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6148 | serge | 1 | /* |
2 | * gain code, gain pitch and pitch delay decoding |
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3 | * |
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4 | * Copyright (c) 2008 Vladimir Voroshilov |
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5 | * |
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6 | * This file is part of FFmpeg. |
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7 | * |
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8 | * FFmpeg is free software; you can redistribute it and/or |
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9 | * modify it under the terms of the GNU Lesser General Public |
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10 | * License as published by the Free Software Foundation; either |
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11 | * version 2.1 of the License, or (at your option) any later version. |
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12 | * |
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13 | * FFmpeg is distributed in the hope that it will be useful, |
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14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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16 | * Lesser General Public License for more details. |
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17 | * |
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18 | * You should have received a copy of the GNU Lesser General Public |
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19 | * License along with FFmpeg; if not, write to the Free Software |
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20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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21 | */ |
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22 | |||
23 | #ifndef AVCODEC_ACELP_PITCH_DELAY_H |
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24 | #define AVCODEC_ACELP_PITCH_DELAY_H |
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25 | |||
26 | #include |
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27 | #include "dsputil.h" |
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28 | |||
29 | #define PITCH_DELAY_MIN 20 |
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30 | #define PITCH_DELAY_MAX 143 |
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31 | |||
32 | /** |
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33 | * @brief Decode pitch delay of the first subframe encoded by 8 bits with 1/3 |
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34 | * resolution. |
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35 | * @param ac_index adaptive codebook index (8 bits) |
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36 | * |
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37 | * @return pitch delay in 1/3 units |
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38 | * |
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39 | * Pitch delay is coded: |
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40 | * with 1/3 resolution, 19 < pitch_delay < 85 |
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41 | * integers only, 85 <= pitch_delay <= 143 |
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42 | */ |
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43 | int ff_acelp_decode_8bit_to_1st_delay3(int ac_index); |
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44 | |||
45 | /** |
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46 | * @brief Decode pitch delay of the second subframe encoded by 5 or 6 bits |
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47 | * with 1/3 precision. |
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48 | * @param ac_index adaptive codebook index (5 or 6 bits) |
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49 | * @param pitch_delay_min lower bound (integer) of pitch delay interval |
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50 | * for second subframe |
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51 | * |
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52 | * @return pitch delay in 1/3 units |
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53 | * |
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54 | * Pitch delay is coded: |
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55 | * with 1/3 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5 |
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56 | * |
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57 | * @remark The routine is used in G.729 @@8k, AMR @@10.2k, AMR @@7.95k, |
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58 | * AMR @@7.4k for the second subframe. |
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59 | */ |
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60 | int ff_acelp_decode_5_6_bit_to_2nd_delay3( |
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61 | int ac_index, |
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62 | int pitch_delay_min); |
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63 | |||
64 | /** |
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65 | * @brief Decode pitch delay with 1/3 precision. |
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66 | * @param ac_index adaptive codebook index (4 bits) |
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67 | * @param pitch_delay_min lower bound (integer) of pitch delay interval for |
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68 | * second subframe |
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69 | * |
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70 | * @return pitch delay in 1/3 units |
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71 | * |
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72 | * Pitch delay is coded: |
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73 | * integers only, -6 < pitch_delay - int(prev_pitch_delay) <= -2 |
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74 | * with 1/3 resolution, -2 < pitch_delay - int(prev_pitch_delay) < 1 |
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75 | * integers only, 1 <= pitch_delay - int(prev_pitch_delay) < 5 |
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76 | * |
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77 | * @remark The routine is used in G.729 @@6.4k, AMR @@6.7k, AMR @@5.9k, |
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78 | * AMR @@5.15k, AMR @@4.75k for the second subframe. |
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79 | */ |
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80 | int ff_acelp_decode_4bit_to_2nd_delay3( |
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81 | int ac_index, |
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82 | int pitch_delay_min); |
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83 | |||
84 | /** |
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85 | * @brief Decode pitch delay of the first subframe encoded by 9 bits |
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86 | * with 1/6 precision. |
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87 | * @param ac_index adaptive codebook index (9 bits) |
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88 | * |
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89 | * @return pitch delay in 1/6 units |
