compandit.c

/**
 *	@file compandit.c - implementation test and example file for integer companding with
 *  compand/uncompand support & IIR correction
 *
 *	@copy copyright (c)  <M. A. Chatterjee>
 *  @author M A Chatterjee <deftio [at] deftio [dot] com>
 *
LICENSE: 

Copyright (c) 2001-2024, M. A. Chatterjee < deftio at deftio dot com >
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice,
  this list of conditions and the following disclaimer in the documentation
  and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 *
 */

#include <stdio.h>
#include <string.h>


#include "companders.h"


//===============================================
//main program for testing the functions
int main (int argc, char *argv[])
{
	int ret_val = 0;
	int i=0,j=0;
	printf("\n============================================================\n");
	printf("compandit library quikie program\n");
	printf("M. A. Chatterjee (c) 2012\n\n");
	printf("These routines were developed for use on embedded projects\n");
	printf("for more info see the accompanying compand.txt\n");
	printf("\n");
	
	//uncomment to 
	//show how linear-->alaw-->linear-->alaw progression / quantization error works
	/*
	
	{
		char alaw=0,alaw2;
		short rev=0;

		for (i= -32768; i <= 32767; i++)
		{
			alaw = DIO_LinearToALaw((short)i);
			rev  = DIO_ALawToLinear(alaw);
			alaw2 =DIO_LinearToALaw(rev);
			if (alaw != alaw2)
				printf("***********");
			printf("%7d  %7d  %7d %7d\n",i,(int)alaw,(int)rev,(int)alaw2);
		}
	}


    // IIR averager examples
    //IIR window length of 8 samples, using fractional precision of 4 bits
    {    
		int a3=0, a4=0;
		unsigned char rad=4; //4 bits fixed-radix fractional precision
		printf(" index   wave  IIRav(i)  IIRav(f)  IIRavP2(i) IIRavP2(f)\n");
		for (i=0; i < 300; i++)
		{
			j=(i&0x3f)-20; // triangle wave with range -20 to + 43
			a3= DIO_IIRavgFR(a3,8,j,rad);		  
			a4= DIO_IIRavgPower2FR(a4,3,j,rad);  
			printf("%6d  %6d  %6d  %9.4f     %6d  %9.4f \n",i,j, 
				DIO_FR2I(a3,rad),DIO_FR2D(a3,rad) ,DIO_FR2I(a4,rad),DIO_FR2D(a4,rad));
		}
	}
    //IIR window length of 64 samples
    {    
		int a3=0, a4=0;
		unsigned char rad=6; //rad is the number of bits of precision 
		printf(" index   wave  IIRav(i)  IIRav(f)  IIRavP2(i) IIRavP2(f)\n");
		for (i=0; i < 300; i++)
		{
			j=(i&0x3f)-20; // triangle wave with range -20 to + 43
			a3= DIO_IIRavgFR(a3,64,j,rad);	   
			a4= DIO_IIRavgPower2FR(a4,6,j,rad); 
			printf("%6d  %6d  %6d  %9.4f     %6d  %9.4f \n",i,j, 
				DIO_FR2I(a3,rad),DIO_FR2D(a3,rad) ,DIO_FR2I(a4,rad),DIO_FR2D(a4,rad));
		}
	}
	// */
	//Typical microcontroller application.  See readme-companders.txt
	// the input here simulates an A/D which has  a range 0..3.3V mapped as 12 bits (0..4095)
	// with a DC bias of 1.55V  ==> (1.55/3.3)*4095 counts = 1923 counts
	
	//now window length of 256 is used for rejecting the resistor bias.  at 8KHz this window
	// would be approx 8000/256 ~= 31 Hz (not quite but explaining Z xforms is beyond what
	// can be explained in this small space.)
	//we seed the DC average at 3.3/2 = 1.65V (we guess its in the middle) and let the long window
	//length hone in on the correct value.  (1.65V/3.3V) *4095 = 2048 counts
    {    
		int actualDCbias     =1923;
		int calculatedDCbias =2048;	//2048 is our initial estimate as outlined above
		unsigned char windowLenPow2InBits = 8; // 8 bit long window = 256 sample long window
		unsigned char rad=6; //rad is the number of bits of precision 

		calculatedDCbias = DIO_I2FR(calculatedDCbias,rad);
		printf(" index   wave  actDCbias  calcDCbias  calcDCbias(f) alaw\n");
		for (i=0; i < 1000; i++)  // if 8000 hz sample rate this represents the number of samples captured
		{
			j=(((i&0x3f)<<1)-63)+1923; // triangle wave w range 0..127  with a bias set at actualDCbias
			calculatedDCbias = DIO_IIRavgPower2FR(calculatedDCbias,windowLenPow2InBits,j,rad); 
			printf("%6d %6d   %6d     %6d      %9.4f     %3d\n",i,j,actualDCbias, 
				DIO_FR2I(calculatedDCbias,rad),DIO_FR2D(calculatedDCbias,rad),
				(int)(DIO_LinearToALaw(j-DIO_FR2I(calculatedDCbias,rad)) ));
		}
	}
	printf("\n");
	return ret_val;
}