--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/a_refl.c	Fri Apr 05 06:08:15 2024 +0000
@@ -0,0 +1,128 @@
+/*
+********************************************************************************
+*
+*      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             : a_refl.c
+*      Purpose          : Convert from direct form coefficients to 
+*                         reflection coefficients
+*
+********************************************************************************
+*/
+/*
+********************************************************************************
+*                         MODULE INCLUDE FILE AND VERSION ID
+********************************************************************************
+*/
+#include "namespace.h"
+#include "a_refl.h"
+const char a_refl_id[] = "@(#)$Id $" a_refl_h;
+ 
+
+/*
+********************************************************************************
+*                         INCLUDE FILES
+********************************************************************************
+*/
+#include "typedef.h"
+#include "basic_op.h"
+#include "oper_32b.h"
+#include "no_count.h"
+#include "cnst.h"
+
+/*
+********************************************************************************
+*                         LOCAL VARIABLES AND TABLES
+********************************************************************************
+*/
+
+/*
+********************************************************************************
+*                         PUBLIC PROGRAM CODE
+********************************************************************************
+*/
+/*
+**************************************************************************
+*
+*  Function    : A_Refl
+*
+**************************************************************************
+*/ 
+void A_Refl(
+   Word16 a[],	      /* i   : Directform coefficients */
+   Word16 refl[]      /* o   : Reflection coefficients */
+)
+{				       
+   /* local variables */
+   Word16 i,j;
+   Word16 aState[M];
+   Word16 bState[M];
+   Word16 normShift;
+   Word16 normProd;
+   Word32 L_acc;
+   Word16 scale;
+   Word32 L_temp;
+   Word16 temp;
+   Word16 mult;
+
+   /* initialize states */
+   for (i = 0; i < M; i++)
+   {
+      aState[i] = a[i];                         move16 ();
+   }
+   
+   /* backward Levinson recursion */
+   for (i = M-1; i >= 0; i--)
+   {
+      if (sub(abs_s(aState[i]), 4096) >= 0)
+      {
+         goto ExitRefl;
+      }
+      
+      refl[i] = shl(aState[i], 3);
+
+      L_temp = L_mult(refl[i], refl[i]);
+      L_acc = L_sub(MAX_32, L_temp);
+      
+      normShift = norm_l(L_acc);
+      scale = sub(15, normShift);
+      
+      L_acc = L_shl(L_acc, normShift);
+      normProd = round(L_acc);
+
+      mult = div_s(16384, normProd);
+      
+      for (j = 0; j < i; j++)
+      {
+         L_acc = L_deposit_h(aState[j]);
+         L_acc = L_msu(L_acc, refl[i], aState[i-j-1]);
+         
+         temp = round(L_acc);
+         L_temp = L_mult(mult, temp);
+         L_temp = L_shr_r(L_temp, scale);
+         
+         if (L_sub(L_abs(L_temp), 32767) > 0)
+         {
+            goto ExitRefl;
+         }
+         
+         bState[j] = extract_l(L_temp);
+      }
+      
+      for (j = 0; j < i; j++)
+      {
+         aState[j] = bState[j];              move16 ();
+      }
+   }
+   return;
+
+ExitRefl:
+   for (i = 0; i < M; i++)
+   {
+      refl[i] = 0;                           move16 ();
+   }
+}