/*
  * AAC coefficients encoder
  * Copyright (C) 2008-2009 Konstantin Shishkov
  *
  * 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 coefficients encoder
  */
 
 /***********************************
  *              TODOs:
  * speedup quantizer selection
  * add sane pulse detection
  ***********************************/
 

 #include "libavutil/libm.h" // brought forward to work around cygwin header breakage
 

 #include <float.h>

 #include "libavutil/mathematics.h"

 #include "mathops.h"

 #include "avcodec.h"
 #include "put_bits.h"
 #include "aac.h"
 #include "aacenc.h"
 #include "aactab.h"

 #include "aacenctab.h"

 #include "aacenc_utils.h"

 #include "aacenc_quantization.h"

 #include "aacenc_is.h"

 #include "aacenc_tns.h"

 #include "aacenc_ltp.h"

 #include "aacenc_pred.h"

 #include "libavcodec/aaccoder_twoloop.h"
 

 /* Parameter of f(x) = a*(lambda/100), defines the maximum fourier spread
  * beyond which no PNS is used (since the SFBs contain tone rather than noise) */

 #define NOISE_SPREAD_THRESHOLD 0.9f

 /* Parameter of f(x) = a*(100/lambda), defines how much PNS is allowed to
  * replace low energy non zero bands */
 #define NOISE_LAMBDA_REPLACE 1.948f

 #include "libavcodec/aaccoder_trellis.h"
 

 /**
  * structure used in optimal codebook search
  */
 typedef struct BandCodingPath {
     int prev_idx; ///< pointer to the previous path point
     float cost;   ///< path cost
     int run;
 } BandCodingPath;
 
 /**
  * Encode band info for single window group bands.
  */
 static void encode_window_bands_info(AACEncContext *s, SingleChannelElement *sce,
                                      int win, int group_len, const float lambda)
 {

     BandCodingPath path[120][CB_TOT_ALL];

     int w, swb, cb, start, size;

     int i, j;

     const int max_sfb  = sce->ics.max_sfb;

     const int run_bits = sce->ics.num_windows == 1 ? 5 : 3;

     const int run_esc  = (1 << run_bits) - 1;

     int idx, ppos, count;
     int stackrun[120], stackcb[120], stack_len;
     float next_minrd = INFINITY;
     int next_mincb = 0;
 

     s->abs_pow34(s->scoefs, sce->coeffs, 1024);

     start = win*128;

     for (cb = 0; cb < CB_TOT_ALL; cb++) {

         path[0][cb].cost     = 0.0f;

         path[0][cb].prev_idx = -1;

         path[0][cb].run      = 0;

     }

     for (swb = 0; swb < max_sfb; swb++) {

         size = sce->ics.swb_sizes[swb];

         if (sce->zeroes[win*16 + swb]) {

             for (cb = 0; cb < CB_TOT_ALL; cb++) {

                 path[swb+1][cb].prev_idx = cb;

                 path[swb+1][cb].cost     = path[swb][cb].cost;
                 path[swb+1][cb].run      = path[swb][cb].run + 1;

             }

         } else {

             float minrd = next_minrd;
             int mincb = next_mincb;
             next_minrd = INFINITY;
             next_mincb = 0;

             for (cb = 0; cb < CB_TOT_ALL; cb++) {

                 float cost_stay_here, cost_get_here;
                 float rd = 0.0f;

                 if (cb >= 12 && sce->band_type[win*16+swb] < aac_cb_out_map[cb] ||
                     cb  < aac_cb_in_map[sce->band_type[win*16+swb]] && sce->band_type[win*16+swb] > aac_cb_out_map[cb]) {
                     path[swb+1][cb].prev_idx = -1;
                     path[swb+1][cb].cost     = INFINITY;
                     path[swb+1][cb].run      = path[swb][cb].run + 1;
                     continue;
                 }

                 for (w = 0; w < group_len; w++) {

                     FFPsyBand *band = &s->psy.ch[s->cur_channel].psy_bands[(win+w)*16+swb];

                     rd += quantize_band_cost(s, &sce->coeffs[start + w*128],
                                              &s->scoefs[start + w*128], size,

                                              sce->sf_idx[(win+w)*16+swb], aac_cb_out_map[cb],

                                              lambda / band->threshold, INFINITY, NULL, NULL, 0);

                 }
                 cost_stay_here = path[swb][cb].cost + rd;
                 cost_get_here  = minrd              + rd + run_bits + 4;

                 if (   run_value_bits[sce->ics.num_windows == 8][path[swb][cb].run]

                     != run_value_bits[sce->ics.num_windows == 8][path[swb][cb].run+1])

                     cost_stay_here += run_bits;
                 if (cost_get_here < cost_stay_here) {
                     path[swb+1][cb].prev_idx = mincb;
                     path[swb+1][cb].cost     = cost_get_here;
                     path[swb+1][cb].run      = 1;
                 } else {
                     path[swb+1][cb].prev_idx = cb;
                     path[swb+1][cb].cost     = cost_stay_here;
                     path[swb+1][cb].run      = path[swb][cb].run + 1;
                 }
                 if (path[swb+1][cb].cost < next_minrd) {
                     next_minrd = path[swb+1][cb].cost;
                     next_mincb = cb;
                 }
             }
         }
         start += sce->ics.swb_sizes[swb];
     }
 
