--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/dec_lag3.c	Sun May 05 22:29:09 2024 +0000
@@ -0,0 +1,144 @@
+/*
+********************************************************************************
+*
+*      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             : dec_lag3.c
+*      Purpose          : Decoding of fractional pitch lag with 1/3 resolution.
+*                         Extract the integer and fraction parts of the pitch lag from
+*                         the received adaptive codebook index.
+*
+********************************************************************************
+*/
+
+/*
+********************************************************************************
+*                         MODULE INCLUDE FILE AND VERSION ID
+********************************************************************************
+*/
+#include "namespace.h"
+#include "dec_lag3.h"
+ 
+/*
+********************************************************************************
+*                         INCLUDE FILES
+********************************************************************************
+*/
+#include "typedef.h"
+#include "basic_op.h"
+#include "no_count.h"
+
+/*
+********************************************************************************
+*                         LOCAL VARIABLES AND TABLES
+********************************************************************************
+*/
+
+/*
+********************************************************************************
+*                         PUBLIC PROGRAM CODE
+********************************************************************************
+*/
+/*************************************************************************
+ *   FUNCTION:   Dec_lag3
+ *
+ *   PURPOSE:  Decoding of fractional pitch lag with 1/3 resolution.
+ *             Extract the integer and fraction parts of the pitch lag from
+ *             the received adaptive codebook index.
+ *
+ *    See "Enc_lag3.c" for more details about the encoding procedure.
+ *
+ *    The fractional lag in 1st and 3rd subframes is encoded with 8 bits
+ *    while that in 2nd and 4th subframes is relatively encoded with 4, 5
+ *    and 6 bits depending on the mode.
+ *
+ *************************************************************************/
+void Dec_lag3(Word16 index,     /* i : received pitch index                 */
+              Word16 t0_min,    /* i : minimum of search range              */
+              Word16 t0_max,    /* i : maximum of search range              */
+              Word16 i_subfr,   /* i : subframe flag                        */
+              Word16 T0_prev,   /* i : integer pitch delay of last subframe
+                                       used in 2nd and 4th subframes        */
+              Word16 * T0,      /* o : integer part of pitch lag            */ 
+              Word16 * T0_frac, /* o : fractional part of pitch lag         */
+              Word16 flag4      /* i : flag for encoding with 4 bits        */
+              )
+{
+    Word16 i;
+    Word16 tmp_lag;
+    
+    test (); 
+    if (i_subfr == 0) {    /* if 1st or 3rd subframe */
+       test ();
+	   if (sub(index, 197) < 0) {
+          
+          *T0 = add(mult(add(index, 2), 10923), 19);
+           
+          i = add(add(*T0, *T0), *T0);
+          *T0_frac = add(sub(index, i), 58);
+       } else {
+          *T0 = sub(index, 112);
+          *T0_frac = 0;                                        move16 ();
+       }
+       
+    } else {    /* 2nd or 4th subframe */
+
+       test ();
+       if (flag4 == 0) {
+          
+          /* 'normal' decoding: either with 5 or 6 bit resolution */
+          
+          i = sub(mult(add(index, 2), 10923), 1);
+          *T0 = add(i, t0_min);
+          
+          i = add(add(i, i), i);
+          *T0_frac = sub(sub(index, 2), i);
+       }
+       else {
+          
+          /* decoding with 4 bit resolution */
+          
+          tmp_lag = T0_prev;                                   move16 ();
+
+          test ();
+          if ( sub( sub(tmp_lag, t0_min), 5) > 0)
+             tmp_lag = add (t0_min, 5);
+          test ();
+          if ( sub( sub(t0_max, tmp_lag), 4) > 0)
+             tmp_lag = sub (t0_max, 4);
+          
+          test ();          
+          if (sub(index, 4) < 0)
+          {
+             i = sub(tmp_lag, 5);
+             *T0 = add(i, index);
+             *T0_frac = 0;                                     move16 ();
+          }
+          else
+          {
+             test ();
+             if (sub(index, 12) < 0)
+             {
+                i = sub(mult(sub(index, 5), 10923), 1);
+                *T0 = add(i, tmp_lag);
+                
+                i = add(add(i, i), i);
+                *T0_frac = sub(sub(index, 9), i);
+             }
+             else
+             {
+                i = add( sub (index, 12), tmp_lag);
+                *T0 = add (i, 1);                
+                *T0_frac = 0;                                  move16 ();
+             }
+          }
+          
+       } /* end if (decoding with 4 bit resolution) */
+    }
+    
+    return;
+}