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 */ 44static inline int ff_acelp_decode_8bit_to_1st_delay3(int ac_index) 45{ 46 ac_index += 58; 47 if (ac_index > 254) 48 ac_index = 3 * ac_index - 510; 49 return ac_index; 50} 51 52/** 53 * @brief Decode pitch delay of the second subframe encoded by 5 or 6 bits 54 * with 1/3 precision. 55 * @param ac_index adaptive codebook index (5 or 6 bits) 56 * @param pitch_delay_min lower bound (integer) of pitch delay interval 57 * for second subframe 58 * 59 * @return pitch delay in 1/3 units 60 * 61 * Pitch delay is coded: 62 * with 1/3 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5 63 * 64 * @remark The routine is used in G.729 @@8k, AMR @@10.2k, AMR @@7.95k, 65 * AMR @@7.4k for the second subframe. 66 */ 67static inline int ff_acelp_decode_5_6_bit_to_2nd_delay3(int ac_index, 68 int pitch_delay_min) 69{ 70 return 3 * pitch_delay_min + ac_index - 2; 71} 72 73/** 74 * @brief Decode pitch delay with 1/3 precision. 75 * @param ac_index adaptive codebook index (4 bits) 76 * @param pitch_delay_min lower bound (integer) of pitch delay interval for 77 * second subframe 78 * 79 * @return pitch delay in 1/3 units 80 * 81 * Pitch delay is coded: 82 * integers only, -6 < pitch_delay - int(prev_pitch_delay) <= -2 83 * with 1/3 resolution, -2 < pitch_delay - int(prev_pitch_delay) < 1 84 * integers only, 1 <= pitch_delay - int(prev_pitch_delay) < 5 85 * 86 * @remark The routine is used in G.729 @@6.4k, AMR @@6.7k, AMR @@5.9k, 87 * AMR @@5.15k, AMR @@4.75k for the second subframe. 88 */ 89static inline int ff_acelp_decode_4bit_to_2nd_delay3(int ac_index, 90 int pitch_delay_min) 91{ 92 if (ac_index < 4) 93 return 3 * (ac_index + pitch_delay_min); 94 else if (ac_index < 12) 95 return 3 * pitch_delay_min + ac_index + 6; 96 else 97 return 3 * (ac_index + pitch_delay_min) - 18; 98} 99 100/** 101 * @brief Decode pitch delay of the first subframe encoded by 9 bits 102 * with 1/6 precision. 103 * @param ac_index adaptive codebook index (9 bits) 104 * 105 * @return pitch delay in 1/6 units 106 * 107 * Pitch delay is coded: 108 * with 1/6 resolution, 17 < pitch_delay < 95 109 * integers only, 95 <= pitch_delay <= 143 110 * 111 * @remark The routine is used in AMR @@12.2k for the first and third subframes. 112 */ 113static inline int ff_acelp_decode_9bit_to_1st_delay6(int ac_index) 114{ 115 if (ac_index < 463) 116 return ac_index + 105; 117 else 118 return 6 * (ac_index - 368); 119} 120 121/** 122 * @brief Decode pitch delay of the second subframe encoded by 6 bits 123 * with 1/6 precision. 124 * @param ac_index adaptive codebook index (6 bits) 125 * @param pitch_delay_min lower bound (integer) of pitch delay interval for 126 * second subframe 127 * 128 * @return pitch delay in 1/6 units 129 * 130 * Pitch delay is coded: 131 * with 1/6 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5 132 * 133 * @remark The routine is used in AMR @@12.2k for the second and fourth subframes. 134 */ 135static inline int ff_acelp_decode_6bit_to_2nd_delay6(int ac_index, 136 int pitch_delay_min) 137{ 138 return 6 * pitch_delay_min + ac_index - 3; 139} 140 141/** 142 * @brief Update past quantized energies 143 * @param[in,out] quant_energy past quantized energies (5.10) 144 * @param gain_corr_factor gain correction factor 145 * @param log2_ma_pred_order log2() of MA prediction order 146 * @param erasure frame erasure flag 147 * 148 * If frame erasure flag is not equal to zero, memory is updated with 149 * averaged energy, attenuated by 4dB: 150 * max(avg(quant_energy[i])-4, -14), i=0,ma_pred_order 151 * 152 * In normal mode memory is updated with 153 * Er - Ep = 20 * log10(gain_corr_factor) 154 * 155 * @remark The routine is used in G.729 and AMR (all modes). 156 */ 157void ff_acelp_update_past_gain( 158 int16_t* quant_energy, 159 int gain_corr_factor, 160 int log2_ma_pred_order, 161 int erasure); 162 163/** 164 * @brief Decode the adaptive codebook gain and add 165 * correction (4.1.5 and 3.9.1 of G.729). 