apps/codecs/libgme/ay_apu.h

   1 // AY-3-8910 sound chip ulator
   2
   3 // Game_Music_Emu 0.6-pre
   4 #ifndef AY_APU_H
   5 #define AY_APU_H
   6
   7 #include "blargg_common.h"
   8 #include "blargg_source.h"
   9 #include "blip_buffer.h"
  10
  11 // Number of registers
  12 enum { ay_reg_count = 16 };
  13 enum { ay_osc_count = 3 };
  14 enum { ay_amp_range = 255 };
  15
  16 struct osc_t
  17 {
  18         blip_time_t  period;
  19         blip_time_t  delay;
  20         short        last_amp;
  21         short        phase;
  22         struct Blip_Buffer* output;
  23 };
  24
  25 struct Ay_Apu {
  26         struct osc_t oscs [ay_osc_count];
  27
  28         blip_time_t last_time;
  29         byte        addr_;
  30         byte        regs [ay_reg_count];
  31
  32         blip_time_t noise_delay;
  33         unsigned    noise_lfsr;
  34
  35         blip_time_t env_delay;
  36         byte const* env_wave;
  37         int         env_pos;
  38         byte        env_modes [8] [48]; // values already passed through volume table
  39
  40         struct Blip_Synth synth_; // used by Ay_Core for beeper sound
  41 };
  42
  43 void Ay_apu_init( struct Ay_Apu* this );
  44
  45 // Writes to address register
  46 static inline void Ay_apu_write_addr( struct Ay_Apu* this, int data ) { this->addr_ = data & 0x0F; }
  47
  48 // Emulates to time t, then writes to current data register
  49 void run_until( struct Ay_Apu* this, blip_time_t final_end_time ) ICODE_ATTR;;
  50 void write_data_( struct Ay_Apu* this, int addr, int data ) ICODE_ATTR;
  51 static inline void Ay_apu_write_data( struct Ay_Apu* this, blip_time_t t, int data )  { run_until( this, t ); write_data_( this, this->addr_, data ); }
  52
  53 // Reads from current data register
  54 int Ay_apu_read( struct Ay_Apu* this );
  55
  56 // Resets sound chip
  57 void Ay_apu_reset( struct Ay_Apu* this );
  58
  59 // Sets overall volume, where 1.0 is normal
  60 static inline void Ay_apu_volume( struct Ay_Apu* this, double v ) { Synth_volume( &this->synth_, 0.7/ay_osc_count/ay_amp_range * v ); }
  61
  62 static inline void Ay_apu_set_output( struct Ay_Apu* this, int i, struct Blip_Buffer* out )
  63 {
  64         assert( (unsigned) i < ay_osc_count );
  65         this->oscs [i].output = out;
  66 }
  67
  68 // Emulates to time t, then subtracts t from the current time.
  69 // OK if previous write call had time slightly after t.
  70 static inline void Ay_apu_end_frame( struct Ay_Apu* this, blip_time_t time )
  71 {
  72         if ( time > this->last_time )
  73                 run_until( this, time );
  74
  75         this->last_time -= time;
  76         assert( this->last_time >= 0 );
  77 }
  78
  79 #endif