diff options
Diffstat (limited to 'plugins/gme/game-music-emu-0.6.0/gme/Nes_Vrc6_Apu.cpp')
| -rw-r--r-- | plugins/gme/game-music-emu-0.6.0/gme/Nes_Vrc6_Apu.cpp | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/plugins/gme/game-music-emu-0.6.0/gme/Nes_Vrc6_Apu.cpp b/plugins/gme/game-music-emu-0.6.0/gme/Nes_Vrc6_Apu.cpp new file mode 100644 index 00000000..d178407c --- /dev/null +++ b/plugins/gme/game-music-emu-0.6.0/gme/Nes_Vrc6_Apu.cpp @@ -0,0 +1,215 @@ +// Nes_Snd_Emu 0.1.8. http://www.slack.net/~ant/ + +#include "Nes_Vrc6_Apu.h" + +/* Copyright (C) 2003-2006 Shay Green. This module is free software; you +can redistribute it and/or modify it under the terms of the GNU Lesser +General Public License as published by the Free Software Foundation; either +version 2.1 of the License, or (at your option) any later version. This +module is distributed in the hope that it will be useful, but WITHOUT ANY +WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS +FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more +details. You should have received a copy of the GNU Lesser General Public +License along with this module; if not, write to the Free Software Foundation, +Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ + +#include "blargg_source.h" + +Nes_Vrc6_Apu::Nes_Vrc6_Apu() +{ + output( NULL ); + volume( 1.0 ); + reset(); +} + +void Nes_Vrc6_Apu::reset() +{ + last_time = 0; + for ( int i = 0; i < osc_count; i++ ) + { + Vrc6_Osc& osc = oscs [i]; + for ( int j = 0; j < reg_count; j++ ) + osc.regs [j] = 0; + osc.delay = 0; + osc.last_amp = 0; + osc.phase = 1; + osc.amp = 0; + } +} + +void Nes_Vrc6_Apu::output( Blip_Buffer* buf ) +{ + for ( int i = 0; i < osc_count; i++ ) + osc_output( i, buf ); +} + +void Nes_Vrc6_Apu::run_until( blip_time_t time ) +{ + require( time >= last_time ); + run_square( oscs [0], time ); + run_square( oscs [1], time ); + run_saw( time ); + last_time = time; +} + +void Nes_Vrc6_Apu::write_osc( blip_time_t time, int osc_index, int reg, int data ) +{ + require( (unsigned) osc_index < osc_count ); + require( (unsigned) reg < reg_count ); + + run_until( time ); + oscs [osc_index].regs [reg] = data; +} + +void Nes_Vrc6_Apu::end_frame( blip_time_t time ) +{ + if ( time > last_time ) + run_until( time ); + + assert( last_time >= time ); + last_time -= time; +} + +void Nes_Vrc6_Apu::save_state( vrc6_apu_state_t* out ) const +{ + assert( sizeof (vrc6_apu_state_t) == 20 ); + out->saw_amp = oscs [2].amp; + for ( int i = 0; i < osc_count; i++ ) + { + Vrc6_Osc const& osc = oscs [i]; + for ( int r = 0; r < reg_count; r++ ) + out->regs [i] [r] = osc.regs [r]; + + out->delays [i] = osc.delay; + out->phases [i] = osc.phase; + } +} + +void Nes_Vrc6_Apu::load_state( vrc6_apu_state_t const& in ) +{ + reset(); + oscs [2].amp = in.saw_amp; + for ( int i = 0; i < osc_count; i++ ) + { + Vrc6_Osc& osc = oscs [i]; + for ( int r = 0; r < reg_count; r++ ) + osc.regs [r] = in.regs [i] [r]; + + osc.delay = in.delays [i]; + osc.phase = in.phases [i]; + } + if ( !oscs [2].phase ) + oscs [2].phase = 1; +} + +void Nes_Vrc6_Apu::run_square( Vrc6_Osc& osc, blip_time_t end_time ) +{ + Blip_Buffer* output = osc.output; + if ( !output ) + return; + output->set_modified(); + + int volume = osc.regs [0] & 15; + if ( !(osc.regs [2] & 0x80) ) + volume = 0; + + int gate = osc.regs [0] & 0x80; + int duty = ((osc.regs [0] >> 4) & 7) + 1; + int delta = ((gate || osc.phase < duty) ? volume : 0) - osc.last_amp; + blip_time_t time = last_time; + if ( delta ) + { + osc.last_amp += delta; + square_synth.offset( time, delta, output ); + } + + time += osc.delay; + osc.delay = 0; + int period = osc.period(); + if ( volume && !gate && period > 4 ) + { + if ( time < end_time ) + { + int phase = osc.phase; + + do + { + phase++; + if ( phase == 16 ) + { + phase = 0; + osc.last_amp = volume; + square_synth.offset( time, volume, output ); + } + if ( phase == duty ) + { + osc.last_amp = 0; + square_synth.offset( time, -volume, output ); + } + time += period; + } + while ( time < end_time ); + + osc.phase = phase; + } + osc.delay = time - end_time; + } +} + +void Nes_Vrc6_Apu::run_saw( blip_time_t end_time ) +{ + Vrc6_Osc& osc = oscs [2]; + Blip_Buffer* output = osc.output; + if ( !output ) + return; + output->set_modified(); + + int amp = osc.amp; + int amp_step = osc.regs [0] & 0x3F; + blip_time_t time = last_time; + int last_amp = osc.last_amp; + if ( !(osc.regs [2] & 0x80) || !(amp_step | amp) ) + { + osc.delay = 0; + int delta = (amp >> 3) - last_amp; + last_amp = amp >> 3; + saw_synth.offset( time, delta, output ); + } + else + { + time += osc.delay; + if ( time < end_time ) + { + int period = osc.period() * 2; + int phase = osc.phase; + + do + { + if ( --phase == 0 ) + { + phase = 7; + amp = 0; + } + + int delta = (amp >> 3) - last_amp; + if ( delta ) + { + last_amp = amp >> 3; + saw_synth.offset( time, delta, output ); + } + + time += period; + amp = (amp + amp_step) & 0xFF; + } + while ( time < end_time ); + + osc.phase = phase; + osc.amp = amp; + } + + osc.delay = time - end_time; + } + + osc.last_amp = last_amp; +} + |