     //convert resulting path from backward-linked list
     stack_len = 0;

     idx       = 0;

     for (cb = 1; cb < CB_TOT_ALL; cb++)

         if (path[max_sfb][cb].cost < path[max_sfb][idx].cost)

             idx = cb;
     ppos = max_sfb;

     while (ppos > 0) {

         av_assert1(idx >= 0);

         cb = idx;
         stackrun[stack_len] = path[ppos][cb].run;
         stackcb [stack_len] = cb;
         idx = path[ppos-path[ppos][cb].run+1][cb].prev_idx;
         ppos -= path[ppos][cb].run;
         stack_len++;
     }
     //perform actual band info encoding
     start = 0;

     for (i = stack_len - 1; i >= 0; i--) {

         cb = aac_cb_out_map[stackcb[i]];
         put_bits(&s->pb, 4, cb);

         count = stackrun[i];

         memset(sce->zeroes + win*16 + start, !cb, count);

         //XXX: memset when band_type is also uint8_t

         for (j = 0; j < count; j++) {

             sce->band_type[win*16 + start] = cb;

             start++;
         }

         while (count >= run_esc) {

             put_bits(&s->pb, run_bits, run_esc);
             count -= run_esc;
         }
         put_bits(&s->pb, run_bits, count);
     }
 }
 

 typedef struct TrellisPath {
     float cost;
     int prev;
 } TrellisPath;
 

 #define TRELLIS_STAGES 121

 #define TRELLIS_STATES (SCALE_MAX_DIFF+1)

 static void set_special_band_scalefactors(AACEncContext *s, SingleChannelElement *sce)
 {

     int w, g;
     int prevscaler_n = -255, prevscaler_i = 0;

     int bands = 0;
 
     for (w = 0; w < sce->ics.num_windows; w += sce->ics.group_len[w]) {

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

             if (sce->zeroes[w*16+g])
                 continue;

             if (sce->band_type[w*16+g] == INTENSITY_BT || sce->band_type[w*16+g] == INTENSITY_BT2) {

                 sce->sf_idx[w*16+g] = av_clip(roundf(log2f(sce->is_ener[w*16+g])*2), -155, 100);

                 bands++;
             } else if (sce->band_type[w*16+g] == NOISE_BT) {

                 sce->sf_idx[w*16+g] = av_clip(3+ceilf(log2f(sce->pns_ener[w*16+g])*2), -100, 155);

                 if (prevscaler_n == -255)
                     prevscaler_n = sce->sf_idx[w*16+g];

                 bands++;
             }
         }
     }
 
     if (!bands)
         return;
 
     /* Clip the scalefactor indices */
     for (w = 0; w < sce->ics.num_windows; w += sce->ics.group_len[w]) {

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

             if (sce->zeroes[w*16+g])
                 continue;

             if (sce->band_type[w*16+g] == INTENSITY_BT || sce->band_type[w*16+g] == INTENSITY_BT2) {

                 sce->sf_idx[w*16+g] = prevscaler_i = av_clip(sce->sf_idx[w*16+g], prevscaler_i - SCALE_MAX_DIFF, prevscaler_i + SCALE_MAX_DIFF);

             } else if (sce->band_type[w*16+g] == NOISE_BT) {

                 sce->sf_idx[w*16+g] = prevscaler_n = av_clip(sce->sf_idx[w*16+g], prevscaler_n - SCALE_MAX_DIFF, prevscaler_n + SCALE_MAX_DIFF);

             }
         }
     }
 }
 

 static void search_for_quantizers_anmr(AVCodecContext *avctx, AACEncContext *s,

                                        SingleChannelElement *sce,
                                        const float lambda)

 {
     int q, w, w2, g, start = 0;

     int i, j;

     int idx;

     TrellisPath paths[TRELLIS_STAGES][TRELLIS_STATES];
     int bandaddr[TRELLIS_STAGES];

     int minq;
     float mincost;

     float q0f = FLT_MAX, q1f = 0.0f, qnrgf = 0.0f;
     int q0, q1, qcnt = 0;
 
     for (i = 0; i < 1024; i++) {
         float t = fabsf(sce->coeffs[i]);
         if (t > 0.0f) {
             q0f = FFMIN(q0f, t);
             q1f = FFMAX(q1f, t);
             qnrgf += t*t;
             qcnt++;
         }
     }
 
     if (!qcnt) {
         memset(sce->sf_idx, 0, sizeof(sce->sf_idx));
         memset(sce->zeroes, 1, sizeof(sce->zeroes));
         return;
     }
 
     //minimum scalefactor index is when minimum nonzero coefficient after quantizing is not clipped

     q0 = av_clip(coef2minsf(q0f), 0, SCALE_MAX_POS-1);

     //maximum scalefactor index is when maximum coefficient after quantizing is still not zero

     q1 = av_clip(coef2maxsf(q1f), 1, SCALE_MAX_POS);

     if (q1 - q0 > 60) {
         int q0low  = q0;
         int q1high = q1;
         //minimum scalefactor index is when maximum nonzero coefficient after quantizing is not clipped

         int qnrg = av_clip_uint8(log2f(sqrtf(qnrgf/qcnt))*4 - 31 + SCALE_ONE_POS - SCALE_DIV_512);

         q1 = qnrg + 30;
         q0 = qnrg - 30;
         if (q0 < q0low) {
             q1 += q0low - q0;
             q0  = q0low;
         } else if (q1 > q1high) {
             q0 -= q1 - q1high;
             q1  = q1high;
         }
     }

