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223 lines
7.5 KiB
223 lines
7.5 KiB
/* |
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* gain code, gain pitch and pitch delay decoding |
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* |
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* Copyright (c) 2008 Vladimir Voroshilov |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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#ifndef AVCODEC_ACELP_PITCH_DELAY_H |
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#define AVCODEC_ACELP_PITCH_DELAY_H |
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#include <stdint.h> |
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#include "dsputil.h" |
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#define PITCH_DELAY_MIN 20 |
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#define PITCH_DELAY_MAX 143 |
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/** |
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* \brief Decode pitch delay of the first subframe encoded by 8 bits with 1/3 |
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* resolution. |
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* \param ac_index adaptive codebook index (8 bits) |
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* |
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* \return pitch delay in 1/3 units |
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* |
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* Pitch delay is coded: |
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* with 1/3 resolution, 19 < pitch_delay < 85 |
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* integers only, 85 <= pitch_delay <= 143 |
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*/ |
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int ff_acelp_decode_8bit_to_1st_delay3(int ac_index); |
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/** |
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* \brief Decode pitch delay of the second subframe encoded by 5 or 6 bits |
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* with 1/3 precision. |
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* \param ac_index adaptive codebook index (5 or 6 bits) |
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* \param pitch_delay_min lower bound (integer) of pitch delay interval |
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* for second subframe |
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* |
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* \return pitch delay in 1/3 units |
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* |
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* Pitch delay is coded: |
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* with 1/3 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5 |
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* |
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* \remark The routine is used in G.729 @8k, AMR @10.2k, AMR @7.95k, |
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* AMR @7.4k for the second subframe. |
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*/ |
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int ff_acelp_decode_5_6_bit_to_2nd_delay3( |
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int ac_index, |
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int pitch_delay_min); |
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/** |
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* \brief Decode pitch delay with 1/3 precision. |
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* \param ac_index adaptive codebook index (4 bits) |
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* \param pitch_delay_min lower bound (integer) of pitch delay interval for |
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* second subframe |
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* |
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* \return pitch delay in 1/3 units |
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* |
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* Pitch delay is coded: |
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* integers only, -6 < pitch_delay - int(prev_pitch_delay) <= -2 |
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* with 1/3 resolution, -2 < pitch_delay - int(prev_pitch_delay) < 1 |
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* integers only, 1 <= pitch_delay - int(prev_pitch_delay) < 5 |
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* |
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* \remark The routine is used in G.729 @6.4k, AMR @6.7k, AMR @5.9k, |
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* AMR @5.15k, AMR @4.75k for the second subframe. |
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*/ |
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int ff_acelp_decode_4bit_to_2nd_delay3( |
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int ac_index, |
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int pitch_delay_min); |
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/** |
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* \brief Decode pitch delay of the first subframe encoded by 9 bits |
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* with 1/6 precision. |
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* \param ac_index adaptive codebook index (9 bits) |
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* \param pitch_delay_min lower bound (integer) of pitch delay interval for |
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* second subframe |
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* |
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* \return pitch delay in 1/6 units |
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* |
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* Pitch delay is coded: |
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* with 1/6 resolution, 17 < pitch_delay < 95 |
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* integers only, 95 <= pitch_delay <= 143 |
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* |
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* \remark The routine is used in AMR @12.2k for the first and third subframes. |
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*/ |
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int ff_acelp_decode_9bit_to_1st_delay6(int ac_index); |
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/** |
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* \brief Decode pitch delay of the second subframe encoded by 6 bits |
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* with 1/6 precision. |
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* \param ac_index adaptive codebook index (6 bits) |
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* \param pitch_delay_min lower bound (integer) of pitch delay interval for |
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* second subframe |
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* |
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* \return pitch delay in 1/6 units |
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* |
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* Pitch delay is coded: |
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* with 1/6 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5 |
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* |
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* \remark The routine is used in AMR @12.2k for the second and fourth subframes. |
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*/ |
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int ff_acelp_decode_6bit_to_2nd_delay6( |
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int ac_index, |
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int pitch_delay_min); |
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/** |
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* \brief Update past quantized energies |
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* \param quant_energy [in/out] past quantized energies (5.10) |
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* \param gain_corr_factor gain correction factor |
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* \param log2_ma_pred_order log2() of MA prediction order |
