companders.c 5.11 KB
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/**
 *	@companders.c - implementation
 *		
 *	@copy Copyright (C) <2012>  <M. A. Chatterjee>
 *  @author M A Chatterjee <deftio [at] deftio [dot] com>
 *	@version 1.01 M. A. Chatterjee, cleaned up naming
 *
 *  This file contains integer math compander functions for analog/audio representations on
 *  embedded systems.  Linear2Alaw derived from Mark Spencer, Sun Microsystem and from 
 *  the A Law specification
 *
 *  @license: 
 *	This software is provided 'as-is', without any express or implied
 *	warranty. In no event will the authors be held liable for any damages
 *	arising from the use of this software.
 *
 *	Permission is granted to anyone to use this software for any purpose,
 *	including commercial applications, and to alter it and redistribute it
 *	freely, subject to the following restrictions:
 *
 *	1. The origin of this software must not be misrepresented; you must not
 *	claim that you wrote the original software. If you use this software
 *	in a product, an acknowledgment in the product documentation would be
 *	appreciated but is not required.
 *
 *	2. Altered source versions must be plainly marked as such, and must not be
 *	misrepresented as being the original software.
 *
 *	3. This notice may not be removed or altered from any source
 *	distribution.
 *
 */

#include "companders.h"

DIO_s8  DIO_LinearToALaw(DIO_s16 sample)
{ 
     const DIO_s16 cClip = 32635;
     const static DIO_s8 LogTable[128] = 
     { 
     1,1,2,2,3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5, 
     6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6, 
     7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, 
     7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7 
     };

     DIO_s32 sign, exponent, mantissa; 
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     DIO_s8 compandedValue;

     sample = (sample ==-32768) ? -32767 : sample;
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     sign = ((~sample) >> 8) & 0x80; 
     if (!sign) 
          sample = (short)-sample; 
     if (sample > cClip) 
          sample = cClip; 
     if (sample >= 256) 
     { 
          exponent = (int)LogTable[(sample >> 8) & 0x7F]; 
          mantissa = (sample >> (exponent + 3) ) & 0x0F; 
          compandedValue = ((exponent << 4) | mantissa); 
     } 
     else 
     { 
          compandedValue = (unsigned char)(sample >> 4); 
     } 
     compandedValue ^= (sign ^ 0x55); 
     return compandedValue; 
}

DIO_s16 DIO_ALawToLinear(DIO_s8 aLawByte)
{
	 const static DIO_s16 ALawDecompTable[256]={
	  5504,  5248,  6016,  5760,  4480,  4224,  4992,  4736,
	  7552,  7296,  8064,  7808,  6528,  6272,  7040,  6784,
	  2752,  2624,  3008,  2880,  2240,  2112,  2496,  2368,
	  3776,  3648,  4032,  3904,  3264,  3136,  3520,  3392,
	 22016, 20992, 24064, 23040, 17920, 16896, 19968, 18944,
	 30208, 29184, 32256, 31232, 26112, 25088, 28160, 27136,
	 11008, 10496, 12032, 11520,  8960,  8448,  9984,  9472,
	 15104, 14592, 16128, 15616, 13056, 12544, 14080, 13568,
	   344,   328,   376,   360,   280,   264,   312,   296,
	   472,   456,   504,   488,   408,   392,   440,   424,
		88,    72,   120,   104,    24,     8,    56,    40,
	   216,   200,   248,   232,   152,   136,   184,   168,
	  1376,  1312,  1504,  1440,  1120,  1056,  1248,  1184,
	  1888,  1824,  2016,  1952,  1632,  1568,  1760,  1696,
	   688,   656,   752,   720,   560,   528,   624,   592,
	   944,   912,  1008,   976,   816,   784,   880,   848,
	 -5504, -5248, -6016, -5760, -4480, -4224, -4992, -4736,
	 -7552, -7296, -8064, -7808, -6528, -6272, -7040, -6784,
	 -2752, -2624, -3008, -2880, -2240, -2112, -2496, -2368,
	 -3776, -3648, -4032, -3904, -3264, -3136, -3520, -3392,
	-22016,-20992,-24064,-23040,-17920,-16896,-19968,-18944,
	-30208,-29184,-32256,-31232,-26112,-25088,-28160,-27136,
	-11008,-10496,-12032,-11520, -8960, -8448, -9984, -9472,
	-15104,-14592,-16128,-15616,-13056,-12544,-14080,-13568,
	  -344,  -328,  -376,  -360,  -280,  -264,  -312,  -296,
	  -472,  -456,  -504,  -488,  -408,  -392,  -440,  -424,
	   -88,   -72,  -120,  -104,   -24,    -8,   -56,   -40,
	  -216,  -200,  -248,  -232,  -152,  -136,  -184,  -168,
	 -1376, -1312, -1504, -1440, -1120, -1056, -1248, -1184,
	 -1888, -1824, -2016, -1952, -1632, -1568, -1760, -1696,
	  -688,  -656,  -752,  -720,  -560,  -528,  -624,  -592,
	  -944,  -912, -1008,  -976,  -816,  -784,  -880,  -848};
	 DIO_s16 addr = ((DIO_s16)aLawByte)+128; // done for compilers with poor expr type enforcement
	 return ALawDecompTable[addr]; 
}

// see companders.h
// fixed-radix IIR averager implementation supporting arbitrarily chosen windows
DIO_s32 DIO_IIRavgFR	   (DIO_s32 prevAvg, DIO_u16 windowLen, DIO_s16 newSample, DIO_u8 radix)
{
	DIO_s32 iirAvg=0;
	iirAvg = ((prevAvg * (windowLen-1)) + (DIO_I2FR(newSample,radix)))/windowLen;
	return iirAvg;
}

// see companders.h
// fixed-radix IIR averager implementation using power-of-2 sized windows
// and only shift operations for cpu efficiency
DIO_s32 DIO_IIRavgPower2FR (DIO_s32 prevAvg, DIO_u8 windowLenInBits, DIO_s16 newSample, DIO_u8 radix)
{
	DIO_s32 iirAvg=0;
	iirAvg = (((prevAvg<<windowLenInBits)-prevAvg) + (DIO_I2FR(newSample,radix)))>>windowLenInBits;
	return iirAvg;
}
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#ifdef MAIN

int main(int argc, char* argv[])
{

  
  
  return 0;
}

#endif