/* * gain code, gain pitch and pitch delay decoding * * Copyright (c) 2008 Vladimir Voroshilov * * This file is part of Libav. * * Libav 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. * * Libav 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 Libav; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #ifndef AVCODEC_ACELP_PITCH_DELAY_H #define AVCODEC_ACELP_PITCH_DELAY_H #include #include "audiodsp.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) * * @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[in,out] quant_energy 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 adsp initialized audio DSP context * @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[in,out] quant_energy past quantized energies (5.10) * @param subframe_size length of subframe * * @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( AudioDSPContext *adsp, 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); /** * Calculate fixed gain (part of section 6.1.3 of AMR spec) * * @param fixed_gain_factor gain correction factor * @param fixed_mean_energy mean decoded algebraic codebook vector energy * @param prediction_error vector of the quantified predictor errors of * the four previous subframes. It is updated by this function. * @param energy_mean desired mean innovation energy * @param pred_table table of four moving average coefficients */ float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy, float *prediction_error, float energy_mean, const float *pred_table); /** * Decode the adaptive codebook index to the integer and fractional parts * of the pitch lag for one subframe at 1/3 fractional precision. * * The choice of pitch lag is described in 3GPP TS 26.090 section 5.6.1. * * @param lag_int integer part of pitch lag of the current subframe * @param lag_frac fractional part of pitch lag of the current subframe * @param pitch_index parsed adaptive codebook (pitch) index * @param prev_lag_int integer part of pitch lag for the previous subframe * @param subframe current subframe number * @param third_as_first treat the third frame the same way as the first */ void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index, const int prev_lag_int, const int subframe, int third_as_first, int resolution); #endif /* AVCODEC_ACELP_PITCH_DELAY_H */