--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libgsmefr/lsp_lsf.c	Fri Nov 25 16:18:21 2022 +0000
@@ -0,0 +1,76 @@
+/*************************************************************************
+ *
+ *   FUNCTIONS:  Lsp_lsf and Lsf_lsp
+ *
+ *   PURPOSE:
+ *      Lsp_lsf:   Transformation lsp to lsf
+ *      Lsf_lsp:   Transformation lsf to lsp
+ *
+ *   DESCRIPTION:
+ *         lsp[i] = cos(2*pi*lsf[i]) and lsf[i] = arccos(lsp[i])/(2*pi)
+ *
+ *   The transformation from lsp[i] to lsf[i] and lsf[i] to lsp[i] are
+ *   approximated by a look-up table and interpolation.
+ *
+ *************************************************************************/
+
+#include "typedef.h"
+#include "basic_op.h"
+#include "count.h"
+
+#include "lsp_lsf.tab"          /* Look-up table for transformations */
+
+void Lsf_lsp (
+    Word16 lsf[],       /* (i) : lsf[m] normalized (range: 0.0<=val<=0.5) */
+    Word16 lsp[],       /* (o) : lsp[m] (range: -1<=val<1)                */
+    Word16 m            /* (i) : LPC order                                */
+)
+{
+    Word16 i, ind, offset;
+    Word32 L_tmp;
+
+    for (i = 0; i < m; i++)
+    {
+        ind = shr (lsf[i], 8);      /* ind    = b8-b15 of lsf[i] */
+        offset = lsf[i] & 0x00ff;   logic16 (); /* offset = b0-b7  of lsf[i] */
+
+        /* lsp[i] = table[ind]+ ((table[ind+1]-table[ind])*offset) / 256 */
+
+        L_tmp = L_mult (sub (table[ind + 1], table[ind]), offset);
+        lsp[i] = add (table[ind], extract_l (L_shr (L_tmp, 9)));
+                                    move16 (); 
+    }
+    return;
+}
+
+void Lsp_lsf (
+    Word16 lsp[],       /* (i)  : lsp[m] (range: -1<=val<1)                */
+    Word16 lsf[],       /* (o)  : lsf[m] normalized (range: 0.0<=val<=0.5) */
+    Word16 m            /* (i)  : LPC order                                */
+)
+{
+    Word16 i, ind;
+    Word32 L_tmp;
+
+    ind = 63;                       /* begin at end of table -1 */
+
+    for (i = m - 1; i >= 0; i--)
+    {
+        /* find value in table that is just greater than lsp[i] */
+        test (); 
+        while (sub (table[ind], lsp[i]) < 0)
+        {
+            ind--;
+            test (); 
+        }
+
+        /* acos(lsp[i])= ind*256 + ( ( lsp[i]-table[ind] ) *
+           slope[ind] )/4096 */
+
+        L_tmp = L_mult (sub (lsp[i], table[ind]), slope[ind]);
+        /*(lsp[i]-table[ind])*slope[ind])>>12*/
+        lsf[i] = round (L_shl (L_tmp, 3));      move16 (); 
+        lsf[i] = add (lsf[i], shl (ind, 8));    move16 (); 
+    }
+    return;
+}