     // q0 == q1 isn't really a legal situation
     if (q0 == q1) {
         // the following is indirect but guarantees q1 != q0 && q1 near q0
         q1 = av_clip(q0+1, 1, SCALE_MAX_POS);
         q0 = av_clip(q1-1, 0, SCALE_MAX_POS - 1);
     }

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

         paths[0][i].cost    = 0.0f;
         paths[0][i].prev    = -1;

     }

     for (j = 1; j < TRELLIS_STAGES; j++) {
         for (i = 0; i < TRELLIS_STATES; i++) {

             paths[j][i].cost    = INFINITY;
             paths[j][i].prev    = -2;
         }

     }

     idx = 1;

     s->abs_pow34(s->scoefs, sce->coeffs, 1024);

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

         start = w*128;

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

             const float *coefs = &sce->coeffs[start];

             float qmin, qmax;
             int nz = 0;
 

             bandaddr[idx] = w * 16 + g;

             qmin = INT_MAX;
             qmax = 0.0f;

             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 (band->energy <= band->threshold || band->threshold == 0.0f) {

                     sce->zeroes[(w+w2)*16+g] = 1;
                     continue;
                 }
                 sce->zeroes[(w+w2)*16+g] = 0;
                 nz = 1;

                 for (i = 0; i < sce->ics.swb_sizes[g]; i++) {

                     float t = fabsf(coefs[w2*128+i]);

                     if (t > 0.0f)

                         qmin = FFMIN(qmin, t);
                     qmax = FFMAX(qmax, t);

                 }
             }

             if (nz) {

                 int minscale, maxscale;
                 float minrd = INFINITY;

                 float maxval;

                 //minimum scalefactor index is when minimum nonzero coefficient after quantizing is not clipped

                 minscale = coef2minsf(qmin);

                 //maximum scalefactor index is when maximum coefficient after quantizing is still not zero

                 maxscale = coef2maxsf(qmax);

                 minscale = av_clip(minscale - q0, 0, TRELLIS_STATES - 1);
                 maxscale = av_clip(maxscale - q0, 0, TRELLIS_STATES);

                 if (minscale == maxscale) {
                     maxscale = av_clip(minscale+1, 1, TRELLIS_STATES);
                     minscale = av_clip(maxscale-1, 0, TRELLIS_STATES - 1);
                 }

                 maxval = find_max_val(sce->ics.group_len[w], sce->ics.swb_sizes[g], s->scoefs+start);

                 for (q = minscale; q < maxscale; q++) {

                     float dist = 0;

                     int cb = find_min_book(maxval, sce->sf_idx[w*16+g]);

                     for (w2 = 0; w2 < sce->ics.group_len[w]; w2++) {

                         FFPsyBand *band = &s->psy.ch[s->cur_channel].psy_bands[(w+w2)*16+g];

                         dist += quantize_band_cost(s, coefs + w2*128, s->scoefs + start + w2*128, sce->ics.swb_sizes[g],

                                                    q + q0, cb, lambda / band->threshold, INFINITY, NULL, NULL, 0);

                     }

                     minrd = FFMIN(minrd, dist);

                     for (i = 0; i < q1 - q0; i++) {

                         float cost;

                         cost = paths[idx - 1][i].cost + dist

                                + ff_aac_scalefactor_bits[q - i + SCALE_DIFF_ZERO];

                         if (cost < paths[idx][q].cost) {

                             paths[idx][q].cost    = cost;
                             paths[idx][q].prev    = i;

                         }
                     }
                 }

             } else {

                 for (q = 0; q < q1 - q0; q++) {

                     paths[idx][q].cost = paths[idx - 1][q].cost + 1;
                     paths[idx][q].prev = q;

                 }
             }
             sce->zeroes[w*16+g] = !nz;
             start += sce->ics.swb_sizes[g];

             idx++;

         }
     }

     idx--;
     mincost = paths[idx][0].cost;
     minq    = 0;

     for (i = 1; i < TRELLIS_STATES; i++) {

         if (paths[idx][i].cost < mincost) {
             mincost = paths[idx][i].cost;
             minq = i;

         }
     }

     while (idx) {

         sce->sf_idx[bandaddr[idx]] = minq + q0;

         minq = FFMAX(paths[idx][minq].prev, 0);

         idx--;

     }
     //set the same quantizers inside window groups

     for (w = 0; w < sce->ics.num_windows; w += sce->ics.group_len[w])

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

             for (w2 = 1; w2 < sce->ics.group_len[w]; w2++)

                 sce->sf_idx[(w+w2)*16+g] = sce->sf_idx[w*16+g];
 }
 
 static void search_for_quantizers_fast(AVCodecContext *avctx, AACEncContext *s,

                                        SingleChannelElement *sce,
                                        const float lambda)

 {

     int start = 0, i, w, w2, g;
     int destbits = avctx->bit_rate * 1024.0 / avctx->sample_rate / avctx->channels * (lambda / 120.f);
     float dists[128] = { 0 }, uplims[128] = { 0 };
     float maxvals[128];
     int fflag, minscaler;
     int its  = 0;
     int allz = 0;
     float minthr = INFINITY;
 
     // for values above this the decoder might end up in an endless loop
     // due to always having more bits than what can be encoded.
     destbits = FFMIN(destbits, 5800);

     //some heuristic to determine initial quantizers will reduce search time

     //determine zero bands and upper limits

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

         start = 0;

