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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.
121 lines
3.3 KiB
C++
121 lines
3.3 KiB
C++
// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/
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#include "Nes_Fme7_Apu.h"
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#include <string.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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void Nes_Fme7_Apu::reset()
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{
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last_time = 0;
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for ( int i = 0; i < osc_count; i++ )
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oscs [i].last_amp = 0;
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fme7_apu_state_t* state = this;
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memset( state, 0, sizeof *state );
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}
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unsigned char const Nes_Fme7_Apu::amp_table [16] =
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{
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#define ENTRY( n ) (unsigned char) (n * amp_range + 0.5)
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ENTRY(0.0000), ENTRY(0.0078), ENTRY(0.0110), ENTRY(0.0156),
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ENTRY(0.0221), ENTRY(0.0312), ENTRY(0.0441), ENTRY(0.0624),
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ENTRY(0.0883), ENTRY(0.1249), ENTRY(0.1766), ENTRY(0.2498),
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ENTRY(0.3534), ENTRY(0.4998), ENTRY(0.7070), ENTRY(1.0000)
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#undef ENTRY
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};
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void Nes_Fme7_Apu::run_until( blip_time_t end_time )
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{
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require( end_time >= last_time );
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for ( int index = 0; index < osc_count; index++ )
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{
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int mode = regs [7] >> index;
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int vol_mode = regs [010 + index];
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int volume = amp_table [vol_mode & 0x0F];
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Blip_Buffer* const osc_output = oscs [index].output;
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if ( !osc_output )
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continue;
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osc_output->set_modified();
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// check for unsupported mode
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#ifndef NDEBUG
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if ( (mode & 011) <= 001 && vol_mode & 0x1F )
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debug_printf( "FME7 used unimplemented sound mode: %02X, vol_mode: %02X\n",
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mode, vol_mode & 0x1F );
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#endif
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if ( (mode & 001) | (vol_mode & 0x10) )
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volume = 0; // noise and envelope aren't supported
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// period
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int const period_factor = 16;
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unsigned period = (regs [index * 2 + 1] & 0x0F) * 0x100 * period_factor +
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regs [index * 2] * period_factor;
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if ( period < 50 ) // around 22 kHz
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{
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volume = 0;
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if ( !period ) // on my AY-3-8910A, period doesn't have extra one added
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period = period_factor;
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}
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// current amplitude
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int amp = volume;
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if ( !phases [index] )
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amp = 0;
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{
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int delta = amp - oscs [index].last_amp;
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if ( delta )
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{
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oscs [index].last_amp = amp;
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synth.offset( last_time, delta, osc_output );
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}
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}
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blip_time_t time = last_time + delays [index];
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if ( time < end_time )
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{
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int delta = amp * 2 - volume;
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if ( volume )
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{
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do
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{
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delta = -delta;
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synth.offset_inline( time, delta, osc_output );
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time += period;
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}
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while ( time < end_time );
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oscs [index].last_amp = (delta + volume) >> 1;
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phases [index] = (delta > 0);
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}
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else
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{
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// maintain phase when silent
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int count = (end_time - time + period - 1) / period;
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phases [index] ^= count & 1;
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time += (blargg_long) count * period;
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}
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}
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delays [index] = time - end_time;
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}
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last_time = end_time;
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}
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