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/common.h"
  24 #include "libavutil/float_dsp.h"
  25 #include "libavutil/mathematics.h"
  26 #include "avcodec.h"
  27 #include "acelp_pitch_delay.h"
  28 #include "celp_math.h"
  29
  30 int ff_acelp_decode_8bit_to_1st_delay3(int ac_index)
  31 {
  32     ac_index += 58;
  33     if(ac_index > 254)
  34         ac_index = 3 * ac_index - 510;
  35     return ac_index;
  36 }
  37
  38 int ff_acelp_decode_4bit_to_2nd_delay3(
  39         int ac_index,
  40         int pitch_delay_min)
  41 {
  42     if(ac_index < 4)
  43         return 3 * (ac_index + pitch_delay_min);
  44     else if(ac_index < 12)
  45         return 3 * pitch_delay_min + ac_index + 6;
  46     else
  47         return 3 * (ac_index + pitch_delay_min) - 18;
  48 }
  49
  50 int ff_acelp_decode_5_6_bit_to_2nd_delay3(
  51         int ac_index,
  52         int pitch_delay_min)
  53 {
  54         return 3 * pitch_delay_min + ac_index - 2;
  55 }
  56
  57 int ff_acelp_decode_9bit_to_1st_delay6(int ac_index)
  58 {
  59     if(ac_index < 463)
  60         return ac_index + 105;
  61     else
  62         return 6 * (ac_index - 368);
  63 }
  64 int ff_acelp_decode_6bit_to_2nd_delay6(
  65         int ac_index,
  66         int pitch_delay_min)
  67 {
  68     return 6 * pitch_delay_min + ac_index - 3;
  69 }
  70
  71 void ff_acelp_update_past_gain(
  72     int16_t* quant_energy,
  73     int gain_corr_factor,
  74     int log2_ma_pred_order,
  75     int erasure)
  76 {
  77     int i;
  78     int avg_gain=quant_energy[(1 << log2_ma_pred_order) - 1]; // (5.10)
  79
  80     for(i=(1 << log2_ma_pred_order) - 1; i>0; i--)
  81     {
  82         avg_gain       += quant_energy[i-1];
  83         quant_energy[i] = quant_energy[i-1];
  84     }
  85
  86     if(erasure)
  87         quant_energy[0] = FFMAX(avg_gain >> log2_ma_pred_order, -10240) - 4096; // -10 and -4 in (5.10)
  88     else
  89         quant_energy[0] = (6165 * ((ff_log2_q15(gain_corr_factor) >> 2) - (13 << 13))) >> 13;
  90 }
  91
  92 int16_t ff_acelp_decode_gain_code(
  93     DSPContext *dsp,
  94     int gain_corr_factor,
  95     const int16_t* fc_v,
  96     int mr_energy,
  97     const int16_t* quant_energy,
  98     const int16_t* ma_prediction_coeff,
  99     int subframe_size,
 100     int ma_pred_order)
 101 {
 102     int i;
 103
 104     mr_energy <<= 10;
 105
 106     for(i=0; i<ma_pred_order; i++)
 107         mr_energy += quant_energy[i] * ma_prediction_coeff[i];
 108
 109     mr_energy = gain_corr_factor * exp(M_LN10 / (20 << 23) * mr_energy) /
 110                 sqrt(dsp->scalarproduct_int16(fc_v, fc_v, subframe_size));
 111     return mr_energy >> 12;
 112 }
 113
 114 float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy,
 115                             float *prediction_error, float energy_mean,
 116                             const float *pred_table)
 117 {
 118     // Equations 66-69:
 119     // ^g_c = ^gamma_gc * 100.05 (predicted dB + mean dB - dB of fixed vector)
 120     // Note 10^(0.05 * -10log(average x2)) = 1/sqrt((average x2)).
 121     float val = fixed_gain_factor *
 122         exp2f(M_LOG2_10 * 0.05 *
 123               (avpriv_scalarproduct_float_c(pred_table, prediction_error, 4) +
 124                energy_mean)) /
 125         sqrtf(fixed_mean_energy);
 126
 127     // update quantified prediction error energy history
 128     memmove(&prediction_error[0], &prediction_error[1],
 129             3 * sizeof(prediction_error[0]));
 130     prediction_error[3] = 20.0 * log10f(fixed_gain_factor);
 131
 132     return val;
 133 }
 134
 135 void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index,
 136                          const int prev_lag_int, const int subframe,
 137                          int third_as_first, int resolution)
 138 {
 139     /* Note n * 10923 >> 15 is floor(x/3) for 0 <= n <= 32767 */
 140     if (subframe == 0 || (subframe == 2 && third_as_first)) {
 141
 142         if (pitch_index < 197)
 143             pitch_index += 59;
 144         else
 145             pitch_index = 3 * pitch_index - 335;
 146
 147     } else {
 148         if (resolution == 4) {
 149             int search_range_min = av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
 150                                            PITCH_DELAY_MAX - 9);
 151
 152             // decoding with 4-bit resolution
 153             if (pitch_index < 4) {
 154                 // integer only precision for [search_range_min, search_range_min+3]
 155                 pitch_index = 3 * (pitch_index + search_range_min) + 1;
 156             } else if (pitch_index < 12) {
 157                 // 1/3 fractional precision for [search_range_min+3 1/3, search_range_min+5 2/3]
 158                 pitch_index += 3 * search_range_min + 7;
 159             } else {
 160                 // integer only precision for [search_range_min+6, search_range_min+9]
 161                 pitch_index = 3 * (pitch_index + search_range_min - 6) + 1;
 162             }
 163         } else {
 164             // decoding with 5 or 6 bit resolution, 1/3 fractional precision
 165             pitch_index--;
 166
 167             if (resolution == 5) {
 168                 pitch_index += 3 * av_clip(prev_lag_int - 10, PITCH_DELAY_MIN,
 169                                            PITCH_DELAY_MAX - 19);
 170             } else
 171                 pitch_index += 3 * av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
 172                                            PITCH_DELAY_MAX - 9);
 173         }
 174     }
 175     *lag_int  = pitch_index * 10923 >> 15;
 176     *lag_frac = pitch_index - 3 * *lag_int - 1;
 177 }