basic_op.c

g729b_pc.rar是G729语音压缩标准的附件B的C语言实现标准源代码。

 |    var1                                                                   |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0xffff 8000 <= var1 <= 0x0000 7fff.                   |
 |                                                                           |
 |    var2                                                                   |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0xffff 8000 <= var1 <= 0x0000 7fff.                   |
 |                                                                           |
 |   Outputs :                                                               |
 |                                                                           |
 |    none                                                                   |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    var_out                                                                |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0xffff 8000 <= var_out <= 0x0000 7fff.                |
 |___________________________________________________________________________|
*/

Word16 shl(Word16 var1,Word16 var2)
  {
   Word16 var_out;
   Word32 resultat;

   if (var2 < 0)
     {
      var_out = shr(var1,-var2);
     }
   else
     {
      resultat = (Word32) var1 * ((Word32) 1 << var2);
     if ((var2 > 15 && var1 != 0) || (resultat != (Word32)((Word16) resultat)))
        {
         Overflow = 1;
         var_out = (var1 > 0) ? MAX_16 : MIN_16;
        }
      else
        {
         var_out = extract_l(resultat);
        }
     }
   return(var_out);
  }

/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : shr                                                     |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |   Arithmetically shift the 16 bit input var1 right var2 positions with    |
 |   sign extension. If var2 is negative, arithmetically shift var1 left by  |
 |   -var2 with sign extension. Saturate the result in case of underflows or |
 |   overflows.                                                              |
 |                                                                           |
 |   Complexity weight : 1                                                   |
 |                                                                           |
 |   Inputs :                                                                |
 |                                                                           |
 |    var1                                                                   |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0xffff 8000 <= var1 <= 0x0000 7fff.                   |
 |                                                                           |
 |    var2                                                                   |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0xffff 8000 <= var1 <= 0x0000 7fff.                   |
 |                                                                           |
 |   Outputs :                                                               |
 |                                                                           |
 |    none                                                                   |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    var_out                                                                |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0xffff 8000 <= var_out <= 0x0000 7fff.                |
 |___________________________________________________________________________|
*/

Word16 shr(Word16 var1,Word16 var2)
  {
   Word16 var_out;

   if (var2 < 0)
     {
      var_out = shl(var1,-var2);
     }
   else
     {
      if (var2 >= 15)
        {
         var_out = (var1 < 0) ? (Word16)(-1) : (Word16)0;
        }
      else
        {
         if (var1 < 0)
           {
     var_out = ~(( ~var1) >> var2 );
           }
         else
           {
            var_out = var1 >> var2;
           }
        }
     }

   return(var_out);
  }

/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : mult                                                    |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |    Performs the multiplication of var1 by var2 and gives a 16 bit result  |
 |    which is scaled i.e.:                                                  |
 |             mult(var1,var2) = shr((var1 times var2),15) and               |
 |             mult(-32768,-32768) = 32767.                                  |
 |                                                                           |
 |   Complexity weight : 1                                                   |
 |                                                                           |
 |   Inputs :                                                                |
 |                                                                           |
 |    var1                                                                   |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0xffff 8000 <= var1 <= 0x0000 7fff.                   |
 |                                                                           |
 |    var2                                                                   |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0xffff 8000 <= var1 <= 0x0000 7fff.                   |
 |                                                                           |
 |   Outputs :                                                               |
 |                                                                           |
 |    none                                                                   |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    var_out                                                                |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0xffff 8000 <= var_out <= 0x0000 7fff.                |
 |___________________________________________________________________________|
*/

Word16 mult(Word16 var1, Word16 var2)
  {
   Word16 var_out;
   Word32 L_produit;

   L_produit = (Word32)var1 * (Word32)var2;

   L_produit = (L_produit & (Word32) 0xffff8000L) >> 15;

   if (L_produit & (Word32) 0x00010000L)
     L_produit = L_produit | (Word32) 0xffff0000L;

   var_out = sature(L_produit);
   return(var_out);
  }


/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : L_mult                                                  |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |   L_mult is the 32 bit result of the multiplication of var1 times var2    |
 |   with one shift left i.e.:                                               |
 |        L_mult(var1,var2) = shl((var1 times var2),1) and                   |
 |        L_mult(-32768,-32768) = 2147483647.                                |
 |                                                                           |
 |   Complexity weight : 1                                                   |
 |                                                                           |
 |   Inputs :                                                                |
 |                                                                           |
 |    var1                                                                   |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0xffff 8000 <= var1 <= 0x0000 7fff.                   |
 |                                                                           |
 |    var2                                                                   |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0xffff 8000 <= var1 <= 0x0000 7fff.                   |
 |                                                                           |
 |   Outputs :                                                               |
 |                                                                           |
 |    none                                                                   |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    L_var_out                                                              |
 |             32 bit long signed integer (Word32) whose value falls in the  |
 |             range : 0x8000 0000 <= L_var_out <= 0x7fff ffff.              |
 |___________________________________________________________________________|
*/

Word32 L_mult(Word16 var1,Word16 var2)
  {
   Word32 L_var_out;

   L_var_out = (Word32)var1 * (Word32)var2;
   if (L_var_out != (Word32)0x40000000L)
     {
      L_var_out *= 2;
     }
   else
     {
      Overflow = 1;
      L_var_out = MAX_32;
     }

   return(L_var_out);
  }


/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : negate                                                  |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |   Negate var1 with saturation, saturate in the case where input is -32768:|
 |                negate(var1) = sub(0,var1).                                |
 |                                                                           |
 |   Complexity weight : 1                                                   |
 |                                                                           |
 |   Inputs :                                                                |
 |                                                                           |
 |    var1                                                                   |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0xffff 8000 <= var1 <= 0x0000 7fff.                   |
 |                                                                           |
 |   Outputs :                                                               |
 |                                                                           |
 |    none                                                                   |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    var_out                                                                |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0xffff 8000 <= var_out <= 0x0000 7fff.                |
 |___________________________________________________________________________|