150 lines
4.1 KiB
C++
150 lines
4.1 KiB
C++
// Nes_Snd_Emu $vers. http://www.slack.net/~ant/
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#include "Nes_Namco_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_Namco_Apu::Nes_Namco_Apu()
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{
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set_output( NULL );
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volume( 1.0 );
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reset();
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}
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void Nes_Namco_Apu::reset()
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{
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last_time = 0;
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addr_reg = 0;
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int i;
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for ( i = 0; i < reg_count; i++ )
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reg [i] = 0;
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for ( i = 0; i < osc_count; i++ )
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{
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Namco_Osc& osc = oscs [i];
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osc.delay = 0;
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osc.last_amp = 0;
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}
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}
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void Nes_Namco_Apu::set_output( Blip_Buffer* buf )
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{
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for ( int i = 0; i < osc_count; ++i )
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set_output( i, buf );
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}
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/*
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void Nes_Namco_Apu::reflect_state( Tagged_Data& data )
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{
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reflect_int16( data, BLARGG_4CHAR('A','D','D','R'), &addr_reg );
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static const char hex [17] = "0123456789ABCDEF";
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int i;
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for ( i = 0; i < reg_count; i++ )
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reflect_int16( data, 'RG\0\0' + hex [i >> 4] * 0x100 + hex [i & 15], ® [i] );
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for ( i = 0; i < osc_count; i++ )
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{
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reflect_int32( data, BLARGG_4CHAR('D','L','Y','0') + i, &oscs [i].delay );
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reflect_int16( data, BLARGG_4CHAR('P','O','S','0') + i, &oscs [i].wave_pos );
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}
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}
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*/
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void Nes_Namco_Apu::end_frame( blip_time_t time )
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{
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if ( time > last_time )
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run_until( time );
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assert( last_time >= time );
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last_time -= time;
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}
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void Nes_Namco_Apu::run_until( blip_time_t nes_end_time )
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{
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int active_oscs = (reg [0x7F] >> 4 & 7) + 1;
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for ( int i = osc_count - active_oscs; i < osc_count; i++ )
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{
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Namco_Osc& osc = oscs [i];
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Blip_Buffer* output = osc.output;
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if ( !output )
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continue;
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blip_resampled_time_t time =
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output->resampled_time( last_time ) + osc.delay;
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blip_resampled_time_t end_time = output->resampled_time( nes_end_time );
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osc.delay = 0;
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if ( time < end_time )
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{
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const BOOST::uint8_t* osc_reg = ® [i * 8 + 0x40];
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if ( !(osc_reg [4] & 0xE0) )
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continue;
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int volume = osc_reg [7] & 15;
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if ( !volume )
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continue;
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int freq = (osc_reg [4] & 3) * 0x10000 + osc_reg [2] * 0x100 + osc_reg [0];
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if ( freq < 64 * active_oscs )
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continue; // prevent low frequencies from excessively delaying freq changes
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int const master_clock_divider = 12; // NES time derived via divider of master clock
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int const n106_divider = 45; // N106 then divides master clock by this
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int const max_freq = 0x3FFFF;
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int const lowest_freq_period = (max_freq + 1) * n106_divider / master_clock_divider;
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// divide by 8 to avoid overflow
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blip_resampled_time_t period =
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output->resampled_duration( lowest_freq_period / 8 ) / freq * 8 * active_oscs;
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int wave_size = 256 - (osc_reg [4] & 0xFC);
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int last_amp = osc.last_amp;
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int wave_pos = osc_reg [5] % wave_size;
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output->set_modified();
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do
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{
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// read wave sample
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int addr = (wave_pos + osc_reg [6]) & 0xFF;
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int sample = reg [addr >> 1] >> (addr << 2 & 4);
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wave_pos++;
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sample = (sample & 15) * volume;
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// output impulse if amplitude changed
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int delta = sample - last_amp;
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if ( delta )
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{
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last_amp = sample;
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synth.offset_resampled( time, delta, output );
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}
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// next sample
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time += period;
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if ( wave_pos >= wave_size )
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wave_pos = 0;
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}
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while ( time < end_time );
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((BOOST::uint8_t*)osc_reg)[5] = wave_pos;
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osc.last_amp = last_amp;
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}
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osc.delay = time - end_time;
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}
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last_time = nes_end_time;
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}
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