git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@7221 65c4cc65-6c06-0410-ace0-fbb531ad65f3
109 lines
1.5 KiB
C
109 lines
1.5 KiB
C
|
|
/******************************************************************
|
|
|
|
iLBC Speech Coder ANSI-C Source Code
|
|
|
|
syntFilter.c
|
|
|
|
Copyright (C) The Internet Society (2004).
|
|
All Rights Reserved.
|
|
|
|
******************************************************************/
|
|
|
|
#include "iLBC_define.h"
|
|
#include "syntFilter.h"
|
|
|
|
/*----------------------------------------------------------------*
|
|
* LP synthesis filter.
|
|
*---------------------------------------------------------------*/
|
|
|
|
void syntFilter(
|
|
float *Out, /* (i/o) Signal to be filtered */
|
|
float *a, /* (i) LP parameters */
|
|
int len, /* (i) Length of signal */
|
|
float *mem /* (i/o) Filter state */
|
|
){
|
|
int i, j;
|
|
float *po, *pi, *pa, *pm;
|
|
|
|
po=Out;
|
|
|
|
/* Filter first part using memory from past */
|
|
|
|
for (i=0; i<LPC_FILTERORDER; i++) {
|
|
pi=&Out[i-1];
|
|
pa=&a[1];
|
|
pm=&mem[LPC_FILTERORDER-1];
|
|
for (j=1; 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 output vector */
|
|
|
|
for (i=LPC_FILTERORDER; i<len; i++) {
|
|
|
|
|
|
pi=&Out[i-1];
|
|
pa=&a[1];
|
|
for (j=1; j<LPC_FILTERORDER+1; j++) {
|
|
*po-=(*pa++)*(*pi--);
|
|
}
|
|
po++;
|
|
}
|
|
|
|
/* Update state vector */
|
|
|
|
memcpy(mem, &Out[len-LPC_FILTERORDER],
|
|
LPC_FILTERORDER*sizeof(float));
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|