cog/Frameworks/GME/gme/Nes_Fds_Apu.cpp

281 lines
7.8 KiB
C++

// Game_Music_Emu $vers. http://www.slack.net/~ant/
#include "Nes_Fds_Apu.h"
/* Copyright (C) 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"
int const fract_range = 65536;
void Nes_Fds_Apu::reset()
{
memset( regs_, 0, sizeof regs_ );
memset( mod_wave, 0, sizeof mod_wave );
last_time = 0;
env_delay = 0;
sweep_delay = 0;
wave_pos = 0;
last_amp = 0;
wave_fract = fract_range;
mod_fract = fract_range;
mod_pos = 0;
mod_write_pos = 0;
static byte const initial_regs [0x0B] = {
0x80, // disable envelope
0, 0, 0xC0, // disable wave and lfo
0x80, // disable sweep
0, 0, 0x80, // disable modulation
0, 0, 0xFF // LFO period // TODO: use 0xE8 as FDS ROM does?
};
for ( int i = 0; i < (int) sizeof initial_regs; i++ )
{
// two writes to set both gain and period for envelope registers
write_( io_addr + wave_size + i, 0 );
write_( io_addr + wave_size + i, initial_regs [i] );
}
}
void Nes_Fds_Apu::write_( unsigned addr, int data )
{
unsigned reg = addr - io_addr;
if ( reg < io_size )
{
if ( reg < wave_size )
{
if ( regs (0x4089) & 0x80 )
regs_ [reg] = data & wave_sample_max;
}
else
{
regs_ [reg] = data;
switch ( addr )
{
case 0x4080:
if ( data & 0x80 )
env_gain = data & 0x3F;
else
env_speed = (data & 0x3F) + 1;
break;
case 0x4084:
if ( data & 0x80 )
sweep_gain = data & 0x3F;
else
sweep_speed = (data & 0x3F) + 1;
break;
case 0x4085:
mod_pos = mod_write_pos;
regs (0x4085) = data & 0x7F;
break;
case 0x4088:
if ( regs (0x4087) & 0x80 )
{
int pos = mod_write_pos;
data &= 0x07;
mod_wave [pos ] = data;
mod_wave [pos + 1] = data;
mod_write_pos = (pos + 2) & (wave_size - 1);
mod_pos = (mod_pos + 2) & (wave_size - 1);
}
break;
}
}
}
}
void Nes_Fds_Apu::set_tempo( double t )
{
lfo_tempo = lfo_base_tempo;
if ( t != 1.0 )
{
lfo_tempo = int ((double) lfo_base_tempo / t + 0.5);
if ( lfo_tempo <= 0 )
lfo_tempo = 1;
}
}
void Nes_Fds_Apu::run_until( blip_time_t final_end_time )
{
int const wave_freq = (regs (0x4083) & 0x0F) * 0x100 + regs (0x4082);
Blip_Buffer* const output_ = this->output_;
if ( wave_freq && output_ && !((regs (0x4089) | regs (0x4083)) & 0x80) )
{
output_->set_modified();
// master_volume
#define MVOL_ENTRY( percent ) (master_vol_max * percent + 50) / 100
static unsigned char const master_volumes [4] = {
MVOL_ENTRY( 100 ), MVOL_ENTRY( 67 ), MVOL_ENTRY( 50 ), MVOL_ENTRY( 40 )
};
int const master_volume = master_volumes [regs (0x4089) & 0x03];
// lfo_period
blip_time_t lfo_period = regs (0x408A) * lfo_tempo;
if ( regs (0x4083) & 0x40 )
lfo_period = 0;
// sweep setup
blip_time_t sweep_time = last_time + sweep_delay;
blip_time_t const sweep_period = lfo_period * sweep_speed;
if ( !sweep_period || regs (0x4084) & 0x80 )
sweep_time = final_end_time;
// envelope setup
blip_time_t env_time = last_time + env_delay;
blip_time_t const env_period = lfo_period * env_speed;
if ( !env_period || regs (0x4080) & 0x80 )
env_time = final_end_time;
// modulation
int mod_freq = 0;
if ( !(regs (0x4087) & 0x80) )
mod_freq = (regs (0x4087) & 0x0F) * 0x100 + regs (0x4086);
blip_time_t end_time = last_time;
do
{
// sweep
