apps/codecs/libgme/nes_fme7_apu.h

   1 // Sunsoft FME-7 sound emulator
   2
   3 // Game_Music_Emu 0.6-pre
   4 #ifndef NES_FME7_APU_H
   5 #define NES_FME7_APU_H
   6
   7 #include "blargg_common.h"
   8 #include "blip_buffer.h"
   9
  10 enum { fme7_reg_count = 14 };
  11
  12 // Mask and addresses of registers
  13 enum { fme7_addr_mask = 0xE000 };
  14 enum { fme7_data_addr = 0xE000 };
  15 enum { fme7_latch_addr = 0xC000 };
  16 enum { fme7_osc_count = 3 };
  17
  18 enum { amp_range = 192 }; // can be any value; this gives best error/quality tradeoff
  19
  20 struct osc_t {
  21         struct Blip_Buffer* output;
  22         int last_amp;
  23 };
  24
  25 // static unsigned char const amp_table [16];
  26
  27 struct Nes_Fme7_Apu {
  28         // fme7 apu state
  29         uint8_t regs [fme7_reg_count];
  30         uint8_t phases [3]; // 0 or 1
  31         uint8_t latch;
  32         uint16_t delays [3]; // a, b, c
  33
  34         struct osc_t oscs [fme7_osc_count];
  35         blip_time_t last_time;
  36
  37         struct Blip_Synth synth;
  38 };
  39
  40 // See Nes_Apu.h for reference
  41 void Fme7_init( struct Nes_Fme7_Apu* this );
  42 void Fme7_reset( struct Nes_Fme7_Apu* this );
  43
  44 static inline void Fme7_volume( struct Nes_Fme7_Apu* this, int v )
  45 {
  46         Synth_volume( &this->synth, (v/2 - (v*3)/25) / amp_range ); // to do: fine-tune
  47 }
  48
  49 static inline void Fme7_osc_output( struct Nes_Fme7_Apu* this, int i, struct Blip_Buffer* buf )
  50 {
  51         assert( (unsigned) i < fme7_osc_count );
  52         this->oscs [i].output = buf;
  53 }
  54
  55 static inline void Fme7_output( struct Nes_Fme7_Apu* this, struct Blip_Buffer* buf )
  56 {
  57         int i;
  58         for ( i = 0; i < fme7_osc_count; i++ )
  59                 Fme7_osc_output( this, i, buf );
  60 }
  61
  62 // (addr & addr_mask) == latch_addr
  63 static inline void Fme7_write_latch( struct Nes_Fme7_Apu* this, int data ) { this->latch = data; }
  64
  65 // (addr & addr_mask) == data_addr
  66 void Fme7_run_until( struct Nes_Fme7_Apu* this, blip_time_t end_time );
  67 static inline void Fme7_write_data( struct Nes_Fme7_Apu* this, blip_time_t time, int data )
  68 {
  69         if ( (unsigned) this->latch >= fme7_reg_count )
  70         {
  71                 #ifdef debug_printf
  72                         debug_printf( "FME7 write to %02X (past end of sound registers)\n", (int) latch );
  73                 #endif
  74                 return;
  75         }
  76
  77         Fme7_run_until( this, time );
  78         this->regs [this->latch] = data;
  79 }
  80
  81 static inline void Fme7_end_frame( struct Nes_Fme7_Apu* this, blip_time_t time )
  82 {
  83         if ( time > this->last_time )
  84                 Fme7_run_until( this, time );
  85
  86         assert( this->last_time >= time );
  87         this->last_time -= time;
  88 }
  89
  90 #endif