--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/bgnscd.c	Tue Apr 16 17:57:21 2024 +0000
@@ -0,0 +1,229 @@
+/*************************************************************************
+*
+*      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.c
+*      Purpose          : Background noise source charateristic detector (SCD)
+*
+********************************************************************************
+*/
+
+/*
+********************************************************************************
+*                         MODULE INCLUDE FILE AND VERSION ID
+********************************************************************************
+*/
+#include "namespace.h"
+#include "bgnscd.h"
+
+#include "typedef.h"
+#include "basic_op.h"
+#include "no_count.h"
+#include "cnst.h"
+#include "memops.h"
+#include "gmed_n.h"
+#include "sqrt_l.h"
+
+/*
+********************************************************************************
+*                         LOCAL VARIABLES AND TABLES
+********************************************************************************
+*/
+/*-----------------------------------------------------------------*
+ *   Decoder constant parameters (defined in "cnst.h")             *
+ *-----------------------------------------------------------------*
+ *   L_FRAME       : Frame size.                                   *
+ *   L_SUBFR       : Sub-frame size.                               *
+ *-----------------------------------------------------------------*/
+
+/*
+********************************************************************************
+*                         PUBLIC PROGRAM CODE
+********************************************************************************
+*/
+/*
+**************************************************************************
+*
+*  Function    : Bgn_scd_reset
+*  Purpose     : Resets state memory
+*
+**************************************************************************
+*/
+void Bgn_scd_reset (Bgn_scdState *state)
+{
+   /* Static vectors to zero */
+   Set_zero (state->frameEnergyHist, L_ENERGYHIST);
+
+   /* Initialize hangover handling */
+   state->bgHangover = 0;
+}
+
+/*
+**************************************************************************
+*
+*  Function    : Bgn_scd
+*  Purpose     : Charaterice synthesis speech and detect background noise
+*  Returns     : background noise decision; 0 = no bgn, 1 = 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                */
+                )
+{
+   Word16 i;
+   Word16 prevVoiced, inbgNoise;
+   Word16 temp;
+   Word16 ltpLimit, frameEnergyMin;
+   Word16 currEnergy, noiseFloor, maxEnergy, maxEnergyLastPart;
+   Word32 s;
+   
+   /* Update the inBackgroundNoise flag (valid for use in next frame if BFI) */
+   /* it now works as a energy detector floating on top                      */ 
+   /* not as good as a VAD.                                                  */
+
+   currEnergy = 0;                                   move16 ();
+   s = (Word32) 0;                                   move32 ();
+
+   for (i = 0; i < L_FRAME; i++)
+   {
+       s = L_mac (s, speech[i], speech[i]);
+   }
+
+   s = L_shl(s, 2);  
+
+   currEnergy = extract_h (s);
+
+   frameEnergyMin = 32767;                     move16 ();
+
+   for (i = 0; i < L_ENERGYHIST; i++)
+   {
+      test ();
+      if (sub(st->frameEnergyHist[i], frameEnergyMin) < 0)
+         frameEnergyMin = st->frameEnergyHist[i];           move16 ();
+   }
+
+   noiseFloor = shl (frameEnergyMin, 4); /* Frame Energy Margin of 16 */
+
+   maxEnergy = st->frameEnergyHist[0];               move16 ();
+   for (i = 1; i < L_ENERGYHIST-4; i++)
+   {
+      test ();
+      if ( sub (maxEnergy, st->frameEnergyHist[i]) < 0)
+      {
+         maxEnergy = st->frameEnergyHist[i];         move16 ();
+      }
+   }
+   
+   maxEnergyLastPart = st->frameEnergyHist[2*L_ENERGYHIST/3]; move16 ();
+   for (i = 2*L_ENERGYHIST/3+1; i < L_ENERGYHIST; i++)
+   {
+      test ();
+      if ( sub (maxEnergyLastPart, st->frameEnergyHist[i] ) < 0)
+      {
+         maxEnergyLastPart = st->frameEnergyHist[i]; move16 ();     
+      }
+   }
+
+   inbgNoise = 0;        /* false */                 move16 (); 
+
+   /* Do not consider silence as noise */
+   /* Do not consider continuous high volume as noise */
+   /* Or if the current noise level is very low */
+   /* Mark as noise if under current noise limit */
+   /* OR if the maximum energy is below the upper limit */
+
+   test (); test (); test (); test (); test (); 
+   if ( (sub(maxEnergy, LOWERNOISELIMIT) > 0) &&
+        (sub(currEnergy, FRAMEENERGYLIMIT) < 0) &&
+        (sub(currEnergy, LOWERNOISELIMIT) > 0) &&
+        ( (sub(currEnergy, noiseFloor) < 0) ||
+          (sub(maxEnergyLastPart, UPPERNOISELIMIT) < 0)))
+   {
+      test ();
+      if (sub(add(st->bgHangover, 1), 30) > 0)
+      {
+         st->bgHangover = 30;                         move16 ();
+      } else
+      {
+         st->bgHangover = add(st->bgHangover, 1);
+      }
+   }
+   else
+   {
+      st->bgHangover = 0;                             move16 ();    
+   }
+   
+   /* make final decision about frame state , act somewhat cautiosly */
+   test ();
+   if (sub(st->bgHangover,1) > 0)
+      inbgNoise = 1;       /* true  */               move16 ();  
+
+   for (i = 0; i < L_ENERGYHIST-1; i++)
+   {
+      st->frameEnergyHist[i] = st->frameEnergyHist[i+1]; move16 ();
+   }
+   st->frameEnergyHist[L_ENERGYHIST-1] = currEnergy;              move16 ();
+   
+   /* prepare for voicing decision; tighten the threshold after some 
+      time in noise */
+   ltpLimit = 13926;             /* 0.85  Q14 */     move16 (); 
+   test ();
+   if (sub(st->bgHangover, 8) > 0)
+   {
+      ltpLimit = 15565;          /* 0.95  Q14 */     move16 ();
+   }
+   test ();
+   if (sub(st->bgHangover, 15) > 0)
+   {
+      ltpLimit = 16383;          /* 1.00  Q14 */     move16 ();
+   }
+
+   /* weak sort of voicing indication. */
+   prevVoiced = 0;        /* false */                move16 ();
+   test ();
+
+   if (sub(gmed_n(&ltpGainHist[4], 5), ltpLimit) > 0)
+   {
+      prevVoiced = 1;     /* true  */                move16 ();
+   }
+   test ();   
+   if (sub(st->bgHangover, 20) > 0) {
+      if (sub(gmed_n(ltpGainHist, 9), ltpLimit) > 0)
+      {
+         prevVoiced = 1;  /* true  */                move16 ();
+      }
+      else
+      {
+         prevVoiced = 0;  /* false  */                move16 ();
+      }
+   }
+   
+   test ();
+   if (prevVoiced)
+   {
+      *voicedHangover = 0;                        move16 ();
+   }
+   else
+   {
+      temp = add(*voicedHangover, 1);
+      test ();
+      if (sub(temp, 10) > 0)
+      {
+         *voicedHangover = 10;                    move16 ();
+      }
+      else
+      {
+         *voicedHangover = temp;                  move16 ();
+      }
+   }
+
+   return inbgNoise;
+}