cor.h

g729 coding ipaddressing

/**************************************************************************
*
* NAME
*		cor
*
* FUNCTION
*
*		compute auto-correlation coefficients by direct multiplication
*
* SYNOPSIS
*
*		subroutine cor(rar, idim, n, c0, c)
*
*	formal 
*						data	I/O
*		name			type	type	function
*		-------------------------------------------------------------------
*		rar 			float	i		Input data frame
*		idim			int 	i		frame size
*		n				int 	i		Number of correlation terms, 
*										 exclusive C0
*		c0				float	o		C(0)
*		c				float	o		Auto correlation terms C(i), i=1,n
*		
***************************************************************************
*		
* DESCRIPTION
*
*		COR computes the autocorrelation coefficients of the data
*		sequence rar according to the following formula:
*
*			   idim
*		C(i) = SUM	 rar(k) * rar(k-i)	 , where i = 0, ..., n lags
*			   k=i+1
*
*		c0 = C(0)
*
*		NOTE:  rar(k-i) is truncated, so C(i) are true autocorrelations.
*
***************************************************************************
*
* CALLED BY
*
*		autohf	distortion
*
* CALLS
*
*
*
**************************************************************************/

static void cor(float *rar, int idim, int n, float *c0, float *c)
{
  int i, k;
  
  for (*c0 = 0.0, i = 0; i < idim; i++)
	*c0 += *(rar+i) * *(rar+i);

  for (i = 0; i < n; i++)
  {
	for (*(c+i) = 0.0, k = i+1; k < idim; k++)
	  *(c+i) += *(rar+k) * *(rar+k-i-1);
  }
}