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/*
* AAC encoder TNS
* Copyright (C) 2015 Rostislav Pehlivanov
*
* 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
* AAC encoder temporal noise shaping
* @author Rostislav Pehlivanov ( atomnuker gmail com )
*/
#include <strings.h>
#include "aacenc.h"
#include "aacenc_tns.h"
#include "aactab.h"
#include "aacenc_utils.h"
#include "aacenc_quantization.h"
static inline void conv_to_int32(int32_t *loc, float *samples, int num, float norm)
{
int i;
for (i = 0; i < num; i++)
loc[i] = ceilf((samples[i]/norm)*INT32_MAX);
}
static inline void conv_to_float(float *arr, int32_t *cof, int num)
{
int i;
for (i = 0; i < num; i++)
arr[i] = (float)cof[i]/INT32_MAX;
}
/* Input: quantized 4 bit coef, output: 1 if first (MSB) 2 bits are the same */
static inline int coef_test_compression(int coef)
{
int tmp = coef >> 2;
int res = ff_ctz(tmp);
if (res > 1)
return 1; /* ...00 -> compressable */
else if (res == 1)
return 0; /* ...10 -> uncompressable */
else if (ff_ctz(tmp >> 1) > 0)
return 0; /* ...0 1 -> uncompressable */
else
return 1; /* ...1 1 -> compressable */
}
static inline int compress_coef(int *coefs, int num)
{
int i, res = 0;
for (i = 0; i < num; i++)
res += coef_test_compression(coefs[i]);
return res == num ? 1 : 0;
}
/**
* Encode TNS data.
* Coefficient compression saves a single bit.
*/
void encode_tns_info(AACEncContext *s, SingleChannelElement *sce)
{
int i, w, filt, coef_len, coef_compress;
const int coef_res = MAX_LPC_PRECISION == 4 ? 1 : 0;
const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE;
put_bits(&s->pb, 1, !!sce->tns.present);
if (!sce->tns.present)
return;
for (i = 0; i < sce->ics.num_windows; i++) {
put_bits(&s->pb, 2 - is8, sce->tns.n_filt[i]);
if (sce->tns.n_filt[i]) {
put_bits(&s->pb, 1, !!coef_res);
for (filt = 0; filt < sce->tns.n_filt[i]; filt++) {
put_bits(&s->pb, 6 - 2 * is8, sce->tns.length[i][filt]);
put_bits(&s->pb, 5 - 2 * is8, sce->tns.order[i][filt]);
if (sce->tns.order[i][filt]) {
coef_compress = compress_coef(sce->tns.coef_idx[i][filt],
sce->tns.order[i][filt]);
put_bits(&s->pb, 1, !!sce->tns.direction[i][filt]);
put_bits(&s->pb, 1, !!coef_compress);
coef_len = coef_res + 3 - coef_compress;
for (w = 0; w < sce->tns.order[i][filt]; w++)
put_bits(&s->pb, coef_len, sce->tns.coef_idx[i][filt][w]);
}
}
}
}
}
static int process_tns_coeffs(TemporalNoiseShaping *tns, float *tns_coefs_raw,
int order, int w, int filt)
{
int i, j;
int *idx = tns->coef_idx[w][filt];
float *lpc = tns->coef[w][filt];
const int iqfac_p = ((1 << (MAX_LPC_PRECISION-1)) - 0.5)/(M_PI/2.0);
const int iqfac_m = ((1 << (MAX_LPC_PRECISION-1)) + 0.5)/(M_PI/2.0);
float temp[TNS_MAX_ORDER] = {0.0f}, out[TNS_MAX_ORDER] = {0.0f};
/* Quantization */
for (i = 0; i < order; i++) {
idx[i] = ceilf(asin(tns_coefs_raw[i])*((tns_coefs_raw[i] >= 0) ? iqfac_p : iqfac_m));
lpc[i] = 2*sin(idx[i]/((idx[i] >= 0) ? iqfac_p : iqfac_m));
}
/* Trim any coeff less than 0.1f from the end */
for (i = order; i > -1; i--) {
lpc[i] = (fabs(lpc[i]) > 0.1f) ? lpc[i] : 0.0f;
if (lpc[i] != 0.0 ) {
order = i;
