/******************************************************************       iLBC Speech Coder ANSI-C Source Code       hpInput.c       Copyright (C) The Internet Society (2004).       All Rights Reserved.   ******************************************************************/   #include "constants.h"   /*----------------------------------------------------------------*    *  Input high-pass filter    *---------------------------------------------------------------*/   void hpInput(       float *In,  /* (i) vector to filter */       int len,    /* (i) length of vector to filter */       float *Out, /* (o) the resulting filtered vector */       float *mem  /* (i/o) the filter state */   ){       int i;       float *pi, *po;       /* all-zero section*/       pi = &In[0];       po = &Out[0];       for (i=0; i<len; i++) {           *po = hpi_zero_coefsTbl[0] * (*pi);           *po += hpi_zero_coefsTbl[1] * mem[0];           *po += hpi_zero_coefsTbl[2] * mem[1];           mem[1] = mem[0];           mem[0] = *pi;           po++;           pi++;       }       /* all-pole section*/       po = &Out[0];       for (i=0; i<len; i++) {           *po -= hpi_pole_coefsTbl[1] * mem[2];           *po -= hpi_pole_coefsTbl[2] * mem[3];           mem[3] = mem[2];           mem[2] = *po;           po++;       }   }