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90 | * |
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91 | * Pitch delay is coded: |
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92 | * with 1/6 resolution, 17 < pitch_delay < 95 |
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93 | * integers only, 95 <= pitch_delay <= 143 |
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94 | * |
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95 | * @remark The routine is used in AMR @@12.2k for the first and third subframes. |
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96 | */ |
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97 | int ff_acelp_decode_9bit_to_1st_delay6(int ac_index); |
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98 | |||
99 | /** |
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100 | * @brief Decode pitch delay of the second subframe encoded by 6 bits |
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101 | * with 1/6 precision. |
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102 | * @param ac_index adaptive codebook index (6 bits) |
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103 | * @param pitch_delay_min lower bound (integer) of pitch delay interval for |
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104 | * second subframe |
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105 | * |
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106 | * @return pitch delay in 1/6 units |
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107 | * |
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108 | * Pitch delay is coded: |
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109 | * with 1/6 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5 |
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110 | * |
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111 | * @remark The routine is used in AMR @@12.2k for the second and fourth subframes. |
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112 | */ |
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113 | int ff_acelp_decode_6bit_to_2nd_delay6( |
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114 | int ac_index, |
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115 | int pitch_delay_min); |
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116 | |||
117 | /** |
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118 | * @brief Update past quantized energies |
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119 | * @param[in,out] quant_energy past quantized energies (5.10) |
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120 | * @param gain_corr_factor gain correction factor |
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121 | * @param log2_ma_pred_order log2() of MA prediction order |
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122 | * @param erasure frame erasure flag |
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123 | * |
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124 | * If frame erasure flag is not equal to zero, memory is updated with |
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125 | * averaged energy, attenuated by 4dB: |
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126 | * max(avg(quant_energy[i])-4, -14), i=0,ma_pred_order |
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127 | * |
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128 | * In normal mode memory is updated with |
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129 | * Er - Ep = 20 * log10(gain_corr_factor) |
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130 | * |
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131 | * @remark The routine is used in G.729 and AMR (all modes). |
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132 | */ |
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133 | void ff_acelp_update_past_gain( |
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134 | int16_t* quant_energy, |
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135 | int gain_corr_factor, |
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136 | int log2_ma_pred_order, |
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137 | int erasure); |
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138 | |||
139 | /** |
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140 | * @brief Decode the adaptive codebook gain and add |
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141 | * correction (4.1.5 and 3.9.1 of G.729). |
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142 | * @param dsp initialized dsputil context |
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143 | * @param gain_corr_factor gain correction factor (2.13) |
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144 | * @param fc_v fixed-codebook vector (2.13) |
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145 | * @param mr_energy mean innovation energy and fixed-point correction (7.13) |
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146 | * @param[in,out] quant_energy past quantized energies (5.10) |
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147 | * @param subframe_size length of subframe |
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148 | * |
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149 | * @return quantized fixed-codebook gain (14.1) |
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150 | * |
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151 | * The routine implements equations 69, 66 and 71 of the G.729 specification (3.9.1) |
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152 | * |
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153 | * Em - mean innovation energy (dB, constant, depends on decoding algorithm) |
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154 | * Ep - mean-removed predicted energy (dB) |
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155 | * Er - mean-removed innovation energy (dB) |
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156 | * Ei - mean energy of the fixed-codebook contribution (dB) |
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157 | * N - subframe_size |
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158 | * M - MA (Moving Average) prediction order |
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159 | * gc - fixed-codebook gain |
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160 | * gc_p - predicted fixed-codebook gain |
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161 | * |
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162 | * Fixed codebook gain is computed using predicted gain gc_p and |
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163 | * correction factor gain_corr_factor as shown below: |
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164 | * |
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165 | * gc = gc_p * gain_corr_factor |
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166 | * |
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167 | * The predicted fixed codebook gain gc_p is found by predicting |
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168 | * the energy of the fixed-codebook contribution from the energy |
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169 | * of previous fixed-codebook contributions. |
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170 | * |
