libavcodec/acelp_pitch_delay.h

   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 #include "dsputil.h"
  28
  29 #define PITCH_DELAY_MIN             20
  30 #define PITCH_DELAY_MAX             143
  31
  32 /**
  33  * \brief Decode pitch delay of the first subframe encoded by 8 bits with 1/3
  34  *        resolution.
  35  * \param ac_index adaptive codebook index (8 bits)
  36  *
  37  * \return pitch delay in 1/3 units
  38  *
  39  * Pitch delay is coded:
  40  *    with 1/3 resolution, 19  < pitch_delay <  85
  41  *    integers only,       85 <= pitch_delay <= 143
  42  */
  43 int ff_acelp_decode_8bit_to_1st_delay3(int ac_index);
  44
  45 /**
  46  * \brief Decode pitch delay of the second subframe encoded by 5 or 6 bits
  47  *        with 1/3 precision.
  48  * \param ac_index adaptive codebook index (5 or 6 bits)
  49  * \param pitch_delay_min lower bound (integer) of pitch delay interval
  50  *                      for second subframe
  51  *
  52  * \return pitch delay in 1/3 units
  53  *
  54  * Pitch delay is coded:
  55  *    with 1/3 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5
  56  *
  57  * \remark The routine is used in G.729 @8k, AMR @10.2k, AMR @7.95k,
  58  *         AMR @7.4k for the second subframe.
  59  */
  60 int ff_acelp_decode_5_6_bit_to_2nd_delay3(
  61         int ac_index,
  62         int pitch_delay_min);
  63
  64 /**
  65  * \brief Decode pitch delay with 1/3 precision.
  66  * \param ac_index adaptive codebook index (4 bits)
  67  * \param pitch_delay_min lower bound (integer) of pitch delay interval for
  68  *                      second subframe
  69  *
  70  * \return pitch delay in 1/3 units
  71  *
  72  * Pitch delay is coded:
  73  *    integers only,          -6  < pitch_delay - int(prev_pitch_delay) <= -2
  74  *    with 1/3 resolution,    -2  < pitch_delay - int(prev_pitch_delay) <  1
  75  *    integers only,           1 <= pitch_delay - int(prev_pitch_delay) <  5
  76  *
  77  * \remark The routine is used in G.729 @6.4k, AMR @6.7k, AMR @5.9k,
  78  *         AMR @5.15k, AMR @4.75k for the second subframe.
  79  */
  80 int ff_acelp_decode_4bit_to_2nd_delay3(
  81         int ac_index,
  82         int pitch_delay_min);
  83
  84 /**
  85  * \brief Decode pitch delay of the first subframe encoded by 9 bits
  86  *        with 1/6 precision.
  87  * \param ac_index adaptive codebook index (9 bits)
  88  * \param pitch_delay_min lower bound (integer) of pitch delay interval for
  89  *                      second subframe
  90  *
  91  * \return pitch delay in 1/6 units
  92  *
  93  * Pitch delay is coded:
  94  *    with 1/6 resolution,  17  < pitch_delay <  95
  95  *    integers only,        95 <= pitch_delay <= 143
  96  *
  97  * \remark The routine is used in AMR @12.2k for the first and third subframes.
  98  */
  99 int ff_acelp_decode_9bit_to_1st_delay6(int ac_index);
 100
 101 /**
 102  * \brief Decode pitch delay of the second subframe encoded by 6 bits
 103  *        with 1/6 precision.
 104  * \param ac_index adaptive codebook index (6 bits)
 105  * \param pitch_delay_min lower bound (integer) of pitch delay interval for
 106  *                      second subframe
 107  *
 108  * \return pitch delay in 1/6 units
 109  *
 110  * Pitch delay is coded:
 111  *    with 1/6 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5
 112  *
 113  * \remark The routine is used in AMR @12.2k for the second and fourth subframes.
 114  */
 115 int ff_acelp_decode_6bit_to_2nd_delay6(
 116         int ac_index,
 117         int pitch_delay_min);
 118
 119 /**
 120  * \brief Update past quantized energies
 121  * \param quant_energy [in/out] past quantized energies (5.10)
 122  * \param gain_corr_factor gain correction factor
 123  * \param log2_ma_pred_order log2() of MA prediction order
 124  * \param erasure frame erasure flag
 125  *
 126  * If frame erasure flag is not equal to zero, memory is updated with
 127  * averaged energy, attenuated by 4dB:
 128  *     max(avg(quant_energy[i])-4, -14), i=0,ma_pred_order
 129  *
 130  * In normal mode memory is updated with
 131  *     Er - Ep = 20 * log10(gain_corr_factor)
 132  *
 133  * \remark The routine is used in G.729 and AMR (all modes).
