channel.c

4.8k/s速率FS1016标准语音压缩源码

          /*LINTLIBRARY*/
          /*PROTOLIB1*/
#include "main.h"
#include <math.h>
#include "channel.h"
#include <stdio.h>
#include <stdlib.h>

#define	Random()	((float)(rand())/(float)(RAND_MAX))

/*double	drand48();
#define	Random()	drand48()*/

/**************************************************************************
*                                                                         *
* ROUTINE
*		Channel
*
* FUNCTION
*		CELP channel
* SYNOPSIS
*		channel(ChannelIn, ChannelType, NumBits, BitError, ChannelOut)
*
*   formal
*
*                       data    I/O
*       name            type    type    function
*       -------------------------------------------------------------------
*	ChannelIn	int	 i	Frame of input channel data
*	ChannelType	int	 i	Type of channel conditions
*	NumBits		int	 i	Number of bits being transmitted
*	BitError	char	 i	Name of bit error pattern file
*	ChannelOut	int	 o	Frame of output channel data
*
**************************************************************************/
void Channel(
int 	ChannelIn[],
int	ChannelType,
int	NumBits,
char	BitError[],
float	ErrorRate,
int	frame_num,
int 	**ChannelOut
)
{
int	i;
float	rand_num;

/*  Memory will have to be allocated for ChannelOut to perform other channel conditions */
	if (ChannelType != CLEAR && ChannelType != OTHER)  {
	  if (frame_num == 1)	{
	    *ChannelOut = (int *) calloc(NumBits, sizeof(int));
	    if(*ChannelOut == NULL)	{
	      fprintf(stderr, "Unable to Calloc for ChannelOut\n");
	      exit(-1);
	    }
	  }
	  for(i=0; i< NumBits; i++)
	    (*ChannelOut)[i] = ChannelIn[i];
	}


	switch(ChannelType)	{
	  case CLEAR:
/*  Clear Channel */
		*ChannelOut = ChannelIn;
		break;
	  case RBER:
/*  Add Random Bit Errors */
		for (i=0; i< NumBits; i++)
		  rand_num = Random();	
		  if (Random() < ErrorRate)	{
		    (*ChannelOut)[i] ^= 0x1;
		  }
		break;
	  case RBLER:
/*  Add Pseudo-Block Random Errors */
		for(i=0; i< NumBits; i++)
		  if(Random() < ErrorRate)
		    if (Random() < 0.5)
		      (*ChannelOut)[i] ^= 0x1;
		break;
	  case OTHER:
		if(frame_num==1)
		  printf("Other Error rate not written, using clear channel\n");
		*ChannelOut = ChannelIn;
		break;
	  default:
/*  Channel is not properly defined */
		printf("Channel is Dead\n");
		exit(876);
		break;
	}
}