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551 lines
12 KiB
C++
551 lines
12 KiB
C++
// Nes_Snd_Emu 0.1.8. http://www.slack.net/~ant/
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#include "Nes_Apu.h"
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/* Copyright (C) 2003-2006 Shay Green. This module is free software; you
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can redistribute it and/or modify it under the terms of the GNU Lesser
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General Public License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version. This
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module is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
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details. You should have received a copy of the GNU Lesser General Public
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License along with this module; if not, write to the Free Software Foundation,
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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */
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#include "blargg_source.h"
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// Nes_Osc
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void Nes_Osc::clock_length( int halt_mask )
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{
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if ( length_counter && !(regs [0] & halt_mask) )
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length_counter--;
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}
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void Nes_Envelope::clock_envelope()
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{
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int period = regs [0] & 15;
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if ( reg_written [3] ) {
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reg_written [3] = false;
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env_delay = period;
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envelope = 15;
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}
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else if ( --env_delay < 0 ) {
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env_delay = period;
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if ( envelope | (regs [0] & 0x20) )
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envelope = (envelope - 1) & 15;
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}
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}
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int Nes_Envelope::volume() const
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{
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return length_counter == 0 ? 0 : (regs [0] & 0x10) ? (regs [0] & 15) : envelope;
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}
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// Nes_Square
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void Nes_Square::clock_sweep( int negative_adjust )
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{
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int sweep = regs [1];
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if ( --sweep_delay < 0 )
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{
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reg_written [1] = true;
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int period = this->period();
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int shift = sweep & shift_mask;
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if ( shift && (sweep & 0x80) && period >= 8 )
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{
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int offset = period >> shift;
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if ( sweep & negate_flag )
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offset = negative_adjust - offset;
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if ( period + offset < 0x800 )
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{
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period += offset;
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// rewrite period
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regs [2] = period & 0xFF;
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regs [3] = (regs [3] & ~7) | ((period >> 8) & 7);
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}
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}
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}
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if ( reg_written [1] ) {
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reg_written [1] = false;
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sweep_delay = (sweep >> 4) & 7;
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}
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}
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// TODO: clean up
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inline nes_time_t Nes_Square::maintain_phase( nes_time_t time, nes_time_t end_time,
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nes_time_t timer_period )
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{
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nes_time_t remain = end_time - time;
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if ( remain > 0 )
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{
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int count = (remain + timer_period - 1) / timer_period;
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phase = (phase + count) & (phase_range - 1);
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time += (blargg_long) count * timer_period;
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}
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return time;
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}
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void Nes_Square::run( nes_time_t time, nes_time_t end_time )
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{
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const int period = this->period();
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const int timer_period = (period + 1) * 2;
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if ( !output )
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{
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delay = maintain_phase( time + delay, end_time, timer_period ) - end_time;
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return;
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}
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output->set_modified();
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int offset = period >> (regs [1] & shift_mask);
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if ( regs [1] & negate_flag )
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offset = 0;
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const int volume = this->volume();
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if ( volume == 0 || period < 8 || (period + offset) >= 0x800 )
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{
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if ( last_amp ) {
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synth.offset( time, -last_amp, output );
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last_amp = 0;
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}
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time += delay;
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time = maintain_phase( time, end_time, timer_period );
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}
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else
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{
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// handle duty select
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int duty_select = (regs [0] >> 6) & 3;
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int duty = 1 << duty_select; // 1, 2, 4, 2
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int amp = 0;
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if ( duty_select == 3 ) {
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duty = 2; // negated 25%
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amp = volume;
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}
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if ( phase < duty )
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amp ^= volume;
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{
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int delta = update_amp( amp );
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if ( delta )
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synth.offset( time, delta, output );
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}
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time += delay;
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if ( time < end_time )
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{
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Blip_Buffer* const output = this->output;
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const Synth& synth = this->synth;
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int delta = amp * 2 - volume;
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int phase = this->phase;
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do {
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phase = (phase + 1) & (phase_range - 1);
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if ( phase == 0 || phase == duty ) {
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delta = -delta;
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synth.offset_inline( time, delta, output );
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}
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time += timer_period;
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}
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while ( time < end_time );
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last_amp = (delta + volume) >> 1;
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this->phase = phase;
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}
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}
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delay = time - end_time;
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}
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// Nes_Triangle
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void Nes_Triangle::clock_linear_counter()
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{
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if ( reg_written [3] )
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linear_counter = regs [0] & 0x7F;
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else if ( linear_counter )
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linear_counter--;
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if ( !(regs [0] & 0x80) )
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reg_written [3] = false;
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}
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inline int Nes_Triangle::calc_amp() const
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{
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int amp = phase_range - phase;
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if ( amp < 0 )
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amp = phase - (phase_range + 1);
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return amp;
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}
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// TODO: clean up
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inline nes_time_t Nes_Triangle::maintain_phase( nes_time_t time, nes_time_t end_time,
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nes_time_t timer_period )
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{
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nes_time_t remain = end_time - time;
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if ( remain > 0 )
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{
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int count = (remain + timer_period - 1) / timer_period;
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phase = ((unsigned) phase + 1 - count) & (phase_range * 2 - 1);
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phase++;
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time += (blargg_long) count * timer_period;
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}
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return time;
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}
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void Nes_Triangle::run( nes_time_t time, nes_time_t end_time )
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{
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const int timer_period = period() + 1;
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if ( !output )
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{
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time += delay;
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delay = 0;
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if ( length_counter && linear_counter && timer_period >= 3 )
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delay = maintain_phase( time, end_time, timer_period ) - end_time;
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return;
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}
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output->set_modified();
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// to do: track phase when period < 3
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// to do: Output 7.5 on dac when period < 2? More accurate, but results in more clicks.
