不韋 呂
Output the audio signal with filtering by graphic equalizer in the *.wav file on the SD card using onboard CODEC. SD カードの *.wav ファイルのオーディオ信号をグラフィック･イコライザを通して，ボードに搭載されているCODEC で出力する．
Dependencies: F746_GUI F746_SAI_IO SD_PlayerSkeleton FrequencyResponseDrawer
Diff: MyGraphicEqualizer/BiquadGrEq.hpp
- Revision:
- 15:ef0acc9fe111
- Child:
- 23:878419f8638b
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/MyGraphicEqualizer/BiquadGrEq.hpp Mon Aug 15 06:37:47 2016 +0000
@@ -0,0 +1,65 @@
+//--------------------------------------------------------------
+// グラフィックイコライザで使う 1D タイプの 2 次のフィルタ
+// Biquad filter of 1D type for graphic equalizer
+// 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] = b0*u[n] + b1*u[n-1] + b2*u[n-2]
+// x[n] : input signal
+// y[n] : output signal
+//
+// 2016/08/10, Copyright (c) 2016 MIKAMI, Naoki
+//--------------------------------------------------------------
+
+#ifndef IIR_BIQUAD_GREQ_HPP
+#define IIR_BIQUAD_GREQ_HPP
+
+#include "mbed.h"
+
+// 2nd order IIR filter
+namespace Mikami
+{
+ class BiquadGrEq
+ {
+ public:
+ struct Coefs { float a1, a2, b0, b1, b2; };
+
+ BiquadGrEq() {} // Default constructore
+
+ BiquadGrEq(const Coefs ck)
+ {
+ SetCoefficients(ck);
+ Clear();
+ }
+
+ void SetCoefficients(const Coefs ck)
+ {
+ a1_ = ck.a1;
+ a2_ = ck.a2;
+ b0_ = ck.b0;
+ b1_ = ck.b1;
+ b2_ = ck.b2;
+ }
+
+ float Execute(float xn)
+ {
+ float un = xn + a1_*un1_ + a2_*un2_;
+ float yn = b0_*un + b1_*un1_ + b2_*un2_;
+
+ un2_ = un1_;
+ un1_ = un;
+
+ return yn;
+ }
+
+ void Clear() { un1_ = un2_ = 0; }
+
+ private:
+ float a1_, a2_, b0_, b1_, b2_;
+ float un1_, un2_;
+
+ // disallow copy constructor
+ BiquadGrEq(const BiquadGrEq&);
+ };
+}
+#endif // IIR_BIQUAD_GREQ_HPP