/**************************************************************************** ROUTINE*               biterror** FUNCTION**               introduce random errors in CELP bitstream** SYNOPSIS*               biterror(ber,mask,stream,streambits,error,total)**   formal**                       data    I/O*       name            type    type    function*       -------------------------------------------------------------------*       ber		float	i	bit error rate*	mask		int	i	error mask*	stream		short	i/o	array of binary bits to be corrupted*	streambits	int	i	number of bits in stream*	error		int	o	number of bits corrputed*	total		int	o	total number of bits through coder****************************************************************************** CALLED BY**	celp** CALLS**	random****************************************************************************** DESCRIPTION*		Bit errors are introduced into the array "stream" at a rate*	"ber".  Individual bits may be reversed while protecting others by*	setting bits of the mask array which is read at the beginning of*	execution.*		To protect a bit set mask(bit) = 1.  If this is*	left at 0, the bit is subjected to reversal at the rate specified*	by "ber".  (The protection scheme above is NOT a function of the*	Hamming error control coding.)***************************************************************************/#include <stdio.h>biterror(ber, mask, stream, streambits, error, total)float ber;int mask[], streambits, *error, *total;short stream[];{  float xx, rate;  int i;					/* protection mask: read in	*/  rate = ber / 100.;  for (i = 0; i < streambits; i++)  {    xx = (random2() + 32768) / 65535.;    if (mask[i] == 0)    {      (*total)++;      if (xx < rate)      {	stream[i] ^= 1;	if (stream[i] != 0 && stream[i] != 1)	{	  fprintf(stderr, "biterror: bit stream not ones and zeros\n");	  exit(1);	}	(*error)++;      }    }  }}