RTL271_1/amrnb/lsfwt.c

/*
********************************************************************************
*
*      GSM AMR-NB speech codec   R98   Version 7.6.0   December 12, 2001
*                                R99   Version 3.3.0                
*                                REL-4 Version 4.1.0                
*
********************************************************************************
*
*      File             : lsfwt.c
*      Purpose          : Compute LSF weighting factors
*
********************************************************************************
*/
 
 
/*
********************************************************************************
*                         MODULE INCLUDE FILE AND VERSION ID
********************************************************************************
*/
#include "lsfwt.h"
const char lsfwt_id[] = "@(#)$Id $" lsfwt_h;
 
/*
********************************************************************************
*                         INCLUDE FILES
********************************************************************************
*/
#include <stdlib.h>
#include <stdio.h>
#include "typedef.h"
#include "basic_op.h"
#include "count.h"
#include "cnst.h"

/*
********************************************************************************
*                         PUBLIC PROGRAM CODE
********************************************************************************
*/
/****************************************************
 *
 * FUNCTION  Lsf_wt                                                         *
 *                                                                          *
 ****************************************************
 * Compute LSF weighting factors                                            *
 *                                                                          *
 *  d[i] = lsf[i+1] - lsf[i-1]                                              *
 *                                                                          *
 *  The weighting factors are approximated by two line segment.             *
 *                                                                          *
 *  First segment passes by the following 2 points:                         *
 *                                                                          *
 *     d[i] = 0Hz     wf[i] = 3.347                                         *
 *     d[i] = 450Hz   wf[i] = 1.8                                           *
 *                                                                          *
 *  Second segment passes by the following 2 points:                        *
 *                                                                          *
 *     d[i] = 450Hz   wf[i] = 1.8                                           *
 *     d[i] = 1500Hz  wf[i] = 1.0                                           *
 *                                                                          *
 *  if( d[i] < 450Hz )                                                      *
 *    wf[i] = 3.347 - ( (3.347-1.8) / (450-0)) *  d[i]                      *
 *  else                                                                    *
 *    wf[i] = 1.8 - ( (1.8-1.0) / (1500-450)) *  (d[i] - 450)               *
 *                                                                          *
 *                                                                          *
 *  if( d[i] < 1843)                                                        *
 *    wf[i] = 3427 - (28160*d[i])>>15                                       *
 *  else                                                                    *
 *    wf[i] = 1843 - (6242*(d[i]-1843))>>15                                 *
 *                                                                          *
 *--------------------------------------------------------------------------*/

void Lsf_wt (
    Word16 *lsf,         /* input : LSF vector                  */
    Word16 *wf)          /* output: square of weighting factors */
{
    Word16 temp;
    Word16 i;
    /* wf[0] = lsf[1] - 0  */
    wf[0] = lsf[1];                                     move16 (); 
    for (i = 1; i < 9; i++)
    {
        wf[i] = sub_ex (lsf[i + 1], lsf[i - 1]);           move16 (); 
    }
    /* wf[9] = 0.5 - lsf[8] */    
    wf[9] = sub_ex (16384, lsf[8]);move16 ();      

    for (i = 0; i < 10; i++)
    {
        temp = sub_ex (wf[i], 1843);
        test (); 
        if (temp < 0)
        {
            wf[i] = sub_ex (3427, mult_ex (wf[i], 28160));    move16 (); 
        }
        else
        {
            wf[i] = sub_ex (1843, mult_ex (temp, 6242));      move16 (); 
        }

        wf[i] = shl_ex (wf[i], 3); move16 (); 
    }
    return;
}