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/* Copyright (C) 2002 Jean-Marc Valin
File: filters.c
Various analysis/synthesis filters
This library 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.
This library 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 this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "filters.h"
#define min(a,b) ((a) < (b) ? (a) : (b))
void bw_lpc(float gamma, float *lpc_in, float *lpc_out, int order)
{
int i;
float tmp=1;
for (i=0;i<order+1;i++)
{
lpc_out[i] = tmp * lpc_in[i];
tmp *= gamma;
}
}
void syn_filt(float *x, float *a, float *y, int N, int ord)
{
int i,j;
for (i=0;i<N;i++)
{
y[i]=x[i];
for (j=1;j<=ord;j++)
y[i] -= a[j]*y[i-j];
}
}
void syn_filt_zero(float *x, float *a, float *y, int N, int ord)
{
int i,j;
for (i=0;i<N;i++)
{
y[i]=x[i];
for (j=1;j<=min(ord,i);j++)
y[i] -= a[j]*y[i-j];
}
}
void syn_filt_mem(float *x, float *a, float *y, int N, int ord, float *mem)
{
int i,j;
for (i=0;i<N;i++)
{
y[i]=x[i];
for (j=1;j<=min(ord,i);j++)
y[i] -= a[j]*y[i-j];
for (j=i+1;j<=ord;j++)
y[i] -= a[j]*mem[j-i-1];
}
for (i=0;i<ord;i++)
mem[i]=y[N-i-1];
}
void residue(float *x, float *a, float *y, int N, int ord)
{
int i,j;
for (i=N-1;i>=0;i--)
{
y[i]=x[i];
for (j=1;j<=ord;j++)
y[i] += a[j]*x[i-j];
}
}
void residue_zero(float *x, float *a, float *y, int N, int ord)
{
int i,j;
for (i=N-1;i>=0;i--)
{
y[i]=x[i];
for (j=1;j<=min(ord,i);j++)
y[i] += a[j]*x[i-j];
}
}
void residue_mem(float *x, float *a, float *y, int N, int ord, float *mem)
{
int i,j;
for (i=N-1;i>=0;i--)
{
y[i]=x[i];
for (j=1;j<=min(ord,i);j++)
y[i] += a[j]*x[i-j];
for (j=i+1;j<=ord;j++)
y[i] += a[j]*mem[j-i-1];
}
for (i=0;i<ord;i++)
mem[i]=x[N-i-1];
}
float xcorr(float *x, float *y, int len)
{
int i;
float sum=0;
for (i=0;i<len;i++)
sum += x[i]*y[i];
return sum;
}
void fir_mem(float *x, float *a, float *y, int N, int M, float *mem)
{
int i,j;
for (i=0;i<N;i++)
{
y[i]=0;
for (j=0;j<=min(M-1,i);j++)
y[i] += a[j]*x[i-j];
for (j=i+1;j<=M-1;j++)
y[i] += a[j]*mem[j-i-1];
}
for (i=0;i<M-1;i++)
mem[i]=x[N-i-1];
}
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