mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-12-23 12:43:46 +02:00
221 lines
7.4 KiB
C
221 lines
7.4 KiB
C
/*
|
|
* gain code, gain pitch and pitch delay decoding
|
|
*
|
|
* Copyright (c) 2008 Vladimir Voroshilov
|
|
*
|
|
* This file is part of FFmpeg.
|
|
*
|
|
* FFmpeg is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 2.1 of the License, or (at your option) any later version.
|
|
*
|
|
* FFmpeg is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with FFmpeg; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*/
|
|
|
|
#ifndef FFMPEG_ACELP_PITCH_DELAY_H
|
|
#define FFMPEG_ACELP_PITCH_DELAY_H
|
|
|
|
#include <stdint.h>
|
|
|
|
#define PITCH_DELAY_MIN 20
|
|
#define PITCH_DELAY_MAX 143
|
|
|
|
/**
|
|
* \brief Decode pitch delay of the first subframe encoded by 8 bits with 1/3
|
|
* resolution.
|
|
* \param ac_index adaptive codebook index (8 bits)
|
|
*
|
|
* \return pitch delay in 1/3 units
|
|
*
|
|
* Pitch delay is coded:
|
|
* with 1/3 resolution, 19 < pitch_delay < 85
|
|
* integers only, 85 <= pitch_delay <= 143
|
|
*/
|
|
int ff_acelp_decode_8bit_to_1st_delay3(int ac_index);
|
|
|
|
/**
|
|
* \brief Decode pitch delay of the second subframe encoded by 5 or 6 bits
|
|
* with 1/3 precision.
|
|
* \param ac_index adaptive codebook index (5 or 6 bits)
|
|
* \param pitch_delay_min lower bound (integer) of pitch delay interval
|
|
* for second subframe
|
|
*
|
|
* \return pitch delay in 1/3 units
|
|
*
|
|
* Pitch delay is coded:
|
|
* with 1/3 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5
|
|
*
|
|
* \remark The routine is used in G.729 @8k, AMR @10.2k, AMR @7.95k,
|
|
* AMR @7.4k for the second subframe.
|
|
*/
|
|
int ff_acelp_decode_5_6_bit_to_2nd_delay3(
|
|
int ac_index,
|
|
int pitch_delay_min);
|
|
|
|
/**
|
|
* \brief Decode pitch delay with 1/3 precision.
|
|
* \param ac_index adaptive codebook index (4 bits)
|
|
* \param pitch_delay_min lower bound (integer) of pitch delay interval for
|
|
* second subframe
|
|
*
|
|
* \return pitch delay in 1/3 units
|
|
*
|
|
* Pitch delay is coded:
|
|
* integers only, -6 < pitch_delay - int(prev_pitch_delay) <= -2
|
|
* with 1/3 resolution, -2 < pitch_delay - int(prev_pitch_delay) < 1
|
|
* integers only, 1 <= pitch_delay - int(prev_pitch_delay) < 5
|
|
*
|
|
* \remark The routine is used in G.729 @6.4k, AMR @6.7k, AMR @5.9k,
|
|
* AMR @5.15k, AMR @4.75k for the second subframe.
|
|
*/
|
|
int ff_acelp_decode_4bit_to_2nd_delay3(
|
|
int ac_index,
|
|
int pitch_delay_min);
|
|
|
|
/**
|
|
* \brief Decode pitch delay of the first subframe encoded by 9 bits
|
|
* with 1/6 precision.
|
|
* \param ac_index adaptive codebook index (9 bits)
|
|
* \param pitch_delay_min lower bound (integer) of pitch delay interval for
|
|
* second subframe
|
|
*
|
|
* \return pitch delay in 1/6 units
|
|
*
|
|
* Pitch delay is coded:
|
|
* with 1/6 resolution, 17 < pitch_delay < 95
|
|
* integers only, 95 <= pitch_delay <= 143
|
|
*
|
|
* \remark The routine is used in AMR @12.2k for the first and third subframes.
|
|
*/
|
|
int ff_acelp_decode_9bit_to_1st_delay6(int ac_index);
|
|
|
|
/**
|
|
* \brief Decode pitch delay of the second subframe encoded by 6 bits
|
|
* with 1/6 precision.
|
|
* \param ac_index adaptive codebook index (6 bits)
|
|
* \param pitch_delay_min lower bound (integer) of pitch delay interval for
|
|
* second subframe
|
|
*
|
|
* \return pitch delay in 1/6 units
|
|
*
|
|
* Pitch delay is coded:
|
|
* with 1/6 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5
|
|
*
|
|
* \remark The routine is used in AMR @12.2k for the second and fourth subframes.
