--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/int_lpc.h	Mon May 06 05:35:21 2024 +0000
@@ -0,0 +1,133 @@
+/*
+********************************************************************************
+*
+*      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.h
+*      Purpose          : Interpolates the LSPs and converts to LPC parameters 
+*
+********************************************************************************
+*/
+#ifndef int_lpc_h
+#define int_lpc_h "$Id $"
+ 
+/*
+********************************************************************************
+*                         INCLUDE FILES
+********************************************************************************
+*/
+#include "typedef.h"
+ 
+/*
+********************************************************************************
+*                         DEFINITION OF DATA TYPES
+********************************************************************************
+*/
+ 
+/*
+********************************************************************************
+*                         DECLARATION OF PROTOTYPES
+********************************************************************************
+*/
+/*
+**************************************************************************
+*
+*  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)                                      */
+);
+
+/*
+**************************************************************************
+*
+*  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)                     */
+);
+
+/*
+**************************************************************************
+*
+*  Function    : Int_lpc_1to3
+*  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 4th 
+*                subframes (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
+*  Returns     : void
+*
+**************************************************************************
+*/
+void Int_lpc_1to3 (
+    Word16 lsp_old[], /* i : LSP vector at the 4th SF of past frame (M)      */
+    Word16 lsp_new[], /* i : LSP vector at the 4th SF of present frame (M)   */
+    Word16 Az[]       /* o : interpolated LP parameters in all SFs (AZ_SIZE) */
+);
+ 
+/*
+**************************************************************************
+*
+*  Function    : Int_lpc_1to3_2
+*  Purpose     : Interpolation of the LPC parameters. Same as the Int_lpc
+*                function but we do not recompute Az() for subframe 4
+*                because it is already available.
+*  Returns     : void
+*
+**************************************************************************
+*/
+void Int_lpc_1to3_2 (
+    Word16 lsp_old[],  /* i : LSP vector at the 4th SF of past frame (M) */
+    Word16 lsp_new[],  /* i : LSP vector at the 4th SF present frame (M) */
+    Word16 Az[]        /* o :interpolated LP parameters in SFs 1, 2, 3 
+                             (AZ_SIZE)                                   */
+);
+ 
+#endif