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

             int nz = 0;
             float uplim = 0.0f, energy = 0.0f;

             for (w2 = 0; w2 < sce->ics.group_len[w]; w2++) {

                 FFPsyBand *band = &s->psy.ch[s->cur_channel].psy_bands[(w+w2)*16+g];

                 uplim += band->threshold;
                 energy += band->energy;
                 if (band->energy <= band->threshold || band->threshold == 0.0f) {

                     sce->zeroes[(w+w2)*16+g] = 1;

                     continue;

                 }

                 nz = 1;

             }

             uplims[w*16+g] = uplim *512;
             sce->band_type[w*16+g] = 0;
             sce->zeroes[w*16+g] = !nz;
             if (nz)
                 minthr = FFMIN(minthr, uplim);
             allz |= nz;
             start += sce->ics.swb_sizes[g];

         }
     }

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

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

             if (sce->zeroes[w*16+g]) {
                 sce->sf_idx[w*16+g] = SCALE_ONE_POS;
                 continue;
             }
             sce->sf_idx[w*16+g] = SCALE_ONE_POS + FFMIN(log2f(uplims[w*16+g]/minthr)*4,59);
         }

     }

 
     if (!allz)
         return;

     s->abs_pow34(s->scoefs, sce->coeffs, 1024);

     ff_quantize_band_cost_cache_init(s);
 
     for (w = 0; w < sce->ics.num_windows; w += sce->ics.group_len[w]) {
         start = w*128;

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

             const float *scaled = s->scoefs + start;
             maxvals[w*16+g] = find_max_val(sce->ics.group_len[w], sce->ics.swb_sizes[g], scaled);
             start += sce->ics.swb_sizes[g];
         }
     }
 
     //perform two-loop search
     //outer loop - improve quality
     do {
         int tbits, qstep;
         minscaler = sce->sf_idx[0];
         //inner loop - quantize spectrum to fit into given number of bits
         qstep = its ? 1 : 32;
         do {
             int prev = -1;
             tbits = 0;
             for (w = 0; w < sce->ics.num_windows; w += sce->ics.group_len[w]) {
                 start = w*128;

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

                     const float *coefs = sce->coeffs + start;
                     const float *scaled = s->scoefs + start;
                     int bits = 0;
                     int cb;
                     float dist = 0.0f;
 
                     if (sce->zeroes[w*16+g] || sce->sf_idx[w*16+g] >= 218) {
                         start += sce->ics.swb_sizes[g];
                         continue;
                     }
                     minscaler = FFMIN(minscaler, sce->sf_idx[w*16+g]);
                     cb = find_min_book(maxvals[w*16+g], sce->sf_idx[w*16+g]);
                     for (w2 = 0; w2 < sce->ics.group_len[w]; w2++) {
                         int b;
                         dist += quantize_band_cost_cached(s, w + w2, g,
                                                           coefs + w2*128,
                                                           scaled + w2*128,
                                                           sce->ics.swb_sizes[g],
                                                           sce->sf_idx[w*16+g],
                                                           cb, 1.0f, INFINITY,
                                                           &b, NULL, 0);
                         bits += b;
                     }
                     dists[w*16+g] = dist - bits;
                     if (prev != -1) {
                         bits += ff_aac_scalefactor_bits[sce->sf_idx[w*16+g] - prev + SCALE_DIFF_ZERO];
                     }
                     tbits += bits;
                     start += sce->ics.swb_sizes[g];
                     prev = sce->sf_idx[w*16+g];
                 }
             }
             if (tbits > destbits) {
                 for (i = 0; i < 128; i++)
                     if (sce->sf_idx[i] < 218 - qstep)
                         sce->sf_idx[i] += qstep;
             } else {
                 for (i = 0; i < 128; i++)
                     if (sce->sf_idx[i] > 60 - qstep)
                         sce->sf_idx[i] -= qstep;
             }
             qstep >>= 1;
             if (!qstep && tbits > destbits*1.02 && sce->sf_idx[0] < 217)
                 qstep = 1;
         } while (qstep);
 
         fflag = 0;
         minscaler = av_clip(minscaler, 60, 255 - SCALE_MAX_DIFF);
 
         for (w = 0; w < sce->ics.num_windows; w += sce->ics.group_len[w]) {
             for (g = 0; g < sce->ics.num_swb; g++) {
                 int prevsc = sce->sf_idx[w*16+g];
                 if (dists[w*16+g] > uplims[w*16+g] && sce->sf_idx[w*16+g] > 60) {
                     if (find_min_book(maxvals[w*16+g], sce->sf_idx[w*16+g]-1))
                         sce->sf_idx[w*16+g]--;
                     else //Try to make sure there is some energy in every band
                         sce->sf_idx[w*16+g]-=2;
                 }
                 sce->sf_idx[w*16+g] = av_clip(sce->sf_idx[w*16+g], minscaler, minscaler + SCALE_MAX_DIFF);
                 sce->sf_idx[w*16+g] = FFMIN(sce->sf_idx[w*16+g], 219);
                 if (sce->sf_idx[w*16+g] != prevsc)
                     fflag = 1;
                 sce->band_type[w*16+g] = find_min_book(maxvals[w*16+g], sce->sf_idx[w*16+g]);
             }
         }
         its++;
     } while (fflag && its < 10);

 }
 

 static void search_for_pns(AACEncContext *s, AVCodecContext *avctx, SingleChannelElement *sce)

