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FFmpeg/libavcodec/ac3enc_template.c

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/*
* AC-3 encoder float/fixed template
* Copyright (c) 2000 Fabrice Bellard
* Copyright (c) 2006-2011 Justin Ruggles <justin.ruggles@gmail.com>
* Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
*
* 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
* AC-3 encoder float/fixed template
*/
#include "config_components.h"
#include <stdint.h>
#include "libavutil/attributes.h"
#include "libavutil/mem_internal.h"
#include "audiodsp.h"
#include "ac3enc.h"
#include "eac3enc.h"
/*
* Apply the MDCT to input samples to generate frequency coefficients.
* This applies the KBD window and normalizes the input to reduce precision
* loss due to fixed-point calculations.
*/
static void apply_mdct(AC3EncodeContext *s)
{
int blk, ch;
for (ch = 0; ch < s->channels; ch++) {
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
const SampleType *input_samples = (SampleType*)s->planar_samples[ch] + blk * AC3_BLOCK_SIZE;
s->fdsp->vector_fmul(s->windowed_samples, input_samples,
s->mdct_window, AC3_BLOCK_SIZE);
s->fdsp->vector_fmul_reverse((SampleType*)s->windowed_samples + AC3_BLOCK_SIZE,
&input_samples[AC3_BLOCK_SIZE],
s->mdct_window, AC3_BLOCK_SIZE);
s->tx_fn(s->tx, block->mdct_coef[ch+1],
s->windowed_samples, sizeof(float));
}
}
}
/*
* Calculate coupling channel and coupling coordinates.
*/
static void apply_channel_coupling(AC3EncodeContext *s)
{
LOCAL_ALIGNED_32(CoefType, cpl_coords, [AC3_MAX_BLOCKS], [AC3_MAX_CHANNELS][16]);
#if AC3ENC_FLOAT
LOCAL_ALIGNED_32(int32_t, fixed_cpl_coords, [AC3_MAX_BLOCKS], [AC3_MAX_CHANNELS][16]);
#else
int32_t (*fixed_cpl_coords)[AC3_MAX_CHANNELS][16] = cpl_coords;
#endif
int av_uninit(blk), ch, bnd, i, j;
CoefSumType energy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][16] = {{{0}}};
int cpl_start, num_cpl_coefs;
memset(cpl_coords, 0, AC3_MAX_BLOCKS * sizeof(*cpl_coords));
#if AC3ENC_FLOAT
memset(fixed_cpl_coords, 0, AC3_MAX_BLOCKS * sizeof(*cpl_coords));
#endif
/* align start to 16-byte boundary. align length to multiple of 32.
note: coupling start bin % 4 will always be 1 */
cpl_start = s->start_freq[CPL_CH] - 1;
num_cpl_coefs = FFALIGN(s->num_cpl_subbands * 12 + 1, 32);
cpl_start = FFMIN(256, cpl_start + num_cpl_coefs) - num_cpl_coefs;
/* calculate coupling channel from fbw channels */
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
CoefType *cpl_coef = &block->mdct_coef[CPL_CH][cpl_start];
if (!block->cpl_in_use)
continue;
memset(cpl_coef, 0, num_cpl_coefs * sizeof(*cpl_coef));
for (ch = 1; ch <= s->fbw_channels; ch++) {
CoefType *ch_coef = &block->mdct_coef[ch][cpl_start];
if (!block->channel_in_cpl[ch])
continue;
for (i = 0; i < num_cpl_coefs; i++)
cpl_coef[i] += ch_coef[i];
}
/* coefficients must be clipped in order to be encoded */
clip_coefficients(&s->adsp, cpl_coef, num_cpl_coefs);
}
/* calculate energy in each band in coupling channel and each fbw channel */
/* TODO: possibly use SIMD to speed up energy calculation */
bnd = 0;
i = s->start_freq[CPL_CH];
while (i < s->cpl_end_freq) {
int band_size = s->cpl_band_sizes[bnd];
for (ch = CPL_CH; ch <= s->fbw_channels; ch++) {
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
if (!block->cpl_in_use || (ch > CPL_CH && !block->channel_in_cpl[ch]))
continue;
for (j = 0; j < band_size; j++) {
CoefType v = block->mdct_coef[ch][i+j];
MAC_COEF(energy[blk][ch][bnd], v, v);
}
}
}
i += band_size;
bnd++;
}
/* calculate coupling coordinates for all blocks for all channels */
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
if (!block->cpl_in_use)
continue;
for (ch = 1; ch <= s->fbw_channels; ch++) {
if (!block->channel_in_cpl[ch])
continue;
for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
cpl_coords[blk][ch][bnd] = calc_cpl_coord(energy[blk][ch][bnd],
energy[blk][CPL_CH][bnd]);
}
}
}
/* determine which blocks to send new coupling coordinates for */
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
AC3Block *block0 = blk ? &s->blocks[blk-1] : NULL;
memset(block->new_cpl_coords, 0, sizeof(block->new_cpl_coords));
if (block->cpl_in_use) {
/* send new coordinates if this is the first block, if previous
* block did not use coupling but this block does, the channels
* using coupling has changed from the previous block, or the
* coordinate difference from the last block for any channel is
* greater than a threshold value. */
if (blk == 0 || !block0->cpl_in_use) {
for (ch = 1; ch <= s->fbw_channels; ch++)
