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// Nes_Snd_Emu 0.1.8. http://www.slack.net/~ant/
#include "Nes_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_Osc
void Nes_Osc::clock_length( int halt_mask )
{
if ( length_counter && !(regs [0] & halt_mask) )
length_counter--;
}
void Nes_Envelope::clock_envelope()
{
int period = regs [0] & 15;
if ( reg_written [3] ) {
reg_written [3] = false;
env_delay = period;
envelope = 15;
}
else if ( --env_delay < 0 ) {
env_delay = period;
if ( envelope | (regs [0] & 0x20) )
envelope = (envelope - 1) & 15;
}
}
int Nes_Envelope::volume() const
{
return length_counter == 0 ? 0 : (regs [0] & 0x10) ? (regs [0] & 15) : envelope;
}
// Nes_Square
void Nes_Square::clock_sweep( int negative_adjust )
{
int sweep = regs [1];
if ( --sweep_delay < 0 )
{
reg_written [1] = true;
int period = this->period();
int shift = sweep & shift_mask;
if ( shift && (sweep & 0x80) && period >= 8 )
{
int offset = period >> shift;
if ( sweep & negate_flag )
offset = negative_adjust - offset;
if ( period + offset < 0x800 )
{
period += offset;
// rewrite period
regs [2] = period & 0xFF;
regs [3] = (regs [3] & ~7) | ((period >> 8) & 7);
}
}
}
if ( reg_written [1] ) {
reg_written [1] = false;
sweep_delay = (sweep >> 4) & 7;
}
}
// TODO: clean up
inline nes_time_t Nes_Square::maintain_phase( nes_time_t time, nes_time_t end_time,
nes_time_t timer_period )
{
nes_time_t remain = end_time - time;
if ( remain > 0 )
{
int count = (remain + timer_period - 1) / timer_period;
phase = (phase + count) & (phase_range - 1);
time += (blargg_long) count * timer_period;
}
return time;
}
void Nes_Square::run( nes_time_t time, nes_time_t end_time )
{
const int period = this->period();
const int timer_period = (period + 1) * 2;
if ( !output )
{
delay = maintain_phase( time + delay, end_time, timer_period ) - end_time;
return;
}
output->set_modified();
int offset = period >> (regs [1] & shift_mask);
if ( regs [1] & negate_flag )
offset = 0;
const int volume = this->volume();
if ( volume == 0 || period < 8 || (period + offset) >= 0x800 )
{
if ( last_amp ) {
synth.offset( time, -last_amp, output );
last_amp = 0;
}
time += delay;
time = maintain_phase( time, end_time, timer_period );
}
else
{
// handle duty select
int duty_select = (regs [0] >> 6) & 3;
int duty = 1 << duty_select; // 1, 2, 4, 2
int amp = 0;
if ( duty_select == 3 ) {
duty = 2; // negated 25%
amp = volume;
}
if ( phase < duty )
amp ^= volume;
{
int delta = update_amp( amp );
if ( delta )
synth.offset( time, delta, output );
}
time += delay;
if ( time < end_time )
{
Blip_Buffer* const output = this->output;
const Synth& synth = this->synth;
int delta = amp * 2 - volume;
int phase = this->phase;
do {
phase = (phase + 1) & (phase_range - 1);
if ( phase == 0 || phase == duty ) {
delta = -delta;
synth.offset_inline( time, delta, output );
}
time += timer_period;
}
while ( time < end_time );
last_amp = (delta + volume) >> 1;
this->phase = phase;
}
}
delay = time - end_time;
}
// Nes_Triangle
void Nes_Triangle::clock_linear_counter()
{
if ( reg_written [3] )
linear_counter = regs [0] & 0x7F;
else if ( linear_counter )
linear_counter--;
if ( !(regs [0] & 0x80) )
reg_written [3] = false;
}
inline int Nes_Triangle::calc_amp() const
{
int amp = phase_range - phase;
if ( amp < 0 )
amp = phase - (phase_range + 1);
return amp;
}
// TODO: clean up
inline nes_time_t Nes_Triangle::maintain_phase( nes_time_t time, nes_time_t end_time,
nes_time_t timer_period )
{
nes_time_t remain = end_time - time;
if ( remain > 0 )
{
int count = (remain + timer_period - 1) / timer_period;
phase = ((unsigned) phase + 1 - count) & (phase_range * 2 - 1);
phase++;
time += (blargg_long) count * timer_period;
}
return time;
}
void Nes_Triangle::run( nes_time_t time, nes_time_t end_time )
{
const int timer_period = period() + 1;
if ( !output )
{
time += delay;
delay = 0;
if ( length_counter && linear_counter && timer_period >= 3 )
delay = maintain_phase( time, end_time, timer_period ) - end_time;
return;
}
output->set_modified();
// to do: track phase when period < 3
// to do: Output 7.5 on dac when period < 2? More accurate, but results in more clicks.
