git.sesse.net Git - ffmpeg/blob - libavcodec/acelp_pitch_delay.c

   1 /*
   2  * gain code, gain pitch and pitch delay decoding
   3  *
   4  * Copyright (c) 2008 Vladimir Voroshilov
   5  *
   6  * This file is part of Libav.
   7  *
   8  * Libav is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * Libav is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with Libav; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include "libavutil/mathematics.h"
  24 #include "avcodec.h"
  25 #include "dsputil.h"
  26 #include "acelp_pitch_delay.h"
  27 #include "celp_math.h"
  28
  29 int ff_acelp_decode_8bit_to_1st_delay3(int ac_index)
  30 {
  31     ac_index += 58;
  32     if(ac_index > 254)
  33         ac_index = 3 * ac_index - 510;
  34     return ac_index;
  35 }
  36
  37 int ff_acelp_decode_4bit_to_2nd_delay3(
  38         int ac_index,
  39         int pitch_delay_min)
  40 {
  41     if(ac_index < 4)
  42         return 3 * (ac_index + pitch_delay_min);
  43     else if(ac_index < 12)
  44         return 3 * pitch_delay_min + ac_index + 6;
  45     else
  46         return 3 * (ac_index + pitch_delay_min) - 18;
  47 }
  48
  49 int ff_acelp_decode_5_6_bit_to_2nd_delay3(
  50         int ac_index,
  51         int pitch_delay_min)
  52 {
  53         return 3 * pitch_delay_min + ac_index - 2;
  54 }
  55
  56 int ff_acelp_decode_9bit_to_1st_delay6(int ac_index)
  57 {
  58     if(ac_index < 463)
  59         return ac_index + 105;
  60     else
  61         return 6 * (ac_index - 368);
  62 }
  63 int ff_acelp_decode_6bit_to_2nd_delay6(
  64         int ac_index,
  65         int pitch_delay_min)
  66 {
  67     return 6 * pitch_delay_min + ac_index - 3;
  68 }
  69
  70 void ff_acelp_update_past_gain(
  71     int16_t* quant_energy,
  72     int gain_corr_factor,
  73     int log2_ma_pred_order,
  74     int erasure)
  75 {
  76     int i;
  77     int avg_gain=quant_energy[(1 << log2_ma_pred_order) - 1]; // (5.10)
  78
  79     for(i=(1 << log2_ma_pred_order) - 1; i>0; i--)
  80     {
  81         avg_gain       += quant_energy[i-1];
  82         quant_energy[i] = quant_energy[i-1];
  83     }
  84
  85     if(erasure)
  86         quant_energy[0] = FFMAX(avg_gain >> log2_ma_pred_order, -10240) - 4096; // -10 and -4 in (5.10)
  87     else
  88         quant_energy[0] = (6165 * ((ff_log2(gain_corr_factor) >> 2) - (13 << 13))) >> 13;
  89 }
  90
  91 int16_t ff_acelp_decode_gain_code(
  92     DSPContext *dsp,
  93     int gain_corr_factor,
  94     const int16_t* fc_v,
  95     int mr_energy,
  96     const int16_t* quant_energy,
  97     const int16_t* ma_prediction_coeff,
  98     int subframe_size,
  99     int ma_pred_order)
 100 {
 101     int i;
 102
 103     mr_energy <<= 10;
 104
 105     for(i=0; i<ma_pred_order; i++)
 106         mr_energy += quant_energy[i] * ma_prediction_coeff[i];
 107
 108     mr_energy = gain_corr_factor * exp(M_LN10 / (20 << 23) * mr_energy) /
 109                 sqrt(dsp->scalarproduct_int16(fc_v, fc_v, subframe_size));
 110     return mr_energy >> 12;
 111 }
 112
 113 float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy,
 114                             float *prediction_error, float energy_mean,
 115                             const float *pred_table)
 116 {
 117     // Equations 66-69:
 118     // ^g_c = ^gamma_gc * 100.05 (predicted dB + mean dB - dB of fixed vector)
 119     // Note 10^(0.05 * -10log(average x2)) = 1/sqrt((average x2)).
 120     float val = fixed_gain_factor *
 121         exp2f(M_LOG2_10 * 0.05 *
 122               (ff_dot_productf(pred_table, prediction_error, 4) +
 123                energy_mean)) /
 124         sqrtf(fixed_mean_energy);
 125
 126     // update quantified prediction error energy history
 127     memmove(&prediction_error[0], &prediction_error[1],
 128             3 * sizeof(prediction_error[0]));
 129     prediction_error[3] = 20.0 * log10f(fixed_gain_factor);
 130
 131     return val;
 132 }
 133
 134 void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index,
 135                          const int prev_lag_int, const int subframe,
 136                          int third_as_first, int resolution)
 137 {
 138     /* Note n * 10923 >> 15 is floor(x/3) for 0 <= n <= 32767 */
 139     if (subframe == 0 || (subframe == 2 && third_as_first)) {
 140
 141         if (pitch_index < 197)
 142             pitch_index += 59;
 143         else
 144             pitch_index = 3 * pitch_index - 335;
 145
 146     } else {
 147         if (resolution == 4) {
 148             int search_range_min = av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
 149                                            PITCH_DELAY_MAX - 9);
 150
 151             // decoding with 4-bit resolution
 152             if (pitch_index < 4) {
 153                 // integer only precision for [search_range_min, search_range_min+3]
 154                 pitch_index = 3 * (pitch_index + search_range_min) + 1;
 155             } else if (pitch_index < 12) {
 156                 // 1/3 fractional precision for [search_range_min+3 1/3, search_range_min+5 2/3]
 157                 pitch_index += 3 * search_range_min + 7;
 158             } else {
 159                 // integer only precision for [search_range_min+6, search_range_min+9]
 160                 pitch_index = 3 * (pitch_index + search_range_min - 6) + 1;
 161             }
 162         } else {
 163             // decoding with 5 or 6 bit resolution, 1/3 fractional precision
 164             pitch_index--;
 165
 166             if (resolution == 5) {
 167                 pitch_index += 3 * av_clip(prev_lag_int - 10, PITCH_DELAY_MIN,
 168                                            PITCH_DELAY_MAX - 19);
 169             } else
 170                 pitch_index += 3 * av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
 171                                            PITCH_DELAY_MAX - 9);
 172         }
 173     }
 174     *lag_int  = pitch_index * 10923 >> 15;
 175     *lag_frac = pitch_index - 3 * *lag_int - 1;
 176 }