1/* 2 * gain code, gain pitch and pitch delay decoding 3 * 4 * Copyright (c) 2008 Vladimir Voroshilov 5 * 6 * This file is part of FFmpeg. 7 * 8 * FFmpeg 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 * FFmpeg 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 FFmpeg; if not, write to the Free Software 20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 21 */ 22 23#ifndef AVCODEC_ACELP_PITCH_DELAY_H 24#define AVCODEC_ACELP_PITCH_DELAY_H 25 26#include <stdint.h> 27 28#include "audiodsp.h" 29 30#define PITCH_DELAY_MIN 20 31#define PITCH_DELAY_MAX 143 32 33/** 34 * @brief Decode pitch delay of the first subframe encoded by 8 bits with 1/3 35 * resolution. 36 * @param ac_index adaptive codebook index (8 bits) 37 * 38 * @return pitch delay in 1/3 units 39 * 40 * Pitch delay is coded: 41 * with 1/3 resolution, 19 < pitch_delay < 85 42 * integers only, 85 <= pitch_delay <= 143 43 */ 44int ff_acelp_decode_8bit_to_1st_delay3(int ac_index); 45 46/** 47 * @brief Decode pitch delay of the second subframe encoded by 5 or 6 bits 48 * with 1/3 precision. 49 * @param ac_index adaptive codebook index (5 or 6 bits) 50 * @param pitch_delay_min lower bound (integer) of pitch delay interval 51 * for second subframe 52 * 53 * @return pitch delay in 1/3 units 54 * 55 * Pitch delay is coded: 56 * with 1/3 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5 57 * 58 * @remark The routine is used in G.729 @@8k, AMR @@10.2k, AMR @@7.95k, 59 * AMR @@7.4k for the second subframe. 60 */ 61int ff_acelp_decode_5_6_bit_to_2nd_delay3( 62 int ac_index, 63 int pitch_delay_min); 64 65/** 66 * @brief Decode pitch delay with 1/3 precision. 67 * @param ac_index adaptive codebook index (4 bits) 68 * @param pitch_delay_min lower bound (integer) of pitch delay interval for 69 * second subframe 70 * 71 * @return pitch delay in 1/3 units 72 * 73 * Pitch delay is coded: 74 * integers only, -6 < pitch_delay - int(prev_pitch_delay) <= -2 75 * with 1/3 resolution, -2 < pitch_delay - int(prev_pitch_delay) < 1 76 * integers only, 1 <= pitch_delay - int(prev_pitch_delay) < 5 77 * 78 * @remark The routine is used in G.729 @@6.4k, AMR @@6.7k, AMR @@5.9k, 79 * AMR @@5.15k, AMR @@4.75k for the second subframe. 80 */ 81int ff_acelp_decode_4bit_to_2nd_delay3( 82 int ac_index, 83 int pitch_delay_min); 84 85/** 86 * @brief Decode pitch delay of the first subframe encoded by 9 bits 87 * with 1/6 precision. 88 * @param ac_index adaptive codebook index (9 bits) 89 * 90 * @return pitch delay in 1/6 units 91 * 92 * Pitch delay is coded: 93 * with 1/6 resolution, 17 < pitch_delay < 95 94 * integers only, 95 <= pitch_delay <= 143 95 * 96 * @remark The routine is used in AMR @@12.2k for the first and third subframes. 97 */ 98int ff_acelp_decode_9bit_to_1st_delay6(int ac_index); 99 100/** 101 * @brief Decode pitch delay of the second subframe encoded by 6 bits 102 * with 1/6 precision. 103 * @param ac_index adaptive codebook index (6 bits) 104 * @param pitch_delay_min lower bound (integer) of pitch delay interval for 105 * second subframe 106 * 107 * @return pitch delay in 1/6 units 108 * 109 * Pitch delay is coded: 110 * with 1/6 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5 111 * 112 * @remark The routine is used in AMR @@12.2k for the second and fourth subframes. 113 */ 114int ff_acelp_decode_6bit_to_2nd_delay6( 115 int ac_index, 116 int pitch_delay_min); 117 118/** 119 * @brief Update past quantized energies 120 * @param[in,out] quant_energy past quantized energies (5.10) 121 * @param gain_corr_factor gain correction factor 122 * @param log2_ma_pred_order log2() of MA prediction order 123 * @param erasure frame erasure flag 124 * 125 * If frame erasure flag is not equal to zero, memory is updated with 126 * averaged energy, attenuated by 4dB: 127 * max(avg(quant_energy[i])-4, -14), i=0,ma_pred_order 128 * 129 * In normal mode memory is updated with 130 * Er - Ep = 20 * log10(gain_corr_factor) 131 * 132 * @remark The routine is used in G.729 and AMR (all modes). 133 */ 134void ff_acelp_update_past_gain( 135 int16_t* quant_energy, 136 int gain_corr_factor, 137 int log2_ma_pred_order, 138 int erasure); 139 140/** 141 * @brief Decode the adaptive codebook gain and add 142 * correction (4.1.5 and 3.9.1 of G.729). 