int delta = update_amp( calc_amp() );
if ( delta )
synth.offset( time, delta, output );
time += delay;
if ( length_counter == 0 || linear_counter == 0 || timer_period < 3 )
{
time = end_time;
}
else if ( time < end_time )
{
Blip_Buffer* const output = this->output;
int phase = this->phase;
int volume = 1;
if ( phase > phase_range ) {
phase -= phase_range;
volume = -volume;
}
do {
if ( --phase == 0 ) {
phase = phase_range;
volume = -volume;
}
else {
synth.offset_inline( time, volume, output );
}
time += timer_period;
}
while ( time < end_time );
if ( volume < 0 )
phase += phase_range;
this->phase = phase;
last_amp = calc_amp();
}
delay = time - end_time;
}
// Nes_Dmc
void Nes_Dmc::reset()
{
address = 0;
dac = 0;
buf = 0;
bits_remain = 1;
bits = 0;
buf_full = false;
silence = true;
next_irq = Nes_Apu::no_irq;
irq_flag = false;
irq_enabled = false;
Nes_Osc::reset();
period = 0x1AC;
}
void Nes_Dmc::recalc_irq()
{
nes_time_t irq = Nes_Apu::no_irq;
if ( irq_enabled && length_counter )
irq = apu->last_dmc_time + delay +
((length_counter - 1) * 8 + bits_remain - 1) * nes_time_t (period) + 1;
if ( irq != next_irq ) {
next_irq = irq;
apu->irq_changed();
}
}
int Nes_Dmc::count_reads( nes_time_t time, nes_time_t* last_read ) const
{
if ( last_read )
*last_read = time;
if ( length_counter == 0 )
return 0; // not reading
nes_time_t first_read = next_read_time();
nes_time_t avail = time - first_read;
if ( avail <= 0 )
return 0;
int count = (avail - 1) / (period * 8) + 1;
if ( !(regs [0] & loop_flag) && count > length_counter )
count = length_counter;
if ( last_read )
{
*last_read = first_read + (count - 1) * (period * 8) + 1;
check( *last_read <= time );
check( count == count_reads( *last_read, NULL ) );
check( count - 1 == count_reads( *last_read - 1, NULL ) );
}
return count;
}
static short const dmc_period_table [2] [16] = {
{428, 380, 340, 320, 286, 254, 226, 214, // NTSC
190, 160, 142, 128, 106, 84, 72, 54},
{398, 354, 316, 298, 276, 236, 210, 198, // PAL
176, 148, 132, 118, 98, 78, 66, 50}
};
inline void Nes_Dmc::reload_sample()
{
address = 0x4000 + regs [2] * 0x40;
length_counter = regs [3] * 0x10 + 1;
}
static byte const dac_table [128] =
{
0, 1, 2, 3, 4, 5, 6, 7, 7, 8, 9,10,11,12,13,14,
15,15,16,17,18,19,20,20,21,22,23,24,24,25,26,27,
27,28,29,30,31,31,32,33,33,34,35,36,36,37,38,38,
39,40,41,41,42,43,43,44,45,45,46,47,47,48,48,49,
50,50,51,52,52,53,53,54,55,55,56,56,57,58,58,59,
59,60,60,61,61,62,63,63,64,64,65,65,66,66,67,67,
68,68,69,70,70,71,71,72,72,73,73,74,74,75,75,75,
76,76,77,77,78,78,79,79,80,80,81,81,82,82,82,83,
};
void Nes_Dmc::write_register( int addr, int data )
{
if ( addr == 0 )
{
period = dmc_period_table [pal_mode] [data & 15];
irq_enabled = (data & 0xC0) == 0x80; // enabled only if loop disabled
irq_flag &= irq_enabled;
recalc_irq();
}
else if ( addr == 1 )
{
int old_dac = dac;
dac = data & 0x7F;
// adjust last_amp so that "pop" amplitude will be properly non-linear
// with respect to change in dac
int faked_nonlinear = dac - (dac_table [dac] - dac_table [old_dac]);
if ( !nonlinear )
last_amp = faked_nonlinear;
}
}
void Nes_Dmc::start()
{
reload_sample();
fill_buffer();
recalc_irq();
}
void Nes_Dmc::fill_buffer()
{
if ( !buf_full && length_counter )
{
