![](/media/cache/img/default_profile.jpg.50x50_q85.jpg)
Spectrum analyzer using DISCO-F746NG. Spectrum is calculated by FFT or linear prediction. The vowel data is in "vowel_data.hpp"
Dependencies: BSP_DISCO_F746NG LCD_DISCO_F746NG TS_DISCO_F746NG UIT_FFT_Real mbed BUTTON_GROUP
Diff: SpactrumAnalysisClasses/LPC_Analysis.cpp
- Revision:
- 0:c35b8a23a863
- Child:
- 1:2ef356b500f2
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/SpactrumAnalysisClasses/LPC_Analysis.cpp Mon Oct 26 08:06:57 2015 +0000 @@ -0,0 +1,62 @@ +//------------------------------------------------------- +// Class for spectrum analysis using linear prediction +// Copyright (c) 2015 MIKAMI, Naoki, 2015/10/26 +//------------------------------------------------------- + +#include "LPC_Analysis.hpp" + +namespace Mikami +{ + LpcAnalyzer::LpcAnalyzer(int nData, int order, int nFft) + : N_DATA_(nData), ORDER_(order), N_FFT_(nFft), + hm_(nData-1, nData-1), lp_(nData-1, order), + fft_(nFft) + { + xData_ = new float[nData]; // Data to be analyzed + an_ = new float[order]; // Linear-predictive coefficients + xFft_ = new float[nFft]; // Input for FFT + yFft_ = new Complex[nFft/2+1]; // Output of FFT + normY_ = new float[nFft/2+1]; // Powerspectrum + } + + LpcAnalyzer::~LpcAnalyzer() + { + delete[] xData_; + delete[] an_; + delete[] xFft_; + delete[] yFft_; + delete[] normY_; + } + + void LpcAnalyzer::Execute(float xn[], float db[]) + { + // Differencing + for (int n=0; n<N_DATA_-1; n++) + xData_[n] = xn[n+1] - xn[n]; + + hm_.Execute(xData_, xData_); // Windowing + float em; + lp_.Execute(xData_, an_, em); + + // To spectrum + xFft_[0] = 1.0f; + for (int n=0; n<ORDER_; n++) xFft_[n+1] = -an_[n]; + for (int n=ORDER_+1; n<N_FFT_; n++) xFft_[n] = 0.0f; + fft_.Execute(xFft_, yFft_); // Execute FFT + + // Squared magnitude + for (int n=0; n<=N_FFT_/2; n++) + normY_[n] = 1.0f/(Sqr(yFft_[n].real()) + Sqr(yFft_[n].imag())); + + // Searce maximum + float max = 0; + for (int n=0; n<=N_FFT_/2; n++) + max = (max > normY_[n]) ? max : normY_[n]; + float invMax = 1.0f/max; + + // Translate to dB + for (int n=0; n<=N_FFT_/2; n++) + db[n] = 10.0f*log10f(invMax*normY_[n]); + } +} +