143 * @param adsp initialized audio DSP context 144 * @param gain_corr_factor gain correction factor (2.13) 145 * @param fc_v fixed-codebook vector (2.13) 146 * @param mr_energy mean innovation energy and fixed-point correction (7.13) 147 * @param[in,out] quant_energy past quantized energies (5.10) 148 * @param subframe_size length of subframe 149 * 150 * @return quantized fixed-codebook gain (14.1) 151 * 152 * The routine implements equations 69, 66 and 71 of the G.729 specification (3.9.1) 153 * 154 * Em - mean innovation energy (dB, constant, depends on decoding algorithm) 155 * Ep - mean-removed predicted energy (dB) 156 * Er - mean-removed innovation energy (dB) 157 * Ei - mean energy of the fixed-codebook contribution (dB) 158 * N - subframe_size 159 * M - MA (Moving Average) prediction order 160 * gc - fixed-codebook gain 161 * gc_p - predicted fixed-codebook gain 162 * 163 * Fixed codebook gain is computed using predicted gain gc_p and 164 * correction factor gain_corr_factor as shown below: 165 * 166 * gc = gc_p * gain_corr_factor 167 * 168 * The predicted fixed codebook gain gc_p is found by predicting 169 * the energy of the fixed-codebook contribution from the energy 170 * of previous fixed-codebook contributions. 171 * 172 * mean = 1/N * sum(i,0,N){ fc_v[i] * fc_v[i] } 173 * 174 * Ei = 10log(mean) 175 * 176 * Er = 10log(1/N * gc^2 * mean) - Em = 20log(gc) + Ei - Em 177 * 178 * Replacing Er with Ep and gc with gc_p we will receive: 179 * 180 * Ep = 10log(1/N * gc_p^2 * mean) - Em = 20log(gc_p) + Ei - Em 181 * 182 * and from above: 183 * 184 * gc_p = 10^((Ep - Ei + Em) / 20) 185 * 186 * Ep is predicted using past energies and prediction coefficients: 187 * 188 * Ep = sum(i,0,M){ ma_prediction_coeff[i] * quant_energy[i] } 189 * 190 * gc_p in fixed-point arithmetic is calculated as following: 191 * 192 * mean = 1/N * sum(i,0,N){ (fc_v[i] / 2^13) * (fc_v[i] / 2^13) } = 193 * = 1/N * sum(i,0,N) { fc_v[i] * fc_v[i] } / 2^26 194 * 195 * Ei = 10log(mean) = -10log(N) - 10log(2^26) + 196 * + 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) 197 * 198 * Ep - Ei + Em = Ep + Em + 10log(N) + 10log(2^26) - 199 * - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) = 200 * = Ep + mr_energy - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) 201 * 202 * gc_p = 10 ^ ((Ep - Ei + Em) / 20) = 203 * = 2 ^ (3.3219 * (Ep - Ei + Em) / 20) = 2 ^ (0.166 * (Ep - Ei + Em)) 204 * 205 * where 206 * 207 * mr_energy = Em + 10log(N) + 10log(2^26) 208 * 209 * @remark The routine is used in G.729 and AMR (all modes). 210 */ 211int16_t ff_acelp_decode_gain_code( 212 AudioDSPContext *adsp, 213 int gain_corr_factor, 214 const int16_t* fc_v, 215 int mr_energy, 216 const int16_t* quant_energy, 217 const int16_t* ma_prediction_coeff, 218 int subframe_size, 219 int max_pred_order); 220 221/** 222 * Calculate fixed gain (part of section 6.1.3 of AMR spec) 223 * 224 * @param fixed_gain_factor gain correction factor 225 * @param fixed_mean_energy mean decoded algebraic codebook vector energy 226 * @param prediction_error vector of the quantified predictor errors of 227 * the four previous subframes. It is updated by this function. 228 * @param energy_mean desired mean innovation energy 229 * @param pred_table table of four moving average coefficients 230 */ 231float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy, 232 float *prediction_error, float energy_mean, 233 const float *pred_table); 234 235 236/** 237 * Decode the adaptive codebook index to the integer and fractional parts 238 * of the pitch lag for one subframe at 1/3 fractional precision. 239 * 240 * The choice of pitch lag is described in 3GPP TS 26.090 section 5.6.1. 241 * 242 * @param lag_int integer part of pitch lag of the current subframe 243 * @param lag_frac fractional part of pitch lag of the current subframe 244 * @param pitch_index parsed adaptive codebook (pitch) index 245 * @param prev_lag_int integer part of pitch lag for the previous subframe 246 * @param subframe current subframe number 247 * @param third_as_first treat the third frame the same way as the first 248 */ 249void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index, 250 const int prev_lag_int, const int subframe, 251 int third_as_first, int resolution); 252 253#endif /* AVCODEC_ACELP_PITCH_DELAY_H */ 254