firfilter.h

g711、VAD的激活算法

// FIRFilter.h: interface for the FIRFilter class.
//
//////////////////////////////////////////////////////////////////////

#ifndef AFX_FIRFILTER_H__2606F3F5_42AA_4DB8_84F6_771D94AE518C__INCLUDED_
#define AFX_FIRFILTER_H__2606F3F5_42AA_4DB8_84F6_771D94AE518C__INCLUDED_

#include <vector>
#include <math.h>

template <class T>
class FIRFilter  
{
public:
	FIRFilter(double *coeffs, int numCoeffs)
	{
		if (numCoeffs > 0)
		{
			for (int i=0; i<numCoeffs; i++)
			{
				coeff.push_back(coeffs[i]);
				history.push_back(0);
			}
		}
		this->numCoeffs = numCoeffs;
		int bits = sizeof(T) * 8;
		maxValue =   pow(2, bits-1) - 1;
		minValue = - pow(2, bits-1);
	}

	virtual ~FIRFilter()
	{
	}

	int DoFIR(void *in, void *out, int numSamples)
	{
		T *input = (T*)in;
		T *output = (T*)out;
		for (int i=0; i<numSamples; i++)
		{
			history.insert(history.begin(), (long)(input[i]));
			history.pop_back();
			double result = 0;
			for (int j=0; j<numCoeffs; j++)
			{
				result += history[j] * coeff[j];
			}
			result = result > maxValue ? maxValue : result;
			result = result < minValue ? minValue : result;
			output[i] = (T)result;
		}
		return 0;
	}

private:
	std::vector<long> history;
	std::vector<double> coeff;
	int	numCoeffs;
	double minValue, maxValue;
};

#endif // !defined(AFX_FIRFILTER_H__2606F3F5_42AA_4DB8_84F6_771D94AE518C__INCLUDED_)