ref: b1d957de163081057eac05c26d502f6c28fc6dc8
dir: /libfaad/tns.c/
/*
** FAAD - Freeware Advanced Audio Decoder
** Copyright (C) 2002 M. Bakker
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** This program 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 General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
**
** $Id: tns.c,v 1.8 2002/03/27 19:09:29 menno Exp $
**/
#include "common.h"
#include "syntax.h"
#include "tns.h"
/* TNS decoding for one channel and frame */
void tns_decode_frame(ic_stream *ics, tns_info *tns, uint8_t sr_index,
uint8_t object_type, real_t *spec)
{
uint8_t w, f, tns_order;
int8_t inc;
uint16_t bottom, top, start, end, size;
real_t lpc[TNS_MAX_ORDER+1];
if (!ics->tns_data_present)
return;
for (w = 0; w < ics->num_windows; w++)
{
bottom = ics->num_swb;
for (f = 0; f < tns->n_filt[w]; f++)
{
top = bottom;
bottom = max(top - tns->length[w][f], 0);
tns_order = min(tns->order[w][f], tns_max_order(ics, sr_index,
object_type));
if (!tns_order)
continue;
tns_decode_coef(tns_order, tns->coef_res[w]+3,
tns->coef_compress[w][f], tns->coef[w][f], lpc);
start = ics->swb_offset[min(bottom,
min(tns_max_bands(ics, sr_index, object_type), ics->max_sfb))];
end = ics->swb_offset[min(top,
min(tns_max_bands(ics, sr_index, object_type), ics->max_sfb))];
if ((size = end - start) <= 0)
continue;
if (tns->direction[w][f])
{
inc = -1;
start = end - 1;
} else
inc = 1;
tns_ar_filter(&spec[(w*128)+start], size, inc, lpc, tns_order);
}
}
}
/* TNS encoding for one channel and frame */
void tns_encode_frame(ic_stream *ics, tns_info *tns, uint8_t sr_index,
uint8_t object_type, real_t *spec)
{
uint8_t w, f, tns_order;
int8_t inc;
uint16_t bottom, top, start, end, size;
real_t lpc[TNS_MAX_ORDER+1];
if (!ics->tns_data_present)
return;
for (w = 0; w < ics->num_windows; w++)
{
bottom = ics->num_swb;
for (f = 0; f < tns->n_filt[w]; f++)
{
top = bottom;
bottom = max(top - tns->length[w][f], 0);
tns_order = min(tns->order[w][f], tns_max_order(ics, sr_index,
object_type));
if (!tns_order)
continue;
tns_decode_coef(tns_order, tns->coef_res[w]+3,
tns->coef_compress[w][f], tns->coef[w][f], lpc);
start = ics->swb_offset[min(bottom,
min(tns_max_bands(ics, sr_index, object_type), ics->max_sfb))];
end = ics->swb_offset[min(top,
min(tns_max_bands(ics, sr_index, object_type), ics->max_sfb))];
if ((size = end - start) <= 0)
continue;
if (tns->direction[w][f])
{
inc = -1;
start = end - 1;
} else
inc = 1;
tns_ma_filter(&spec[(w*128)+start], size, inc, lpc, tns_order);
}
}
}
/* Decoder transmitted coefficients for one TNS filter */
static void tns_decode_coef(uint8_t order, uint8_t coef_res_bits, uint8_t coef_compress,
uint8_t *coef, real_t *a)
{
uint8_t i, m;
uint8_t coef_res2, s_mask, n_mask;
int8_t tmp[TNS_MAX_ORDER+1];
real_t tmp2[TNS_MAX_ORDER+1], b[TNS_MAX_ORDER+1];
real_t iqfac;
/* Some internal tables */
static uint8_t sgn_mask[] = { 0x2, 0x4, 0x8 };
static uint8_t neg_mask[] = { ~0x3, ~0x7, ~0xf };
/* size used for transmission */
coef_res2 = coef_res_bits - coef_compress;
s_mask = sgn_mask[coef_res2 - 2]; /* mask for sign bit */
n_mask = neg_mask[coef_res2 - 2]; /* mask for padding neg. values */
/* Conversion to signed integer */
for (i = 0; i < order; i++)
tmp[i] = (coef[i] & s_mask) ? (coef[i] | n_mask) : coef[i];
/* Inverse quantization */
if (tmp[i] >= 0)
