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718112a8fe
Currently none of these is being used, but eventually they will, once more code gets ported over. So it's better to have them right away and avoid editing the project file too much, only to revert that later.
334 lines
8.5 KiB
C++
334 lines
8.5 KiB
C++
// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/
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#include "Sap_Apu.h"
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#include <string.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 max_frequency = 12000; // pure waves above this frequency are silenced
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static void gen_poly( blargg_ulong mask, int count, byte* out )
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{
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blargg_ulong n = 1;
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do
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{
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int bits = 0;
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int b = 0;
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do
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{
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// implemented using "Galios configuration"
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bits |= (n & 1) << b;
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n = (n >> 1) ^ (mask & -(n & 1));
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}
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while ( b++ < 7 );
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*out++ = bits;
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}
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while ( --count );
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}
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// poly5
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int const poly5_len = (1 << 5) - 1;
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blargg_ulong const poly5_mask = (1UL << poly5_len) - 1;
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blargg_ulong const poly5 = 0x167C6EA1;
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inline blargg_ulong run_poly5( blargg_ulong in, int shift )
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{
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return (in << shift & poly5_mask) | (in >> (poly5_len - shift));
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}
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#define POLY_MASK( width, tap1, tap2 ) \
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((1UL << (width - 1 - tap1)) | (1UL << (width - 1 - tap2)))
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Sap_Apu_Impl::Sap_Apu_Impl()
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{
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gen_poly( POLY_MASK( 4, 1, 0 ), sizeof poly4, poly4 );
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gen_poly( POLY_MASK( 9, 5, 0 ), sizeof poly9, poly9 );
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gen_poly( POLY_MASK( 17, 5, 0 ), sizeof poly17, poly17 );
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if ( 0 ) // comment out to recauculate poly5 constant
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{
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byte poly5 [4];
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gen_poly( POLY_MASK( 5, 2, 0 ), sizeof poly5, poly5 );
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blargg_ulong n = poly5 [3] * 0x1000000L + poly5 [2] * 0x10000L +
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poly5 [1] * 0x100L + poly5 [0];
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blargg_ulong rev = n & 1;
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for ( int i = 1; i < poly5_len; i++ )
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rev |= (n >> i & 1) << (poly5_len - i);
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debug_printf( "poly5: 0x%08lX\n", rev );
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}
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}
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Sap_Apu::Sap_Apu()
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{
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impl = 0;
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for ( int i = 0; i < osc_count; i++ )
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osc_output( i, 0 );
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}
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void Sap_Apu::reset( Sap_Apu_Impl* new_impl )
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{
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impl = new_impl;
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last_time = 0;
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poly5_pos = 0;
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poly4_pos = 0;
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polym_pos = 0;
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control = 0;
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for ( int i = 0; i < osc_count; i++ )
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memset( &oscs [i], 0, offsetof (osc_t,output) );
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}
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inline void Sap_Apu::calc_periods()
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{
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// 15/64 kHz clock
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int divider = 28;
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if ( this->control & 1 )
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divider = 114;
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for ( int i = 0; i < osc_count; i++ )
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{
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osc_t* const osc = &oscs [i];
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int const osc_reload = osc->regs [0]; // cache
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blargg_long period = (osc_reload + 1) * divider;
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static byte const fast_bits [osc_count] = { 1 << 6, 1 << 4, 1 << 5, 1 << 3 };
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if ( this->control & fast_bits [i] )
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{
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period = osc_reload + 4;
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if ( i & 1 )
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{
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period = osc_reload * 0x100L + osc [-1].regs [0] + 7;
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if ( !(this->control & fast_bits [i - 1]) )
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period = (period - 6) * divider;
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if ( (osc [-1].regs [1] & 0x1F) > 0x10 )
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debug_printf( "Use of slave channel in 16-bit mode not supported\n" );
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}
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}
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osc->period = period;
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}
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}
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void Sap_Apu::run_until( blip_time_t end_time )
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{
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calc_periods();
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Sap_Apu_Impl* const impl = this->impl; // cache
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// 17/9-bit poly selection
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byte const* polym = impl->poly17;
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int polym_len = poly17_len;
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if ( this->control & 0x80 )
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{
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polym_len = poly9_len;
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polym = impl->poly9;
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}
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polym_pos %= polym_len;
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for ( int i = 0; i < osc_count; i++ )
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{
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osc_t* const osc = &oscs [i];
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blip_time_t time = last_time + osc->delay;
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blip_time_t const period = osc->period;
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// output
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Blip_Buffer* output = osc->output;
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if ( output )
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{
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output->set_modified();
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int const osc_control = osc->regs [1]; // cache
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int volume = (osc_control & 0x0F) * 2;
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if ( !volume || osc_control & 0x10 || // silent, DAC mode, or inaudible frequency
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((osc_control & 0xA0) == 0xA0 && period < 1789773 / 2 / max_frequency) )
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{
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if ( !(osc_control & 0x10) )
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volume >>= 1; // inaudible frequency = half volume
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int delta = volume - osc->last_amp;
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if ( delta )
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{
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osc->last_amp = volume;
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impl->synth.offset( last_time, delta, output );
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}
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// TODO: doesn't maintain high pass flip-flop (very minor issue)
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}
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else
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{
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// high pass
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static byte const hipass_bits [osc_count] = { 1 << 2, 1 << 1, 0, 0 };
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blip_time_t period2 = 0; // unused if no high pass
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blip_time_t time2 = end_time;
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if ( this->control & hipass_bits [i] )
