gzdoom-gles/libraries/game-music-emu/gme/Nes_Vrc6_Apu.h

// Konami VRC6 sound chip emulator

// Nes_Snd_Emu 0.1.8
#ifndef NES_VRC6_APU_H
#define NES_VRC6_APU_H

#include "blargg_common.h"
#include "Blip_Buffer.h"

struct vrc6_apu_state_t;

class Nes_Vrc6_Apu {
public:
	// See Nes_Apu.h for reference
	void reset();
	void volume( double );
	void treble_eq( blip_eq_t const& );
	void output( Blip_Buffer* );
	enum { osc_count = 3 };
	void osc_output( int index, Blip_Buffer* );
	void end_frame( blip_time_t );
	void save_state( vrc6_apu_state_t* ) const;
	void load_state( vrc6_apu_state_t const& );
	
	// Oscillator 0 write-only registers are at $9000-$9002
	// Oscillator 1 write-only registers are at $A000-$A002
	// Oscillator 2 write-only registers are at $B000-$B002
	enum { reg_count = 3 };
	enum { base_addr = 0x9000 };
	enum { addr_step = 0x1000 };
	void write_osc( blip_time_t, int osc, int reg, int data );
	
public:
	Nes_Vrc6_Apu();
	BLARGG_DISABLE_NOTHROW
private:
	// noncopyable
	Nes_Vrc6_Apu( const Nes_Vrc6_Apu& );
	Nes_Vrc6_Apu& operator = ( const Nes_Vrc6_Apu& );
	
	struct Vrc6_Osc
	{
		uint8_t regs [3];
		Blip_Buffer* output;
		int delay;
		int last_amp;
		int phase;
		int amp; // only used by saw
		
		int period() const
		{
			return (regs [2] & 0x0F) * 0x100L + regs [1] + 1;
		}
	};
	
	Vrc6_Osc oscs [osc_count];
	blip_time_t last_time;
	
	Blip_Synth<blip_med_quality,1> saw_synth;
	Blip_Synth<blip_good_quality,1> square_synth;
	
	void run_until( blip_time_t );
	void run_square( Vrc6_Osc& osc, blip_time_t );
	void run_saw( blip_time_t );
};

struct vrc6_apu_state_t
{
	uint8_t regs [3] [3];
	uint8_t saw_amp;
	uint16_t delays [3];
	uint8_t phases [3];
	uint8_t unused;
};

inline void Nes_Vrc6_Apu::osc_output( int i, Blip_Buffer* buf )
{
	assert( (unsigned) i < osc_count );
	oscs [i].output = buf;
}

inline void Nes_Vrc6_Apu::volume( double v )
{
	double const factor = 0.0967 * 2;
	saw_synth.volume( factor / 31 * v );
	square_synth.volume( factor * 0.5 / 15 * v );
}

inline void Nes_Vrc6_Apu::treble_eq( blip_eq_t const& eq )
{
	saw_synth.treble_eq( eq );
	square_synth.treble_eq( eq );
}

#endif