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* \param erasure frame erasure flag |
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* |
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* If frame erasure flag is not equal to zero, memory is updated with |
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* averaged energy, attenuated by 4dB: |
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* max(avg(quant_energy[i])-4, -14), i=0,ma_pred_order |
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* |
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* In normal mode memory is updated with |
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* Er - Ep = 20 * log10(gain_corr_factor) |
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* |
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* \remark The routine is used in G.729 and AMR (all modes). |
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*/ |
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void ff_acelp_update_past_gain( |
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int16_t* quant_energy, |
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int gain_corr_factor, |
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int log2_ma_pred_order, |
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int erasure); |
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/** |
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* \brief Decode the adaptive codebook gain and add |
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* correction (4.1.5 and 3.9.1 of G.729). |
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* \param dsp initialized dsputil context |
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* \param gain_corr_factor gain correction factor (2.13) |
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* \param fc_v fixed-codebook vector (2.13) |
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* \param mr_energy mean innovation energy and fixed-point correction (7.13) |
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* \param quant_energy [in/out] past quantized energies (5.10) |
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* \param subframe_size length of subframe |
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* \param ma_pred_order MA prediction order |
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* |
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* \return quantized fixed-codebook gain (14.1) |
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* |
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* The routine implements equations 69, 66 and 71 of the G.729 specification (3.9.1) |
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* |
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* Em - mean innovation energy (dB, constant, depends on decoding algorithm) |
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* Ep - mean-removed predicted energy (dB) |
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* Er - mean-removed innovation energy (dB) |
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* Ei - mean energy of the fixed-codebook contribution (dB) |
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* N - subframe_size |
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* M - MA (Moving Average) prediction order |
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* gc - fixed-codebook gain |
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* gc_p - predicted fixed-codebook gain |
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* |
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* Fixed codebook gain is computed using predicted gain gc_p and |
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* correction factor gain_corr_factor as shown below: |
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* |
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* gc = gc_p * gain_corr_factor |
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* |
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* The predicted fixed codebook gain gc_p is found by predicting |
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* the energy of the fixed-codebook contribution from the energy |
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* of previous fixed-codebook contributions. |
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* |
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* mean = 1/N * sum(i,0,N){ fc_v[i] * fc_v[i] } |
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* |
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* Ei = 10log(mean) |
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* |
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* Er = 10log(1/N * gc^2 * mean) - Em = 20log(gc) + Ei - Em |
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* |
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* Replacing Er with Ep and gc with gc_p we will receive: |
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* |
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* Ep = 10log(1/N * gc_p^2 * mean) - Em = 20log(gc_p) + Ei - Em |
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* |
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* and from above: |
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* |
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* gc_p = 10^((Ep - Ei + Em) / 20) |
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* |
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* Ep is predicted using past energies and prediction coefficients: |
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* |
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* Ep = sum(i,0,M){ ma_prediction_coeff[i] * quant_energy[i] } |
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* |
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* gc_p in fixed-point arithmetic is calculated as following: |
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* |
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* mean = 1/N * sum(i,0,N){ (fc_v[i] / 2^13) * (fc_v[i] / 2^13) } = |
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* = 1/N * sum(i,0,N) { fc_v[i] * fc_v[i] } / 2^26 |
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* |
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* Ei = 10log(mean) = -10log(N) - 10log(2^26) + |
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* + 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) |
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* |
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* Ep - Ei + Em = Ep + Em + 10log(N) + 10log(2^26) - |
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* - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) = |
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* = Ep + mr_energy - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) |
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* |
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* gc_p = 10 ^ ((Ep - Ei + Em) / 20) = |
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* = 2 ^ (3.3219 * (Ep - Ei + Em) / 20) = 2 ^ (0.166 * (Ep - Ei + Em)) |
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* |
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* where |
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* |
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* mr_energy = Em + 10log(N) + 10log(2^26) |
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* |
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* \remark The routine is used in G.729 and AMR (all modes). |
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*/ |
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int16_t ff_acelp_decode_gain_code( |
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DSPContext *dsp, |
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int gain_corr_factor, |
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const int16_t* fc_v, |
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int mr_energy, |
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const int16_t* quant_energy, |
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const int16_t* ma_prediction_coeff, |
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int subframe_size, |
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int max_pred_order); |
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#endif /* AVCODEC_ACELP_PITCH_DELAY_H */
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