--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/b_cn_cod.h	Fri Apr 05 17:31:49 2024 +0000
@@ -0,0 +1,104 @@
+/*
+********************************************************************************
+*
+*      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             : b_cn_cod.h
+*      Purpose          : Contains function for comfort noise generation.
+*
+********************************************************************************
+*/
+#ifndef b_cn_cod_h
+#define b_cn_cod_h "$Id $"
+
+/*
+********************************************************************************
+*                         INCLUDE FILES
+********************************************************************************
+*/
+#include "typedef.h"
+
+/*
+********************************************************************************
+*                         DEFINITION OF DATA TYPES
+********************************************************************************
+*/
+
+/*
+********************************************************************************
+*                         DECLARATION OF PROTOTYPES
+********************************************************************************
+*/
+
+/*************************************************************************
+ *
+ *   FUNCTION NAME: pseudonoise
+ *
+ *   PURPOSE: Generate a random integer value to use in comfort noise
+ *            generation. The algorithm uses polynomial x^31 + x^3 + 1
+ *            (length of PN sequence is 2^31 - 1).
+ *
+ *   INPUTS:      *shift_reg    Old CN generator shift register state
+ *
+ *
+ *   OUTPUTS:     *shift_reg    Updated CN generator shift register state
+ *
+ *   RETURN VALUE: Generated random integer value
+ *
+ *************************************************************************/
+
+Word16 pseudonoise (
+    Word32 *shift_reg, /* i/o : Old CN generator shift register state */
+    Word16 no_bits     /* i   : Number of bits                        */
+);
+
+/*************************************************************************
+ *
+ *   FUNCTION NAME: build_CN_code
+ *
+ *   PURPOSE: Compute the comfort noise fixed codebook excitation. The
+ *            gains of the pulses are always +/-1.
+ *
+ *   INPUTS:      *seed         Old CN generator shift register state
+ *
+ *   OUTPUTS:     cod[0..39]    Generated comfort noise fixed codebook vector
+ *                *seed         Updated CN generator shift register state
+ *
+ *   RETURN VALUE: none
+ *
+ *************************************************************************/
+void build_CN_code (
+    Word32 *seed,         /* i/o : Old CN generator shift register state */
+    Word16 cod[]          /* o   : Generated CN fixed codebook vector    */
+);
+
+/*************************************************************************
+ *
+ *   FUNCTION NAME: build_CN_param
+ *
+ *   PURPOSE: Randomize the speech parameters. So that they 
+ *            do not produce tonal artifacts if used by ECU.
+ *
+ *   INPUTS:      *seed            Old CN generator shift register state
+ *                n_param,         Number of parameters to randomize
+ *                parm_size_table, 
+ *                  
+ *
+ *   OUTPUTS:      parm    CN Generated Parameters
+ *                *seed    Updated CN generator shift register state
+ *
+ *   RETURN VALUE: none
+ *
+ *************************************************************************/
+void build_CN_param (
+    Word16 *seed,              /* i/o : Old CN generator shift register state */
+    const Word16 n_param,            /* i : number of params     */  
+    const Word16 param_size_table[], /* i : size of params       */   
+    Word16 parm[]              /* o   : CN Generated Params*/
+);
+
+#endif