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int delta = update_amp( calc_amp() );
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if ( delta )
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synth.offset( time, delta, output );
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time += delay;
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if ( length_counter == 0 || linear_counter == 0 || timer_period < 3 )
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{
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time = end_time;
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}
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else if ( time < end_time )
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{
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Blip_Buffer* const output = this->output;
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int phase = this->phase;
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int volume = 1;
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if ( phase > phase_range ) {
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phase -= phase_range;
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volume = -volume;
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}
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do {
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if ( --phase == 0 ) {
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phase = phase_range;
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volume = -volume;
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}
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else {
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synth.offset_inline( time, volume, output );
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}
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time += timer_period;
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}
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while ( time < end_time );
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if ( volume < 0 )
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phase += phase_range;
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this->phase = phase;
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last_amp = calc_amp();
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}
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delay = time - end_time;
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}
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// Nes_Dmc
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void Nes_Dmc::reset()
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{
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address = 0;
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dac = 0;
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buf = 0;
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bits_remain = 1;
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bits = 0;
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buf_full = false;
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silence = true;
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next_irq = Nes_Apu::no_irq;
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irq_flag = false;
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irq_enabled = false;
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Nes_Osc::reset();
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period = 0x1AC;
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}
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void Nes_Dmc::recalc_irq()
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{
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nes_time_t irq = Nes_Apu::no_irq;
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if ( irq_enabled && length_counter )
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irq = apu->last_dmc_time + delay +
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((length_counter - 1) * 8 + bits_remain - 1) * nes_time_t (period) + 1;
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if ( irq != next_irq ) {
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next_irq = irq;
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apu->irq_changed();
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}
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}
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int Nes_Dmc::count_reads( nes_time_t time, nes_time_t* last_read ) const
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{
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if ( last_read )
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*last_read = time;
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if ( length_counter == 0 )
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return 0; // not reading
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nes_time_t first_read = next_read_time();
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nes_time_t avail = time - first_read;
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if ( avail <= 0 )
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return 0;
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int count = (avail - 1) / (period * 8) + 1;
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if ( !(regs [0] & loop_flag) && count > length_counter )
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count = length_counter;
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if ( last_read )
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{
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*last_read = first_read + (count - 1) * (period * 8) + 1;
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check( *last_read <= time );
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check( count == count_reads( *last_read, NULL ) );
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check( count - 1 == count_reads( *last_read - 1, NULL ) );
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}
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return count;
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}
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static short const dmc_period_table [2] [16] = {
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{428, 380, 340, 320, 286, 254, 226, 214, // NTSC
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190, 160, 142, 128, 106, 84, 72, 54},
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{398, 354, 316, 298, 276, 236, 210, 198, // PAL
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176, 148, 132, 118, 98, 78, 66, 50}
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};
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inline void Nes_Dmc::reload_sample()
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{
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address = 0x4000 + regs [2] * 0x40;
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length_counter = regs [3] * 0x10 + 1;
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}
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static byte const dac_table [128] =
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{
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0, 1, 2, 3, 4, 5, 6, 7, 7, 8, 9,10,11,12,13,14,
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15,15,16,17,18,19,20,20,21,22,23,24,24,25,26,27,
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27,28,29,30,31,31,32,33,33,34,35,36,36,37,38,38,
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39,40,41,41,42,43,43,44,45,45,46,47,47,48,48,49,
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50,50,51,52,52,53,53,54,55,55,56,56,57,58,58,59,
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59,60,60,61,61,62,63,63,64,64,65,65,66,66,67,67,
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68,68,69,70,70,71,71,72,72,73,73,74,74,75,75,75,
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76,76,77,77,78,78,79,79,80,80,81,81,82,82,82,83,
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};
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void Nes_Dmc::write_register( int addr, int data )
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{
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if ( addr == 0 )
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{
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period = dmc_period_table [pal_mode] [data & 15];
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irq_enabled = (data & 0xC0) == 0x80; // enabled only if loop disabled
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irq_flag &= irq_enabled;
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recalc_irq();
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}
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else if ( addr == 1 )
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{
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int old_dac = dac;
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dac = data & 0x7F;
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// adjust last_amp so that "pop" amplitude will be properly non-linear
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// with respect to change in dac
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int faked_nonlinear = dac - (dac_table [dac] - dac_table [old_dac]);
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if ( !nonlinear )
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last_amp = faked_nonlinear;
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}
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}
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void Nes_Dmc::start()
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{
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reload_sample();
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fill_buffer();
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recalc_irq();
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}
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void Nes_Dmc::fill_buffer()
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{
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if ( !buf_full && length_counter )
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{
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require( prg_reader ); // prg_reader must be set
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buf = prg_reader( prg_reader_data, 0x8000u + address );
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address = (address + 1) & 0x7FFF;
