godot/servers/audio/audio_filter_sw.h

/*************************************************************************/
/*  audio_filter_sw.h                                                    */
/*************************************************************************/
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/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2017 Juan Linietsky, Ariel Manzur.                 */
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#ifndef AUDIO_FILTER_SW_H
#define AUDIO_FILTER_SW_H


#include "math_funcs.h"

class AudioFilterSW {
public:

	struct Coeffs {

		float a1,a2;
		float b0,b1,b2;

		//bool operator==(const Coeffs &p_rv) { return (FLOATS_EQ(a1,p_rv.a1) && FLOATS_EQ(a2,p_rv.a2) && FLOATS_EQ(b1,p_rv.b1) && FLOATS_EQ(b2,p_rv.b2) && FLOATS_EQ(b0,p_rv.b0) ); }
		Coeffs() { a1=a2=b0=b1=b2=0.0; }
	};

	enum Mode {
		BANDPASS,
		HIGHPASS,
		LOWPASS,
		NOTCH,
		PEAK,
		BANDLIMIT,
		LOWSHELF,
		HIGHSHELF

	};

	class Processor { // simple filter processor

		AudioFilterSW * filter;
		Coeffs coeffs;
		float ha1,ha2,hb1,hb2; //history
	public:
		void set_filter(AudioFilterSW * p_filter);
		void process(float *p_samples,int p_amount, int p_stride=1);
		void update_coeffs();
		_ALWAYS_INLINE_ void process_one(float& p_sample);

		Processor();
	};

private:


	float cutoff;
	float resonance;
	float gain;
	float sampling_rate;
	int stages;
	Mode mode;



public:

	float get_response(float p_freq,Coeffs *p_coeffs);

	void set_mode(Mode p_mode);
	void set_cutoff(float p_cutoff);
	void set_resonance(float p_resonance);
	void set_gain(float p_gain);
	void set_sampling_rate(float p_srate);
	void set_stages(int p_stages); //adjust for multiple stages

	void prepare_coefficients(Coeffs *p_coeffs);

	AudioFilterSW();

};




/* inline methods */


void AudioFilterSW::Processor::process_one(float &p_val) {

	float pre=p_val;
	p_val = (p_val * coeffs.b0 + hb1 * coeffs.b1  + hb2 * coeffs.b2 + ha1 * coeffs.a1 + ha2 * coeffs.a2);
	ha2=ha1;
	hb2=hb1;
	hb1=pre;
	ha1=p_val;
}


#endif // AUDIO_FILTER_SW_H