ref: fb8a80fe67f1f45374b735f15a2a49ed0c9bdf8c
dir: /libfaac/filtbank.c/
/*
* FAAC - Freeware Advanced Audio Coder
* Copyright (C) 2001 Menno 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: filtbank.c,v 1.4 2001/02/28 18:39:34 menno Exp $
*/
/*
* CHANGES:
* 2001/01/17: menno: Added frequency cut off filter.
*
*/
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include "coder.h"
#include "filtbank.h"
#include "frame.h"
#include "fft.h"
#include "util.h"
#define TWOPI 2*M_PI
void FilterBankInit(faacEncHandle hEncoder)
{
unsigned int i, channel;
for (channel = 0; channel < hEncoder->numChannels; channel++) {
hEncoder->freqBuff[channel] = (double*)malloc(2*FRAME_LEN*sizeof(double));
hEncoder->overlapBuff[channel] = (double*)malloc(FRAME_LEN*sizeof(double));
memset(hEncoder->overlapBuff[channel], 0, FRAME_LEN*sizeof(double));
}
hEncoder->sin_window_long = (double*)malloc(BLOCK_LEN_LONG*sizeof(double));
hEncoder->sin_window_short = (double*)malloc(BLOCK_LEN_SHORT*sizeof(double));
hEncoder->kbd_window_long = (double*)malloc(BLOCK_LEN_LONG*sizeof(double));
hEncoder->kbd_window_short = (double*)malloc(BLOCK_LEN_SHORT*sizeof(double));
for( i=0; i<BLOCK_LEN_LONG; i++ )
hEncoder->sin_window_long[i] = sin((M_PI/(2*BLOCK_LEN_LONG)) * (i + 0.5));
for( i=0; i<BLOCK_LEN_SHORT; i++ )
hEncoder->sin_window_short[i] = sin((M_PI/(2*BLOCK_LEN_SHORT)) * (i + 0.5));
CalculateKBDWindow(hEncoder->kbd_window_long, 4, BLOCK_LEN_LONG*2);
CalculateKBDWindow(hEncoder->kbd_window_short, 6, BLOCK_LEN_SHORT*2);
}
void FilterBankEnd(faacEncHandle hEncoder)
{
unsigned int channel;
for (channel = 0; channel < hEncoder->numChannels; channel++) {
if (hEncoder->freqBuff[channel]) free(hEncoder->freqBuff[channel]);
if (hEncoder->overlapBuff[channel]) free(hEncoder->overlapBuff[channel]);
}
if (hEncoder->sin_window_long) free(hEncoder->sin_window_long);
if (hEncoder->sin_window_short) free(hEncoder->sin_window_short);
if (hEncoder->kbd_window_long) free(hEncoder->kbd_window_long);
if (hEncoder->kbd_window_short) free(hEncoder->kbd_window_short);
}
void FilterBank(faacEncHandle hEncoder,
CoderInfo *coderInfo,
double *p_in_data,
double *p_out_mdct,
double *p_overlap)
{
double *transf_buf;
double *p_o_buf, *first_window, *second_window;
int k, i;
int block_type = coderInfo->block_type;
transf_buf = (double*)malloc(2*BLOCK_LEN_LONG*sizeof(double));
/* create / shift old values */
/* We use p_overlap here as buffer holding the last frame time signal*/
memcpy(transf_buf, p_overlap, FRAME_LEN*sizeof(double));
memcpy(transf_buf+BLOCK_LEN_LONG, p_in_data, FRAME_LEN*sizeof(double));
memcpy(p_overlap, p_in_data, FRAME_LEN*sizeof(double));
/* Window shape processing */
switch (coderInfo->prev_window_shape){
case SINE_WINDOW:
if ( (block_type == ONLY_LONG_WINDOW) || (block_type == LONG_SHORT_WINDOW))
first_window = hEncoder->sin_window_long;