 {

     FFPsyBand *band;

     int w, g, w2, i;

     int wlen = 1024 / sce->ics.num_windows;
     int bandwidth, cutoff;

     float *PNS = &s->scoefs[0*128], *PNS34 = &s->scoefs[1*128];
     float *NOR34 = &s->scoefs[3*128];

     uint8_t nextband[128];

     const float lambda = s->lambda;

     const float freq_mult = avctx->sample_rate*0.5f/wlen;

     const float thr_mult = NOISE_LAMBDA_REPLACE*(100.0f/lambda);

     const float spread_threshold = FFMIN(0.75f, NOISE_SPREAD_THRESHOLD*FFMAX(0.5f, lambda/100.f));
     const float dist_bias = av_clipf(4.f * 120 / lambda, 0.25f, 4.0f);
     const float pns_transient_energy_r = FFMIN(0.7f, lambda / 140.f);
 
     int refbits = avctx->bit_rate * 1024.0 / avctx->sample_rate

         / ((avctx->flags & AV_CODEC_FLAG_QSCALE) ? 2.0f : avctx->channels)

         * (lambda / 120.f);
 
     /** Keep this in sync with twoloop's cutoff selection */
     float rate_bandwidth_multiplier = 1.5f;

     int prev = -1000, prev_sf = -1;

     int frame_bit_rate = (avctx->flags & AV_CODEC_FLAG_QSCALE)

         ? (refbits * rate_bandwidth_multiplier * avctx->sample_rate / 1024)
         : (avctx->bit_rate / avctx->channels);
 
     frame_bit_rate *= 1.15f;
 
     if (avctx->cutoff > 0) {
         bandwidth = avctx->cutoff;
     } else {
         bandwidth = FFMAX(3000, AAC_CUTOFF_FROM_BITRATE(frame_bit_rate, 1, avctx->sample_rate));
     }
 
     cutoff = bandwidth * 2 * wlen / avctx->sample_rate;

     memcpy(sce->band_alt, sce->band_type, sizeof(sce->band_type));

     ff_init_nextband_map(sce, nextband);

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

         int wstart = w*128;

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

             int noise_sfi;

             float dist1 = 0.0f, dist2 = 0.0f, noise_amp;

             float pns_energy = 0.0f, pns_tgt_energy, energy_ratio, dist_thresh;

             float sfb_energy = 0.0f, threshold = 0.0f, spread = 2.0f;
             float min_energy = -1.0f, max_energy = 0.0f;

             const int start = wstart+sce->ics.swb_offset[g];

             const float freq = (start-wstart)*freq_mult;

             const float freq_boost = FFMAX(0.88f*freq/NOISE_LOW_LIMIT, 1.0f);

             if (freq < NOISE_LOW_LIMIT || (start-wstart) >= cutoff) {
                 if (!sce->zeroes[w*16+g])
                     prev_sf = sce->sf_idx[w*16+g];

                 continue;

             }

             for (w2 = 0; w2 < sce->ics.group_len[w]; w2++) {
                 band = &s->psy.ch[s->cur_channel].psy_bands[(w+w2)*16+g];

                 sfb_energy += band->energy;

                 spread     = FFMIN(spread, band->spread);

                 threshold  += band->threshold;

                 if (!w2) {
                     min_energy = max_energy = band->energy;
                 } else {
                     min_energy = FFMIN(min_energy, band->energy);
                     max_energy = FFMAX(max_energy, band->energy);
                 }

             }
 

             /* Ramps down at ~8000Hz and loosens the dist threshold */

             dist_thresh = av_clipf(2.5f*NOISE_LOW_LIMIT/freq, 0.5f, 2.5f) * dist_bias;
 
             /* PNS is acceptable when all of these are true:
              * 1. high spread energy (noise-like band)
              * 2. near-threshold energy (high PE means the random nature of PNS content will be noticed)
              * 3. on short window groups, all windows have similar energy (variations in energy would be destroyed by PNS)
              *
              * At this stage, point 2 is relaxed for zeroed bands near the noise threshold (hole avoidance is more important)

              */

             if ((!sce->zeroes[w*16+g] && !ff_sfdelta_can_remove_band(sce, nextband, prev_sf, w*16+g)) ||
                 ((sce->zeroes[w*16+g] || !sce->band_alt[w*16+g]) && sfb_energy < threshold*sqrtf(1.0f/freq_boost)) || spread < spread_threshold ||

                 (!sce->zeroes[w*16+g] && sce->band_alt[w*16+g] && sfb_energy > threshold*thr_mult*freq_boost) ||
                 min_energy < pns_transient_energy_r * max_energy ) {

                 sce->pns_ener[w*16+g] = sfb_energy;

                 if (!sce->zeroes[w*16+g])
                     prev_sf = sce->sf_idx[w*16+g];

                 continue;
             }
 

             pns_tgt_energy = sfb_energy*FFMIN(1.0f, spread*spread);

             noise_sfi = av_clip(roundf(log2f(pns_tgt_energy)*2), -100, 155); /* Quantize */

             noise_amp = -ff_aac_pow2sf_tab[noise_sfi + POW_SF2_ZERO];    /* Dequantize */

             if (prev != -1000) {
                 int noise_sfdiff = noise_sfi - prev + SCALE_DIFF_ZERO;
                 if (noise_sfdiff < 0 || noise_sfdiff > 2*SCALE_MAX_DIFF) {
                     if (!sce->zeroes[w*16+g])
                         prev_sf = sce->sf_idx[w*16+g];
                     continue;
                 }
             }

             for (w2 = 0; w2 < sce->ics.group_len[w]; w2++) {

                 float band_energy, scale, pns_senergy;

                 const int start_c = (w+w2)*128+sce->ics.swb_offset[g];

                 band = &s->psy.ch[s->cur_channel].psy_bands[(w+w2)*16+g];

                 for (i = 0; i < sce->ics.swb_sizes[g]; i++) {
                     s->random_state  = lcg_random(s->random_state);
                     PNS[i] = s->random_state;

