--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/sid_sync.c	Mon May 06 19:58:22 2024 +0000
@@ -0,0 +1,100 @@
+/*
+*****************************************************************************
+*
+*      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             : sid_sync.c
+*
+*****************************************************************************
+*/
+/*
+*****************************************************************************
+*                         MODULE INCLUDE FILE AND VERSION ID
+*****************************************************************************
+*/
+#include "namespace.h"
+#include "sid_sync.h"
+ 
+/*
+*****************************************************************************
+*                         INCLUDE FILES
+*****************************************************************************
+*/
+#include "tw_amr.h"
+#include "typedef.h"
+#include "basic_op.h"
+#include "no_count.h"
+
+/*
+*****************************************************************************
+*                         LOCAL VARIABLES AND TABLES
+*****************************************************************************
+*/
+
+/*
+*****************************************************************************
+*                         PUBLIC PROGRAM CODE
+*****************************************************************************
+*/
+
+void sid_sync_reset (sid_syncState *st)
+{
+    st->sid_update_rate = 8;
+    st->sid_update_counter = 3;
+    st->sid_handover_debt = 0;
+    st->prev_ft = TX_SPEECH_GOOD;
+}
+
+int sid_sync_set_handover_debt (sid_syncState *st,
+                                Word16 debtFrames) 
+{
+   /* debtFrames >= 0 */ 
+   st->sid_handover_debt = debtFrames;
+   return 0;
+}
+
+void sid_sync (sid_syncState *st, enum Mode mode,
+               enum TXFrameType *tx_frame_type)
+{
+    if (mode == MRDTX)
+    {
+        st->sid_update_counter--;
+        if (st->prev_ft == TX_SPEECH_GOOD) 
+        {
+           *tx_frame_type = TX_SID_FIRST;
+           st->sid_update_counter = 3;
+        } 
+        else 
+        {
+           /* TX_SID_UPDATE or TX_NO_DATA */
+           if ((st->sid_handover_debt > 0) &&
+               (st->sid_update_counter > 2) )
+           {
+              /* ensure extra updates are  properly delayed after 
+                 a possible SID_FIRST */
+              *tx_frame_type = TX_SID_UPDATE;
+              st->sid_handover_debt--;
+           }
+           else 
+           {
+              if (st->sid_update_counter == 0)
+              {
+                 *tx_frame_type = TX_SID_UPDATE;
+                 st->sid_update_counter = st->sid_update_rate;
+              } else {
+                 *tx_frame_type = TX_NO_DATA;
+              }
+           }
+        }
+    }
+    else
+    {
+       st->sid_update_counter = st->sid_update_rate ;
+       *tx_frame_type = TX_SPEECH_GOOD;
+    }
+    st->prev_ft = *tx_frame_type;
+}