i <= FFMIN(m, order); i++)
                     sce->coeffs[start] += lpc[i-1]*sce->pcoeffs[start - i*inc];

         }
     }
 }
 

 void ff_aac_search_for_tns(AACEncContext *s, SingleChannelElement *sce)

 {
     TemporalNoiseShaping *tns = &sce->tns;

     int w, w2, g, count = 0;
     const int mmm = FFMIN(sce->ics.tns_max_bands, sce->ics.max_sfb);

     const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE;

     const int order = is8 ? 7 : s->profile == FF_PROFILE_AAC_LOW ? 12 : TNS_MAX_ORDER;

 
     int sfb_start = av_clip(tns_min_sfb[is8][s->samplerate_index], 0, mmm);
     int sfb_end   = av_clip(sce->ics.num_swb, 0, mmm);

     for (w = 0; w < sce->ics.num_windows; w++) {

         float e_ratio = 0.0f, threshold = 0.0f, spread = 0.0f, en[2] = {0.0, 0.0f};

         double gain = 0.0f, coefs[MAX_LPC_ORDER] = {0};
         int coef_start = w*sce->ics.num_swb + sce->ics.swb_offset[sfb_start];
         int coef_len = sce->ics.swb_offset[sfb_end] - sce->ics.swb_offset[sfb_start];
 

         for (g = 0;  g < sce->ics.num_swb; g++) {

             if (w*16+g < sfb_start || w*16+g > sfb_end)
                 continue;
             for (w2 = 0; w2 < sce->ics.group_len[w]; w2++) {
                 FFPsyBand *band = &s->psy.ch[s->cur_channel].psy_bands[(w+w2)*16+g];
                 if ((w+w2)*16+g > sfb_start + ((sfb_end - sfb_start)/2))

                     en[1] += band->energy;

                 else

                     en[0] += band->energy;

                 threshold += band->threshold;
                 spread += band->spread;

             }
         }
 

         if (coef_len <= 0 || (sfb_end - sfb_start) <= 0)

             continue;

         else
             e_ratio = en[0]/en[1];

 
         /* LPC */

         gain = ff_lpc_calc_ref_coefs_f(&s->lpc, &sce->coeffs[coef_start],
                                        coef_len, order, coefs);
 

         if (gain > TNS_GAIN_THRESHOLD_LOW && gain < TNS_GAIN_THRESHOLD_HIGH &&
             (en[0]+en[1]) > TNS_GAIN_THRESHOLD_LOW*threshold &&
             spread < TNS_SPREAD_THRESHOLD && order) {
             if (is8 || order < 2 || (e_ratio > TNS_E_RATIO_LOW && e_ratio < TNS_E_RATIO_HIGH)) {
                 tns->n_filt[w] = 1;
                 for (g = 0; g < tns->n_filt[w]; g++) {
                     tns->length[w][g] = sfb_end - sfb_start;
                     tns->direction[w][g] = en[0] < en[1];
                     tns->order[w][g] = order;
                     quantize_coefs(coefs, tns->coef_idx[w][g], tns->coef[w][g],
                                    order);
                 }
             } else {  /* 2 filters due to energy disbalance */
                 tns->n_filt[w] = 2;
                 for (g = 0; g < tns->n_filt[w]; g++) {
                     tns->direction[w][g] = en[g] < en[!g];
                     tns->order[w][g] = !g ? order/2 : order - tns->order[w][g-1];
                     tns->length[w][g] = !g ? (sfb_end - sfb_start)/2 : \
                                     (sfb_end - sfb_start) - tns->length[w][g-1];
                     quantize_coefs(&coefs[!g ? 0 : order - tns->order[w][g-1]],
                                    tns->coef_idx[w][g], tns->coef[w][g],
                                    tns->order[w][g]);
                 }

             }
             count++;
         }
     }
 
     sce->tns.present = !!count;
 }