getext1k.c

完整的EVRC压缩解压缩算法源码,附带一个简单的例子程序。

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/*======================================================================*/
/*     Enhanced Variable Rate Codec - Bit-Exact C Specification         */
/*     Copyright (C) 1997-1998 Telecommunications Industry Association. */
/*     All rights reserved.                                             */
/*----------------------------------------------------------------------*/
/* Note:  Reproduction and use of this software for the design and      */
/*     development of North American Wideband CDMA Digital              */
/*     Cellular Telephony Standards is authorized by the TIA.           */
/*     The TIA does not authorize the use of this software for any      */
/*     other purpose.                                                   */
/*                                                                      */
/*     The availability of this software does not provide any license   */
/*     by implication, estoppel, or otherwise under any patent rights   */
/*     of TIA member companies or others covering any use of the        */
/*     contents herein.                                                 */
/*                                                                      */
/*     Any copies of this software or derivative works must include     */
/*     this and all other proprietary notices.                          */
/*======================================================================*/
/*  Memory Usage:                                                       */
/*      ROM:                0                                           */
/*      Static/Global RAM:  9                                           */
/*      Stack/Local RAM:    4                                           */
/*----------------------------------------------------------------------*/

/****************************************************************************
* Routine name: GetExc800bps.                                               *
* Function: Energy quantization of the residual signal.                     *
* Inputs: input - signal array.                                             *
*         length - size of signal array.                                    *
* Output: output - quantized signal.                                        *
****************************************************************************/
#include "macro.h"
#include "rom.h"
#include <stdio.h>
//#include <math.h>
#include "mathevrc.h"
#include "mathdp31.h"
#include "mathadv.h"

short ran0(short *seed0)
{
long	Ltemp;
Ltemp = 0.0;
Ltemp = L_mac(27698, 25173, *seed0);
Ltemp = L_shr(Ltemp, 1);
Ltemp = Ltemp & 0x0000ffffL; 
*seed0 = extract_l(Ltemp);
return (extract_h(L_shl(Ltemp,15))); 
}

short ran_g(short *seed0)
{
	static int iset = 0;
	static long gset;
	long rsq, ltemp1, ltemp2;
	short sv1, sv2, rsq_s;
	short shft_fctr, stemp1;
	short shft_fctr1;

/* ======================================================================== */
	long ltmp1, ltmp2;
	short ans = 0;
	short stmp2;
/* ======================================================================== */
	if (iset == 0)
	{
		
		
			sv1 = shl(sub(ran0(seed0), 16384), 1);

			sv2 = shl(sub(ran0(seed0), 16384), 1);

			/* rsq = sv1 * sv1 + sv2 * sv2; */
			ltemp1 = L_mult(sv1, sv1);
			ltemp2 = L_mult(sv2, sv2);

			rsq = L_add(L_shr(ltemp1, 1), L_shr(ltemp2, 1));

		
		if (rsq >= 1073741824 || rsq == 0){
		  /* If condition not met, don't iterate; use */
		  /* rough approximation. */
		   ans = shr(sv1,3);
		   ans = add(ans, shr(sv2,3));
		   ans = add(ans, shr(sub(ran0(seed0), 16384),2));
		 
		   return (ans);
		}
/*
 * error in rsq doesn't seem to contribute to the final error in ran_g
 */

		/*
		 * rsq scale down by two: input to fnLog must be scaled up by 2.
		 */
		rsq = L_shl(rsq, 1);

		/* stemp1 = round32(L_negate(fnLog(rsq)));  */
		ltmp1 = L_negate(fnLog(rsq));

		/*
		 * rsq must be greater than the log of lsq for the fractional
		 * divide to work. therfore normalize rsq.
		 */
		shft_fctr = norm_l(rsq); 
		rsq_s = round32(L_shl(rsq, shft_fctr));
		stmp2 = (divide_s(round32(ltmp1), rsq_s));

		/* 
		 * stemp2 must be normalized before taking its square root.
		 * (increases precision).
		 */
		shft_fctr1 = norm_s(stmp2);
		ltmp2 = L_deposit_h(shl(stmp2, shft_fctr1));
		stemp1 = sqroot(ltmp2);

		/* 
		 * shifting involved before taking the square root:
		 * LEFT << shft_fctr. (LEFT because rsq is in the denominator
		 *          of ltemp2 quotion).   
		 * LEFT << 6. (multiply by 2 in original code and multiply by 32
		 *        because output of fnLog scaled down by 32).
		 * RIGHT >> shft_fctr1. (normalization taken before sqroot).
		 */
		shft_fctr = shft_fctr + 6 - shft_fctr1;

		/*
		 * PROPERTY: sqrt(2^n) = 2^(n/2)
		 * if shft_fctr is odd; multiply stemp1 by sqrt(2)/2  and
		 * increment number of shifts by 1. Can now use shft_fctr / 2.
		 */
		if (shft_fctr & 0x0001)
		{
			stemp1 = mult(stemp1, 23170);
			shft_fctr++;
		}

		shft_fctr = shr(shft_fctr, 1);

		/*
		 * normalize stemp1 for the following multiplication.
		 * adjust shft_fctr accordingly.
		 */
		shft_fctr1 = norm_s(stemp1);
		stemp1 = shl(stemp1, shft_fctr1);
		shft_fctr = shft_fctr - shft_fctr1;

		gset = L_mult(sv1, stemp1);

		/*
		 * final output is scaled down by 4, therefore shift up by
		 * shft_fctr - 2.
		 */
		gset = L_shl(gset, shft_fctr - 2);

		iset = 1;
		return round32(L_shl(L_mult(sv2, stemp1), shft_fctr - 2));
	}
	else
	{
		iset = 0;
		return round32(gset);
	}
}


short e_ran_g(short *seed0)
{
	static int iset = 0;
	static long gset;
	long rsq, ltemp1, ltemp2;
	short sv1, sv2, rsq_s;
	short shft_fctr, stemp1;
	short shft_fctr1;

/* ======================================================================== */
	long ltmp1, ltmp2;
	short ans = 0;
	short stmp2;
/* ======================================================================== */
	if (iset == 0)
	{
		
		
			sv1 = shl(sub(ran0(seed0), 16384), 1);

			sv2 = shl(sub(ran0(seed0), 16384), 1);

			/* rsq = sv1 * sv1 + sv2 * sv2; */
			ltemp1 = L_mult(sv1, sv1);
			ltemp2 = L_mult(sv2, sv2);

			rsq = L_add(L_shr(ltemp1, 1), L_shr(ltemp2, 1));