+
−/*
+
−********************************************************************************
+
−*
+
−*      GSM AMR-NB speech codec   R98   Version 7.6.0   December 12, 2001
+
−*                                R99   Version 3.3.0                
+
−*                                REL-4 Version 4.1.0                
+
−*
+
−********************************************************************************
+
−*
+
−*      File             : syn_filt.c
+
−*      Purpose          : Perform synthesis filtering through 1/A(z).
+
−*
+
−********************************************************************************
+
−*/
+
−/*
+
−********************************************************************************
+
−*                         MODULE INCLUDE FILE AND VERSION ID
+
−********************************************************************************
+
−*/
+
−#include "namespace.h"
+
−#include "syn_filt.h"
+
−
+
−/*
+
−********************************************************************************
+
−*                         INCLUDE FILES
+
−********************************************************************************
+
−*/
+
−#include "typedef.h"
+
−#include "basic_op.h"
+
−#include "no_count.h"
+
−#include "cnst.h"
+
−
+
−/*
+
−********************************************************************************
+
−*                         LOCAL VARIABLES AND TABLES
+
−********************************************************************************
+
−*/
+
−/*
+
−*--------------------------------------*
+
−* Constants (defined in cnst.h         *
+
−*--------------------------------------*
+
−*  M         : LPC order               *
+
−*--------------------------------------*
+
−*/
+
−
+
−/*
+
−********************************************************************************
+
−*                         PUBLIC PROGRAM CODE
+
−********************************************************************************
+
−*/
+
−void Syn_filt (
+
−    Word16 a[],     /* (i)     : a[M+1] prediction coefficients   (M=10)  */
+
−    Word16 x[],     /* (i)     : input signal                             */
+
−    Word16 y[],     /* (o)     : output signal                            */
+
−    Word16 lg,      /* (i)     : size of filtering                        */
+
−    Word16 mem[],   /* (i/o)   : memory associated with this filtering.   */
+
−    Word16 update   /* (i)     : 0=no update, 1=update of memory.         */
+
−)
+
−{
+
−    Word16 i, j;
+
−    Word32 s;
+
−    Word16 tmp[80];   /* This is usually done by memory allocation (lg+M) */
+
−    Word16 *yy;
+
−
+
−    /* Copy mem[] to yy[] */
+
−
+
−    yy = tmp;                           move16 (); 
+
−
+
−    for (i = 0; i < M; i++)
+
−    {
+
−        *yy++ = mem[i];                 move16 (); 
+
−    } 
+
−
+
−    /* Do the filtering. */
+
−
+
−    for (i = 0; i < lg; i++)
+
−    {
+
−        s = L_mult (x[i], a[0]);
+
−        for (j = 1; j <= M; j++)
+
−        {
+
−            s = L_msu (s, a[j], yy[-j]);
+
−        }
+
−        s = L_shl (s, 3);
+
−        *yy++ = round (s);              move16 (); 
+
−    }
+
−
+
−    for (i = 0; i < lg; i++)
+
−    {
+
−        y[i] = tmp[i + M];              move16 (); 
+
−    }
+
−
+
−    /* Update of memory if update==1 */
+
−
+
−    test (); 
+
−    if (update != 0)
+
−    {
+
−        for (i = 0; i < M; i++)
+
−        {
+
−            mem[i] = y[lg - M + i];     move16 (); 
+
−        }
+
−    }
+
−    return;
+
−}