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// Nes_Snd_Emu 0.2.0-pre. http://www.slack.net/~ant/
#include "Nes_Namco_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_Namco_Apu::Nes_Namco_Apu()
{
set_output( NULL );
volume( 1.0 );
reset();
}
void Nes_Namco_Apu::reset()
{
last_time = 0;
addr_reg = 0;
int i;
for ( i = 0; i < reg_count; i++ )
reg [i] = 0;
for ( i = 0; i < osc_count; i++ )
{
Namco_Osc& osc = oscs [i];
osc.delay = 0;
osc.last_amp = 0;
osc.wave_pos = 0;
}
}
void Nes_Namco_Apu::set_output( Blip_Buffer* buf )
{
for ( int i = 0; i < osc_count; ++i )
set_output( i, buf );
}
/*
void Nes_Namco_Apu::reflect_state( Tagged_Data& data )
{
reflect_int16( data, BLARGG_4CHAR('A','D','D','R'), &addr_reg );
static const char hex [17] = "0123456789ABCDEF";
int i;
for ( i = 0; i < reg_count; i++ )
reflect_int16( data, 'RG\0\0' + hex [i >> 4] * 0x100 + hex [i & 15], ® [i] );
for ( i = 0; i < osc_count; i++ )
{
reflect_int32( data, BLARGG_4CHAR('D','L','Y','0') + i, &oscs [i].delay );
reflect_int16( data, BLARGG_4CHAR('P','O','S','0') + i, &oscs [i].wave_pos );
}
}
*/
void Nes_Namco_Apu::end_frame( blip_time_t time )
{
if ( time > last_time )
run_until( time );
assert( last_time >= time );
last_time -= time;
}
void Nes_Namco_Apu::run_until( blip_time_t nes_end_time )
{
int active_oscs = (reg [0x7F] >> 4 & 7) + 1;
for ( int i = osc_count - active_oscs; i < osc_count; i++ )
{
Namco_Osc& osc = oscs [i];
Blip_Buffer* output = osc.output;
if ( !output )
continue;
blip_resampled_time_t time =
output->resampled_time( last_time ) + osc.delay;
blip_resampled_time_t end_time = output->resampled_time( nes_end_time );
osc.delay = 0;
if ( time < end_time )
{
const BOOST::uint8_t* osc_reg = ® [i * 8 + 0x40];
if ( !(osc_reg [4] & 0xE0) )
continue;
int volume = osc_reg [7] & 15;
if ( !volume )
continue;
int freq = (osc_reg [4] & 3) * 0x10000 + osc_reg [2] * 0x100 + osc_reg [0];
if ( freq < 64 * active_oscs )
continue; // prevent low frequencies from excessively delaying freq changes
int const master_clock_divider = 12; // NES time derived via divider of master clock
int const n106_divider = 45; // N106 then divides master clock by this
int const max_freq = 0x3FFFF;
int const lowest_freq_period = (max_freq + 1) * n106_divider / master_clock_divider;
// divide by 8 to avoid overflow
blip_resampled_time_t period =
output->resampled_duration( lowest_freq_period / 8 ) / freq * 8 * active_oscs;
int wave_size = 32 - (osc_reg [4] >> 2 & 7) * 4;
if ( !wave_size )
continue;
int last_amp = osc.last_amp;
int wave_pos = osc.wave_pos;
output->set_modified();
do
{
// read wave sample
int addr = wave_pos + osc_reg [6];
int sample = reg [addr >> 1] >> (addr << 2 & 4);
wave_pos++;
sample = (sample & 15) * volume;
// output impulse if amplitude changed
int delta = sample - last_amp;
if ( delta )
{
last_amp = sample;
synth.offset_resampled( time, delta, output );
}
// next sample
time += period;
if ( wave_pos >= wave_size )
wave_pos = 0;
}
while ( time < end_time );
osc.wave_pos = wave_pos;
osc.last_amp = last_amp;
}
osc.delay = time - end_time;
}
last_time = nes_end_time;
}
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