                 }

                 band_energy = s->fdsp->scalarproduct_float(PNS, PNS, sce->ics.swb_sizes[g]);
                 scale = noise_amp/sqrtf(band_energy);
                 s->fdsp->vector_fmul_scalar(PNS, PNS, scale, sce->ics.swb_sizes[g]);

                 pns_senergy = s->fdsp->scalarproduct_float(PNS, PNS, sce->ics.swb_sizes[g]);
                 pns_energy += pns_senergy;

                 s->abs_pow34(NOR34, &sce->coeffs[start_c], sce->ics.swb_sizes[g]);
                 s->abs_pow34(PNS34, PNS, sce->ics.swb_sizes[g]);

                 dist1 += quantize_band_cost(s, &sce->coeffs[start_c],

                                             NOR34,
                                             sce->ics.swb_sizes[g],
                                             sce->sf_idx[(w+w2)*16+g],
                                             sce->band_alt[(w+w2)*16+g],

                                             lambda/band->threshold, INFINITY, NULL, NULL, 0);
                 /* Estimate rd on average as 5 bits for SF, 4 for the CB, plus spread energy * lambda/thr */
                 dist2 += band->energy/(band->spread*band->spread)*lambda*dist_thresh/band->threshold;
             }

             if (g && sce->band_type[w*16+g-1] == NOISE_BT) {

                 dist2 += 5;
             } else {
                 dist2 += 9;

             }

             energy_ratio = pns_tgt_energy/pns_energy; /* Compensates for quantization error */
             sce->pns_ener[w*16+g] = energy_ratio*pns_tgt_energy;

             if (sce->zeroes[w*16+g] || !sce->band_alt[w*16+g] || (energy_ratio > 0.85f && energy_ratio < 1.25f && dist2 < dist1)) {

                 sce->band_type[w*16+g] = NOISE_BT;
                 sce->zeroes[w*16+g] = 0;

                 prev = noise_sfi;

             } else {
                 if (!sce->zeroes[w*16+g])
                     prev_sf = sce->sf_idx[w*16+g];

             }
         }
     }
 }
 

 static void mark_pns(AACEncContext *s, AVCodecContext *avctx, SingleChannelElement *sce)
 {
     FFPsyBand *band;
     int w, g, w2;
     int wlen = 1024 / sce->ics.num_windows;
     int bandwidth, cutoff;
     const float lambda = s->lambda;
     const float freq_mult = avctx->sample_rate*0.5f/wlen;
     const float spread_threshold = FFMIN(0.75f, NOISE_SPREAD_THRESHOLD*FFMAX(0.5f, lambda/100.f));
     const float pns_transient_energy_r = FFMIN(0.7f, lambda / 140.f);
 
     int refbits = avctx->bit_rate * 1024.0 / avctx->sample_rate

         / ((avctx->flags & AV_CODEC_FLAG_QSCALE) ? 2.0f : avctx->channels)

         * (lambda / 120.f);
 
     /** Keep this in sync with twoloop's cutoff selection */
     float rate_bandwidth_multiplier = 1.5f;

     int frame_bit_rate = (avctx->flags & AV_CODEC_FLAG_QSCALE)

         ? (refbits * rate_bandwidth_multiplier * avctx->sample_rate / 1024)
         : (avctx->bit_rate / avctx->channels);
 
     frame_bit_rate *= 1.15f;
 
     if (avctx->cutoff > 0) {
         bandwidth = avctx->cutoff;
     } else {
         bandwidth = FFMAX(3000, AAC_CUTOFF_FROM_BITRATE(frame_bit_rate, 1, avctx->sample_rate));
     }
 
     cutoff = bandwidth * 2 * wlen / avctx->sample_rate;
 
     memcpy(sce->band_alt, sce->band_type, sizeof(sce->band_type));
     for (w = 0; w < sce->ics.num_windows; w += sce->ics.group_len[w]) {

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

             float sfb_energy = 0.0f, threshold = 0.0f, spread = 2.0f;
             float min_energy = -1.0f, max_energy = 0.0f;
             const int start = sce->ics.swb_offset[g];
             const float freq = start*freq_mult;
             const float freq_boost = FFMAX(0.88f*freq/NOISE_LOW_LIMIT, 1.0f);
             if (freq < NOISE_LOW_LIMIT || start >= cutoff) {
                 sce->can_pns[w*16+g] = 0;
                 continue;
             }
             for (w2 = 0; w2 < sce->ics.group_len[w]; w2++) {
                 band = &s->psy.ch[s->cur_channel].psy_bands[(w+w2)*16+g];
                 sfb_energy += band->energy;
                 spread     = FFMIN(spread, band->spread);
                 threshold  += band->threshold;
                 if (!w2) {
                     min_energy = max_energy = band->energy;
                 } else {
                     min_energy = FFMIN(min_energy, band->energy);
                     max_energy = FFMAX(max_energy, band->energy);
                 }
             }
 
