1 files changed, 62 insertions, 0 deletions

diff --git a/apps/codecs/libgme/nes_vrc6_apu.h b/apps/codecs/libgme/nes_vrc6_apu.h
new file mode 100644
index 0000000000..540438f4a2
--- /dev/null
+++ b/apps/codecs/libgme/nes_vrc6_apu.h
@@ -0,0 +1,62 @@
+// 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"
+
+enum { vrc6_osc_count = 3 };
+enum { vrc6_reg_count = 3 };
+enum { vrc6_base_addr = 0x9000 };
+enum { vrc6_addr_step = 0x1000 };
+
+struct Vrc6_Osc
+{
+        uint8_t regs [vrc6_reg_count];
+        struct Blip_Buffer* output;
+        int delay;
+        int last_amp;
+        int phase;
+        int amp; // only used by saw
+};
+
+static inline int Vrc6_osc_period( struct Vrc6_Osc* this )
+{
+        return (this->regs [2] & 0x0F) * 0x100 + this->regs [1] + 1;
+}
+
+struct Nes_Vrc6_Apu {
+        struct Vrc6_Osc oscs [vrc6_osc_count];
+        blip_time_t last_time;
+        
+        struct Blip_Synth saw_synth;
+        struct Blip_Synth square_synth;
+};
+
+// See Nes_Apu.h for reference
+void Vrc6_init( struct Nes_Vrc6_Apu* this );
+void Vrc6_reset( struct Nes_Vrc6_Apu* this );
+void Vrc6_output( struct Nes_Vrc6_Apu* this, struct Blip_Buffer* );
+void Vrc6_end_frame( struct Nes_Vrc6_Apu* this, blip_time_t ) ICODE_ATTR;
+        
+// 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
+void Vrc6_write_osc( struct Nes_Vrc6_Apu* this, blip_time_t, int osc, int reg, int data ) ICODE_ATTR;
+
+static inline void Vrc6_osc_output( struct Nes_Vrc6_Apu* this, int i, struct Blip_Buffer* buf )
+{
+        assert( (unsigned) i < vrc6_osc_count );
+        this->oscs [i].output = buf;
+}
+
+static inline void Vrc6_volume( struct Nes_Vrc6_Apu* this, double v )
+{
+        double const factor = 0.0967 * 2;
+        Synth_volume( &this->saw_synth, factor / 31 * v );
+        Synth_volume( &this->square_synth, factor * 0.5 / 15 * v );
+}
+
+#endif