• Main Page
  • Related Pages
  • Modules
  • Data Structures
  • Files
  • Examples
  • File List
  • Globals

libavcodec/acelp_pitch_delay.c

Go to the documentation of this file.
00001 /*
00002  * gain code, gain pitch and pitch delay decoding
00003  *
00004  * Copyright (c) 2008 Vladimir Voroshilov
00005  *
00006  * This file is part of Libav.
00007  *
00008  * Libav is free software; you can redistribute it and/or
00009  * modify it under the terms of the GNU Lesser General Public
00010  * License as published by the Free Software Foundation; either
00011  * version 2.1 of the License, or (at your option) any later version.
00012  *
00013  * Libav is distributed in the hope that it will be useful,
00014  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00015  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00016  * Lesser General Public License for more details.
00017  *
00018  * You should have received a copy of the GNU Lesser General Public
00019  * License along with Libav; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00021  */
00022 
00023 #include "libavutil/mathematics.h"
00024 #include "avcodec.h"
00025 #include "dsputil.h"
00026 #include "acelp_pitch_delay.h"
00027 #include "celp_math.h"
00028 
00029 int ff_acelp_decode_8bit_to_1st_delay3(int ac_index)
00030 {
00031     ac_index += 58;
00032     if(ac_index > 254)
00033         ac_index = 3 * ac_index - 510;
00034     return ac_index;
00035 }
00036 
00037 int ff_acelp_decode_4bit_to_2nd_delay3(
00038         int ac_index,
00039         int pitch_delay_min)
00040 {
00041     if(ac_index < 4)
00042         return 3 * (ac_index + pitch_delay_min);
00043     else if(ac_index < 12)
00044         return 3 * pitch_delay_min + ac_index + 6;
00045     else
00046         return 3 * (ac_index + pitch_delay_min) - 18;
00047 }
00048 
00049 int ff_acelp_decode_5_6_bit_to_2nd_delay3(
00050         int ac_index,
00051         int pitch_delay_min)
00052 {
00053         return 3 * pitch_delay_min + ac_index - 2;
00054 }
00055 
00056 int ff_acelp_decode_9bit_to_1st_delay6(int ac_index)
00057 {
00058     if(ac_index < 463)
00059         return ac_index + 105;
00060     else
00061         return 6 * (ac_index - 368);
00062 }
00063 int ff_acelp_decode_6bit_to_2nd_delay6(
00064         int ac_index,
00065         int pitch_delay_min)
00066 {
00067     return 6 * pitch_delay_min + ac_index - 3;
00068 }
00069 
00070 void ff_acelp_update_past_gain(
00071     int16_t* quant_energy,
00072     int gain_corr_factor,
00073     int log2_ma_pred_order,
00074     int erasure)
00075 {
00076     int i;
00077     int avg_gain=quant_energy[(1 << log2_ma_pred_order) - 1]; // (5.10)
00078 
00079     for(i=(1 << log2_ma_pred_order) - 1; i>0; i--)
00080     {
00081         avg_gain       += quant_energy[i-1];
00082         quant_energy[i] = quant_energy[i-1];
00083     }
00084 
00085     if(erasure)
00086         quant_energy[0] = FFMAX(avg_gain >> log2_ma_pred_order, -10240) - 4096; // -10 and -4 in (5.10)
00087     else
00088         quant_energy[0] = (6165 * ((ff_log2(gain_corr_factor) >> 2) - (13 << 13))) >> 13;
00089 }
00090 
00091 int16_t ff_acelp_decode_gain_code(
00092     DSPContext *dsp,
00093     int gain_corr_factor,
00094     const int16_t* fc_v,
00095     int mr_energy,
00096     const int16_t* quant_energy,
00097     const int16_t* ma_prediction_coeff,
00098     int subframe_size,
00099     int ma_pred_order)
00100 {
00101     int i;
00102 
00103     mr_energy <<= 10;
00104 
00105     for(i=0; i<ma_pred_order; i++)
00106         mr_energy += quant_energy[i] * ma_prediction_coeff[i];
00107 
00108     mr_energy = gain_corr_factor * exp(M_LN10 / (20 << 23) * mr_energy) /
00109                 sqrt(dsp->scalarproduct_int16(fc_v, fc_v, subframe_size, 0));
00110     return mr_energy >> 12;
00111 }
00112 
00113 float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy,
00114                             float *prediction_error, float energy_mean,
00115                             const float *pred_table)
00116 {
00117     // Equations 66-69:
00118     // ^g_c = ^gamma_gc * 100.05 (predicted dB + mean dB - dB of fixed vector)
00119     // Note 10^(0.05 * -10log(average x2)) = 1/sqrt((average x2)).
00120     float val = fixed_gain_factor *
00121         exp2f(M_LOG2_10 * 0.05 *
00122               (ff_dot_productf(pred_table, prediction_error, 4) +
00123                energy_mean)) /
00124         sqrtf(fixed_mean_energy);
00125 
00126     // update quantified prediction error energy history
00127     memmove(&prediction_error[0], &prediction_error[1],
00128             3 * sizeof(prediction_error[0]));
00129     prediction_error[3] = 20.0 * log10f(fixed_gain_factor);
00130 
00131     return val;
00132 }
00133 
00134 void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index,
00135                          const int prev_lag_int, const int subframe,
00136                          int third_as_first, int resolution)
00137 {
00138     /* Note n * 10923 >> 15 is floor(x/3) for 0 <= n <= 32767 */
00139     if (subframe == 0 || (subframe == 2 && third_as_first)) {
00140 
00141         if (pitch_index < 197)
00142             pitch_index += 59;
00143         else
00144             pitch_index = 3 * pitch_index - 335;
00145 
00146     } else {
00147         if (resolution == 4) {
00148             int search_range_min = av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
00149                                            PITCH_DELAY_MAX - 9);
00150 
00151             // decoding with 4-bit resolution
00152             if (pitch_index < 4) {
00153                 // integer only precision for [search_range_min, search_range_min+3]
00154                 pitch_index = 3 * (pitch_index + search_range_min) + 1;
00155             } else if (pitch_index < 12) {
00156                 // 1/3 fractional precision for [search_range_min+3 1/3, search_range_min+5 2/3]
00157                 pitch_index += 3 * search_range_min + 7;
00158             } else {
00159                 // integer only precision for [search_range_min+6, search_range_min+9]
00160                 pitch_index = 3 * (pitch_index + search_range_min - 6) + 1;
00161             }
00162         } else {
00163             // decoding with 5 or 6 bit resolution, 1/3 fractional precision
00164             pitch_index--;
00165 
00166             if (resolution == 5) {
00167                 pitch_index += 3 * av_clip(prev_lag_int - 10, PITCH_DELAY_MIN,
00168                                            PITCH_DELAY_MAX - 19);
00169             } else
00170                 pitch_index += 3 * av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
00171                                            PITCH_DELAY_MAX - 9);
00172         }
00173     }
00174     *lag_int  = pitch_index * 10923 >> 15;
00175     *lag_frac = pitch_index - 3 * *lag_int - 1;
00176 }
Generated on Thu Jan 24 2013 17:08:50 for Libav by doxygen 1.7.1