--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libgsmefr/lag_wind.c	Fri Nov 25 16:18:21 2022 +0000
@@ -0,0 +1,37 @@
+/*************************************************************************
+ *
+ *  FUNCTION:  Lag_window()
+ *
+ *  PURPOSE:  Lag windowing of autocorrelations.
+ *
+ *  DESCRIPTION:
+ *         r[i] = r[i]*lag_wind[i],   i=1,...,10
+ *
+ *     r[i] and lag_wind[i] are in special double precision format.
+ *     See "oper_32b.c" for the format.
+ *
+ *************************************************************************/
+
+#include "typedef.h"
+#include "basic_op.h"
+#include "oper_32b.h"
+#include "count.h"
+
+#include "lag_wind.tab"
+
+void Lag_window (
+    Word16 m,           /* (i)     : LPC order                        */
+    Word16 r_h[],       /* (i/o)   : Autocorrelations  (msb)          */
+    Word16 r_l[]        /* (i/o)   : Autocorrelations  (lsb)          */
+)
+{
+    Word16 i;
+    Word32 x;
+
+    for (i = 1; i <= m; i++)
+    {
+        x = Mpy_32 (r_h[i], r_l[i], lag_h[i - 1], lag_l[i - 1]);
+        L_Extract (x, &r_h[i], &r_l[i]);
+    }
+    return;
+}