else
first_window = hEncoder->sin_window_short;
break;
case KBD_WINDOW:
if ( (block_type == ONLY_LONG_WINDOW) || (block_type == LONG_SHORT_WINDOW))
first_window = hEncoder->kbd_window_long;
else
first_window = hEncoder->kbd_window_short;
break;
}
switch (coderInfo->window_shape){
case SINE_WINDOW:
if ( (block_type == ONLY_LONG_WINDOW) || (block_type == SHORT_LONG_WINDOW))
second_window = hEncoder->sin_window_long;
else
second_window = hEncoder->sin_window_short;
break;
case KBD_WINDOW:
if ( (block_type == ONLY_LONG_WINDOW) || (block_type == SHORT_LONG_WINDOW))
second_window = hEncoder->kbd_window_long;
else
second_window = hEncoder->kbd_window_short;
break;
}
/* Set ptr to transf-Buffer */
p_o_buf = transf_buf;
/* Separate action for each Block Type */
switch( block_type ) {
case ONLY_LONG_WINDOW :
for ( i = 0 ; i < BLOCK_LEN_LONG ; i++){
p_out_mdct[i] = p_o_buf[i] * first_window[i];
p_out_mdct[i+BLOCK_LEN_LONG] = p_o_buf[i+BLOCK_LEN_LONG] * second_window[BLOCK_LEN_LONG-i-1];
}
MDCT( p_out_mdct, 2*BLOCK_LEN_LONG );
break;
case LONG_SHORT_WINDOW :
for ( i = 0 ; i < BLOCK_LEN_LONG ; i++)
p_out_mdct[i] = p_o_buf[i] * first_window[i];
memcpy(p_out_mdct+BLOCK_LEN_LONG,p_o_buf+BLOCK_LEN_LONG,NFLAT_LS*sizeof(double));
for ( i = 0 ; i < BLOCK_LEN_SHORT ; i++)
p_out_mdct[i+BLOCK_LEN_LONG+NFLAT_LS] = p_o_buf[i+BLOCK_LEN_LONG+NFLAT_LS] * second_window[BLOCK_LEN_SHORT-i-1];
memset(p_out_mdct+BLOCK_LEN_LONG+NFLAT_LS+BLOCK_LEN_SHORT,0,NFLAT_LS*sizeof(double));
MDCT( p_out_mdct, 2*BLOCK_LEN_LONG );
break;
case SHORT_LONG_WINDOW :
memset(p_out_mdct,0,NFLAT_LS*sizeof(double));
for ( i = 0 ; i < BLOCK_LEN_SHORT ; i++)
p_out_mdct[i+NFLAT_LS] = p_o_buf[i+NFLAT_LS] * first_window[i];
memcpy(p_out_mdct+NFLAT_LS+BLOCK_LEN_SHORT,p_o_buf+NFLAT_LS+BLOCK_LEN_SHORT,NFLAT_LS*sizeof(double));
for ( i = 0 ; i < BLOCK_LEN_LONG ; i++)
p_out_mdct[i+BLOCK_LEN_LONG] = p_o_buf[i+BLOCK_LEN_LONG] * second_window[BLOCK_LEN_LONG-i-1];
MDCT( p_out_mdct, 2*BLOCK_LEN_LONG );
break;
case ONLY_SHORT_WINDOW :
p_o_buf += NFLAT_LS;
for ( k=0; k < MAX_SHORT_WINDOWS; k++ ) {
for ( i = 0 ; i < BLOCK_LEN_SHORT ; i++ ){
p_out_mdct[i] = p_o_buf[i] * first_window[i];
p_out_mdct[i+BLOCK_LEN_SHORT] = p_o_buf[i+BLOCK_LEN_SHORT] * second_window[BLOCK_LEN_SHORT-i-1];
}
MDCT( p_out_mdct, 2*BLOCK_LEN_SHORT );
p_out_mdct += BLOCK_LEN_SHORT;
p_o_buf += BLOCK_LEN_SHORT;
first_window = second_window;
}
break;
}
if (transf_buf) free(transf_buf);
}
void specFilter(double *freqBuff,
int sampleRate,
int lowpassFreq,
int specLen
)
{
int lowpass,xlowpass;
/* calculate the last line which is not zero */
lowpass = (lowpassFreq * specLen) / (sampleRate>>1) + 1;
xlowpass = (lowpass < specLen) ? lowpass : specLen ;
memset(freqBuff+xlowpass,0,(specLen-xlowpass)*sizeof(double));
}
static double Izero(double x)
{
const double IzeroEPSILON = 1E-41; /* Max error acceptable in Izero */
