amf_fir.c

ADI SHARC DSP 音频算法标准模块库

// Copyright(c) 2005 Analog Devices, Inc. All Rights Reserved.
// This software is proprietary and confidential to Analog Devices, Inc. and its licensors.

// File    : $Id: //depot/development/visualaudio/modules/2.5.0/SHARC/Source/AMF_FIR.c#3 $ 
// Part of : VisualAudio V2.5.0 
// Updated : $Date: 2006/10/12 $ by $Author: Fernando $



#include "AMF_FIR.h"
#include "VA_GeneralHelperFunctions.h"

void AMF_FIR_Render(AMF_FIR * restrict instance,float * restrict * buffers,int tickSize);

// NOTE: The C version of this function is for reference only (it is
//       intended just to show the general algorithm that the module
//       uses), and it may not have been fully tested
#if 0        // example C code

// circular buffered fir - based on Tim Stilson's synthCore FIR
SEG_MOD_FAST_CODE  void AMF_FIR_Render(AMF_FIR * restrict instance,float * restrict * buffers,int tickSize) {
    int i, j, k;
    int filterSize = instance->filterSize;                    // filter size
    float pm *stateBuffer = &instance->stateBuffer[0];        // state buffer
    int stateIndex = instance->statePtr - stateBuffer;        // current state buffer index
    float *coefs = &instance->coefs[0];                        // filter coefs
    float tmp;
    float *in = buffers[0];
    float *out = buffers[1];

    for (i=0; i<tickSize; i++) {
        
        stateBuffer[stateIndex] = in[i];        // update the state
        tmp = 0;                        // reset tmp
        
        for (j = 0; j < filterSize - 1; j++) {
            k = j + stateIndex;            // circular buffer
            if (k > filterSize - 1)
                k -= filterSize;
            tmp += coefs[j] * stateBuffer[k];
        }

        if (--stateIndex < 0)             // decr state index and check for wrap
            stateIndex = filterSize - 1;// the filter delay is updated
                                        // 'backwards' so memory reads for
                                        // the filter are then 'forward'
        out[i] = tmp;                    // output
    }
    instance->statePtr = stateBuffer+stateIndex;
}
#endif


SEG_MOD_SLOW_CONST const AMF_ModuleClass AMFClassFIR = {
    
    /* Flags */
    0,
     
    /* Render function */
    (AMF_RenderFunction)AMF_FIR_Render,  // render function 
    
    /* Default bypass */
    (void *)0,
    
    /* Input descriptor - 1 input, and it is mono. */
    1, 0,

    /* Output descriptor - 1 output, and it is mono. */
    1, 0,
};