--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/int_lpc.c	Mon May 06 05:35:21 2024 +0000
@@ -0,0 +1,256 @@
+/*
+********************************************************************************
+*
+*      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             : int_lpc.c
+*
+********************************************************************************
+*/
+/*
+********************************************************************************
+*                         MODULE INCLUDE FILE AND VERSION ID
+********************************************************************************
+*/
+#include "namespace.h"
+#include "int_lpc.h"
+ 
+/*
+********************************************************************************
+*                         INCLUDE FILES
+********************************************************************************
+*/
+#include "typedef.h"
+#include "basic_op.h"
+#include "no_count.h"
+#include "cnst.h"
+#include "lsp_az.h" 
+
+/*
+********************************************************************************
+*                         LOCAL VARIABLES AND TABLES
+********************************************************************************
+*/
+/*
+*--------------------------------------*
+* Constants (defined in cnst.h)        *
+*--------------------------------------*
+*  M         : LPC order               *
+*  MP1       : LPC order + 1           *
+*--------------------------------------*
+*/
+ 
+/*
+********************************************************************************
+*                         PUBLIC PROGRAM CODE
+********************************************************************************
+*/
+/*
+**************************************************************************
+*
+*  Function    : Int_lpc_1and3
+*  Purpose     : Interpolates the LSPs and converts to LPC parameters 
+*                to get a different LP filter in each subframe.
+*  Description : The 20 ms speech frame is divided into 4 subframes.
+*                The LSPs are quantized and transmitted at the 2nd and 
+*                4th subframes (twice per frame) and interpolated at the
+*                1st and 3rd subframe.
+*
+*                      |------|------|------|------|
+*                         sf1    sf2    sf3    sf4
+*                   F0            Fm            F1
+*      
+*                 sf1:   1/2 Fm + 1/2 F0         sf3:   1/2 F1 + 1/2 Fm
+*                 sf2:       Fm                  sf4:       F1
+*  Returns     : void
+*
+**************************************************************************
+*/
+void Int_lpc_1and3 (
+    Word16 lsp_old[],  /* i : LSP vector at the 4th subfr. of past frame (M) */
+    Word16 lsp_mid[],  /* i : LSP vector at the 2nd subfr. of
+                              present frame (M)                              */
+    Word16 lsp_new[],  /* i : LSP vector at the 4th subfr. of
+                              present frame (M)                              */
+    Word16 Az[]        /* o : interpolated LP parameters in all subfr.
+                              (AZ_SIZE)                                      */
+)
+{
+    Word16 i;
+    Word16 lsp[M];
+
+    /*  lsp[i] = lsp_mid[i] * 0.5 + lsp_old[i] * 0.5 */
+
+    for (i = 0; i < M; i++)
+    {
+        lsp[i] = add (shr (lsp_mid[i], 1), shr (lsp_old[i], 1));
+                                move16 (); 
+    }
+
+    Lsp_Az (lsp, Az);           /* Subframe 1 */
+    Az += MP1;                  move16 (); 
+
+    Lsp_Az (lsp_mid, Az);       /* Subframe 2 */
+    Az += MP1;                  move16 (); 
+
+    for (i = 0; i < M; i++)
+    {
+        lsp[i] = add (shr (lsp_mid[i], 1), shr (lsp_new[i], 1));
+                                move16 (); 
+    }
+
+    Lsp_Az (lsp, Az);           /* Subframe 3 */
+    Az += MP1;                  move16 (); 
+
+    Lsp_Az (lsp_new, Az);       /* Subframe 4 */
+
+    return;
+}
+
+/*
+**************************************************************************
+*
+*  Function    : Int_lpc_1and3_2
+*  Purpose     : Interpolation of the LPC parameters. Same as the Int_lpc
+*                function but we do not recompute Az() for subframe 2 and
+*                4 because it is already available.
