72 lines
1.5 KiB
C
72 lines
1.5 KiB
C
|
|
/******************************************************************
|
|
|
|
iLBC Speech Coder ANSI-C Source Code
|
|
|
|
anaFilter.c
|
|
|
|
Copyright (C) The Internet Society (2004).
|
|
All Rights Reserved.
|
|
|
|
******************************************************************/
|
|
|
|
#include <string.h>
|
|
#include "anaFilter.h"
|
|
#include "iLBC_define.h"
|
|
|
|
/*----------------------------------------------------------------*
|
|
* LP analysis filter.
|
|
|
|
|
|
*---------------------------------------------------------------*/
|
|
|
|
void anaFilter(
|
|
float *In, /* (i) Signal to be filtered */
|
|
float *a, /* (i) LP parameters */
|
|
int len,/* (i) Length of signal */
|
|
float *Out, /* (o) Filtered signal */
|
|
float *mem /* (i/o) Filter state */
|
|
){
|
|
int i, j;
|
|
float *po, *pi, *pm, *pa;
|
|
|
|
po = Out;
|
|
|
|
/* Filter first part using memory from past */
|
|
|
|
for (i=0; i<LPC_FILTERORDER; i++) {
|
|
pi = &In[i];
|
|
pm = &mem[LPC_FILTERORDER-1];
|
|
pa = a;
|
|
*po=0.0;
|
|
for (j=0; j<=i; j++) {
|
|
*po+=(*pa++)*(*pi--);
|
|
}
|
|
for (j=i+1; j<LPC_FILTERORDER+1; j++) {
|
|
|
|
*po+=(*pa++)*(*pm--);
|
|
}
|
|
po++;
|
|
}
|
|
|
|
/* Filter last part where the state is entierly
|
|
in the input vector */
|
|
|
|
for (i=LPC_FILTERORDER; i<len; i++) {
|
|
pi = &In[i];
|
|
pa = a;
|
|
*po=0.0;
|
|
for (j=0; j<LPC_FILTERORDER+1; j++) {
|
|
*po+=(*pa++)*(*pi--);
|
|
}
|
|
po++;
|
|
}
|
|
|
|
/* Update state vector */
|
|
|
|
memcpy(mem, &In[len-LPC_FILTERORDER],
|
|
LPC_FILTERORDER*sizeof(float));
|
|
}
|
|
|
|
|