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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"
void Vrc6_init( struct Nes_Vrc6_Apu* this )
{
Synth_init( &this->saw_synth );
Synth_init( &this->square_synth );
Vrc6_output( this, NULL );
Vrc6_volume( this, (int)FP_ONE_VOLUME );
Vrc6_reset( this );
}
void Vrc6_reset( struct Nes_Vrc6_Apu* this )
{
this->last_time = 0;
int i;
for ( i = 0; i < vrc6_osc_count; i++ )
{
struct Vrc6_Osc* osc = &this->oscs [i];
int j;
for ( j = 0; j < vrc6_reg_count; j++ )
osc->regs [j] = 0;
osc->delay = 0;
osc->last_amp = 0;
osc->phase = 1;
osc->amp = 0;
}
}
void Vrc6_output( struct Nes_Vrc6_Apu* this, struct Blip_Buffer* buf )
{
int i;
for ( i = 0; i < vrc6_osc_count; i++ )
Vrc6_osc_output( this, i, buf );
}
void run_square( struct Nes_Vrc6_Apu* this, struct Vrc6_Osc* osc, blip_time_t end_time );
void run_saw( struct Nes_Vrc6_Apu* this, blip_time_t end_time );
static void Vrc6_run_until( struct Nes_Vrc6_Apu* this, blip_time_t time )
{
require( time >= this->last_time );
run_square( this, &this->oscs [0], time );
run_square( this, &this->oscs [1], time );
run_saw( this, time );
this->last_time = time;
}
void Vrc6_write_osc( struct Nes_Vrc6_Apu* this, blip_time_t time, int osc_index, int reg, int data )
{
require( (unsigned) osc_index < vrc6_osc_count );
require( (unsigned) reg < vrc6_reg_count );
Vrc6_run_until( this, time );
this->oscs [osc_index].regs [reg] = data;
}
void Vrc6_end_frame( struct Nes_Vrc6_Apu* this, blip_time_t time )
{
if ( time > this->last_time )
Vrc6_run_until( this, time );
assert( this->last_time >= time );
this->last_time -= time;
}
void run_square( struct Nes_Vrc6_Apu* this, struct Vrc6_Osc* osc, blip_time_t end_time )
{
struct Blip_Buffer* output = osc->output;
if ( !output )
return;
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 = this->last_time;
if ( delta )
{
osc->last_amp += delta;
Blip_set_modified( output );
Synth_offset( &this->square_synth, time, delta, output );
}
time += osc->delay;
osc->delay = 0;
int period = Vrc6_osc_period( osc );
if ( volume && !gate && period > 4 )
{
if ( time < end_time )
{
int phase = osc->phase;
Blip_set_modified( output );
do
{
phase++;
if ( phase == 16 )
{
phase = 0;
osc->last_amp = volume;
Synth_offset( &this->square_synth, time, volume, output );
}
if ( phase == duty )
{
osc->last_amp = 0;
Synth_offset( &this->square_synth, time, -volume, output );
}
time += period;
}
while ( time < end_time );
osc->phase = phase;
}
osc->delay = time - end_time;
}
}
void run_saw( struct Nes_Vrc6_Apu* this, blip_time_t end_time )
{
struct Vrc6_Osc* osc = &this->oscs [2];
struct Blip_Buffer* output = osc->output;
if ( !output )
return;
Blip_set_modified( output );
int amp = osc->amp;
int amp_step = osc->regs [0] & 0x3F;
blip_time_t time = this->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;
Synth_offset( &this->saw_synth, time, delta, output );
}
else
{
time += osc->delay;
if ( time < end_time )
{
int period = Vrc6_osc_period( osc ) * 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;
Synth_offset( &this->saw_synth, 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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