             /* PNS is acceptable when all of these are true:
              * 1. high spread energy (noise-like band)
              * 2. near-threshold energy (high PE means the random nature of PNS content will be noticed)
              * 3. on short window groups, all windows have similar energy (variations in energy would be destroyed by PNS)
              */
             sce->pns_ener[w*16+g] = sfb_energy;
             if (sfb_energy < threshold*sqrtf(1.5f/freq_boost) || spread < spread_threshold || min_energy < pns_transient_energy_r * max_energy) {
                 sce->can_pns[w*16+g] = 0;
             } else {
                 sce->can_pns[w*16+g] = 1;
             }
         }
     }
 }
 

 static void search_for_ms(AACEncContext *s, ChannelElement *cpe)

 {

     int start = 0, i, w, w2, g, sid_sf_boost, prev_mid, prev_side;
     uint8_t nextband0[128], nextband1[128];

     float *M   = s->scoefs + 128*0, *S   = s->scoefs + 128*1;
     float *L34 = s->scoefs + 128*2, *R34 = s->scoefs + 128*3;
     float *M34 = s->scoefs + 128*4, *S34 = s->scoefs + 128*5;

     const float lambda = s->lambda;

     const float mslambda = FFMIN(1.0f, lambda / 120.f);

     SingleChannelElement *sce0 = &cpe->ch[0];
     SingleChannelElement *sce1 = &cpe->ch[1];

     if (!cpe->common_window)

         return;

     /** Scout out next nonzero bands */
     ff_init_nextband_map(sce0, nextband0);
     ff_init_nextband_map(sce1, nextband1);
 
     prev_mid = sce0->sf_idx[0];
     prev_side = sce1->sf_idx[0];
     for (w = 0; w < sce0->ics.num_windows; w += sce0->ics.group_len[w]) {

         start = 0;

         for (g = 0; g < sce0->ics.num_swb; g++) {

             float bmax = bval2bmax(g * 17.0f / sce0->ics.num_swb) / 0.0045f;

             if (!cpe->is_mask[w*16+g])
                 cpe->ms_mask[w*16+g] = 0;
             if (!sce0->zeroes[w*16+g] && !sce1->zeroes[w*16+g] && !cpe->is_mask[w*16+g]) {

                 float Mmax = 0.0f, Smax = 0.0f;
 
                 /* Must compute mid/side SF and book for the whole window group */

                 for (w2 = 0; w2 < sce0->ics.group_len[w]; w2++) {
                     for (i = 0; i < sce0->ics.swb_sizes[g]; i++) {

                         M[i] = (sce0->coeffs[start+(w+w2)*128+i]
                               + sce1->coeffs[start+(w+w2)*128+i]) * 0.5;

                         S[i] =  M[i]

                               - sce1->coeffs[start+(w+w2)*128+i];

                     }

                     s->abs_pow34(M34, M, sce0->ics.swb_sizes[g]);
                     s->abs_pow34(S34, S, sce0->ics.swb_sizes[g]);

                     for (i = 0; i < sce0->ics.swb_sizes[g]; i++ ) {
                         Mmax = FFMAX(Mmax, M34[i]);
                         Smax = FFMAX(Smax, S34[i]);
                     }
                 }
 
                 for (sid_sf_boost = 0; sid_sf_boost < 4; sid_sf_boost++) {
                     float dist1 = 0.0f, dist2 = 0.0f;
                     int B0 = 0, B1 = 0;
                     int minidx;
                     int mididx, sididx;
                     int midcb, sidcb;
 
                     minidx = FFMIN(sce0->sf_idx[w*16+g], sce1->sf_idx[w*16+g]);

                     mididx = av_clip(minidx, 0, SCALE_MAX_POS - SCALE_DIV_512);
                     sididx = av_clip(minidx - sid_sf_boost * 3, 0, SCALE_MAX_POS - SCALE_DIV_512);

                     if (sce0->band_type[w*16+g] != NOISE_BT && sce1->band_type[w*16+g] != NOISE_BT

                         && (   !ff_sfdelta_can_replace(sce0, nextband0, prev_mid, mididx, w*16+g)
                             || !ff_sfdelta_can_replace(sce1, nextband1, prev_side, sididx, w*16+g))) {

                         /* scalefactor range violation, bad stuff, will decrease quality unacceptably */
                         continue;
                     }
 

                     midcb = find_min_book(Mmax, mididx);
                     sidcb = find_min_book(Smax, sididx);
 

                     /* No CB can be zero */
                     midcb = FFMAX(1,midcb);
                     sidcb = FFMAX(1,sidcb);
 
                     for (w2 = 0; w2 < sce0->ics.group_len[w]; w2++) {
                         FFPsyBand *band0 = &s->psy.ch[s->cur_channel+0].psy_bands[(w+w2)*16+g];
                         FFPsyBand *band1 = &s->psy.ch[s->cur_channel+1].psy_bands[(w+w2)*16+g];
                         float minthr = FFMIN(band0->threshold, band1->threshold);
                         int b1,b2,b3,b4;
                         for (i = 0; i < sce0->ics.swb_sizes[g]; i++) {
                             M[i] = (sce0->coeffs[start+(w+w2)*128+i]
                                   + sce1->coeffs[start+(w+w2)*128+i]) * 0.5;
                             S[i] =  M[i]
                                   - sce1->coeffs[start+(w+w2)*128+i];
                         }
 

