--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/dec_gain.c	Sun May 05 22:24:42 2024 +0000
@@ -0,0 +1,156 @@
+/*
+********************************************************************************
+*
+*      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             : dec_gain.c
+*      Purpose          : Decode the pitch and codebook gains
+*
+********************************************************************************
+*/
+
+/*
+********************************************************************************
+*                         MODULE INCLUDE FILE AND VERSION ID
+********************************************************************************
+*/
+#include "namespace.h"
+#include "dec_gain.h"
+ 
+/*
+********************************************************************************
+*                         INCLUDE FILES
+********************************************************************************
+*/
+#include <stddef.h>
+#include "tw_amr.h"
+#include "typedef.h"
+#include "basic_op.h"
+#include "oper_32b.h"
+#include "no_count.h"
+#include "cnst.h"
+#include "pow2.h"
+#include "log2.h"
+#include "gc_pred.h"
+#include "qua_gain_tab.h"
+
+/*
+********************************************************************************
+*                         PUBLIC PROGRAM CODE
+********************************************************************************
+*/
+
+/*************************************************************************
+ *
+ *   FUNCTION:  Dec_gain()
+ *
+ *   PURPOSE: Decode the pitch and codebook gains
+ *
+ ************************************************************************/
+void Dec_gain(
+    gc_predState *pred_state, /* i/o: MA predictor state           */
+    enum Mode mode,           /* i  : AMR mode                     */
+    Word16 index,             /* i  : index of quantization.       */
+    Word16 code[],            /* i  : Innovative vector.           */
+    Word16 evenSubfr,         /* i  : Flag for even subframes      */     
+    Word16 * gain_pit,        /* o  : Pitch gain.                  */
+    Word16 * gain_cod         /* o  : Code gain.                   */
+)
+{
+    const Word16 *p;
+    Word16 frac, gcode0, exp, qua_ener, qua_ener_MR122;
+    Word16 g_code;
+    Word32 L_tmp;
+    
+    /* Read the quantized gains (table depends on mode) */
+    index = shl (index, 2);
+    
+    test(); test(); test();
+    if (    sub (mode, MR102) == 0
+         || sub (mode, MR74) == 0
+         || sub (mode, MR67) == 0)
+    {
+        p = &table_gain_highrates[index];                  move16 ();
+        
+        *gain_pit = *p++;                                  move16 ();
+        g_code = *p++;                                     move16 ();
+        qua_ener_MR122 = *p++;                             move16 ();
+        qua_ener = *p;                                     move16 ();
+    }
+    else
+    {
+        test();
+        if (sub (mode, MR475) == 0)
+        {
+            index = add (index, shl(sub(1, evenSubfr), 1));
+            p = &table_gain_MR475[index];                  move16 ();
+            
+            *gain_pit = *p++;                              move16 ();
+            g_code = *p++;                                 move16 ();
+            
+            /*---------------------------------------------------------*
+             *  calculate predictor update values (not stored in 4.75  *
+             *  quantizer table to save space):                        *
+             *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  *
+             *                                                         *
+             *   qua_ener       = log2(g)                              *
+             *   qua_ener_MR122 = 20*log10(g)                          *
+             *---------------------------------------------------------*/
+
+            /* Log2(x Q12) = log2(x) + 12 */
+            Log2 (L_deposit_l (g_code), &exp, &frac); 
+            exp = sub(exp, 12);
+    
+            qua_ener_MR122 = add (shr_r (frac, 5), shl (exp, 10));
+    
+            /* 24660 Q12 ~= 6.0206 = 20*log10(2) */
+            L_tmp = Mpy_32_16(exp, frac, 24660);
+            qua_ener = round (L_shl (L_tmp, 13)); /* Q12 * Q0 = Q13 -> Q10 */
+        }
+        else
+        {
+            p = &table_gain_lowrates[index];                move16 ();
+            
+            *gain_pit = *p++;                               move16 ();
+            g_code = *p++;                                  move16 ();
+            qua_ener_MR122 = *p++;                          move16 ();
+            qua_ener = *p;                                  move16 ();
+        }
+    }
+    
+    /*-------------------------------------------------------------------*
+     *  predict codebook gain                                            *
+     *  ~~~~~~~~~~~~~~~~~~~~~                                            *
+     *  gc0     = Pow2(int(d)+frac(d))                                   *
+     *          = 2^exp + 2^frac                                         *
+     *                                                                   *
+     *  gcode0 (Q14) = 2^14*2^frac = gc0 * 2^(14-exp)                    *
+     *-------------------------------------------------------------------*/
+
+    gc_pred(pred_state, mode, code, &exp, &frac, NULL, NULL);
+
+    gcode0 = extract_l(Pow2(14, frac));
+
+    /*------------------------------------------------------------------*
+     *  read quantized gains, update table of past quantized energies   *
+     *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   *
+     *  st->past_qua_en(Q10) = 20 * Log10(g_fac) / constant             *
+     *                       = Log2(g_fac)                              *
+     *                       = qua_ener                                 *
+     *                                           constant = 20*Log10(2) *
+     *------------------------------------------------------------------*/
+
+    L_tmp = L_mult(g_code, gcode0);
+    L_tmp = L_shr(L_tmp, sub(10, exp));
+    *gain_cod = extract_h(L_tmp);
+
+    /* update table of past quantized energies */
+
+    gc_pred_update(pred_state, qua_ener_MR122, qua_ener);
+
+    return;
+}