omxsp_iirone_direct_s16.c

The OpenMAX DL (Development Layer) APIs contain a comprehensive set of audio, video, signal processi

/**
 * 
 * File Name:  omxSP_IIROne_Direct_S16.c
 * OpenMAX DL: v1.0.2
 * Revision:   10586
 * Date:       Wednesday, March 5, 2008
 * 
 * (c) Copyright 2007-2008 ARM Limited. All Rights Reserved.
 * 
 * 
 *
 * Description:
 * This file contains module for single sample IIR filtering
 *
 */

#include "omxtypes.h"
#include "armOMX.h"
#include "omxSP.h"
#include "armCOMM.h"
#include "armSP.h"

/**
 * Function:  omxSP_IIROne_Direct_S16   (2.2.3.2.2)
 *
 * Description:
 * Single sample IIR filtering for 16-bit data.  This function applies the 
 * direct form II IIR filter defined by the coefficient vector pTaps to a 
 * single sample of input data. The internal accumulator width must be at 
 * least 32 bits, and the result is saturated if the operation produces a 
 * value outside the range of a signed 16-bit integer, i.e., the output will 
 * saturate to 0x8000 (-32768) for a negative overflow or 0x7fff (32767) for a 
 * positive overflow.  The result is undefined if any of the partially 
 * accumulated values exceeds the range of a signed 32-bit integer. 
 *
 * Input Arguments:
 *   
 *   val - the single input sample to which the filter is 
 *            applied.  
 *   pTaps - pointer to the 2L+2 -element vector that contains the combined 
 *            numerator and denominator filter coefficients from the system 
 *            transfer function, H(z). Coefficient scaling and coefficient 
 *            vector organization should follow the conventions described 
 *            above. The value of the coefficient scaleFactor exponent must be 
 *            non-negative (sf>=0). 
 *   order - the maximum of the degrees of the numerator and denominator 
 *            coefficient polynomials from the system transfer function, H(z). 
 *            In the notation of section 2.2.3.2, the parameter 
 *            order=max(K,M)=L gives the maximum delay, in samples, used to 
 *            compute each output sample. 
 *   pDelayLine - pointer to the L-element filter memory buffer (state). The 
 *            user is responsible for allocation, initialization, and 
 *            deallocation. The filter memory elements are initialized to zero 
 *            in most applications. 
 *
 * Output Arguments:
 *   
 *   pResult - pointer to the filtered output sample 
 *
 * Return Value:
 *    
 *    OMX_Sts_NoErr - no error 
 *    OMX_Sts_BadArgErr - bad arguments; returned if one or more of the 
 *              following is true: 
 *    -    one or more of the following pointers is NULL: pResult, 
 *              pTaps, or pDelayLine. 
 *    -    order < 1 
 *    -    pTaps[order+1] < 0 (negative scaling) 
 *
 */

OMXResult omxSP_IIROne_Direct_S16 (
     OMX_S16 val,
     OMX_S16 * pResult,
     const OMX_S16 * pTaps,
     OMX_INT order,
     OMX_S32 * pDelayLine
 )
{
    const OMX_S16 *pTapsAk;
    const OMX_S16 *pTapsBm;
    OMX_S32       macAk,macBm,temp;
    OMX_INT       scaleFactor,tapNum;
    
    /* Argument Check */
    armRetArgErrIf( pResult    == NULL, OMX_Sts_BadArgErr);
    armRetArgErrIf( pDelayLine == NULL, OMX_Sts_BadArgErr);
    armRetArgErrIf( pTaps      == NULL, OMX_Sts_BadArgErr);
    armRetArgErrIf( order      <  0   , OMX_Sts_BadArgErr);
    armRetArgErrIf( pTaps[order + 1]  <  0 , OMX_Sts_BadArgErr);

    /* Processing */
    order       = order + 1;
    scaleFactor = pTaps[order + 1];
    pTapsAk     = pTaps + order + 1;
    pTapsBm     = pTaps;


    macAk    = 0;
    macBm    = 0;
    pDelayLine--;
    
    for(tapNum = order; tapNum != 0; tapNum--)
    {
        macAk = armSatMac_S16S32_S32(macAk, pDelayLine[tapNum], pTapsAk[tapNum]);
        macBm = armSatMac_S16S32_S32(macBm, pDelayLine[tapNum], pTapsBm[tapNum]);
        
        /*shifting the delay line*/
        if(tapNum != 1)
        {
            pDelayLine[tapNum] = pDelayLine[tapNum - 1];
        }
    }
    
    temp  = armSatRoundLeftShift_S32(val, scaleFactor);
    macAk = armSatSub_S32( temp , macAk);
    
    macAk = armSatRoundLeftShift_S32(macAk,-scaleFactor);
    macBm = armSatMac_S16S32_S32(macBm,macAk,pTapsBm[0]);
    
    pDelayLine[1] = macAk;
    *pResult      = armSatRoundRightShift_S32_S16(macBm, scaleFactor);

    return OMX_Sts_NoErr;
}

/*End of File*/