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// 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;
}
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