break;
}
}
if (!order)
return 0;
/* Step up procedure, convert to LPC coeffs */
out[0] = 1.0f;
for (i = 1; i <= order; i++) {
for (j = 1; j < i; j++) {
temp[j] = out[j] + lpc[i]*out[i-j];
}
for (j = 1; j <= i; j++) {
out[j] = temp[j];
}
out[i] = lpc[i-1];
}
memcpy(lpc, out, TNS_MAX_ORDER*sizeof(float));
return order;
}
static void apply_tns_filter(float *out, float *in, int order, int direction,
float *tns_coefs, int ltp_used, int w, int filt, int start_i, int len)
{
int i, j, inc, start = start_i;
float tmp[TNS_MAX_ORDER+1];
if (direction) {
inc = -1;
start = (start + len) - 1;
} else {
inc = 1;
}
if (!ltp_used) { /* AR filter */
for (i = 0; i < len; i++, start += inc)
out[i] = in[start];
for (j = 1; j <= FFMIN(i, order); j++)
out[i] += tns_coefs[j]*in[start - j*inc];
} else { /* MA filter */
for (i = 0; i < len; i++, start += inc) {
tmp[0] = out[i] = in[start];
for (j = 1; j <= FFMIN(i, order); j++)
out[i] += tmp[j]*tns_coefs[j];
for (j = order; j > 0; j--)
tmp[j] = tmp[j - 1];
}
}
}
void search_for_tns(AACEncContext *s, SingleChannelElement *sce)
{
TemporalNoiseShaping *tns = &sce->tns;
int w, g, order, sfb_start, sfb_len, coef_start, shift[MAX_LPC_ORDER], count = 0;
const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE;
const int tns_max_order = is8 ? 7 : s->profile == FF_PROFILE_AAC_LOW ? 12 : TNS_MAX_ORDER;
const float freq_mult = mpeg4audio_sample_rates[s->samplerate_index]/(1024.0f/sce->ics.num_windows)/2.0f;
float max_coef = 0.0f;
for (coef_start = 0; coef_start < 1024; coef_start++)
max_coef = FFMAX(max_coef, sce->pcoeffs[coef_start]);
for (w = 0; w < sce->ics.num_windows; w++) {
int filters = 1, start = 0, coef_len = 0;
int32_t conv_coeff[1024] = {0};
int32_t coefs_t[MAX_LPC_ORDER][MAX_LPC_ORDER] = {{0}};
/* Determine start sfb + coef - excludes anything below threshold */
for (g = 0; g < sce->ics.num_swb; g++) {
if (start*freq_mult > TNS_LOW_LIMIT) {
sfb_start = w*16+g;
sfb_len = (w+1)*16 + g - sfb_start;
coef_start = sce->ics.swb_offset[sfb_start];
coef_len = sce->ics.swb_offset[sfb_start + sfb_len] - coef_start;
break;
}
start += sce->ics.swb_sizes[g];
}
if (coef_len <= 0)
continue;
conv_to_int32(conv_coeff, &sce->pcoeffs[coef_start], coef_len, max_coef);
/* LPC */
order = ff_lpc_calc_coefs(&s->lpc, conv_coeff, coef_len,
TNS_MIN_PRED_ORDER, tns_max_order,
32, coefs_t, shift,
FF_LPC_TYPE_LEVINSON, 10,
ORDER_METHOD_EST, MAX_LPC_SHIFT, 0) - 1;
/* Works surprisingly well, remember to tweak MAX_LPC_SHIFT if you want to play around with this */
if (shift[order] > 3) {
int direction = 0;
float tns_coefs_raw[TNS_MAX_ORDER];
tns->n_filt[w] = filters++;
conv_to_float(tns_coefs_raw, coefs_t[order], order);
for (g = 0; g < tns->n_filt[w]; g++) {
process_tns_coeffs(tns, tns_coefs_raw, order, w, g);
apply_tns_filter(&sce->coeffs[coef_start], sce->pcoeffs, order, direction, tns->coef[w][g],
sce->ics.ltp.present, w, g, coef_start, coef_len);
tns->order[w][g] = order;
tns->length[w][g] = sfb_len;
tns->direction[w][g] = direction;
}
count++;
}
}
sce->tns.present = !!count;
}
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