Nes_Fme7_Apu.h

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// Sunsoft FME-7 sound emulator
 
// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/
#ifndef NES_FME7_APU_H
#define NES_FME7_APU_H
 
#include "blargg_common.h"
#include "Blip_Buffer.h"
 
struct fme7_apu_state_t
{
        enum { reg_count = 14 };
        uint8_t regs [reg_count];
        uint8_t phases [3]; // 0 or 1
        uint8_t latch;
        uint16_t delays [3]; // a, b, c
};
 
class Nes_Fme7_Apu : private fme7_apu_state_t {
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( fme7_apu_state_t* ) const;
        void load_state( fme7_apu_state_t const& );
        
        // Mask and addresses of registers
        enum { addr_mask = 0xE000 };
        enum { data_addr = 0xE000 };
        enum { latch_addr = 0xC000 };
        
        // (addr & addr_mask) == latch_addr
        void write_latch( int );
        
        // (addr & addr_mask) == data_addr
        void write_data( blip_time_t, int data );
        
public:
        Nes_Fme7_Apu();
        BLARGG_DISABLE_NOTHROW
private:
        // noncopyable
        Nes_Fme7_Apu( const Nes_Fme7_Apu& );
        Nes_Fme7_Apu& operator = ( const Nes_Fme7_Apu& );
        
        static unsigned char const amp_table [16];
        
        struct {
                Blip_Buffer* output;
                int last_amp;
        } oscs [osc_count];
        blip_time_t last_time;
        
        enum { amp_range = 192 }; // can be any value; this gives best error/quality tradeoff
        Blip_Synth<blip_good_quality,1> synth;
        
        void run_until( blip_time_t );
};
 
inline void Nes_Fme7_Apu::volume( double v )
{
        synth.volume( 0.38 / amp_range * v ); // to do: fine-tune
}
 
inline void Nes_Fme7_Apu::treble_eq( blip_eq_t const& eq )
{
        synth.treble_eq( eq );
}
 
inline void Nes_Fme7_Apu::osc_output( int i, Blip_Buffer* buf )
{
        assert( (unsigned) i < osc_count );
        oscs [i].output = buf;
}
 
inline void Nes_Fme7_Apu::output( Blip_Buffer* buf )
{
        for ( int i = 0; i < osc_count; i++ )
                osc_output( i, buf );
}
 
inline Nes_Fme7_Apu::Nes_Fme7_Apu()
{
        output( NULL );
        volume( 1.0 );
        reset();
}
 
inline void Nes_Fme7_Apu::write_latch( int data ) { latch = data; }
 
inline void Nes_Fme7_Apu::write_data( blip_time_t time, int data )
{
        if ( (unsigned) latch >= reg_count )
        {
                #ifdef debug_printf
                        debug_printf( "FME7 write to %02X (past end of sound registers)\n", (int) latch );
                #endif
                return;
        }
        
        run_until( time );
        regs [latch] = data;
}
 
inline void Nes_Fme7_Apu::end_frame( blip_time_t time )
{
        if ( time > last_time )
                run_until( time );
        
        assert( last_time >= time );
        last_time -= time;
}
 
inline void Nes_Fme7_Apu::save_state( fme7_apu_state_t* out ) const
{
        *out = *this;
}
 
inline void Nes_Fme7_Apu::load_state( fme7_apu_state_t const& in )
{
        reset();
        fme7_apu_state_t* state = this;
        *state = in;
}
 
#endif