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171 | * mean = 1/N * sum(i,0,N){ fc_v[i] * fc_v[i] } |
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172 | * |
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173 | * Ei = 10log(mean) |
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174 | * |
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175 | * Er = 10log(1/N * gc^2 * mean) - Em = 20log(gc) + Ei - Em |
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176 | * |
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177 | * Replacing Er with Ep and gc with gc_p we will receive: |
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178 | * |
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179 | * Ep = 10log(1/N * gc_p^2 * mean) - Em = 20log(gc_p) + Ei - Em |
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180 | * |
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181 | * and from above: |
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182 | * |
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183 | * gc_p = 10^((Ep - Ei + Em) / 20) |
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184 | * |
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185 | * Ep is predicted using past energies and prediction coefficients: |
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186 | * |
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187 | * Ep = sum(i,0,M){ ma_prediction_coeff[i] * quant_energy[i] } |
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188 | * |
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189 | * gc_p in fixed-point arithmetic is calculated as following: |
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190 | * |
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191 | * mean = 1/N * sum(i,0,N){ (fc_v[i] / 2^13) * (fc_v[i] / 2^13) } = |
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192 | * = 1/N * sum(i,0,N) { fc_v[i] * fc_v[i] } / 2^26 |
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193 | * |
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194 | * Ei = 10log(mean) = -10log(N) - 10log(2^26) + |
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195 | * + 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) |
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196 | * |
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197 | * Ep - Ei + Em = Ep + Em + 10log(N) + 10log(2^26) - |
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198 | * - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) = |
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199 | * = Ep + mr_energy - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) |
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200 | * |
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201 | * gc_p = 10 ^ ((Ep - Ei + Em) / 20) = |
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202 | * = 2 ^ (3.3219 * (Ep - Ei + Em) / 20) = 2 ^ (0.166 * (Ep - Ei + Em)) |
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203 | * |
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204 | * where |
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205 | * |
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206 | * mr_energy = Em + 10log(N) + 10log(2^26) |
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207 | * |
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208 | * @remark The routine is used in G.729 and AMR (all modes). |
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209 | */ |
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210 | int16_t ff_acelp_decode_gain_code( |
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211 | DSPContext *dsp, |
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212 | int gain_corr_factor, |
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213 | const int16_t* fc_v, |
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214 | int mr_energy, |
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215 | const int16_t* quant_energy, |
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216 | const int16_t* ma_prediction_coeff, |
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217 | int subframe_size, |
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218 | int max_pred_order); |
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219 | |||
220 | /** |
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221 | * Calculate fixed gain (part of section 6.1.3 of AMR spec) |
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222 | * |
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223 | * @param fixed_gain_factor gain correction factor |
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224 | * @param fixed_mean_energy mean decoded algebraic codebook vector energy |
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225 | * @param prediction_error vector of the quantified predictor errors of |
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226 | * the four previous subframes. It is updated by this function. |
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227 | * @param energy_mean desired mean innovation energy |
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228 | * @param pred_table table of four moving average coefficients |
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229 | */ |
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230 | float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy, |
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231 | float *prediction_error, float energy_mean, |
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232 | const float *pred_table); |
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233 | |||
234 | |||
235 | /** |
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236 | * Decode the adaptive codebook index to the integer and fractional parts |
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237 | * of the pitch lag for one subframe at 1/3 fractional precision. |
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238 | * |
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239 | * The choice of pitch lag is described in 3GPP TS 26.090 section 5.6.1. |
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240 | * |
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241 | * @param lag_int integer part of pitch lag of the current subframe |
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242 | * @param lag_frac fractional part of pitch lag of the current subframe |
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243 | * @param pitch_index parsed adaptive codebook (pitch) index |
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244 | * @param prev_lag_int integer part of pitch lag for the previous subframe |
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245 | * @param subframe current subframe number |
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246 | * @param third_as_first treat the third frame the same way as the first |
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247 | */ |
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248 | void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index, |
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249 | const int prev_lag_int, const int subframe, |
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250 | int third_as_first, int resolution); |
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251 | |||
252 | #endif /* AVCODEC_ACELP_PITCH_DELAY_H */>>=>=>>>>=>>>=>>>>=>=>>> |