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/****************************************************************** 
 
    iLBC Speech Coder ANSI-C Source Code 
 
    syntFilter.c  
 
    Copyright (c) 2001, 
    Global IP Sound AB. 
    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)); 
}