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mels_utils.cc
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/*
* mels_util.cc
* Copyright (C) 2019 xiaominfc(武汉鸣鸾信息科技有限公司) <[email protected]>
*
* Distributed under terms of the MIT license.
*/
#include "mels_utils.h"
#include "api/api.h"
//#include <math.h>
double hz_to_mel(double frequencies){
double mels = (frequencies - MIN_F) / FSP;
if(frequencies >= MIN_LOG_HZ) {
mels = (MIN_LOG_HZ - MIN_F)/FSP + log(frequencies / MIN_LOG_HZ) / LOG_STEP;
}
return mels;
}
double mel_to_hz(double mels) {
double freqs = MIN_F + FSP * mels;
if(mels >= MIN_LOG_MEL) {
freqs = MIN_LOG_HZ * exp(LOG_STEP * (mels - MIN_LOG_MEL));
}
return freqs;
}
//mel 单元
void filters_mel(float sr,uint n_fft,uint n_mels,float fmin,float fmax, Matrix<double64> &mel_basis) {
if(fmax == 0.0) {
fmax = sr / 2.0;
}
uint rows = 1+n_fft/2;
mel_basis.Resize(n_mels,rows);
// gen mel_frequencies
double min_mel = hz_to_mel(fmin);
double max_mel = hz_to_mel(fmax);
Vector<double64> mels;
mels.Resize(n_mels + 2);
double offset_mel = (max_mel - min_mel)/(n_mels + 1);
double offset_hz = sr/n_fft;
mels(0) = mel_to_hz(min_mel);
mels(1) = mel_to_hz(min_mel + offset_mel);
mels(mels.Dim() - 1) = mel_to_hz(max_mel);
for(int i = 2; i < mels.Dim(); i ++) {
double down_hz= mels(i - 2);
double up_hz = mel_to_hz(min_mel + offset_mel*i);
mels(i) = up_hz;
for(int j = 0; j < rows; j++ ) {
double lower = -1.0 * (down_hz - offset_hz*j) / (mels(i-1)-down_hz);
double upper = (up_hz -offset_hz*j) / (up_hz - mels(i-1));
double min = lower < upper? lower:upper;
min = min > 0?min:0.0;
mel_basis(i-2,j) = min*2.0/ (up_hz-down_hz);
}
}
}
//hanning窗
void hanning_w(int frame_length,Vector<double64>& window) {
window.Resize(frame_length);
double PI = 3.141592653589793;
double PI_2 = PI * 2.0;
double a = PI_2 / (frame_length);
//printf("a:%.10lf\n",a);
for (int32 i = 0; i < frame_length; i++) {
double i_fl = static_cast<double>(i);
window(i) = 0.5 - 0.5*cos(a * i_fl);
}
}
//数据分帧
void frame_data(Vector<double64> &data,int frame_length,int hop_length, Matrix<double64> &frames){
int n_frames = (data.Dim() - frame_length ) / hop_length + 1;
frames.Resize(frame_length,n_frames);
for(int i=0; i < frame_length; i ++) {
for(int j = 0; j < n_frames; j ++) {
int index = i + j * hop_length;
if(index < data.Dim()) {
frames(i,j) = data.Data()[index];
}else {
printf("index to large:%d\n",index);
}
}
}
}
//补数据 顺便把数据缩到[-1.0 , 1.0]之间
void pad_data(SubVector<BaseFloat> &data, int hop_length,Vector<double64>& outData) {
size_t len = data.Dim();
outData.Resize(len + hop_length*2);
int end = len - hop_length - 2;
for(int i = 0 ; i < len; i++) {
double v = static_cast<double>(data.Data()[i])/32767.0;// convert to float [-1.0 , 1.0]
outData.Data()[hop_length + i] = v;
if(i > 0 && i <=hop_length) {
outData.Data()[hop_length-i] = v;
}
if(i > end && i < len - 1) {
int index = len * 2 - i - 2 + hop_length;
outData.Data()[index] = v;
}
}
}
void melspectrogram(SubVector<BaseFloat> &data,float sr,uint n_fft,uint hop_length,uint n_mels,Matrix<double64> &result){
uint half_n_fft = n_fft / 2;
Matrix<double64> mel_basis;
filters_mel(sr,n_fft,n_mels,0.0,MAXFRE,mel_basis);
Vector<double64> padData;
pad_data(data,half_n_fft,padData);
Matrix<double64> frames;
frame_data(padData,n_fft , hop_length ,frames);
Vector<double64> window;
hanning_w(n_fft,window);
frames.MulRowsVec(window);
Matrix<double64> fft_result;
fft_result.Resize(half_n_fft + 1,frames.NumCols());
const uint N = frames.NumRows();
if(N & N-1){
printf("use fftw for %d examples\n",N);
double* din = (double*)fftw_malloc(sizeof(double) * N);
fftw_plan p;
fftw_complex* out = (fftw_complex*) fftw_malloc(sizeof(fftw_complex) * N);
for(uint i = 0; i < frames.NumCols(); i ++) {
for(uint j = 0; j < N;j++) {
din[j] = frames(j,i);
}
p = fftw_plan_dft_r2c_1d(N, din, out, FFTW_ESTIMATE);
fftw_execute(p);
for(uint j = 0; j < fft_result.NumRows(); j ++) {
double v = sqrt(out[j][0] * out[j][0] +out[j][1] * out[j][1]);
fft_result(j,i) = pow(v,2.0);
}
fftw_destroy_plan(p);
}
fftw_free(din);
fftw_free(out);
}else {
//fftw有点大 故保留旧版本实现 对于2的N次幂样本数的计算 可以考虑移除fftw
complex *pSignal = new complex[N];
for(uint i = 0; i < frames.NumCols(); i ++) {
for(uint j = 0; j < N;j++) {
pSignal[j] = frames(j,i);
}
CFFT::Forward(pSignal,N);
for(uint j = 0; j < fft_result.NumRows(); j ++) {
double norm = pSignal[j].norm();
double v = sqrt(norm);
fft_result(j,i) = pow(v,2.0);
//fft_result(j,i) = pSignal[j].norm();
}
}
delete[] pSignal;
}
result.Resize(fft_result.NumCols(),mel_basis.NumRows());
for(int i = 0; i < result.NumRows(); i ++) {
for(int j = 0; j < result.NumCols(); j ++) {
double sum = 0;
for(int index = 0; index < half_n_fft + 1; index++ ){
sum += fft_result(index,i)*mel_basis(j,index);
}
result(i,j) = sum;
}
}
}