text: /*
   * gain code, gain pitch and pitch delay decoding
   *
   * Copyright (c) 2008 Vladimir Voroshilov
   *
   * 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
   */
  
  #include "avcodec.h"
  #include "dsputil.h"
  #include "acelp_pitch_delay.h"
  #include "celp_math.h"
  
  int ff_acelp_decode_8bit_to_1st_delay3(int ac_index)
  {
      ac_index += 58;
      if(ac_index > 254)
          ac_index = 3 * ac_index - 510;
      return ac_index;
  }
  
  int ff_acelp_decode_4bit_to_2nd_delay3(
          int ac_index,
          int pitch_delay_min)
  {
      if(ac_index < 4)
          return 3 * (ac_index + pitch_delay_min);
      else if(ac_index < 12)
          return 3 * pitch_delay_min + ac_index + 6;
      else
          return 3 * (ac_index + pitch_delay_min) - 18;
  }
  
  int ff_acelp_decode_5_6_bit_to_2nd_delay3(
          int ac_index,
          int pitch_delay_min)
  {
          return 3 * pitch_delay_min + ac_index - 2;
  }
  
  int ff_acelp_decode_9bit_to_1st_delay6(int ac_index)
  {
      if(ac_index < 463)
          return ac_index + 105;
      else
          return 6 * (ac_index - 368);
  }
  int ff_acelp_decode_6bit_to_2nd_delay6(
          int ac_index,
          int pitch_delay_min)
  {
      return 6 * pitch_delay_min + ac_index - 3;
  }
  
  void ff_acelp_update_past_gain(
      int16_t* quant_energy,
      int gain_corr_factor,
      int log2_ma_pred_order,
      int erasure)
  {
      int i;
      int avg_gain=quant_energy[(1 << log2_ma_pred_order) - 1]; // (5.10)
  
      for(i=(1 << log2_ma_pred_order) - 1; i>0; i--)
      {
          avg_gain       += quant_energy[i-1];
          quant_energy[i] = quant_energy[i-1];
      }
  
      if(erasure)
          quant_energy[0] = FFMAX(avg_gain >> log2_ma_pred_order, -10240) - 4096; // -10 and -4 in (5.10)
      else
          quant_energy[0] = (6165 * ((ff_log2(gain_corr_factor) >> 2) - (13 << 13))) >> 13;
  }
  
  int16_t ff_acelp_decode_gain_code(
      DSPContext *dsp,
      int gain_corr_factor,
      const int16_t* fc_v,
      int mr_energy,
      const int16_t* quant_energy,
      const int16_t* ma_prediction_coeff,
      int subframe_size,
      int ma_pred_order)
  {
      int i;
  
      mr_energy <<= 10;
  
      for(i=0; i<ma_pred_order; i++)
          mr_energy += quant_energy[i] * ma_prediction_coeff[i];
  
  #ifdef G729_BITEXACT
      mr_energy += (((-6165LL * ff_log2(dsp->scalarproduct_int16(fc_v, fc_v, subframe_size, 0))) >> 3) & ~0x3ff);
  
      mr_energy = (5439 * (mr_energy >> 15)) >> 8;           // (0.15) = (0.15) * (7.23)
  
      return bidir_sal(
                 ((ff_exp2(mr_energy & 0x7fff) + 16) >> 5) * (gain_corr_factor >> 1),
                 (mr_energy >> 15) - 25
             );
  #else
      mr_energy = gain_corr_factor * exp(M_LN10 / (20 << 23) * mr_energy) /
                  sqrt(dsp->scalarproduct_int16(fc_v, fc_v, subframe_size, 0));
      return mr_energy >> 12;
  #endif
  }
  
  float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy,
                              float *prediction_error, float energy_mean,
                              const float *pred_table)
  {
      // Equations 66-69:
      // ^g_c = ^gamma_gc * 100.05 (predicted dB + mean dB - dB of fixed vector)
      // Note 10^(0.05 * -10log(average x2)) = 1/sqrt((average x2)).
      float val = fixed_gain_factor *
          exp2f(M_LOG2_10 * 0.05 *
                (ff_dot_productf(pred_table, prediction_error, 4) +
                 energy_mean)) /
          sqrtf(fixed_mean_energy);
  
      // update quantified prediction error energy history
      memmove(&prediction_error[0], &prediction_error[1],
              3 * sizeof(prediction_error[0]));
      prediction_error[3] = 20.0 * log10f(fixed_gain_factor);
  
      return val;
  }
  
  void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index,
                           const int prev_lag_int, const int subframe,
                           int third_as_first, int resolution)
  {
      /* Note n * 10923 >> 15 is floor(x/3) for 0 <= n <= 32767 */
      if (subframe == 0 || (subframe == 2 && third_as_first)) {
  
          if (pitch_index < 197)
              pitch_index += 59;
          else
              pitch_index = 3 * pitch_index - 335;
  
      } else {
          if (resolution == 4) {
              int search_range_min = av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
                                             PITCH_DELAY_MAX - 9);
  
              // decoding with 4-bit resolution
              if (pitch_index < 4) {
                  // integer only precision for [search_range_min, search_range_min+3]
                  pitch_index = 3 * (pitch_index + search_range_min) + 1;
              } else if (pitch_index < 12) {
                  // 1/3 fractional precision for [search_range_min+3 1/3, search_range_min+5 2/3]
                  pitch_index += 3 * search_range_min + 7;
              } else {
                  // integer only precision for [search_range_min+6, search_range_min+9]
                  pitch_index = 3 * (pitch_index + search_range_min - 6) + 1;
              }
          } else {
              // decoding with 5 or 6 bit resolution, 1/3 fractional precision
              pitch_index--;
  
              if (resolution == 5) {
                  pitch_index += 3 * av_clip(prev_lag_int - 10, PITCH_DELAY_MIN,
                                             PITCH_DELAY_MAX - 19);
              } else
                  pitch_index += 3 * av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
                                             PITCH_DELAY_MAX - 9);
          }
      }
      *lag_int  = pitch_index * 10923 >> 15;
      *lag_frac = pitch_index - 3 * *lag_int - 1;
  }
  