LPC_Analyzer.cpp

00001 //-------------------------------------------------------
00002 //  Class for spectrum analysis using linear prediction
00003 //
00004 //  2017/02/11, Copyright (c) 2017 MIKAMI, Naoki
00005 //-------------------------------------------------------
00006 
00007 #include "LPC_Analyzer.hpp"
00008 
00009 namespace Mikami
00010 {
00011     LpcAnalyzer::LpcAnalyzer(int nData, int nFft, int order)
00012         : AnalyzerBase(nData, nFft, nData-1), order_(order),
00013           lp_(nData-1, order),
00014           an_(order), xFft_(nFft), yFft_(nFft/2+1) {}
00015 
00016     void LpcAnalyzer::Analyze(const float xn[], float yn[])
00017     {
00018         float em;
00019         lp_.Execute(xn, an_, em);
00020 
00021         // To spectrum
00022         xFft_[0] = 1.0f;
00023         for (int n=0; n<order_; n++) xFft_[n+1] = -an_[n];
00024         for (int n=order_+1; n<N_FFT_; n++) xFft_[n] = 0.0f;
00025         fft_.Execute(xFft_, yFft_); // execute FFT
00026 
00027         // Translate to dB
00028         for (int n=0; n<=N_FFT_/2; n++)
00029             yn[n] = 10.0f*log10f(em/Norm(yFft_[n]));
00030     }
00031 }