block->new_cpl_coords[ch] = 1;
} else {
for (ch = 1; ch <= s->fbw_channels; ch++) {
if (!block->channel_in_cpl[ch])
continue;
if (!block0->channel_in_cpl[ch]) {
block->new_cpl_coords[ch] = 1;
} else {
CoefSumType coord_diff = 0;
for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
coord_diff += FFABS(cpl_coords[blk-1][ch][bnd] -
cpl_coords[blk ][ch][bnd]);
}
coord_diff /= s->num_cpl_bands;
if (coord_diff > NEW_CPL_COORD_THRESHOLD)
block->new_cpl_coords[ch] = 1;
}
}
}
}
}
av_assert1(s->fbw_channels > 0);
/* calculate final coupling coordinates, taking into account reusing of
coordinates in successive blocks */
for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
blk = 0;
while (blk < s->num_blocks) {
int av_uninit(blk1);
AC3Block *block = &s->blocks[blk];
if (!block->cpl_in_use) {
blk++;
continue;
}
for (ch = 1; ch <= s->fbw_channels; ch++) {
CoefSumType energy_ch, energy_cpl;
if (!block->channel_in_cpl[ch])
continue;
energy_cpl = energy[blk][CPL_CH][bnd];
energy_ch = energy[blk][ch][bnd];
blk1 = blk+1;
while (blk1 < s->num_blocks && !s->blocks[blk1].new_cpl_coords[ch]) {
if (s->blocks[blk1].cpl_in_use) {
energy_cpl += energy[blk1][CPL_CH][bnd];
energy_ch += energy[blk1][ch][bnd];
}
blk1++;
}
cpl_coords[blk][ch][bnd] = calc_cpl_coord(energy_ch, energy_cpl);
}
blk = blk1;
}
}
/* calculate exponents/mantissas for coupling coordinates */
for (blk = 0; blk < s->num_blocks; blk++) {
AC3Block *block = &s->blocks[blk];
if (!block->cpl_in_use)
continue;
#if AC3ENC_FLOAT
s->ac3dsp.float_to_fixed24(fixed_cpl_coords[blk][1],
cpl_coords[blk][1],
s->fbw_channels * 16);
#endif
s->ac3dsp.extract_exponents(block->cpl_coord_exp[1],
fixed_cpl_coords[blk][1],
s->fbw_channels * 16);
for (ch = 1; ch <= s->fbw_channels; ch++) {
int bnd, min_exp, max_exp, master_exp;
if (!block->new_cpl_coords[ch])
continue;
/* determine master exponent */
min_exp = max_exp = block->cpl_coord_exp[ch][0];
for (bnd = 1; bnd < s->num_cpl_bands; bnd++) {
int exp = block->cpl_coord_exp[ch][bnd];
min_exp = FFMIN(exp, min_exp);
max_exp = FFMAX(exp, max_exp);
}
master_exp = ((max_exp - 15) + 2) / 3;
master_exp = FFMAX(master_exp, 0);
while (min_exp < master_exp * 3)
master_exp--;
for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
block->cpl_coord_exp[ch][bnd] = av_clip(block->cpl_coord_exp[ch][bnd] -
master_exp * 3, 0, 15);
}
block->cpl_master_exp[ch] = master_exp;
/* quantize mantissas */
for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
int cpl_exp = block->cpl_coord_exp[ch][bnd];
int cpl_mant = (fixed_cpl_coords[blk][ch][bnd] << (5 + cpl_exp + master_exp * 3)) >> 24;
if (cpl_exp == 15)
cpl_mant >>= 1;
else
cpl_mant -= 16;
block->cpl_coord_mant[ch][bnd] = cpl_mant;
}
}
}
if (AC3ENC_FLOAT && CONFIG_EAC3_ENCODER && s->eac3)
ff_eac3_set_cpl_states(s);
}
/*
* Determine rematrixing flags for each block and band.
*/
static void compute_rematrixing_strategy(AC3EncodeContext *s)
{
int nb_coefs;
int blk, bnd;
AC3Block *block, *block0 = NULL;
if (s->channel_mode != AC3_CHMODE_STEREO)
return;
for (blk = 0; blk < s->num_blocks; blk++) {
block = &s->blocks[blk];
block->new_rematrixing_strategy = !blk;
block->num_rematrixing_bands = 4;
if (block->cpl_in_use) {
block->num_rematrixing_bands -= (s->start_freq[CPL_CH] <= 61);
block->num_rematrixing_bands -= (s->start_freq[CPL_CH] == 37);
if (blk && block->num_rematrixing_bands != block0->num_rematrixing_bands)
block->new_rematrixing_strategy = 1;
}
nb_coefs = FFMIN(block->end_freq[1], block->end_freq[2]);
if (!s->rematrixing_enabled) {
block0 = block;
continue;
}
for (bnd = 0; bnd < block->num_rematrixing_bands; bnd++) {
/* calculate sum of squared coeffs for one band in one block */
int start = ff_ac3_rematrix_band_tab[bnd];
int end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
CoefSumType sum[4];
sum_square_butterfly(s, sum, block->mdct_coef[1] + start,
block->mdct_coef[2] + start, end - start);
/* compare sums to determine if rematrixing will be used for this band */
if (FFMIN(sum[2], sum[3]) < FFMIN(sum[0], sum[1]))
block->rematrixing_flags[bnd] = 1;
else
block->rematrixing_flags[bnd] = 0;
/* determine if new rematrixing flags will be sent */
if (blk &&
block->rematrixing_flags[bnd] != block0->rematrixing_flags[bnd]) {
block->new_rematrixing_strategy = 1;
}
}
block0 = block;
}
}
static void encode_frame(AC3EncodeContext *s)
{
apply_mdct(s);
s->cpl_on = s->cpl_enabled;
ff_ac3_compute_coupling_strategy(s);
if (s->cpl_on)
apply_channel_coupling(s);
compute_rematrixing_strategy(s);
#if AC3ENC_FLOAT
scale_coefficients(s);
#endif
}