CepstrumAnalysis.cpp

00001 //-------------------------------------------------------
00002 //  Class for spectrum analysis using cepstrum
00003 //
00004 //  2015/12/15, Copyright (c) 2015 MIKAMI, Naoki
00005 //-------------------------------------------------------
00006 
00007 #include "CepstrumAnalysis.hpp"
00008 
00009 namespace Mikami
00010 {
00011     CepstrumAnalyzer::CepstrumAnalyzer(int nData, int nFft, int nLifter)
00012             : AnalyzerBase(nData, nFft, nFft), N_LIFTER_(nLifter),
00013               yFft_(new Complex[nFft/2+1]), lifter_(new float[nLifter]),
00014               db_(new Complex[nFft/2+1]), cep_(new float[nFft]),
00015               cepLft_(new float[nFft]), cepFt_(new Complex[nFft/2+1])
00016     {
00017         // Generate lifter
00018         float pi2N = 3.1415926536f/nLifter;
00019         for (int n=0; n<nLifter; n++)
00020             lifter_[n] = 0.54f + 0.46f*cosf(pi2N*n);
00021     }
00022 
00023     CepstrumAnalyzer::~CepstrumAnalyzer()
00024     {
00025         delete[] yFft_;
00026         delete[] lifter_;
00027         delete[] db_;
00028         delete[] cep_;
00029         delete[] cepLft_;
00030         delete[] cepFt_;
00031     }
00032 
00033     void CepstrumAnalyzer::Analyze(const float xn[], float yn[])
00034     {
00035         fft_.Execute(xn, yFft_);    // Execute FFT
00036 
00037         // Translate to dB and to complex
00038         for (int n=0; n<=N_FFT_/2; n++)
00039             db_[n] = Complex(10.0f*log10f(Norm(yFft_[n])), 0);
00040 
00041         fft_.ExecuteIfft(db_, cep_);    // To cepstrum
00042         
00043         // Liftering
00044         cepLft_[0] = cep_[0];
00045         for (int n=1; n<N_LIFTER_; n++)
00046             cepLft_[n] = 2.0f*lifter_[n]*cep_[n];
00047         for (int n=N_LIFTER_; n<N_FFT_; n++)
00048             cepLft_[n] = 0.0f;
00049             
00050         // Smoothed spectrum
00051         fft_.Execute(cepLft_, cepFt_);
00052         for (int n=0; n<=N_FFT_/2; n++)
00053             yn[n] = cepFt_[n].real();
00054     }
00055 }