Diff: MyGraphicEqualizer/GrEqParamsCalculator.hpp

Revision:

15:fac50dd1de44

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MyGraphicEqualizer/GrEqParamsCalculator.hpp	Thu Apr 13 23:23:30 2017 +0000
@@ -0,0 +1,87 @@
+//------------------------------------------------------------------------------
+//  Parameters calculator class of buquad unit for graphic equalizer
+//  グラフィックイコライザで使う biquad フィルタの係数を計算するクラス
+//
+//   2017/03/28, Copyright (c) 2017 MIKAMI, Naoki
+//------------------------------------------------------------------------------
+
+#ifndef GRAPHIC_EQALIZER_PARAMETER_CALCULATOR_HPP
+#define GRAPHIC_EQALIZER_PARAMETER_CALCULATOR_HPP
+
+#include "mbed.h"
+#include "BiquadGrEq.hpp"
+
+namespace Mikami
+{
+    class GrEqParams
+    {
+    public:
+        // Constructor
+        GrEqParams(int bands, float fs) : BANDS_(bands), FS_(fs) {}
+
+        // 係数を計算する
+        //      gDb : 利得（dB単位）
+        BiquadGrEq::Coefs Execute(int band, float f0, float gDb, float qVal)
+        {
+            const float PI = 3.1415926536f;
+            BiquadGrEq::Coefs coefs;
+            
+            float gSqrt = sqrtf(powf(10, gDb/20.0f));
+            float w0 = 2.0f*PI*f0/FS_;
+            
+            if ( (band != 0) && (band != BANDS_-1) )    // ピーキングフィルタ
+            {
+                float alpha = sinf(w0)/(2.0f*qVal);
+                float beta = 1.0f + alpha/gSqrt;
+                coefs.a1 = 2.0f*cosf(w0)/beta;
+                coefs.a2 = -(1.0f - alpha/gSqrt)/beta;
+                coefs.b0 = (1.0f + alpha*gSqrt)/beta;
+                coefs.b1 = -coefs.a1;
+                coefs.b2 = (1.0f - alpha*gSqrt)/beta;
+            }
+            else                                        // シェルビングフィルタ
+            {                                           // Q は固定
+                w0 = (band == 0) ? w0*1.414f : w0/1.414f;
+                float alpha = sinf(w0)/sqrtf(2.0f); // Q = 1/sqrt(2)
+                float g_a = sqrtf(gSqrt);
+                float cosW0 = cosf(w0);
+                float gSqrtP1 = gSqrt+1.0f;
+                float gSqrtM1 = gSqrt-1.0f;
+                if (band == 0)      // ローシェルビング
+                {                   
+                    float beta = gSqrtP1 + gSqrtM1*cosW0
+                               + 2.0f*g_a*alpha;
+                    coefs.a1 = 2.0f*(gSqrtM1 + gSqrtP1*cosW0)/beta;
+                    coefs.a2 = -(gSqrtP1 + gSqrtM1*cosW0
+                               - 2.0f*g_a*alpha)/beta;
+                    coefs.b0 = gSqrt*(gSqrtP1 - gSqrtM1*cosW0
+                               + 2.0f*g_a*alpha)/beta;
+                    coefs.b1 = 2.0f*gSqrt*(gSqrtM1
+                               - gSqrtP1*cosW0)/beta;
+                    coefs.b2 = gSqrt*(gSqrtP1 - gSqrtM1*cosW0
+                               - 2.0f*g_a*alpha)/beta;
+                }
+                else                // ハイシェルビング
+                {
+                    float beta = gSqrtP1 - gSqrtM1*cosW0
+                               + 2.0f*g_a*alpha;
+                    coefs.a1 = -2.0f*(gSqrtM1 - gSqrtP1*cosW0)/beta;
+                    coefs.a2 = -(gSqrtP1 - gSqrtM1*cosW0
+                               - 2.0f*g_a*alpha)/beta;
+                    coefs.b0 = gSqrt*(gSqrtP1 + gSqrtM1*cosW0
+                               + 2.0f*g_a*alpha)/beta;
+                    coefs.b1 = -2.0f*gSqrt*(gSqrtM1 + gSqrtP1*cosW0)/beta;
+                    coefs.b2 = gSqrt*(gSqrtP1 + gSqrtM1*cosW0
+                               - 2.0f*g_a*alpha)/beta;
+                }
+            }
+
+            return coefs;
+        }
+
+    private:
+        const int BANDS_;
+        const float FS_;
+    };
+}
+#endif  // GRAPHIC_EQALIZER_PARAMETER_CALCULATOR_HPP