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libavcodec/acelp_pitch_delay.c

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00001 /*
00002  * gain code, gain pitch and pitch delay decoding
00003  *
00004  * Copyright (c) 2008 Vladimir Voroshilov
00005  *
00006  * This file is part of FFmpeg.
00007  *
00008  * FFmpeg 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  * FFmpeg 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 FFmpeg; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00021  */
00022 
00023 #include "avcodec.h"
00024 #include "dsputil.h"
00025 #include "acelp_pitch_delay.h"
00026 #include "celp_math.h"
00027 
00028 int ff_acelp_decode_8bit_to_1st_delay3(int ac_index)
00029 {
00030     ac_index += 58;
00031     if(ac_index > 254)
00032         ac_index = 3 * ac_index - 510;
00033     return ac_index;
00034 }
00035 
00036 int ff_acelp_decode_4bit_to_2nd_delay3(
00037         int ac_index,
00038         int pitch_delay_min)
00039 {
00040     if(ac_index < 4)
00041         return 3 * (ac_index + pitch_delay_min);
00042     else if(ac_index < 12)
00043         return 3 * pitch_delay_min + ac_index + 6;
00044     else
00045         return 3 * (ac_index + pitch_delay_min) - 18;
00046 }
00047 
00048 int ff_acelp_decode_5_6_bit_to_2nd_delay3(
00049         int ac_index,
00050         int pitch_delay_min)
00051 {
00052         return 3 * pitch_delay_min + ac_index - 2;
00053 }
00054 
00055 int ff_acelp_decode_9bit_to_1st_delay6(int ac_index)
00056 {
00057     if(ac_index < 463)
00058         return ac_index + 105;
00059     else
00060         return 6 * (ac_index - 368);
00061 }
00062 int ff_acelp_decode_6bit_to_2nd_delay6(
00063         int ac_index,
00064         int pitch_delay_min)
00065 {
00066     return 6 * pitch_delay_min + ac_index - 3;
00067 }
00068 
00069 void ff_acelp_update_past_gain(
00070     int16_t* quant_energy,
00071     int gain_corr_factor,
00072     int log2_ma_pred_order,
00073     int erasure)
00074 {
00075     int i;
00076     int avg_gain=quant_energy[(1 << log2_ma_pred_order) - 1]; // (5.10)
00077 
00078     for(i=(1 << log2_ma_pred_order) - 1; i>0; i--)
00079     {
00080         avg_gain       += quant_energy[i-1];
00081         quant_energy[i] = quant_energy[i-1];
00082     }
00083 
00084     if(erasure)
00085         quant_energy[0] = FFMAX(avg_gain >> log2_ma_pred_order, -10240) - 4096; // -10 and -4 in (5.10)
00086     else
00087         quant_energy[0] = (6165 * ((ff_log2(gain_corr_factor) >> 2) - (13 << 13))) >> 13;
00088 }
00089 
00090 int16_t ff_acelp_decode_gain_code(
00091     DSPContext *dsp,
00092     int gain_corr_factor,
00093     const int16_t* fc_v,
00094     int mr_energy,
00095     const int16_t* quant_energy,
00096     const int16_t* ma_prediction_coeff,
00097     int subframe_size,
00098     int ma_pred_order)
00099 {
00100     int i;
00101 
00102     mr_energy <<= 10;
00103 
00104     for(i=0; i<ma_pred_order; i++)
00105         mr_energy += quant_energy[i] * ma_prediction_coeff[i];
00106 
00107 #ifdef G729_BITEXACT
00108     mr_energy += (((-6165LL * ff_log2(dsp->scalarproduct_int16(fc_v, fc_v, subframe_size, 0))) >> 3) & ~0x3ff);
00109 
00110     mr_energy = (5439 * (mr_energy >> 15)) >> 8;           // (0.15) = (0.15) * (7.23)
00111 
00112     return bidir_sal(
00113                ((ff_exp2(mr_energy & 0x7fff) + 16) >> 5) * (gain_corr_factor >> 1),
00114                (mr_energy >> 15) - 25
00115            );
00116 #else
00117     mr_energy = gain_corr_factor * exp(M_LN10 / (20 << 23) * mr_energy) /
00118                 sqrt(dsp->scalarproduct_int16(fc_v, fc_v, subframe_size, 0));
00119     return mr_energy >> 12;
00120 #endif
00121 }
00122 
00123 float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy,
00124                             float *prediction_error, float energy_mean,
00125                             const float *pred_table)
00126 {
00127     // Equations 66-69:
00128     // ^g_c = ^gamma_gc * 100.05 (predicted dB + mean dB - dB of fixed vector)
00129     // Note 10^(0.05 * -10log(average x2)) = 1/sqrt((average x2)).
00130     float val = fixed_gain_factor *
00131         exp2f(M_LOG2_10 * 0.05 *
00132               (ff_dot_productf(pred_table, prediction_error, 4) +
00133                energy_mean)) /
00134         sqrtf(fixed_mean_energy);
00135 
00136     // update quantified prediction error energy history
00137     memmove(&prediction_error[0], &prediction_error[1],
00138             3 * sizeof(prediction_error[0]));
00139     prediction_error[3] = 20.0 * log10f(fixed_gain_factor);
00140 
00141     return val;
00142 }
00143 
00144 void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index,
00145                          const int prev_lag_int, const int subframe,
00146                          int third_as_first, int resolution)
00147 {
00148     /* Note n * 10923 >> 15 is floor(x/3) for 0 <= n <= 32767 */
00149     if (subframe == 0 || (subframe == 2 && third_as_first)) {
00150 
00151         if (pitch_index < 197)
00152             pitch_index += 59;
00153         else
00154             pitch_index = 3 * pitch_index - 335;
00155 
00156     } else {
00157         if (resolution == 4) {
00158             int search_range_min = av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
00159                                            PITCH_DELAY_MAX - 9);
00160 
00161             // decoding with 4-bit resolution
00162             if (pitch_index < 4) {
00163                 // integer only precision for [search_range_min, search_range_min+3]
00164                 pitch_index = 3 * (pitch_index + search_range_min) + 1;
00165             } else if (pitch_index < 12) {
00166                 // 1/3 fractional precision for [search_range_min+3 1/3, search_range_min+5 2/3]
00167                 pitch_index += 3 * search_range_min + 7;
00168             } else {
00169                 // integer only precision for [search_range_min+6, search_range_min+9]
00170                 pitch_index = 3 * (pitch_index + search_range_min - 6) + 1;
00171             }
00172         } else {
00173             // decoding with 5 or 6 bit resolution, 1/3 fractional precision
00174             pitch_index--;
00175 
00176             if (resolution == 5) {
00177                 pitch_index += 3 * av_clip(prev_lag_int - 10, PITCH_DELAY_MIN,
00178                                            PITCH_DELAY_MAX - 19);
00179             } else
00180                 pitch_index += 3 * av_clip(prev_lag_int - 5, PITCH_DELAY_MIN,
00181                                            PITCH_DELAY_MAX - 9);
00182         }
00183     }
00184     *lag_int  = pitch_index * 10923 >> 15;
00185     *lag_frac = pitch_index - 3 * *lag_int - 1;
00186 }

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