基於eigen 實現mfcc提取特徵矩陣的實現

MatrixXd mfcc_m(double *x, int length, int fs, int p, int framesize, int inc)

{

MatrixXd bank = melbankm(p, framesize, fs, 0, 0.5, 1);

//bank.operator/=(splab::max(splab::max(bank)));

bank = bank / bank.array().maxCoeff();

//DCT係數,p2*p

int p2 = p / 2;

//Vector<Type> n(p, splab::linspace((Type)0, (Type)(p - 1), p));

VectorXd n = VectorXd::LinSpaced(p, 0, p-1);

MatrixXd dctcoef(p2, p);

for (int k = 1; k < p2 + 1; k++)

{

//dctcoef.setRow(cos(((Type)2 * n + (Type)1)*(Type)k*PI / ((Type)2 * p)), k - 1);

dctcoef.row(k - 1) = ((2 * n.array() + 1)*k*M_PI / (2 * p)).cos();

}

//% 歸一化倒譜提升窗口

VectorXd w = 1 + 6 * sin(M_PI*VectorXd::LinSpaced(p2, 1, p2).array() / p2);

w = w / w.maxCoeff();

//% 預加重濾波器

Type * yy = new Type[length];

yy = pre_emphasizing(x, length, 0.9375);

//語音信號分幀

MatrixXd xx = enframe(yy, length, framesize, inc);

delete[] yy;

Type n2 = (int)(framesize / 2) + 1;

int xx_col_length = (int)xx.cols();

int xx_row_length = (int)xx.rows();

VectorXd s(xx_col_length);

VectorXd y(xx_col_length);

VectorXd t(xx_col_length);

VectorXd c1(p2);

VectorXd c2(p2);

MatrixXd m(xx_row_length, p2);

FFT<Type> fft;

Eigen::VectorXcd tmpc(xx_col_length);

// 計算每幀的MFCC參數

for (int i = 0; i < xx_row_length; i++)

{

y = xx.row(i);

s=y.array()*gencoswin(framesize, 0, true).array();

fft.fwd(tmpc, s);

t = abs(tmpc.array()).pow(2);

c1 = dctcoef*(bank*t.head((int)n2)).array().log().matrix();

c2 = c1*w.transpose();

m.row(i) = c1.array()*w.array();

}

//差分係數

//Matrix<Type>dtm(xx.dim(1), p2, (Type)0);

MatrixXd dtm = MatrixXd::Zero(xx_row_length, p2);

for (int i = 3; i < xx_row_length - 1; i++)

{

//dtm.setRow(-(Type)2 * m.getRow(i - 3) - m.getRow(i - 2)

//+ m.getRow(i) + (Type)2 * m.getRow(i + 1), i - 1);

dtm.row(i - 1) = -2 * m.row(i - 3) - m.row(i - 2)

+ m.row(i) + 2 * m.row(i + 1);

}

dtm = dtm /3;

//dtm.operator/=((Type)3);

//合併MFCC參數和一階差分MFCC參數

//去除首尾兩幀(共四幀)，因為這兩幀的一階差分參數為0

//Matrix<Type> ccc(m.dim(1) - 4, p);

MatrixXd ccc(xx_row_length-4, p);

//ccc << m.rightCols(p2 - 2), dtm.leftCols(p2 - 2);

ccc << m.middleRows(2, xx_row_length - 4), dtm.middleRows(2, xx_row_length - 4);

return ccc;

}

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