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