gaincode.h

g729 coding ipaddressing

/**************************************************************************
*
* ROUTINE
*				gainencode
*
* FUNCTION
*
*				encode and quantize code book gain
*
* SYNOPSIS
*				subroutine gainencode(input, index)
*
*	formal
*
*						data	I/O
*		name			type	type	function
*		-------------------------------------------------------------------
*		input			int 	i		code book gain input (true value)
*		index			float	o		encoded code book gain ZERO BASED index
*		gainencode		float	func	encoded code book gain
*
***************************************************************************
*
* DESCRIPTION
*
*
*	   Fast code book gain quantizer to allow practical quantization
*	   inside the code book search loop. A binary tree search quantization 
*	   is implemented below.
*
*
***************************************************************************
*
* CALLED BY
*
*		cbsearch cgain
*
* CALLS
*
*
***************************************************************************
*
* REFERENCES
*
*
**************************************************************************/
 /* *Log quantization								*/

static const float gainlog5[32] =
{
 -1330., -870., -660., -520., -418., -340., -278., -224.,
 -178., -136.,	-98.,  -64.,  -35.,  -13.,	 -3.,	-1.,
	1.,    3.,	 13.,	35.,   64.,   98.,	136.,  178.,
  224.,  278.,	340.,  418.,  520.,  660.,	870., 1330.
};

static float gainencode(float input, int *index)
{
  int i;
  static const float midpoints[31] = 
  {
	-1100., -765., -590., -469., -379., -309., -251., -201.,
	 -157., -117.,	-81.,  -49.5, -24.,   -8.,	 -2.,	 0.,
		2.,    8.,	 24.,	49.5,  81.,  117.,	157.,  201.,
	  251.,  309.,	379.,  469.,  590.,  765., 1100.
  };

  /* *Binary tree search for closest gain								 */

  for (*index = 15, i = 8; i >= 1; i = i >> 1)
  {
	if (input > midpoints[*index])
	  *index += i;
	else
	  *index -= i;
  }
  if (input > midpoints[*index])
	(*index)++;

  /* *Return quantized gain and ZERO based index						 */

  return (gainlog5[*index]);
}
   

/**************************************************************************
*
* ROUTINE
*				gainencode2
*
* FUNCTION
*
*				encode and quantize code book gain
*
* SYNOPSIS
*				subroutine gainencode2(numer, denom, index)
*
*	formal
*
*						data	I/O
*		name			type	type	function
*		-------------------------------------------------------------------
*		numer			int 	i		code book gain numerator
*		denom			int 	i		code book gain denominator
*		index			float	o		encoded code book gain ZERO BASED index
*		gainencode2 	float	func	encoded code book gain
*
***************************************************************************
*
* DESCRIPTION
*
*
*	  Fast nonuniform division for code book gain quantization to allow
*	  practical quantization inside the code book search loop.	A binary
*	  tree search with cross multiply quantization is implemented below.
*
*
*
***************************************************************************
*
* CALLED BY
*
*		cbsearch cgain
*
* CALLS
*
*
***************************************************************************
*
* REFERENCES
*
*
**************************************************************************/

float gainencode2(float numer, float denom, int *index)
{

  /* *Hard coded for 5 bit quantization to achieve high speed			*/

  int i;
  static const float midpoints[31] = 
  {
	-1100., -765., -590., -469., -379., -309., -251., -201.,
	 -157., -117.,	-81.,  -49.5, -24.,   -8.,	 -2.,	 0.,
		2.,    8.,	 24.,	49.5,  81.,  117.,	157.,  201.,
	  251.,  309.,	379.,  469.,  590.,  765., 1100.
  };

  /* *Binary tree search for closest gain								 */

  for (*index = 15, i = 8; i >= 1; i = i >> 1)
  {
	if (numer  > denom * midpoints[*index])
	  *index += i;
	else
	  *index -= i;
  }
  if (numer > denom * midpoints[*index])
	(*index)++;

  /* *Return quantized gain and ZERO based index						 */

  return (gainlog5[*index]);
}
   
/**************************************************************************
*
* ROUTINE
*				gaindecode
*
* FUNCTION
*
*				decode code book gain from the gain index (gindex)
*				and bit index (bits).
*
* SYNOPSIS
*				subroutine gaindecode(gindex, bits, gain)
*
*	formal
*
*						data	I/O
*		name			type	type	function
*		-------------------------------------------------------------------
*		gindex			int 	i		gain index value
*		bits			int 	i		# bits for encode
*		gain			float	o		decoded code book gain value
*
***************************************************************************
*
* CALLED BY
*
*		dcodcbg 
*
* CALLS
*
*
***************************************************************************
*
* REFERENCES
*
*		Quantizing for Minimum Distorion
*		J. Max
*		IRE Trans. Inform. Theory, vol. IT-6, pp.7-12, Mar. 1960
*
***************************************************************************
*
*		The data used in the table generation is from 3m3f.spd.
*
**************************************************************************/

void gaindecode(int a_gindex, int bits, float *gain)
{
  /* Choose appropriate gain										 */

  if (bits == 5)
	*gain = gainlog5[a_gindex];
  else {
#ifdef CELPDIAG
    fprintf(stderr, "gaindecode: unquantized cbgain\n");
#endif
	CELP_ERROR(CELP_ERR_GAINDECODE);
  }
}