                         s->abs_pow34(L34, sce0->coeffs+start+(w+w2)*128, sce0->ics.swb_sizes[g]);
                         s->abs_pow34(R34, sce1->coeffs+start+(w+w2)*128, sce0->ics.swb_sizes[g]);
                         s->abs_pow34(M34, M,                         sce0->ics.swb_sizes[g]);
                         s->abs_pow34(S34, S,                         sce0->ics.swb_sizes[g]);

                         dist1 += quantize_band_cost(s, &sce0->coeffs[start + (w+w2)*128],
                                                     L34,
                                                     sce0->ics.swb_sizes[g],

                                                     sce0->sf_idx[w*16+g],
                                                     sce0->band_type[w*16+g],

                                                     lambda / band0->threshold, INFINITY, &b1, NULL, 0);
                         dist1 += quantize_band_cost(s, &sce1->coeffs[start + (w+w2)*128],
                                                     R34,
                                                     sce1->ics.swb_sizes[g],

                                                     sce1->sf_idx[w*16+g],
                                                     sce1->band_type[w*16+g],

                                                     lambda / band1->threshold, INFINITY, &b2, NULL, 0);
                         dist2 += quantize_band_cost(s, M,
                                                     M34,
                                                     sce0->ics.swb_sizes[g],

                                                     mididx,
                                                     midcb,

                                                     lambda / minthr, INFINITY, &b3, NULL, 0);
                         dist2 += quantize_band_cost(s, S,
                                                     S34,
                                                     sce1->ics.swb_sizes[g],

                                                     sididx,
                                                     sidcb,

                                                     mslambda / (minthr * bmax), INFINITY, &b4, NULL, 0);
                         B0 += b1+b2;
                         B1 += b3+b4;

                         dist1 -= b1+b2;
                         dist2 -= b3+b4;

                     }
                     cpe->ms_mask[w*16+g] = dist2 <= dist1 && B1 < B0;
                     if (cpe->ms_mask[w*16+g]) {

                         if (sce0->band_type[w*16+g] != NOISE_BT && sce1->band_type[w*16+g] != NOISE_BT) {

                             sce0->sf_idx[w*16+g] = mididx;
                             sce1->sf_idx[w*16+g] = sididx;
                             sce0->band_type[w*16+g] = midcb;
                             sce1->band_type[w*16+g] = sidcb;

                         } else if ((sce0->band_type[w*16+g] != NOISE_BT) ^ (sce1->band_type[w*16+g] != NOISE_BT)) {
                             /* ms_mask unneeded, and it confuses some decoders */
                             cpe->ms_mask[w*16+g] = 0;

                         }
                         break;
                     } else if (B1 > B0) {
                         /* More boost won't fix this */
                         break;
                     }

                 }
             }

             if (!sce0->zeroes[w*16+g] && sce0->band_type[w*16+g] < RESERVED_BT)
                 prev_mid = sce0->sf_idx[w*16+g];
             if (!sce1->zeroes[w*16+g] && !cpe->is_mask[w*16+g] && sce1->band_type[w*16+g] < RESERVED_BT)
                 prev_side = sce1->sf_idx[w*16+g];

             start += sce0->ics.swb_sizes[g];
         }
     }
 }
 

 const AACCoefficientsEncoder ff_aac_coders[AAC_CODER_NB] = {

     [AAC_CODER_ANMR] = {

         search_for_quantizers_anmr,
         encode_window_bands_info,
         quantize_and_encode_band,

         ff_aac_encode_tns_info,

         ff_aac_encode_ltp_info,

         ff_aac_encode_main_pred,

         ff_aac_adjust_common_pred,

         ff_aac_adjust_common_ltp,

         ff_aac_apply_main_pred,

         ff_aac_apply_tns,

         ff_aac_update_ltp,
         ff_aac_ltp_insert_new_frame,

         set_special_band_scalefactors,

         search_for_pns,

         mark_pns,

         ff_aac_search_for_tns,

         ff_aac_search_for_ltp,

         search_for_ms,

         ff_aac_search_for_is,
         ff_aac_search_for_pred,

     },

     [AAC_CODER_TWOLOOP] = {

         search_for_quantizers_twoloop,

         codebook_trellis_rate,

         quantize_and_encode_band,

         ff_aac_encode_tns_info,

         ff_aac_encode_ltp_info,

         ff_aac_encode_main_pred,

         ff_aac_adjust_common_pred,

         ff_aac_adjust_common_ltp,

         ff_aac_apply_main_pred,

         ff_aac_apply_tns,

         ff_aac_update_ltp,
         ff_aac_ltp_insert_new_frame,

         set_special_band_scalefactors,

         search_for_pns,

         mark_pns,

         ff_aac_search_for_tns,

         ff_aac_search_for_ltp,

         search_for_ms,

         ff_aac_search_for_is,
         ff_aac_search_for_pred,

     },

     [AAC_CODER_FAST] = {

         search_for_quantizers_fast,

         codebook_trellis_rate,

         quantize_and_encode_band,

         ff_aac_encode_tns_info,

         ff_aac_encode_ltp_info,

         ff_aac_encode_main_pred,

         ff_aac_adjust_common_pred,

         ff_aac_adjust_common_ltp,

         ff_aac_apply_main_pred,

         ff_aac_apply_tns,

         ff_aac_update_ltp,
         ff_aac_ltp_insert_new_frame,

         set_special_band_scalefactors,

         search_for_pns,

         mark_pns,

         ff_aac_search_for_tns,

         ff_aac_search_for_ltp,

         search_for_ms,

         ff_aac_search_for_is,
         ff_aac_search_for_pred,

     },
 };