/*
  * 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 "libavutil/libm.h"

 #include "aacenc.h"
 #include "aacenc_tns.h"
 #include "aactab.h"
 #include "aacenc_utils.h"
 #include "aacenc_quantization.h"
 

 /* Could be set to 3 to save an additional bit at the cost of little quality */
 #define TNS_Q_BITS 4
 
 /* Coefficient resolution in short windows */

 #define TNS_Q_BITS_IS8 4

 /* We really need the bits we save here elsewhere */
 #define TNS_ENABLE_COEF_COMPRESSION

 /* TNS will only be used if the LPC gain is within these margins */

 #define TNS_GAIN_THRESHOLD_LOW      1.4f
 #define TNS_GAIN_THRESHOLD_HIGH     1.16f*TNS_GAIN_THRESHOLD_LOW

 static inline int compress_coeffs(int *coef, int order, int c_bits)
 {

     int i;

     const int low_idx   = c_bits ?  4 : 2;
     const int shift_val = c_bits ?  8 : 4;
     const int high_idx  = c_bits ? 11 : 5;

 #ifndef TNS_ENABLE_COEF_COMPRESSION
     return 0;
 #endif /* TNS_ENABLE_COEF_COMPRESSION */
     for (i = 0; i < order; i++)
         if (coef[i] >= low_idx && coef[i] <= high_idx)
             return 0;

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

         coef[i] -= (coef[i] > high_idx) ? shift_val : 0;
     return 1;

 }
 

 /**
  * Encode TNS data.

  * Coefficient compression is simply not lossless as it should be
  * on any decoder tested and as such is not active.

  */

 void ff_aac_encode_tns_info(AACEncContext *s, SingleChannelElement *sce)

 {

     TemporalNoiseShaping *tns = &sce->tns;

     int i, w, filt, coef_compress = 0, coef_len;

     const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE;
     const int c_bits = is8 ? TNS_Q_BITS_IS8 == 4 : TNS_Q_BITS == 4;

 
     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])
             continue;
         put_bits(&s->pb, 1, c_bits);
         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])
                 continue;
             put_bits(&s->pb, 1, tns->direction[i][filt]);
             coef_compress = compress_coeffs(tns->coef_idx[i][filt],
                                             tns->order[i][filt], c_bits);
             put_bits(&s->pb, 1, coef_compress);
             coef_len = c_bits + 3 - coef_compress;
             for (w = 0; w < tns->order[i][filt]; w++)
                 put_bits(&s->pb, coef_len, tns->coef_idx[i][filt][w]);

         }
     }
 }
 

 /* 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];

                 }
             }

         }
     }
 }
 

 /*
  * c_bits - 1 if 4 bit coefficients, 0 if 3 bit coefficients
  */
 static inline void quantize_coefs(double *coef, int *idx, float *lpc, int order,
                                   int c_bits)
 {
     int i;
     const float *quant_arr = tns_tmp2_map[c_bits];
     for (i = 0; i < order; i++) {

         idx[i] = quant_array_idx(coef[i], quant_arr, c_bits ? 16 : 8);

         lpc[i] = quant_arr[idx[i]];
     }
 }
 
 /*
  * 3 bits per coefficient with 8 short windows
  */

 void ff_aac_search_for_tns(AACEncContext *s, SingleChannelElement *sce)

 {
     TemporalNoiseShaping *tns = &sce->tns;

     int w, g, count = 0;

     double gain, coefs[MAX_LPC_ORDER];

     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 c_bits = is8 ? TNS_Q_BITS_IS8 == 4 : TNS_Q_BITS == 4;

     const int sfb_start = av_clip(tns_min_sfb[is8][s->samplerate_index], 0, mmm);
     const int sfb_end   = av_clip(sce->ics.num_swb, 0, mmm);
     const int order = is8 ? 7 : s->profile == FF_PROFILE_AAC_LOW ? 12 : TNS_MAX_ORDER;

     const int slant = sce->ics.window_sequence[0] == LONG_STOP_SEQUENCE  ? 1 :
                       sce->ics.window_sequence[0] == LONG_START_SEQUENCE ? 0 : 2;

     const int sfb_len = sfb_end - sfb_start;
     const int coef_len = sce->ics.swb_offset[sfb_end] - sce->ics.swb_offset[sfb_start];
 
     if (coef_len <= 0 || sfb_len <= 0) {
         sce->tns.present = 0;
         return;
     }

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

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

         int oc_start = 0, os_start = 0;

         int coef_start = sce->ics.swb_offset[sfb_start];

         for (g = sfb_start; g < sce->ics.num_swb && g <= sfb_end; g++) {
             FFPsyBand *band = &s->psy.ch[s->cur_channel].psy_bands[w*16+g];
             if (g > sfb_start + (sfb_len/2))
                 en[1] += band->energy;
             else
                 en[0] += band->energy;

         }
 
         /* LPC */

         gain = ff_lpc_calc_ref_coefs_f(&s->lpc, &sce->coeffs[w*128 + coef_start],

                                        coef_len, order, coefs);
 

         if (!order || !isfinite(gain) || gain < TNS_GAIN_THRESHOLD_LOW || gain > TNS_GAIN_THRESHOLD_HIGH)

             continue;

 
         tns->n_filt[w] = is8 ? 1 : order != TNS_MAX_ORDER ? 2 : 3;
         for (g = 0; g < tns->n_filt[w]; g++) {
             tns->direction[w][g] = slant != 2 ? slant : en[g] < en[!g];
             tns->order[w][g] = g < tns->n_filt[w] ? order/tns->n_filt[w] : order - oc_start;
             tns->length[w][g] = g < tns->n_filt[w] ? sfb_len/tns->n_filt[w] : sfb_len - os_start;
             quantize_coefs(&coefs[oc_start], tns->coef_idx[w][g], tns->coef[w][g],
                             tns->order[w][g], c_bits);
             oc_start += tns->order[w][g];
             os_start += tns->length[w][g];

         }

         count++;

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