if ( sweep_time <= end_time )
{
sweep_time += sweep_period;
int mode = regs (0x4084) >> 5 & 2;
int new_sweep_gain = sweep_gain + mode - 1;
if ( (unsigned) new_sweep_gain <= (unsigned) 0x80 >> mode )
sweep_gain = new_sweep_gain;
else
regs (0x4084) |= 0x80; // optimization only
}
// envelope
if ( env_time <= end_time )
{
env_time += env_period;
int mode = regs (0x4080) >> 5 & 2;
int new_env_gain = env_gain + mode - 1;
if ( (unsigned) new_env_gain <= (unsigned) 0x80 >> mode )
env_gain = new_env_gain;
else
regs (0x4080) |= 0x80; // optimization only
}
// new end_time
blip_time_t const start_time = end_time;
end_time = final_end_time;
if ( end_time > env_time ) end_time = env_time;
if ( end_time > sweep_time ) end_time = sweep_time;
// frequency modulation
int freq = wave_freq;
if ( mod_freq )
{
// time of next modulation clock
blip_time_t mod_time = start_time + (mod_fract + mod_freq - 1) / mod_freq;
if ( end_time > mod_time )
end_time = mod_time;
// run modulator up to next clock and save old sweep_bias
int sweep_bias = regs (0x4085);
mod_fract -= (end_time - start_time) * mod_freq;
if ( mod_fract <= 0 )
{
mod_fract += fract_range;
check( (unsigned) mod_fract <= fract_range );
static short const mod_table [8] = { 0, +1, +2, +4, 0, -4, -2, -1 };
int mod = mod_wave [mod_pos];
mod_pos = (mod_pos + 1) & (wave_size - 1);
int new_sweep_bias = (sweep_bias + mod_table [mod]) & 0x7F;
if ( mod == 4 )
new_sweep_bias = 0;
regs (0x4085) = new_sweep_bias;
}
// apply frequency modulation
sweep_bias = (sweep_bias ^ 0x40) - 0x40;
int factor = sweep_bias * sweep_gain;
int extra = factor & 0x0F;
factor >>= 4;
if ( extra )
{
factor--;
if ( sweep_bias >= 0 )
factor += 3;
}
if ( factor > 193 ) factor -= 258;
if ( factor < -64 ) factor += 256;
freq += (freq * factor) >> 6;
if ( freq <= 0 )
continue;
}
// wave
int wave_fract = this->wave_fract;
blip_time_t delay = (wave_fract + freq - 1) / freq;
blip_time_t time = start_time + delay;
if ( time <= end_time )
{
// at least one wave clock within start_time...end_time
blip_time_t const min_delay = fract_range / freq;
int wave_pos = this->wave_pos;
int volume = env_gain;
if ( volume > vol_max )
volume = vol_max;
volume *= master_volume;
int const min_fract = min_delay * freq;
do
{
// clock wave
int amp = regs_ [wave_pos] * volume;
wave_pos = (wave_pos + 1) & (wave_size - 1);
int delta = amp - last_amp;
if ( delta )
{
last_amp = amp;
synth.offset_inline( time, delta, output_ );
}
wave_fract += fract_range - delay * freq;
check( unsigned (fract_range - wave_fract) < freq );
// delay until next clock
delay = min_delay;
if ( wave_fract > min_fract )
delay++;
check( delay && delay == (wave_fract + freq - 1) / freq );
time += delay;
}
while ( time <= end_time ); // TODO: using < breaks things, but <= is wrong
this->wave_pos = wave_pos;
}
this->wave_fract = wave_fract - (end_time - (time - delay)) * freq;
check( this->wave_fract > 0 );
}
while ( end_time < final_end_time );
env_delay = env_time - final_end_time; check( env_delay >= 0 );
sweep_delay = sweep_time - final_end_time; check( sweep_delay >= 0 );
}
last_time = final_end_time;
}