double sum, u, halfx, temp;
int n;
sum = u = n = 1;
halfx = x/2.0;
do {
temp = halfx/(double)n;
n += 1;
temp *= temp;
u *= temp;
sum += u;
} while (u >= IzeroEPSILON*sum);
return(sum);
}
static void CalculateKBDWindow(double* win, double alpha, int length)
{
int i;
double IBeta;
double tmp;
double sum = 0.0;
alpha *= M_PI;
IBeta = 1.0/Izero(alpha);
/* calculate lower half of Kaiser Bessel window */
for(i=0; i<(length>>1); i++) {
tmp = 4.0*(double)i/(double)length - 1.0;
win[i] = Izero(alpha*sqrt(1.0-tmp*tmp))*IBeta;
sum += win[i];
}
sum = 1.0/sum;
tmp = 0.0;
/* calculate lower half of window */
for(i=0; i<(length>>1); i++) {
tmp += win[i];
win[i] = sqrt(tmp*sum);
}
}
static void MDCT(double *data, int N)
{
double *xi, *xr;
double tempr, tempi, c, s, cold, cfreq, sfreq; /* temps for pre and post twiddle */
double freq = TWOPI / N;
double cosfreq8, sinfreq8;
int i, n;
xi = (double*)malloc((N >> 2)*sizeof(double));
xr = (double*)malloc((N >> 2)*sizeof(double));
/* prepare for recurrence relation in pre-twiddle */
cfreq = cos (freq);
sfreq = sin (freq);
cosfreq8 = cos (freq * 0.125);
sinfreq8 = sin (freq * 0.125);
c = cosfreq8;
s = sinfreq8;
for (i = 0; i < (N >> 2); i++) {
/* calculate real and imaginary parts of g(n) or G(p) */
n = (N >> 1) - 1 - 2 * i;
if (i < (N >> 3))
tempr = data [(N >> 2) + n] + data [N + (N >> 2) - 1 - n]; /* use second form of e(n) for n = N / 2 - 1 - 2i */
else
tempr = data [(N >> 2) + n] - data [(N >> 2) - 1 - n]; /* use first form of e(n) for n = N / 2 - 1 - 2i */
n = 2 * i;
if (i < (N >> 3))
tempi = data [(N >> 2) + n] - data [(N >> 2) - 1 - n]; /* use first form of e(n) for n=2i */
else
tempi = data [(N >> 2) + n] + data [N + (N >> 2) - 1 - n]; /* use second form of e(n) for n=2i*/
/* calculate pre-twiddled FFT input */
xr[i] = tempr * c + tempi * s;
xi[i] = tempi * c - tempr * s;
/* use recurrence to prepare cosine and sine for next value of i */
cold = c;
c = c * cfreq - s * sfreq;
s = s * cfreq + cold * sfreq;
}
/* Perform in-place complex FFT of length N/4 */
switch (N) {
case 256:
srfft(xr, xi, 6);
break;
case 2048:
srfft(xr, xi, 9);
}
/* prepare for recurrence relations in post-twiddle */
c = cosfreq8;
s = sinfreq8;
/* post-twiddle FFT output and then get output data */
for (i = 0; i < (N >> 2); i++) {
/* get post-twiddled FFT output */
tempr = 2. * (xr[i] * c + xi[i] * s);
tempi = 2. * (xi[i] * c - xr[i] * s);
/* fill in output values */
data [2 * i] = -tempr; /* first half even */
data [(N >> 1) - 1 - 2 * i] = tempi; /* first half odd */
data [(N >> 1) + 2 * i] = -tempi; /* second half even */
data [N - 1 - 2 * i] = tempr; /* second half odd */
/* use recurrence to prepare cosine and sine for next value of i */
cold = c;
c = c * cfreq - s * sfreq;
s = s * cfreq + cold * sfreq;
}
if (xr) free(xr);
if (xi) free(xi);
}