operg722.c

来自「Reference Implementation of G.711 standa」· C语言 代码 · 共 684 行 · 第 1/3 页

 |             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 
sub (var1, var2)
Word16 var1;
Word16 var2;
{
  Word16          var_out;
  Word32          L_diff;

  L_diff = (Word32) var1 - (Word32) var2;
  var_out = sature (L_diff);
  return (var_out);
}
/* ....................... end of sub() ............................ */


/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : shl                                                     |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |   Arithmetically shift the 16 bit input var1 left var2 positions.Zero fill|
 |   the var2 LSB of the result. If var2 is negative, arithmetically shift   |
 |   var1 right 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 
shl (var1, var2)
Word16 var1;
Word16 var2;
{
  Word16          var_out;
  Word32          L_result;

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

  return (var_out);
}
/* ....................... end of shl() ............................ */


/*___________________________________________________________________________
 |                                                                           |
 |   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 (var1, var2)
Word16 var1;
Word16 var2;
{
  Word16          var_out;

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

  return (var_out);
}
/* ....................... end of shr() ............................ */


/*___________________________________________________________________________
 |                                                                           |
 |   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 (var1, var2)
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 |= (Word32) 0xffff0000L;
  }
  var_out = sature (L_produit);
  return (var_out);
}
/* ....................... end of mult() ............................ */


/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : negate                                                  |
 |                                                                           |
 |   Purpose :                                                               |