GrEqualizerFrqResp.hpp

00001 //-----------------------------------------------------------
00002 //  グラフィックイコライザで使う IIR フィルタの周波数応答
00003 //  Frequency response for graphic equalizer
00004 //
00005 //  2017/03/28, Copyright (c) 2017 MIKAMI, Naoki
00006 //-----------------------------------------------------------
00007 
00008 #ifndef GRAPHIC_EQUALIZER_FREQUENCY_RESPONSE_HPP
00009 #define GRAPHIC_EQUALIZER_FREQUENCY_RESPONSE_HPP
00010 
00011 #include "FrequancyResponseBase.hpp"
00012 #include "BiquadGrEq.hpp"
00013 #include "Array.hpp"
00014 
00015 namespace Mikami
00016 {
00017     class GrEqualizerFrqResp : public FrequencyResponse
00018     {
00019     public:
00020         GrEqualizerFrqResp(int bands)
00021             : BANDS_(bands), ck_(bands) {}
00022         
00023         virtual ~GrEqualizerFrqResp() {}
00024 
00025         // フィルタの係数設定
00026         void SetParams(BiquadGrEq::Coefs ck[])
00027         {   for (int n=0; n<BANDS_; n++) ck_[n] = ck[n]; }
00028         
00029         void SetParam(BiquadGrEq::Coefs ck, int n)
00030         {   ck_[n] = ck; }
00031 
00032         // 周波数応答の絶対値を返す関数, 引数: z^(-1)
00033         virtual float AbsH_z(Complex u)
00034         {
00035             Complex h = 1;
00036             for (int k=0; k<BANDS_; k++)
00037                 h = h*(ck_[k].b0 + (ck_[k].b1 + ck_[k].b2*u)*u)
00038                      /(1.0f - (ck_[k].a1 + ck_[k].a2*u)*u);
00039             return abs(h);
00040         }
00041 
00042     private:
00043         const int BANDS_;
00044         Array<BiquadGrEq::Coefs> ck_;
00045 
00046         // disallow copy constructor and assignment operator
00047         GrEqualizerFrqResp(const GrEqualizerFrqResp&);
00048         GrEqualizerFrqResp& operator=(const GrEqualizerFrqResp&);
00049     };
00050 }
00051 #endif  // GRAPHIC_EQUALIZER_FREQUENCY_RESPONSE_HPP