stdafx.cpp

在VC下实现FFT对信号滤波,包括实现低通和带通滤波,图形显示

//stdafx.cpp : source file that includes just the standard includes
//TestFilter.pch will be the pre-compiled header
//stdafx.obj will contain the pre-compiled type information

#include "stdafx.h"

void GetResult(float *pfRealBuffer,float *pfImagBuffer,float *pfResBuffer,int iNum)
{
	//返回复数的模
	//abs(z)=sqrt(Re(z)^2+Im(z)^2);
	//I needed fast scaling,so I placed a /10 in here
	//I will have a control for this plus log Scale
	//later. I have no time now
	//(isn't that funny,I have read that excuse in thousands
	//of sourcecodes?)
	int i;
	for(i=0;i<iNum;i++)
	{
		pfResBuffer[i]=(float)sqrt(pfRealBuffer[i]*pfRealBuffer[i]+pfImagBuffer[i]*pfImagBuffer[i])/10;
	}
}

void FourieTrans(float *pfReal,float *pfImag,unsigned int iNumOfSamples)
{
	//公式直接方法求傅立叶转换,速度慢.
	//ianliu
	float pfTemp[4096*2];
	unsigned int k,n;
	memcpy(pfTemp,pfReal,iNumOfSamples*2*sizeof(float));
	for(k=0;k<iNumOfSamples;k++)
	{
		pfReal[k]=0;
	}
	for(k=0;k<iNumOfSamples;k++)
	{
		for(n=0;n<iNumOfSamples;n++)
		{
       		pfReal[k]=(float)(pfReal[k]+(pfTemp[n]*cos((TWO_PI/iNumOfSamples)*k*n)));
       		pfImag[k]=(float)(pfImag[k]-(pfTemp[n]*sin((TWO_PI/iNumOfSamples)*k*n)));
		}
	}
}

void GetReal(float *pfReal,float *pfRes,unsigned int iNumOfSamples)
{
	//从复数pfRes中取实部
	//ianliu
	unsigned int k,n;
	for(k=0;k<iNumOfSamples;k++)
	{
		{
       		pfReal[k]=(float)(pfRes[k]*cos((TWO_PI/iNumOfSamples)));
		}
	}
}

void GetImag(float *pfImag,float *pfRes,unsigned int iNumOfSamples)
{
	//从复数pfRes中取虚部
	//ianliu
	unsigned int k,n;
	for(k=0;k<iNumOfSamples;k++)
	{
		{
       		pfImag[k]=(float)(pfRes[k]*sin((TWO_PI/iNumOfSamples)));
		}
	}
}

void IFourieTrans(float *pfReal,float *pfImag,unsigned int iNumOfSamples)
{
	//公式直接方法求傅立叶转换,速度慢.
	//ianliu
	float pfTemp[4096*2];
	unsigned int k,n;
	memcpy(pfTemp,pfReal,iNumOfSamples*2*sizeof(float));
	for(k=0;k<iNumOfSamples;k++)
	{
		pfReal[k]=0;
	}

	for(k=0;k<iNumOfSamples;k++)
	{
		for(n=0;n<iNumOfSamples;n++)
		{
       		pfReal[k]=((float)(pfReal[k]+(pfTemp[n]*cos((TWO_PI/iNumOfSamples)*k*n))));
       		pfImag[k]=((float)(pfImag[k]+(pfTemp[n]*sin((TWO_PI/iNumOfSamples)*k*n))));
		}
	}
}

void CopyAudioData(PBYTE pbAudioBuffer,float *pfRealBuffer,float *pfImagBuffer,int iNumBytes) 
{
 	int i,n;
 	short sAudioSample;	
  	for(i=0,n=0;i<iNumBytes;i+=2,n++)
  	{ 
		//we need to align the data,because it has the wrong byte order
 		sAudioSample=((pbAudioBuffer[i+1]<<8)&0xFF00)|(pbAudioBuffer[i]&0x00FF);
		pfImagBuffer[n]=0;
		pfRealBuffer[n]=sAudioSample;	//this is the correct 16bit SampleValue
  	}
}