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 #include "audiodsp.h"
  30
  31 int ff_acelp_decode_8bit_to_1st_delay3(int ac_index)
  32 {
  33     ac_index += 58;
  34     if(ac_index > 254)
  35         ac_index = 3 * ac_index - 510;
  36     return ac_index;
  37 }
  38
  39 int ff_acelp_decode_4bit_to_2nd_delay3(
  40         int ac_index,
  41         int pitch_delay_min)
  42 {
  43     if(ac_index < 4)
  44         return 3 * (ac_index + pitch_delay_min);
  45     else if(ac_index < 12)
  46         return 3 * pitch_delay_min + ac_index + 6;
  47     else
  48         return 3 * (ac_index + pitch_delay_min) - 18;
  49 }
  50
  51 int ff_acelp_decode_5_6_bit_to_2nd_delay3(
  52         int ac_index,
  53         int pitch_delay_min)
  54 {
  55         return 3 * pitch_delay_min + ac_index - 2;
  56 }
  57
  58 int ff_acelp_decode_9bit_to_1st_delay6(int ac_index)
  59 {
  60     if(ac_index < 463)
  61         return ac_index + 105;
  62     else
  63         return 6 * (ac_index - 368);
  64 }
  65 int ff_acelp_decode_6bit_to_2nd_delay6(
  66         int ac_index,
  67         int pitch_delay_min)
  68 {
  69     return 6 * pitch_delay_min + ac_index - 3;
  70 }
  71
  72 void ff_acelp_update_past_gain(
  73     int16_t* quant_energy,
  74     int gain_corr_factor,
  75     int log2_ma_pred_order,
  76     int erasure)
  77 {
  78     int i;
  79     int avg_gain=quant_energy[(1 << log2_ma_pred_order) - 1]; // (5.10)
  80
  81     for(i=(1 << log2_ma_pred_order) - 1; i>0; i--)
  82     {
  83         avg_gain       += quant_energy[i-1];
  84         quant_energy[i] = quant_energy[i-1];
  85     }
  86
  87     if(erasure)
  88         quant_energy[0] = FFMAX(avg_gain >> log2_ma_pred_order, -10240) - 4096; // -10 and -4 in (5.10)
  89     else
  90         quant_energy[0] = (6165 * ((ff_log2_q15(gain_corr_factor) >> 2) - (13 << 13))) >> 13;
  91 }
  92
  93 int16_t ff_acelp_decode_gain_code(
  94     AudioDSPContext *adsp,
  95     int gain_corr_factor,
  96     const int16_t* fc_v,
  97     int mr_energy,
  98     const int16_t* quant_energy,
  99     const int16_t* ma_prediction_coeff,
 100     int subframe_size,
 101     int ma_pred_order)
 102 {
 103     int i;
 104
 105     mr_energy <<= 10;
 106
 107     for(i=0; i<ma_pred_order; i++)
 108         mr_energy += quant_energy[i] * ma_prediction_coeff[i];
 109
 110     mr_energy = gain_corr_factor * exp(M_LN10 / (20 << 23) * mr_energy) /
 111                 sqrt(adsp->scalarproduct_int16(fc_v, fc_v, subframe_size));
 112     return mr_energy >> 12;
 113 }
 114
 115 float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy,
 116                             float *prediction_error, float energy_mean,
 117                             const float *pred_table)
 118 {
 119     // Equations 66-69:
 120     // ^g_c = ^gamma_gc * 100.05 (predicted dB + mean dB - dB of fixed vector)
 121     // Note 10^(0.05 * -10log(average x2)) = 1/sqrt((average x2)).
 122     float val = fixed_gain_factor *
 123         exp2f(M_LOG2_10 * 0.05 *
 124               (avpriv_scalarproduct_float_c(pred_table, prediction_error, 4) +
 125                energy_mean)) /
 126         sqrtf(fixed_mean_energy);
 127
 128     // update quantified prediction error energy history
 129     memmove(&prediction_error[0], &prediction_error[1],
 130             3 * sizeof(prediction_error[0]));
 131     prediction_error[3] = 20.0 * log10f(fixed_gain_factor);
 132
 133     return val;
 134 }
 135
 136 void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index,
 137                          const int prev_lag_int, const int subframe,
 138                          int third_as_first, int resolution)
 139 {
 140     /* Note n * 10923 >> 15 is floor(x/3) for 0 <= n <= 32767 */
 141     if (subframe == 0 || (subframe == 2 && third_as_first)) {
 142
 143         if (pitch_index < 197)
 144             pitch_index += 59;
 145         else
 146             pitch_index = 3 * pitch_index - 335;
 147
 148     } else {
 149         if (resolution == 4) {
 150             int search_range_min = av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
 151                                            PITCH_DELAY_MAX - 9);
 152
 153             // decoding with 4-bit resolution
 154             if (pitch_index < 4) {
 155                 // integer only precision for [search_range_min, search_range_min+3]
 156                 pitch_index = 3 * (pitch_index + search_range_min) + 1;
 157             } else if (pitch_index < 12) {
 158                 // 1/3 fractional precision for [search_range_min+3 1/3, search_range_min+5 2/3]
 159                 pitch_index += 3 * search_range_min + 7;
 160             } else {
 161                 // integer only precision for [search_range_min+6, search_range_min+9]
 162                 pitch_index = 3 * (pitch_index + search_range_min - 6) + 1;
 163             }
 164         } else {
 165             // decoding with 5 or 6 bit resolution, 1/3 fractional precision
 166             pitch_index--;
 167
 168             if (resolution == 5) {
 169                 pitch_index += 3 * av_clip(prev_lag_int - 10, PITCH_DELAY_MIN,
 170                                            PITCH_DELAY_MAX - 19);
 171             } else
 172                 pitch_index += 3 * av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
 173                                            PITCH_DELAY_MAX - 9);
 174         }
 175     }
 176     *lag_int  = pitch_index * 10923 >> 15;
 177     *lag_frac = pitch_index - 3 * *lag_int - 1;
 178 }