|
|
*/
|
|
int ff_acelp_decode_6bit_to_2nd_delay6(
|
|
int ac_index,
|
|
int pitch_delay_min);
|
|
|
|
/**
|
|
* \brief Update past quantized energies
|
|
* \param quant_energy [in/out] past quantized energies (5.10)
|
|
* \param gain_corr_factor gain correction factor
|
|
* \param log2_ma_pred_order log2() of MA prediction order
|
|
* \param erasure frame erasure flag
|
|
*
|
|
* If frame erasure flag is not equal to zero, memory is updated with
|
|
* averaged energy, attenuated by 4dB:
|
|
* max(avg(quant_energy[i])-4, -14), i=0,ma_pred_order
|
|
*
|
|
* In normal mode memory is updated with
|
|
* Er - Ep = 20 * log10(gain_corr_factor)
|
|
*
|
|
* \remark The routine is used in G.729 and AMR (all modes).
|
|
*/
|
|
void ff_acelp_update_past_gain(
|
|
int16_t* quant_energy,
|
|
int gain_corr_factor,
|
|
int log2_ma_pred_order,
|
|
int erasure);
|
|
|
|
/**
|
|
* \brief Decode the adaptive codebook gain and add
|
|
* correction (4.1.5 and 3.9.1 of G.729).
|
|
* \param gain_corr_factor gain correction factor (2.13)
|
|
* \param fc_v fixed-codebook vector (2.13)
|
|
* \param mr_energy mean innovation energy and fixed-point correction (7.13)
|
|
* \param quant_energy [in/out] past quantized energies (5.10)
|
|
* \param subframe_size length of subframe
|
|
* \param ma_pred_order MA prediction order
|
|
*
|
|
* \return quantized fixed-codebook gain (14.1)
|
|
*
|
|
* The routine implements equations 69, 66 and 71 of the G.729 specification (3.9.1)
|
|
*
|
|
* Em - mean innovation energy (dB, constant, depends on decoding algorithm)
|
|
* Ep - mean-removed predicted energy (dB)
|
|
* Er - mean-removed innovation energy (dB)
|
|
* Ei - mean energy of the fixed-codebook contribution (dB)
|
|
* N - subframe_size
|
|
* M - MA (Moving Average) prediction order
|
|
* gc - fixed-codebook gain
|
|
* gc_p - predicted fixed-codebook gain
|
|
*
|
|
* Fixed codebook gain is computed using predicted gain gc_p and
|
|
* correction factor gain_corr_factor as shown below:
|
|
*
|
|
* gc = gc_p * gain_corr_factor
|
|
*
|
|
* The predicted fixed codebook gain gc_p is found by predicting
|
|
* the energy of the fixed-codebook contribution from the energy
|
|
* of previous fixed-codebook contributions.
|
|
*
|
|
* mean = 1/N * sum(i,0,N){ fc_v[i] * fc_v[i] }
|
|
*
|
|
* Ei = 10log(mean)
|
|
*
|
|
* Er = 10log(1/N * gc^2 * mean) - Em = 20log(gc) + Ei - Em
|
|
*
|
|
* Replacing Er with Ep and gc with gc_p we will receive:
|
|
*
|
|
* Ep = 10log(1/N * gc_p^2 * mean) - Em = 20log(gc_p) + Ei - Em
|
|
*
|
|
* and from above:
|
|
*
|
|
* gc_p = 10^((Ep - Ei + Em) / 20)
|
|
*
|
|
* Ep is predicted using past energies and prediction coefficients:
|
|
*
|
|
* Ep = sum(i,0,M){ ma_prediction_coeff[i] * quant_energy[i] }
|
|
*
|
|
* gc_p in fixed-point arithmetic is calculated as following:
|
|
*
|
|
* mean = 1/N * sum(i,0,N){ (fc_v[i] / 2^13) * (fc_v[i] / 2^13) } =
|
|
* = 1/N * sum(i,0,N) { fc_v[i] * fc_v[i] } / 2^26
|
|
*
|
|
* Ei = 10log(mean) = -10log(N) - 10log(2^26) +
|
|
* + 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })
|
|
*
|
|
* Ep - Ei + Em = Ep + Em + 10log(N) + 10log(2^26) -
|
|
* - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) =
|
|
* = Ep + mr_energy - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })
|
|
*
|
|
* gc_p = 10 ^ ((Ep - Ei + Em) / 20) =
|
|
* = 2 ^ (3.3219 * (Ep - Ei + Em) / 20) = 2 ^ (0.166 * (Ep - Ei + Em))
|
|
*
|
|
* where
|
|
*
|
|
* mr_energy = Em + 10log(N) + 10log(2^26)
|
|
*
|
|
* \remark The routine is used in G.729 and AMR (all modes).
|
|
*/
|
|
int16_t ff_acelp_decode_gain_code(
|
|
int gain_corr_factor,
|
|
const int16_t* fc_v,
|
|
int mr_energy,
|
|
const int16_t* quant_energy,
|
|
const int16_t* ma_prediction_coeff,
|
|
int subframe_size,
|
|
int max_pred_order);
|
|
|
|
#endif /* FFMPEG_ACELP_PITCH_DELAY_H */
|