不韋 呂
Demo program of digital signal processing: Variable LPF/HPF, Vocal canceller, Pitch shifter, Reverbrator. ディジタル信号処理のデモプログラム． 遮断周波数可変 LPF/HPF，ボーカルキャンセラ，ピッチシフタ，残響生成器．
Dependencies: Array_Matrix F446_AD_DA UIT_AQM1602 mbed
Diff: SignalProcessing/Biquad.hpp
- Revision:
- 0:fa74b1130cc3
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/SignalProcessing/Biquad.hpp Sun Jan 29 09:11:30 2017 +0000
@@ -0,0 +1,60 @@
+//--------------------------------------------------------------
+// 縦続形 IIR フィルタで使う 1D タイプの 2 次のフィルタ
+// Biquad filter of 1D type for IIR filter of cascade structure
+// このクラスでは，係数は実行中に書き換えられることを想定している
+//
+// u[n] = x[n] + a1*u[n-1] + a2*u[n-2]
+// y[n] = u[n] + b1*u[n-1] + b2*u[n-2]
+// x[n] : input signal
+// y[n] : output signal
+// b0 = 1
+//
+// 2017/01/26, Copyright (c) 2017 MIKAMI, Naoki
+//--------------------------------------------------------------
+
+#ifndef IIR_BIQUAD_HPP
+#define IIR_BIQUAD_HPP
+
+#include "mbed.h"
+
+// 2nd order IIR filter
+namespace Mikami
+{
+ class Biquad
+ {
+ public:
+ struct Coefs { float a1, a2, b1, b2; };
+
+ Biquad(const Coefs ck = (Coefs){0, 0, 0, 0})
+ {
+ SetCoefs(ck);
+ Clear();
+ }
+
+ void SetCoefs(const Coefs cf) { cf_ = cf; }
+
+ void GetCoefs(Coefs &cf) { cf = cf_; }
+
+ float Execute(float xn)
+ {
+ float un = xn + cf_.a1*un1_ + cf_.a2*un2_;
+ float yn = un + cf_.b1*un1_ + cf_.b2*un2_;
+
+ un2_ = un1_;
+ un1_ = un;
+
+ return yn;
+ }
+
+ void Clear() { un1_ = un2_ = 0; }
+
+ private:
+ Coefs cf_;
+ float un1_, un2_;
+
+ // disallow copy constructor and assignment operator
+ Biquad(const Biquad&);
+ Biquad& operator=(const Biquad&);
+ };
+}
+#endif // IIR_BIQUAD_HPP