122 lines
3.4 KiB
C++
122 lines
3.4 KiB
C++
// $package. http://www.slack.net/~ant/
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#include "Nes_Fme7_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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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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// 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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dprintf( "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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osc_output->set_modified();
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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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osc_output->set_modified();
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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 += 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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