iqfac = ((1 << (coef_res_bits-1)) - 0.5f) / M_PI_2;
else
iqfac = ((1 << (coef_res_bits-1)) + 0.5f) / M_PI_2;
for (i = 0; i < order; i++)
tmp2[i] = (real_t)sin(tmp[i] / iqfac);
/* Conversion to LPC coefficients */
a[0] = 1;
for (m = 1; m <= order; m++)
{
for (i = 1; i < m; i++) /* loop only while i<m */
b[i] = a[i] + tmp2[m-1] * a[m-i];
for (i = 1; i < m; i++) /* loop only while i<m */
a[i] = b[i];
a[m] = tmp2[m-1]; /* changed */
}
}
static void tns_ar_filter(real_t *spectrum, uint16_t size, int8_t inc, real_t *lpc,
uint8_t order)
{
/*
- Simple all-pole filter of order "order" defined by
y(n) = x(n) - lpc[1]*y(n-1) - ... - lpc[order]*y(n-order)
- The state variables of the filter are initialized to zero every time
- The output data is written over the input data ("in-place operation")
- An input vector of "size" samples is processed and the index increment
to the next data sample is given by "inc"
*/
uint8_t j;
uint16_t i;
real_t y, state[TNS_MAX_ORDER];
for (i = 0; i < order; i++)
state[i] = 0;
for (i = 0; i < size; i++)
{
y = *spectrum;
for (j = 0; j < order; j++)
y -= lpc[j+1] * state[j];
for (j = order-1; j > 0; j--)
state[j] = state[j-1];
state[0] = y;
*spectrum = y;
spectrum += inc;
}
}
static void tns_ma_filter(real_t *spectrum, uint16_t size, int8_t inc, real_t *lpc,
uint8_t order)
{
/*
- Simple all-zero filter of order "order" defined by
y(n) = x(n) + a(2)*x(n-1) + ... + a(order+1)*x(n-order)
- The state variables of the filter are initialized to zero every time
- The output data is written over the input data ("in-place operation")
- An input vector of "size" samples is processed and the index increment
to the next data sample is given by "inc"
*/
uint8_t j;
uint16_t i;
real_t y, state[TNS_MAX_ORDER];
for (i = 0; i < order; i++)
state[i] = 0;
for (i = 0; i < size; i++)
{
y = *spectrum;
for (j = 0; j < order; j++)
y += lpc[j+1] * state[j];
for (j = order-1; j > 0; j--)
state[j] = state[j-1];
state[0] = *spectrum;
*spectrum = y;
spectrum += inc;
}
}
static uint8_t tns_max_bands_table[12][5] =
{
/* entry for each sampling rate
* 1 Main/LC long window
* 2 Main/LC short window
* 3 SSR long window
* 4 SSR short window
* 5 LD 512 window
*/
{ 31, 9, 28, 7, 0 }, /* 96000 */
{ 31, 9, 28, 7, 0 }, /* 88200 */
{ 34, 10, 27, 7, 0 }, /* 64000 */
{ 40, 14, 26, 6, 31 }, /* 48000 */
{ 42, 14, 26, 6, 32 }, /* 44100 */
{ 51, 14, 26, 6, 37 }, /* 32000 */
{ 46, 14, 29, 7, 31 }, /* 24000 */
{ 46, 14, 29, 7, 31 }, /* 22050 */
{ 42, 14, 23, 8, 0 }, /* 16000 */
{ 42, 14, 23, 8, 0 }, /* 12000 */
{ 42, 14, 23, 8, 0 }, /* 11025 */
{ 39, 14, 19, 7, 0 }, /* 8000 */
};
static uint8_t tns_max_bands(ic_stream *ics, uint8_t sr_index,
uint8_t object_type)
{
uint8_t i;
i = (ics->window_sequence == EIGHT_SHORT_SEQUENCE) ? 1 : 0;
#ifdef LD_DEC
i = (object_type == LD) ? 4 : i;
#endif
return tns_max_bands_table[sr_index][i];
}
static uint8_t tns_max_order(ic_stream *ics, uint8_t sr_index,
uint8_t object_type)
{
/* Correction in 14496-3 Cor. 1
Works like MPEG2-AAC (13818-7) now
For other object types (scalable) the following goes for tns max order
for long windows:
if (sr_index <= 5)
return 12;
else
return 20;
*/
if (ics->window_sequence != EIGHT_SHORT_SEQUENCE)
{
switch (object_type)
{
case MAIN:
return 20;
case LTP:
return 20;
#ifdef LD_DEC
case LD:
return 20;
#endif
case LC:
case SSR:
return 12;
}
} else {
return 7;
}
return 0;
}