dcodtau.c

语音CELP压缩解压源代码（C语音)

/**************************************************************************
*
* ROUTINE
*		dcodtau
*
* FUNCTION
*		 Decodes all pitch tau values for a frame
*
*
* SYNOPSIS
*		subroutine dcodtau(taubits,taudelta,bitsum1,bitsum2,bitpointer,
*				   nn,stream,pddecode,pdtabi,taus)
*
*   formal
*
*                       data    I/O
*       name            type    type    function
*       -------------------------------------------------------------------
*	taubits		int	i	number of bits for quantization
*	taudelta	int	i	number of bits for even frame delta
*	bitsum1		int	i	number of bits for odd subframes
*	bitsum2		int	i	number of bits for even subframes
*	bitpointer	int	i/o	number of bits used
*	nn		int	i	number of subframes/frame
*	stream		short	i	bit stream
*	pddecode	real	i	pitch delay permutation table
*	pdtabi		int	i	pitch delay table index
*	taus		float	o	vector of pitch delays "taus"
*
*   external
*
*       name            type    type    function
*       -------------------------------------------------------------------
*
*	plevel1		int		number of full search pitch delays
*	plevel2		int		number of delta search pitch delays
*	pdelay[]	float		pitch delay coding table
*
***************************************************************************
*
* DESCRIPTION
*
*		This routine converts the pitch delay bits of the 
*	bitstream to actual delay values.  These delays are output
*	to the main routine in taus(i), one delay for each of four
*	subframes.
*
***************************************************************************
*
* CALLED BY
*
*       celp
*
* CALLS
*
*       unpack
*
***************************************************************************
*
* REFERENCES
*
*
**************************************************************************/
#include "ccsub.h"
extern int plevel1, plevel2;
extern float pdelay[MAXPD];

dcodtau(taubits, taudelta, bitsum1, bitsum2, bitpointer, nn, stream,
         pddecode, pdtabi, taus)

int taubits, taudelta, bitsum1, bitsum2, *bitpointer;
int pdtabi[], nn;
short stream[];
float pddecode[], taus[];

{
  int i, pointer, tptr, mxptr, mnptr;
  static int lptr = 0;

  pointer = *bitpointer;
  for (i = 0; i < nn; i++)
  {
    if (((i + 1) % 2) != 0)
    {
      unpack(stream, taubits, &tptr, &pointer);
      taus[i] = pddecode[tptr];
      pointer += bitsum1 - taubits;
    }
    else
    {
      unpack(stream, taudelta, &tptr, &pointer);
      pointer += bitsum2 - taudelta;
      mnptr = lptr - (plevel2 / 2 - 1);
      mxptr = lptr + (plevel2 / 2);
      if (mnptr < 0)
        mnptr = 0;
      if (mxptr > plevel1 - 1)
        mnptr = plevel1 - plevel2;
      taus[i] = pdelay[tptr + mnptr];
    }
    lptr = pdtabi[tptr];
  }
  *bitpointer += taubits;
}