166 * @param adsp initialized audio DSP context 167 * @param gain_corr_factor gain correction factor (2.13) 168 * @param fc_v fixed-codebook vector (2.13) 169 * @param mr_energy mean innovation energy and fixed-point correction (7.13) 170 * @param[in,out] quant_energy past quantized energies (5.10) 171 * @param subframe_size length of subframe 172 * 173 * @return quantized fixed-codebook gain (14.1) 174 * 175 * The routine implements equations 69, 66 and 71 of the G.729 specification (3.9.1) 176 * 177 * Em - mean innovation energy (dB, constant, depends on decoding algorithm) 178 * Ep - mean-removed predicted energy (dB) 179 * Er - mean-removed innovation energy (dB) 180 * Ei - mean energy of the fixed-codebook contribution (dB) 181 * N - subframe_size 182 * M - MA (Moving Average) prediction order 183 * gc - fixed-codebook gain 184 * gc_p - predicted fixed-codebook gain 185 * 186 * Fixed codebook gain is computed using predicted gain gc_p and 187 * correction factor gain_corr_factor as shown below: 188 * 189 * gc = gc_p * gain_corr_factor 190 * 191 * The predicted fixed codebook gain gc_p is found by predicting 192 * the energy of the fixed-codebook contribution from the energy 193 * of previous fixed-codebook contributions. 194 * 195 * mean = 1/N * sum(i,0,N){ fc_v[i] * fc_v[i] } 196 * 197 * Ei = 10log(mean) 198 * 199 * Er = 10log(1/N * gc^2 * mean) - Em = 20log(gc) + Ei - Em 200 * 201 * Replacing Er with Ep and gc with gc_p we will receive: 202 * 203 * Ep = 10log(1/N * gc_p^2 * mean) - Em = 20log(gc_p) + Ei - Em 204 * 205 * and from above: 206 * 207 * gc_p = 10^((Ep - Ei + Em) / 20) 208 * 209 * Ep is predicted using past energies and prediction coefficients: 210 * 211 * Ep = sum(i,0,M){ ma_prediction_coeff[i] * quant_energy[i] } 212 * 213 * gc_p in fixed-point arithmetic is calculated as following: 214 * 215 * mean = 1/N * sum(i,0,N){ (fc_v[i] / 2^13) * (fc_v[i] / 2^13) } = 216 * = 1/N * sum(i,0,N) { fc_v[i] * fc_v[i] } / 2^26 217 * 218 * Ei = 10log(mean) = -10log(N) - 10log(2^26) + 219 * + 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) 220 * 221 * Ep - Ei + Em = Ep + Em + 10log(N) + 10log(2^26) - 222 * - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) = 223 * = Ep + mr_energy - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) 224 * 225 * gc_p = 10 ^ ((Ep - Ei + Em) / 20) = 226 * = 2 ^ (3.3219 * (Ep - Ei + Em) / 20) = 2 ^ (0.166 * (Ep - Ei + Em)) 227 * 228 * where 229 * 230 * mr_energy = Em + 10log(N) + 10log(2^26) 231 * 232 * @remark The routine is used in G.729 and AMR (all modes). 233 */ 234int16_t ff_acelp_decode_gain_code( 235 AudioDSPContext *adsp, 236 int gain_corr_factor, 237 const int16_t* fc_v, 238 int mr_energy, 239 const int16_t* quant_energy, 240 const int16_t* ma_prediction_coeff, 241 int subframe_size, 242 int max_pred_order); 243 244/** 245 * Calculate fixed gain (part of section 6.1.3 of AMR spec) 246 * 247 * @param fixed_gain_factor gain correction factor 248 * @param fixed_mean_energy mean decoded algebraic codebook vector energy 249 * @param prediction_error vector of the quantified predictor errors of 250 * the four previous subframes. It is updated by this function. 251 * @param energy_mean desired mean innovation energy 252 * @param pred_table table of four moving average coefficients 253 */ 254float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy, 255 float *prediction_error, float energy_mean, 256 const float *pred_table); 257 258 259/** 260 * Decode the adaptive codebook index to the integer and fractional parts 261 * of the pitch lag for one subframe at 1/3 fractional precision. 262 * 263 * The choice of pitch lag is described in 3GPP TS 26.090 section 5.6.1. 264 * 265 * @param lag_int integer part of pitch lag of the current subframe 266 * @param lag_frac fractional part of pitch lag of the current subframe 267 * @param pitch_index parsed adaptive codebook (pitch) index 268 * @param prev_lag_int integer part of pitch lag for the previous subframe 269 * @param subframe current subframe number 270 * @param third_as_first treat the third frame the same way as the first 271 */ 272void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index, 273 const int prev_lag_int, const int subframe, 274 int third_as_first, int resolution); 275 276#endif /* AVCODEC_ACELP_PITCH_DELAY_H */ 277