Ay_Apu.h

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// AY-3-8910 sound chip emulator
 
// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/
#ifndef AY_APU_H
#define AY_APU_H
 
#include "blargg_common.h"
#include "Blip_Buffer.h"
 
class Ay_Apu {
public:
        // Set buffer to generate all sound into, or disable sound if NULL
        void output( Blip_Buffer* );
        
        // Reset sound chip
        void reset();
        
        // Write to register at specified time
        enum { reg_count = 16 };
        void write( blip_time_t time, int addr, int data );
        
        // Run sound to specified time, end current time frame, then start a new
        // time frame at time 0. Time frames have no effect on emulation and each
        // can be whatever length is convenient.
        void end_frame( blip_time_t length );
        
// Additional features
        
        // Set sound output of specific oscillator to buffer, where index is
        // 0, 1, or 2. If buffer is NULL, the specified oscillator is muted.
        enum { osc_count = 3 };
        void osc_output( int index, Blip_Buffer* );
        
        // Set overall volume (default is 1.0)
        void volume( double );
        
        // Set treble equalization (see documentation)
        void treble_eq( blip_eq_t const& );
        
public:
        Ay_Apu();
        typedef unsigned char byte;
private:
        struct osc_t
        {
                blip_time_t period;
                blip_time_t delay;
                short last_amp;
                short phase;
                Blip_Buffer* output;
        } oscs [osc_count];
        blip_time_t last_time;
        byte regs [reg_count];
        
        struct {
                blip_time_t delay;
                blargg_ulong lfsr;
        } noise;
        
        struct {
                blip_time_t delay;
                byte const* wave;
                int pos;
                byte modes [8] [48]; // values already passed through volume table
        } env;
        
        void run_until( blip_time_t );
        void write_data_( int addr, int data );
public:
        enum { amp_range = 255 };
        Blip_Synth<blip_good_quality,1> synth_;
};
 
inline void Ay_Apu::volume( double v ) { synth_.volume( 0.7 / osc_count / amp_range * v ); }
 
inline void Ay_Apu::treble_eq( blip_eq_t const& eq ) { synth_.treble_eq( eq ); }
 
inline void Ay_Apu::write( blip_time_t time, int addr, int data )
{
        run_until( time );
        write_data_( addr, data );
}
 
inline void Ay_Apu::osc_output( int i, Blip_Buffer* buf )
{
        assert( (unsigned) i < osc_count );
        oscs [i].output = buf;
}
 
inline void Ay_Apu::output( Blip_Buffer* buf )
{
        osc_output( 0, buf );
        osc_output( 1, buf );
        osc_output( 2, buf );
}
 
inline void Ay_Apu::end_frame( blip_time_t time )
{
        if ( time > last_time )
                run_until( time );
        
        assert( last_time >= time );
        last_time -= time;
}
 
#endif