+*  Returns     : void
+*
+**************************************************************************
+*/
+void Int_lpc_1and3_2 (
+    Word16 lsp_old[],  /* i : LSP vector at the 4th subfr. of past frame (M) */
+    Word16 lsp_mid[],  /* i : LSP vector at the 2nd subframe of
+                             present frame (M)                                  */
+    Word16 lsp_new[],  /* i : LSP vector at the 4th subframe of
+                             present frame (M)                                  */
+    Word16 Az[]        /* o :interpolated LP parameters
+                             in subframes 1 and 3 (AZ_SIZE)                     */
+)
+{
+    Word16 i;
+    Word16 lsp[M];
+
+    /*  lsp[i] = lsp_mid[i] * 0.5 + lsp_old[i] * 0.5 */
+
+    for (i = 0; i < M; i++)
+    {
+        lsp[i] = add (shr (lsp_mid[i], 1), shr (lsp_old[i], 1));
+                                move16 (); 
+    }
+    Lsp_Az (lsp, Az);           /* Subframe 1 */
+    Az += MP1 * 2;              move16 (); 
+
+    for (i = 0; i < M; i++)
+    {
+        lsp[i] = add (shr (lsp_mid[i], 1), shr (lsp_new[i], 1));
+                                move16 (); 
+    }
+    Lsp_Az (lsp, Az);           /* Subframe 3 */
+
+    return;
+}
+/*************************************************************************
+ *
+ *  FUNCTION:  Int_lpc_1to3()
+ *
+ *  PURPOSE:  Interpolates the LSPs and convert to LP parameters to get
+ *            a different LP filter in each subframe.
+ *
+ *  DESCRIPTION:
+ *     The 20 ms speech frame is divided into 4 subframes.
+ *     The LSPs are quantized and transmitted at the 4th subframe
+ *     (once per frame) and interpolated at the 1st, 2nd and 3rd subframe.
+ *
+ *          |------|------|------|------|
+ *             sf1    sf2    sf3    sf4
+ *       F0                          F1
+ *
+ *     sf1:   3/4 F0 + 1/4 F1         sf3:   1/4 F0 + 3/4 F1
+ *     sf2:   1/2 F0 + 1/2 F1         sf4:       F1
+ *
+ *************************************************************************/
+void Int_lpc_1to3(
+    Word16 lsp_old[], /* input : LSP vector at the 4th SF of past frame    */
+    Word16 lsp_new[], /* input : LSP vector at the 4th SF of present frame */
+    Word16 Az[]       /* output: interpolated LP parameters in all SFs     */
+)
+{
+    Word16 i;
+    Word16 lsp[M];
+
+    for (i = 0; i < M; i++) {
+        lsp[i] = add(shr(lsp_new[i], 2), sub(lsp_old[i], shr(lsp_old[i], 2)));
+		                    move16 ();
+    }
+
+    Lsp_Az(lsp, Az);        /* Subframe 1 */
+    Az += MP1;              move16 (); 
+
+
+    for (i = 0; i < M; i++) {
+        lsp[i] = add(shr(lsp_old[i], 1), shr(lsp_new[i], 1));
+		                    move16 ();
+    }
+
+    Lsp_Az(lsp, Az);        /* Subframe 2 */
+    Az += MP1;              move16 ();
+
+    for (i = 0; i < M; i++) {
+        lsp[i] = add(shr(lsp_old[i], 2), sub(lsp_new[i], shr(lsp_new[i], 2)));
+		                    move16 ();
+    }
+
+    Lsp_Az(lsp, Az);       /* Subframe 3 */
+    Az += MP1;              move16 ();
+
+    Lsp_Az(lsp_new, Az);        /* Subframe 4 */
+
+    return;
+}
+
+/*************************************************************************
+ * Function Int_lpc_1to3_2()
+ * Interpolation of the LPC parameters.
+ * Same as the previous function but we do not recompute Az() for
+ * subframe 4 because it is already available.
+ *************************************************************************/
+
+void Int_lpc_1to3_2(
+     Word16 lsp_old[],  /* input : LSP vector at the 4th SF of past frame    */
+     Word16 lsp_new[],  /* input : LSP vector at the 4th SF of present frame */
+     Word16 Az[]        /* output: interpolated LP parameters in SFs 1,2,3   */
+)
+{
+    Word16 i;
+    Word16 lsp[M];
+
+    for (i = 0; i < M; i++) {
+        lsp[i] = add(shr(lsp_new[i], 2), sub(lsp_old[i], shr(lsp_old[i], 2)));
+		                    move16 ();
+    }
+
+    Lsp_Az(lsp, Az);        /* Subframe 1 */
+    Az += MP1;              move16 ();
+
+    for (i = 0; i < M; i++) {
+        lsp[i] = add(shr(lsp_old[i], 1), shr(lsp_new[i], 1));
+		                    move16 ();
+    }
+
+    Lsp_Az(lsp, Az);        /* Subframe 2 */
+    Az += MP1;              move16 ();
+
+    for (i = 0; i < M; i++) {
+        lsp[i] = add(shr(lsp_old[i], 2), sub(lsp_new[i], shr(lsp_new[i], 2)));
+		                    move16 ();
+    }
+
+    Lsp_Az(lsp, Az);        /* Subframe 3 */
+
+    return;
+}