???/******************************************************************

???????iLBC?Speech?Coder?ANSI-C?Source?Code

???????anaFilter.c

???????Copyright?（C）?The?Internet?Society?（2004）.
???????All?Rights?Reserved.

???******************************************************************/

???#include?
???#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???????????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
???????????????*po+=（*pa++）*（*pm--）;
???????????}
???????????po++;
???????}

???????/*?Filter?last?part?where?the?state?is?entirely
??????????in?the?input?vector?*/

???????for?（i=LPC_FILTERORDER;?i???????????pi?=?&In[i];
???????????pa?=?a;
???????????*po=0.0;
???????????for?（j=0;?j???????????????*po+=（*pa++）*（*pi--）;
???????????}
???????????po++;
???????}

???????/*?Update?state?vector?*/

???????memcpy（mem?&In[len-LPC_FILTERORDER]
???????????LPC_FILTERORDER*sizeof（float））;
???}