gmed_n.c

arm音频编解码库

/*
********************************************************************************
*
*      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             : gmed_n.c
*      Purpose          : calculates N-point median.
*
********************************************************************************
*/
/*
********************************************************************************
*                         MODULE INCLUDE FILE AND VERSION ID
********************************************************************************
*/
#include "gmed_n.h"
const char gmed_n_id[] = "@(#)$Id $" gmed_n_h;
 
/*
********************************************************************************
*                         INCLUDE FILES
********************************************************************************
*/
#include <stdlib.h>
#include <stdio.h>
#include "typedef.h"
#include "basic_op.h"
#include "count.h"
 
/*
********************************************************************************
*                         LOCAL VARIABLES AND TABLES
********************************************************************************
*/

#define NMAX 9  /* largest N used in median calculation */

/*
********************************************************************************
*                         PUBLIC PROGRAM CODE
********************************************************************************
*/
/*************************************************************************
 *
 *  FUNCTION:   gmed_n
 *
 *  PURPOSE:    calculates N-point median.
 *
 *  DESCRIPTION:
 *             
 *************************************************************************/

Word16 gmed_n (   /* o : index of the median value (0...N-1)      */
    Word16 ind[], /* i : Past gain values                         */
    Word16 n      /* i : The number of gains; this routine        */
                  /*     is only valid for a odd number of gains  */
                  /*     (n <= NMAX)                              */
)
{
    Word16 i, j, ix = 0;
    Word16 max;
    Word16 medianIndex;
    Word16 tmp[NMAX];
    Word16 tmp2[NMAX];

    for (i = 0; i < n; i++)
    {
        tmp2[i] = ind[i];                                      move16 (); 
    }

    for (i = 0; i < n; i++)
    {
        max = -32767;                                          move16 (); 
        for (j = 0; j < n; j++)
        {
            test (); 
            if (sub (tmp2[j], max) >= 0)
            {
                max = tmp2[j];                                 move16 (); 
                ix = j;                                        move16 (); 
            }
        }
        tmp2[ix] = -32768;                                     move16 (); 
        tmp[i] = ix;                                           move16 (); 
    }

    medianIndex=tmp[ shr(n,1) ]; move16 (); /* account for complex addressing */
    return (ind[medianIndex]);                                     
}