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buf_full = true;
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if ( --length_counter == 0 )
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{
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if ( regs [0] & loop_flag ) {
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reload_sample();
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}
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else {
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apu->osc_enables &= ~0x10;
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irq_flag = irq_enabled;
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next_irq = Nes_Apu::no_irq;
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apu->irq_changed();
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}
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}
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}
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}
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void Nes_Dmc::run( nes_time_t time, nes_time_t end_time )
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{
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int delta = update_amp( dac );
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if ( !output )
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{
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silence = true;
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}
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else
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{
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output->set_modified();
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if ( delta )
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synth.offset( time, delta, output );
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}
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time += delay;
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if ( time < end_time )
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{
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int bits_remain = this->bits_remain;
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if ( silence && !buf_full )
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{
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int count = (end_time - time + period - 1) / period;
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bits_remain = (bits_remain - 1 + 8 - (count % 8)) % 8 + 1;
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time += count * period;
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}
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else
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{
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Blip_Buffer* const output = this->output;
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const int period = this->period;
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int bits = this->bits;
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int dac = this->dac;
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do
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{
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if ( !silence )
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{
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int step = (bits & 1) * 4 - 2;
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bits >>= 1;
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if ( unsigned (dac + step) <= 0x7F ) {
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dac += step;
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synth.offset_inline( time, step, output );
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}
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}
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time += period;
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if ( --bits_remain == 0 )
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{
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bits_remain = 8;
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if ( !buf_full ) {
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silence = true;
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}
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else {
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silence = false;
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bits = buf;
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buf_full = false;
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if ( !output )
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silence = true;
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fill_buffer();
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}
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}
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}
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while ( time < end_time );
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this->dac = dac;
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this->last_amp = dac;
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this->bits = bits;
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}
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this->bits_remain = bits_remain;
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}
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delay = time - end_time;
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}
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// Nes_Noise
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static short const noise_period_table [16] = {
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0x004, 0x008, 0x010, 0x020, 0x040, 0x060, 0x080, 0x0A0,
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0x0CA, 0x0FE, 0x17C, 0x1FC, 0x2FA, 0x3F8, 0x7F2, 0xFE4
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};
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void Nes_Noise::run( nes_time_t time, nes_time_t end_time )
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{
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int period = noise_period_table [regs [2] & 15];
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if ( !output )
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{
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// TODO: clean up
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time += delay;
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delay = time + (end_time - time + period - 1) / period * period - end_time;
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return;
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}
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output->set_modified();
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const int volume = this->volume();
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int amp = (noise & 1) ? volume : 0;
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{
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int delta = update_amp( amp );
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if ( delta )
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synth.offset( time, delta, output );
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}
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time += delay;
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if ( time < end_time )
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{
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const int mode_flag = 0x80;
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if ( !volume )
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{
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// round to next multiple of period
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time += (end_time - time + period - 1) / period * period;
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// approximate noise cycling while muted, by shuffling up noise register
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// to do: precise muted noise cycling?
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if ( !(regs [2] & mode_flag) ) {
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int feedback = (noise << 13) ^ (noise << 14);
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noise = (feedback & 0x4000) | (noise >> 1);
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}
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}
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else
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{
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Blip_Buffer* const output = this->output;
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// using resampled time avoids conversion in synth.offset()
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blip_resampled_time_t rperiod = output->resampled_duration( period );
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blip_resampled_time_t rtime = output->resampled_time( time );
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int noise = this->noise;
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int delta = amp * 2 - volume;
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const int tap = (regs [2] & mode_flag ? 8 : 13);
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do {
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int feedback = (noise << tap) ^ (noise << 14);
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time += period;
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if ( (noise + 1) & 2 ) {
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// bits 0 and 1 of noise differ
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delta = -delta;
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synth.offset_resampled( rtime, delta, output );
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}
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rtime += rperiod;
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noise = (feedback & 0x4000) | (noise >> 1);
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}
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while ( time < end_time );
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last_amp = (delta + volume) >> 1;
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this->noise = noise;
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}
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}
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|
|
delay = time - end_time;
|
|
}
|
|
|