--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/g_adapt.c	Mon May 06 03:01:15 2024 +0000
@@ -0,0 +1,197 @@
+/*
+********************************************************************************
+*
+*      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             : g_adapt.c
+*      Purpose          : gain adaptation for MR795 gain quantization
+*
+********************************************************************************
+*/
+
+/*
+********************************************************************************
+*                         MODULE INCLUDE FILE AND VERSION ID
+********************************************************************************
+*/
+#include "namespace.h"
+#include "g_adapt.h"
+
+/*
+********************************************************************************
+*                         INCLUDE FILES
+********************************************************************************
+*/
+#include "typedef.h"
+#include "basic_op.h"
+#include "oper_32b.h"
+#include "no_count.h"
+#include "cnst.h"
+#include "gmed_n.h"
+
+/*
+********************************************************************************
+*                         LOCAL VARIABLES AND TABLES
+********************************************************************************
+*/
+#define LTP_GAIN_THR1 2721 /* 2721 Q13 = 0.3322 ~= 1.0 / (10*log10(2)) */
+#define LTP_GAIN_THR2 5443 /* 5443 Q13 = 0.6644 ~= 2.0 / (10*log10(2)) */
+
+/*
+********************************************************************************
+*                         PUBLIC PROGRAM CODE
+********************************************************************************
+*/
+
+/*************************************************************************
+*
+*  Function:   gain_adapt_reset
+*  Purpose:    Initializes state memory to zero
+*
+**************************************************************************
+*/
+void gain_adapt_reset (GainAdaptState *st)
+{
+    Word16 i;
+
+    st->onset = 0;
+    st->prev_alpha = 0;
+    st->prev_gc = 0;
+
+    for (i = 0; i < LTPG_MEM_SIZE; i++)
+    {
+        st->ltpg_mem[i] = 0;
+    }
+}
+
+/*************************************************************************
+ *
+ *  Function:   gain_adapt()
+ *  Purpose:    calculate pitch/codebook gain adaptation factor alpha
+ *              (and update the adaptor state)
+ *
+ **************************************************************************
+ */
+void gain_adapt(
+    GainAdaptState *st,  /* i  : state struct                  */
+    Word16 ltpg,         /* i  : ltp coding gain (log2()), Q13 */
+    Word16 gain_cod,     /* i  : code gain,                Q1  */
+    Word16 *alpha        /* o  : gain adaptation factor,   Q15 */
+)
+{
+    Word16 adapt;      /* adaptdation status; 0, 1, or 2       */
+    Word16 result;     /* alpha factor, Q13                    */
+    Word16 filt;       /* median-filtered LTP coding gain, Q13 */
+    Word16 tmp, i;
+    
+    /* basic adaptation */
+    test ();
+    if (sub (ltpg, LTP_GAIN_THR1) <= 0)
+    {
+        adapt = 0;                            move16 ();
+    }
+    else
+    {
+        test ();
+        if (sub (ltpg, LTP_GAIN_THR2) <= 0)
+        {
+            adapt = 1;                        move16 ();
+        }
+        else
+        {
+            adapt = 2;                        move16 ();
+        }
+    }
+
+    /*
+     * // onset indicator
+     * if ((cbGain > onFact * cbGainMem[0]) && (cbGain > 100.0))
+     *     onset = 8;
+     * else
+     *     if (onset)
+     *         onset--;
+     */
+    /* tmp = cbGain / onFact; onFact = 2.0; 200 Q1 = 100.0 */
+    tmp = shr_r (gain_cod, 1);
+    test (); test ();
+    if ((sub (tmp, st->prev_gc) > 0) && sub(gain_cod, 200) > 0)
+    {
+        st->onset = 8;                            move16 ();
+    }
+    else
+    {
+        test ();
+        if (st->onset != 0)
+        {
+            st->onset = sub (st->onset, 1);       move16 ();
+        }
+    }
+
+    /*
+     *  // if onset, increase adaptor state
+     *  if (onset && (gainAdapt < 2)) gainAdapt++;
+     */
+    test(); test ();
+    if ((st->onset != 0) && (sub (adapt, 2) < 0))
+    {
+        adapt = add (adapt, 1);
+    }
+
+    st->ltpg_mem[0] = ltpg;                       move16 ();
+    filt = gmed_n (st->ltpg_mem, 5);   move16 (); /* function result */
+
+    test ();
+    if (adapt == 0)
+    {
+        test ();
+        if (sub (filt, 5443) > 0) /* 5443 Q13 = 0.66443... */
+        {
+            result = 0; move16 ();
+        }
+        else
+        {
+            test ();
+            if (filt < 0)
+            {
+                result = 16384; move16 ();  /* 16384 Q15 = 0.5 */
+            }
+            else
+            {   /* result       =   0.5 - 0.75257499*filt     */
+                /* result (Q15) = 16384 - 24660 * (filt << 2) */
+                filt = shl (filt, 2); /* Q15 */
+                result = sub (16384, mult (24660, filt));
+            }
+        }
+    }
+    else
+    {
+        result = 0; move16 ();
+    }
+    /*
+     *  if (prevAlpha == 0.0) result = 0.5 * (result + prevAlpha);
+     */
+    test ();
+    if (st->prev_alpha == 0)
+    {
+        result = shr (result, 1);
+    }
+
+    /* store the result */
+    *alpha = result;                           move16 ();
+    
+    /* update adapter state memory */
+    st->prev_alpha = result;                   move16 ();
+    st->prev_gc = gain_cod;                    move16 ();
+
+    for (i = LTPG_MEM_SIZE-1; i > 0; i--)
+    {
+        st->ltpg_mem[i] = st->ltpg_mem[i-1];   move16 ();
+    }
+    /* mem[0] is just present for convenience in calling the gmed_n[5]
+     * function above. The memory depth is really LTPG_MEM_SIZE-1.
+     */
+}