不韋 呂
Realtime sound spectrogram using FFT or linear prediction. Spectrogram is displayed on the display of PC. リアルタイム･スペクトログラム．解析の手法：FFT，線形予測法．スペクトログラムは PC のディスプレー装置に表示される．PC 側のプログラム：F446_Spectrogram.
Dependencies: Array_Matrix mbed SerialTxRxIntr F446_AD_DA UIT_FFT_Real
Diff: MySpectrogram/LPC_Analyzer.cpp
- Revision:
- 0:a539141b9dec
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/MySpectrogram/LPC_Analyzer.cpp Fri Feb 17 04:55:10 2017 +0000
@@ -0,0 +1,31 @@
+//-------------------------------------------------------
+// Class for spectrum analysis using linear prediction
+//
+// 2017/02/11, Copyright (c) 2017 MIKAMI, Naoki
+//-------------------------------------------------------
+
+#include "LPC_Analyzer.hpp"
+
+namespace Mikami
+{
+ LpcAnalyzer::LpcAnalyzer(int nData, int nFft, int order)
+ : AnalyzerBase(nData, nFft, nData-1), order_(order),
+ lp_(nData-1, order),
+ an_(order), xFft_(nFft), yFft_(nFft/2+1) {}
+
+ void LpcAnalyzer::Analyze(const float xn[], float yn[])
+ {
+ float em;
+ lp_.Execute(xn, 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
+
+ // Translate to dB
+ for (int n=0; n<=N_FFT_/2; n++)
+ yn[n] = 10.0f*log10f(em/Norm(yFft_[n]));
+ }
+}