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g722.c
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/*
* G.722 ADPCM audio encoder/decoder
*
* Copyright (c) CMU 1993 Computer Science, Speech Group
* Chengxiang Lu and Alex Hauptmann
* Copyright (c) 2005 Steve Underwood <steveu at coppice.org>
* Copyright (c) 2009 Kenan Gillet
* Copyright (c) 2010 Martin Storsjo
*
* 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
*/
/**
* @file
* G.722 ADPCM audio codec
*
* This G.722 decoder is a bit-exact implementation of the ITU G.722
* specification for all three specified bitrates - 64000bps, 56000bps
* and 48000bps. It passes the ITU tests.
*
* @note For the 56000bps and 48000bps bitrates, the lowest 1 or 2 bits
* respectively of each byte are ignored.
*/
#include "mathops.h"
#include "g722.h"
static const int8_t sign_lookup[2] = { -1, 1 };
static const int16_t inv_log2_table[32] = {
2048, 2093, 2139, 2186, 2233, 2282, 2332, 2383,
2435, 2489, 2543, 2599, 2656, 2714, 2774, 2834,
2896, 2960, 3025, 3091, 3158, 3228, 3298, 3371,
3444, 3520, 3597, 3676, 3756, 3838, 3922, 4008
};
static const int16_t high_log_factor_step[2] = { 798, -214 };
const int16_t ff_g722_high_inv_quant[4] = { -926, -202, 926, 202 };
/**
* low_log_factor_step[index] == wl[rl42[index]]
*/
static const int16_t low_log_factor_step[16] = {
-60, 3042, 1198, 538, 334, 172, 58, -30,
3042, 1198, 538, 334, 172, 58, -30, -60
};
const int16_t ff_g722_low_inv_quant4[16] = {
0, -2557, -1612, -1121, -786, -530, -323, -150,
2557, 1612, 1121, 786, 530, 323, 150, 0
};
const int16_t ff_g722_low_inv_quant6[64] = {
-17, -17, -17, -17, -3101, -2738, -2376, -2088,
-1873, -1689, -1535, -1399, -1279, -1170, -1072, -982,
-899, -822, -750, -682, -618, -558, -501, -447,
-396, -347, -300, -254, -211, -170, -130, -91,
3101, 2738, 2376, 2088, 1873, 1689, 1535, 1399,
1279, 1170, 1072, 982, 899, 822, 750, 682,
618, 558, 501, 447, 396, 347, 300, 254,
211, 170, 130, 91, 54, 17, -54, -17
};
static inline void s_zero(int cur_diff, struct G722Band *band)
{
int s_zero = 0;
#define ACCUM(k, x, d) do { \
int tmp = x; \
band->zero_mem[k] = ((band->zero_mem[k] * 255) >> 8) + \
d*((band->diff_mem[k]^cur_diff) < 0 ? -128 : 128); \
band->diff_mem[k] = tmp; \
s_zero += (tmp * band->zero_mem[k]) >> 15; \
} while (0)
if (cur_diff) {
ACCUM(5, band->diff_mem[4], 1);
ACCUM(4, band->diff_mem[3], 1);
ACCUM(3, band->diff_mem[2], 1);
ACCUM(2, band->diff_mem[1], 1);
ACCUM(1, band->diff_mem[0], 1);
ACCUM(0, cur_diff * 2, 1);
} else {
ACCUM(5, band->diff_mem[4], 0);
ACCUM(4, band->diff_mem[3], 0);
ACCUM(3, band->diff_mem[2], 0);
ACCUM(2, band->diff_mem[1], 0);
ACCUM(1, band->diff_mem[0], 0);
ACCUM(0, cur_diff * 2, 0);
}
#undef ACCUM
band->s_zero = s_zero;
}
/**
* adaptive predictor
*
* @param cur_diff the dequantized and scaled delta calculated from the
* current codeword
*/
static void do_adaptive_prediction(struct G722Band *band, const int cur_diff)
{
int sg[2], limit, cur_qtzd_reconst;
const int cur_part_reconst = band->s_zero + cur_diff < 0;
sg[0] = sign_lookup[cur_part_reconst != band->part_reconst_mem[0]];
sg[1] = sign_lookup[cur_part_reconst == band->part_reconst_mem[1]];
band->part_reconst_mem[1] = band->part_reconst_mem[0];
band->part_reconst_mem[0] = cur_part_reconst;
band->pole_mem[1] = av_clip((sg[0] * av_clip(band->pole_mem[0], -8191, 8191) >> 5) +
(sg[1] * 128) + (band->pole_mem[1] * 127 >> 7), -12288, 12288);
limit = 15360 - band->pole_mem[1];
band->pole_mem[0] = av_clip(-192 * sg[0] + (band->pole_mem[0] * 255 >> 8), -limit, limit);
s_zero(cur_diff, band);
cur_qtzd_reconst = av_clip_int16((band->s_predictor + cur_diff) * 2);
band->s_predictor = av_clip_int16(band->s_zero +
(band->pole_mem[0] * cur_qtzd_reconst >> 15) +
(band->pole_mem[1] * band->prev_qtzd_reconst >> 15));
band->prev_qtzd_reconst = cur_qtzd_reconst;
}
static inline int linear_scale_factor(const int log_factor)
{
const int wd1 = inv_log2_table[(log_factor >> 6) & 31];
const int shift = log_factor >> 11;
return shift < 0 ? wd1 >> -shift : wd1 << shift;
}
void ff_g722_update_low_predictor(struct G722Band *band, const int ilow)
{
do_adaptive_prediction(band,
band->scale_factor * ff_g722_low_inv_quant4[ilow] >> 10);
// quantizer adaptation
band->log_factor = av_clip((band->log_factor * 127 >> 7) +
low_log_factor_step[ilow], 0, 18432);
band->scale_factor = linear_scale_factor(band->log_factor - (8 << 11));
}
void ff_g722_update_high_predictor(struct G722Band *band, const int dhigh,
const int ihigh)
{
do_adaptive_prediction(band, dhigh);
// quantizer adaptation
band->log_factor = av_clip((band->log_factor * 127 >> 7) +
high_log_factor_step[ihigh&1], 0, 22528);
band->scale_factor = linear_scale_factor(band->log_factor - (10 << 11));
}