--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/bgnscd.h	Tue Apr 16 17:57:21 2024 +0000
@@ -0,0 +1,85 @@
+/*
+********************************************************************************
+*
+*      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             : bgnscd.h
+*      Purpose          : Background noise source charateristic detector (SCD)
+*
+********************************************************************************
+*/
+#ifndef bgnscd_h
+#define bgnscd_h "$Id $"
+ 
+/*
+********************************************************************************
+*                         INCLUDE FILES
+********************************************************************************
+*/
+#include "typedef.h"
+#include "cnst.h"
+
+/*
+********************************************************************************
+*                         LOCAL VARIABLES AND TABLES
+********************************************************************************
+*/
+#define L_ENERGYHIST 60
+#define INV_L_FRAME 102
+
+
+/* 2*(160*x)^2 / 65536  where x is FLP values 150,5 and 50 */
+#define FRAMEENERGYLIMIT  17578         /* 150 */
+#define LOWERNOISELIMIT      20         /*   5 */
+#define UPPERNOISELIMIT    1953         /*  50 */
+
+/*
+********************************************************************************
+*                         DEFINITION OF DATA TYPES
+********************************************************************************
+*/
+typedef struct{
+   /* history vector of past synthesis speech energy */
+   Word16 frameEnergyHist[L_ENERGYHIST];
+   
+   /* state flags */
+   Word16 bgHangover;       /* counter; number of frames after last speech frame */
+
+} Bgn_scdState;
+ 
+/*
+********************************************************************************
+*                         DECLARATION OF PROTOTYPES
+********************************************************************************
+*/
+/*
+**************************************************************************
+*
+*  Function    : Bgn_scd_reset
+*  Purpose     : Resets state memory
+*  Returns     : 0 on success
+*
+**************************************************************************
+*/
+void Bgn_scd_reset (Bgn_scdState *st);
+ 
+/*
+**************************************************************************
+*
+*  Function    : Bgn_scd
+*  Purpose     : Charaterice synthesis speech and detect background noise
+*  Returns     : background noise decision; 0 = bgn, 1 = no bgn
+*
+**************************************************************************
+*/
+Word16 Bgn_scd (Bgn_scdState *st,      /* i : State variables for bgn SCD         */
+                Word16 ltpGainHist[],  /* i : LTP gain history                    */
+                Word16 speech[],       /* o : synthesis speech frame              */
+                Word16 *voicedHangover /* o : # of frames after last voiced frame */
+);
+ 
+#endif