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{
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period2 = osc [2].period;
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time2 = last_time + osc [2].delay;
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if ( osc->invert )
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{
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// trick inner wave loop into inverting output
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osc->last_amp -= volume;
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volume = -volume;
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}
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}
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if ( time < end_time || time2 < end_time )
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{
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// poly source
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static byte const poly1 [] = { 0x55, 0x55 }; // square wave
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byte const* poly = poly1;
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int poly_len = 8 * sizeof poly1; // can be just 2 bits, but this is faster
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int poly_pos = osc->phase & 1;
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int poly_inc = 1;
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if ( !(osc_control & 0x20) )
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{
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poly = polym;
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poly_len = polym_len;
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poly_pos = polym_pos;
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if ( osc_control & 0x40 )
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{
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poly = impl->poly4;
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poly_len = poly4_len;
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poly_pos = poly4_pos;
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}
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poly_inc = period % poly_len;
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poly_pos = (poly_pos + osc->delay) % poly_len;
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}
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poly_inc -= poly_len; // allows more optimized inner loop below
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// square/poly5 wave
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blargg_ulong wave = poly5;
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check( poly5 & 1 ); // low bit is set for pure wave
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int poly5_inc = 0;
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if ( !(osc_control & 0x80) )
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{
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wave = run_poly5( wave, (osc->delay + poly5_pos) % poly5_len );
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poly5_inc = period % poly5_len;
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}
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// Run wave and high pass interleved with each catching up to the other.
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// Disabled high pass has no performance effect since inner wave loop
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// makes no compromise for high pass, and only runs once in that case.
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int osc_last_amp = osc->last_amp;
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do
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{
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// run high pass
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if ( time2 < time )
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{
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int delta = -osc_last_amp;
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if ( volume < 0 )
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delta += volume;
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if ( delta )
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{
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osc_last_amp += delta - volume;
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volume = -volume;
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impl->synth.offset( time2, delta, output );
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}
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}
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while ( time2 <= time ) // must advance *past* time to avoid hang
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time2 += period2;
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// run wave
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blip_time_t end = end_time;
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if ( end > time2 )
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end = time2;
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while ( time < end )
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{
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if ( wave & 1 )
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{
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int amp = volume & -(poly [poly_pos >> 3] >> (poly_pos & 7) & 1);
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if ( (poly_pos += poly_inc) < 0 )
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poly_pos += poly_len;
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int delta = amp - osc_last_amp;
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if ( delta )
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{
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osc_last_amp = amp;
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impl->synth.offset( time, delta, output );
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}
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}
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wave = run_poly5( wave, poly5_inc );
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time += period;
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}
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}
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while ( time < end_time || time2 < end_time );
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osc->phase = poly_pos;
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osc->last_amp = osc_last_amp;
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}
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osc->invert = 0;
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if ( volume < 0 )
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{
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// undo inversion trickery
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osc->last_amp -= volume;
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osc->invert = 1;
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}
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}
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}
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// maintain divider
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blip_time_t remain = end_time - time;
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if ( remain > 0 )
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{
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blargg_long count = (remain + period - 1) / period;
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osc->phase ^= count;
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time += count * period;
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}
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osc->delay = time - end_time;
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}
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// advance polies
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blip_time_t duration = end_time - last_time;
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last_time = end_time;
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poly4_pos = (poly4_pos + duration) % poly4_len;
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poly5_pos = (poly5_pos + duration) % poly5_len;
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polym_pos += duration; // will get %'d on next call
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}
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void Sap_Apu::write_data( blip_time_t time, unsigned addr, int data )
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{
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run_until( time );
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int i = (addr ^ 0xD200) >> 1;
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if ( i < osc_count )
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{
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oscs [i].regs [addr & 1] = data;
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}
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else if ( addr == 0xD208 )
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{
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control = data;
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}
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else if ( addr == 0xD209 )
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{
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oscs [0].delay = 0;
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oscs [1].delay = 0;
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oscs [2].delay = 0;
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oscs [3].delay = 0;
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}
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/*
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// TODO: are polynomials reset in this case?
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else if ( addr == 0xD20F )
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{
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if ( (data & 3) == 0 )
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polym_pos = 0;
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}
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*/
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}
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void Sap_Apu::end_frame( blip_time_t end_time )
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{
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if ( end_time > last_time )
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run_until( end_time );
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last_time -= end_time;
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}
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