require( prg_reader ); // prg_reader must be set
buf = prg_reader( prg_reader_data, 0x8000u + address );
address = (address + 1) & 0x7FFF;
buf_full = true;
if ( --length_counter == 0 )
{
if ( regs [0] & loop_flag ) {
reload_sample();
}
else {
apu->osc_enables &= ~0x10;
irq_flag = irq_enabled;
next_irq = Nes_Apu::no_irq;
apu->irq_changed();
}
}
}
}
void Nes_Dmc::run( nes_time_t time, nes_time_t end_time )
{
int delta = update_amp( dac );
if ( !output )
{
silence = true;
}
else
{
output->set_modified();
if ( delta )
synth.offset( time, delta, output );
}
time += delay;
if ( time < end_time )
{
int bits_remain = this->bits_remain;
if ( silence && !buf_full )
{
int count = (end_time - time + period - 1) / period;
bits_remain = (bits_remain - 1 + 8 - (count % 8)) % 8 + 1;
time += count * period;
}
else
{
Blip_Buffer* const output = this->output;
const int period = this->period;
int bits = this->bits;
int dac = this->dac;
do
{
if ( !silence )
{
int step = (bits & 1) * 4 - 2;
bits >>= 1;
if ( unsigned (dac + step) <= 0x7F ) {
dac += step;
synth.offset_inline( time, step, output );
}
}
time += period;
if ( --bits_remain == 0 )
{
bits_remain = 8;
if ( !buf_full ) {
silence = true;
}
else {
silence = false;
bits = buf;
buf_full = false;
if ( !output )
silence = true;
fill_buffer();
}
}
}
while ( time < end_time );
this->dac = dac;
this->last_amp = dac;
this->bits = bits;
}
this->bits_remain = bits_remain;
}
delay = time - end_time;
}
// Nes_Noise
static short const noise_period_table [16] = {
0x004, 0x008, 0x010, 0x020, 0x040, 0x060, 0x080, 0x0A0,
0x0CA, 0x0FE, 0x17C, 0x1FC, 0x2FA, 0x3F8, 0x7F2, 0xFE4
};
void Nes_Noise::run( nes_time_t time, nes_time_t end_time )
{
int period = noise_period_table [regs [2] & 15];
if ( !output )
{
// TODO: clean up
time += delay;
delay = time + (end_time - time + period - 1) / period * period - end_time;
return;
}
output->set_modified();
const int volume = this->volume();
int amp = (noise & 1) ? volume : 0;
{
int delta = update_amp( amp );
if ( delta )
synth.offset( time, delta, output );
}
time += delay;
if ( time < end_time )
{
const int mode_flag = 0x80;
if ( !volume )
{
// round to next multiple of period
time += (end_time - time + period - 1) / period * period;
// approximate noise cycling while muted, by shuffling up noise register
// to do: precise muted noise cycling?
if ( !(regs [2] & mode_flag) ) {
int feedback = (noise << 13) ^ (noise << 14);
noise = (feedback & 0x4000) | (noise >> 1);
}
}
else
{
Blip_Buffer* const output = this->output;
// using resampled time avoids conversion in synth.offset()
blip_resampled_time_t rperiod = output->resampled_duration( period );
blip_resampled_time_t rtime = output->resampled_time( time );
int noise = this->noise;
int delta = amp * 2 - volume;
const int tap = (regs [2] & mode_flag ? 8 : 13);
do {
int feedback = (noise << tap) ^ (noise << 14);
time += period;
if ( (noise + 1) & 2 ) {
// bits 0 and 1 of noise differ
delta = -delta;
synth.offset_resampled( rtime, delta, output );
}
rtime += rperiod;
noise = (feedback & 0x4000) | (noise >> 1);
}
while ( time < end_time );
last_amp = (delta + volume) >> 1;
this->noise = noise;
}
}
delay = time - end_time;
}
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