 134  */
 135 void ff_acelp_update_past_gain(
 136         int16_t* quant_energy,
 137         int gain_corr_factor,
 138         int log2_ma_pred_order,
 139         int erasure);
 140
 141 /**
 142  * \brief Decode the adaptive codebook gain and add
 143  *        correction (4.1.5 and 3.9.1 of G.729).
 144  * \param dsp initialized dsputil context
 145  * \param gain_corr_factor gain correction factor (2.13)
 146  * \param fc_v fixed-codebook vector (2.13)
 147  * \param mr_energy mean innovation energy and fixed-point correction (7.13)
 148  * \param quant_energy [in/out] past quantized energies (5.10)
 149  * \param subframe_size length of subframe
 150  * \param ma_pred_order MA prediction order
 151  *
 152  * \return quantized fixed-codebook gain (14.1)
 153  *
 154  * The routine implements equations 69, 66 and 71 of the G.729 specification (3.9.1)
 155  *
 156  *    Em   - mean innovation energy (dB, constant, depends on decoding algorithm)
 157  *    Ep   - mean-removed predicted energy (dB)
 158  *    Er   - mean-removed innovation energy (dB)
 159  *    Ei   - mean energy of the fixed-codebook contribution (dB)
 160  *    N    - subframe_size
 161  *    M    - MA (Moving Average) prediction order
 162  *    gc   - fixed-codebook gain
 163  *    gc_p - predicted fixed-codebook gain
 164  *
 165  *    Fixed codebook gain is computed using predicted gain gc_p and
 166  *    correction factor gain_corr_factor as shown below:
 167  *
 168  *        gc = gc_p * gain_corr_factor
 169  *
 170  *    The predicted fixed codebook gain gc_p is found by predicting
 171  *    the energy of the fixed-codebook contribution from the energy
 172  *    of previous fixed-codebook contributions.
 173  *
 174  *        mean = 1/N * sum(i,0,N){ fc_v[i] * fc_v[i] }
 175  *
 176  *        Ei = 10log(mean)
 177  *
 178  *        Er = 10log(1/N * gc^2 * mean) - Em = 20log(gc) + Ei - Em
 179  *
 180  *    Replacing Er with Ep and gc with gc_p we will receive:
 181  *
 182  *        Ep = 10log(1/N * gc_p^2 * mean) - Em = 20log(gc_p) + Ei - Em
 183  *
 184  *    and from above:
 185  *
 186  *        gc_p = 10^((Ep - Ei + Em) / 20)
 187  *
 188  *    Ep is predicted using past energies and prediction coefficients:
 189  *
 190  *        Ep = sum(i,0,M){ ma_prediction_coeff[i] * quant_energy[i] }
 191  *
 192  *    gc_p in fixed-point arithmetic is calculated as following:
 193  *
 194  *        mean = 1/N * sum(i,0,N){ (fc_v[i] / 2^13) * (fc_v[i] / 2^13) } =
 195  *        = 1/N * sum(i,0,N) { fc_v[i] * fc_v[i] } / 2^26
 196  *
 197  *        Ei = 10log(mean) = -10log(N) - 10log(2^26) +
 198  *        + 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })
 199  *
 200  *        Ep - Ei + Em = Ep + Em + 10log(N) + 10log(2^26) -
 201  *        - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) =
 202  *        = Ep + mr_energy - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })
 203  *
 204  *        gc_p = 10 ^ ((Ep - Ei + Em) / 20) =
 205  *        = 2 ^ (3.3219 * (Ep - Ei + Em) / 20) = 2 ^ (0.166 * (Ep - Ei + Em))
 206  *
 207  *    where
 208  *
 209  *        mr_energy = Em + 10log(N) + 10log(2^26)
 210  *
 211  * \remark The routine is used in G.729 and AMR (all modes).
 212  */
 213 int16_t ff_acelp_decode_gain_code(
 214     DSPContext *dsp,
 215     int gain_corr_factor,
 216     const int16_t* fc_v,
 217     int mr_energy,
 218     const int16_t* quant_energy,
 219     const int16_t* ma_prediction_coeff,
 220     int subframe_size,
 221     int max_pred_order);
 222
 223 #endif /* AVCODEC_ACELP_PITCH_DELAY_H */