fe_delta.cpp

来自「这是一个语音特征提取的程序源码」· C++ 代码 · 共 78 行

///////////////////////////////////////////////////////////////////////////////
// This is a part of the Feature program.
// Version: 1.0
// Date: February 22, 2003
// Programmer: Oh-Wook Kwon
// Copyright(c) 2003 Oh-Wook Kwon. All rights reserved. [e-mail]
///////////////////////////////////////////////////////////////////////////////

/****************************************************************************
 * 	Computing delta coefficients, cepstral liftering, preemphasis
 ****************************************************************************/
#include "StdAfx.h"
#include "FE_feature.h"


/************************************************************************
 *   	Compute Delta coefficients
 ************************************************************************/

int Fe::delta_compute(FeMatrix<float>& input, int filterLen, FeMatrix<float>& output)
{
	int num_frames=input.size();
	if(num_frames==0) return 0;
	int dim=input[0].size();
	output.Resize(num_frames,dim);
	vector<float> filterCoeff(filterLen);
	delta_init_filter(&filterCoeff[0], filterLen);
	delta_basic(input, output, &filterCoeff[0], filterLen);
	return(1);
}


int Fe::delta_basic(FeMatrix<float>& input, FeMatrix<float>& output, float *filterCoeff, int filterLen)
{
	int num_frames=input.size();
	if(num_frames==0) return 0;
	int dim=input[0].size();
	int	i,j,n;
	int delta = (filterLen-1)/2;
	for(n=0;n<num_frames;n++){
		for(i=0;i<dim;i++){
			float sum = 0;
			for(j=0; j<filterLen; j++){
				float x = (n-delta+j >= 0) ? ((n-delta+j < num_frames) ? input[n-delta+j][i]: input[num_frames-1][i]) : input[0][i];
				sum += x * filterCoeff[j];
			}
			output[n][i] = sum;
		}
	}
	return(1);
}


int Fe::delta_init_filter(float *filterCoeff, int filterLen)
{
	if(filterLen == 1){
		filterCoeff[0] = 1;
		return 1;
	}
	int	j;
	int center = (filterLen-1)/2;
	float sqsum = 0;
	for (j=0; j<filterLen; j++) {
		filterCoeff[j] = (float)(j-center);
		sqsum += (filterCoeff[j])*(filterCoeff[j]);
	}
	/*      Assuming that cepstrum parameters are uncorrelated,      */
	/*      variances of cepstrum and delta cepstrum are set       */
	/*      approximately equal through the SQRT operation          */
	for (j=0; j<filterLen; j++) {
		filterCoeff[j] /= (float)sqrt(sqsum);
	}

	return(1);
}