670 lines
14 KiB
C++
670 lines
14 KiB
C++
// Gb_Snd_Emu 0.2.0. http://www.slack.net/~ant/
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#include "Gb_Apu.h"
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/* Copyright (C) 2003-2007 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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namespace GBA {
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bool const cgb_02 = false; // enables bug in early CGB units that causes problems in some games
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bool const cgb_05 = false; // enables CGB-05 zombie behavior
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int const trigger_mask = 0x80;
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int const length_enabled = 0x40;
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void Gb_Osc::reset()
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{
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output = 0;
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last_amp = 0;
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delay = 0;
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phase = 0;
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enabled = false;
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}
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inline void Gb_Osc::update_amp( blip_time_t time, int new_amp )
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{
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output->set_modified();
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int delta = new_amp - last_amp;
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if ( delta )
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{
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last_amp = new_amp;
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med_synth->offset( time, delta, output );
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}
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}
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// Units
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void Gb_Osc::clock_length()
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{
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if ( (regs [4] & length_enabled) && length_ctr )
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{
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if ( --length_ctr <= 0 )
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enabled = false;
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}
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}
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inline int Gb_Env::reload_env_timer()
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{
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int raw = regs [2] & 7;
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env_delay = (raw ? raw : 8);
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return raw;
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}
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void Gb_Env::clock_envelope()
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{
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if ( env_enabled && --env_delay <= 0 && reload_env_timer() )
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{
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int v = volume + (regs [2] & 0x08 ? +1 : -1);
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if ( 0 <= v && v <= 15 )
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volume = v;
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else
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env_enabled = false;
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}
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}
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inline void Gb_Sweep_Square::reload_sweep_timer()
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{
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sweep_delay = (regs [0] & period_mask) >> 4;
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if ( !sweep_delay )
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sweep_delay = 8;
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}
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void Gb_Sweep_Square::calc_sweep( bool update )
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{
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int const shift = regs [0] & shift_mask;
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int const delta = sweep_freq >> shift;
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sweep_neg = (regs [0] & 0x08) != 0;
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int const freq = sweep_freq + (sweep_neg ? -delta : delta);
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if ( freq > 0x7FF )
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{
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enabled = false;
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}
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else if ( shift && update )
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{
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sweep_freq = freq;
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regs [3] = freq & 0xFF;
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regs [4] = (regs [4] & ~0x07) | (freq >> 8 & 0x07);
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}
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}
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void Gb_Sweep_Square::clock_sweep()
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{
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if ( --sweep_delay <= 0 )
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{
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reload_sweep_timer();
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if ( sweep_enabled && (regs [0] & period_mask) )
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{
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calc_sweep( true );
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calc_sweep( false );
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}
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}
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}
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int Gb_Wave::access( unsigned addr ) const
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{
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if ( enabled && mode != Gb_Apu::mode_agb )
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{
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addr = phase & (bank_size - 1);
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if ( mode == Gb_Apu::mode_dmg )
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{
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addr++;
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if ( delay > clk_mul )
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return -1; // can only access within narrow time window while playing
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}
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addr >>= 1;
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}
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return addr & 0x0F;
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}
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// write_register
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int Gb_Osc::write_trig( int frame_phase, int max_len, int old_data )
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{
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int data = regs [4];
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if ( (frame_phase & 1) && !(old_data & length_enabled) && length_ctr )
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{
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if ( (data & length_enabled) || cgb_02 )
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length_ctr--;
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}
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if ( data & trigger_mask )
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{
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enabled = true;
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if ( !length_ctr )
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{
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length_ctr = max_len;
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if ( (frame_phase & 1) && (data & length_enabled) )
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length_ctr--;
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}
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}
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if ( !length_ctr )
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enabled = false;
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return data & trigger_mask;
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}
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inline void Gb_Env::zombie_volume( int old, int data )
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{
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int v = volume;
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if ( mode == Gb_Apu::mode_agb || cgb_05 )
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{
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// CGB-05 behavior, very close to AGB behavior as well
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if ( (old ^ data) & 8 )
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{
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if ( !(old & 8) )
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{
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v++;
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if ( old & 7 )
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v++;
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}
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v = 16 - v;
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}
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else if ( (old & 0x0F) == 8 )
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{
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v++;
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}
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}
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else
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{
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// CGB-04&02 behavior, very close to MGB behavior as well
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if ( !(old & 7) && env_enabled )
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v++;
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else if ( !(old & 8) )
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v += 2;
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if ( (old ^ data) & 8 )
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v = 16 - v;
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}
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volume = v & 0x0F;
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}
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bool Gb_Env::write_register( int frame_phase, int reg, int old, int data )
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{
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int const max_len = 64;
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switch ( reg )
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{
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case 1:
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length_ctr = max_len - (data & (max_len - 1));
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break;
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case 2:
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if ( !dac_enabled() )
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enabled = false;
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zombie_volume( old, data );
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if ( (data & 7) && env_delay == 8 )
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{
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env_delay = 1;
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clock_envelope(); // TODO: really happens at next length clock
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}
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break;
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case 4:
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if ( write_trig( frame_phase, max_len, old ) )
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{
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volume = regs [2] >> 4;
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reload_env_timer();
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env_enabled = true;
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if ( frame_phase == 7 )
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env_delay++;
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if ( !dac_enabled() )
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enabled = false;
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return true;
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}
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}
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return false;
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}
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bool Gb_Square::write_register( int frame_phase, int reg, int old_data, int data )
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{
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bool result = Gb_Env::write_register( frame_phase, reg, old_data, data );
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if ( result )
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delay = (delay & (4 * clk_mul - 1)) + period();
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return result;
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}
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inline void Gb_Noise::write_register( int frame_phase, int reg, int old_data, int data )
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{
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if ( Gb_Env::write_register( frame_phase, reg, old_data, data ) )
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{
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phase = 0x7FFF;
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delay += 8 * clk_mul;
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}
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}
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inline void Gb_Sweep_Square::write_register( int frame_phase, int reg, int old_data, int data )
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{
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if ( reg == 0 && sweep_enabled && sweep_neg && !(data & 0x08) )
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enabled = false; // sweep negate disabled after used
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if ( Gb_Square::write_register( frame_phase, reg, old_data, data ) )
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{
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sweep_freq = frequency();
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sweep_neg = false;
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reload_sweep_timer();
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sweep_enabled = (regs [0] & (period_mask | shift_mask)) != 0;
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if ( regs [0] & shift_mask )
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calc_sweep( false );
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}
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}
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void Gb_Wave::corrupt_wave()
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{
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int pos = ((phase + 1) & (bank_size - 1)) >> 1;
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if ( pos < 4 )
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wave_ram [0] = wave_ram [pos];
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else
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for ( int i = 4; --i >= 0; )
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wave_ram [i] = wave_ram [(pos & ~3) + i];
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}
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inline void Gb_Wave::write_register( int frame_phase, int reg, int old_data, int data )
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{
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int const max_len = 256;
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switch ( reg )
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{
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case 0:
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if ( !dac_enabled() )
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enabled = false;
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break;
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case 1:
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length_ctr = max_len - data;
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break;
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case 4:
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bool was_enabled = enabled;
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if ( write_trig( frame_phase, max_len, old_data ) )
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{
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if ( !dac_enabled() )
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enabled = false;
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else if ( mode == Gb_Apu::mode_dmg && was_enabled &&
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(unsigned) (delay - 2 * clk_mul) < 2 * clk_mul )
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corrupt_wave();
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phase = 0;
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delay = period() + 6 * clk_mul;
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}
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}
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}
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void Gb_Apu::write_osc( int index, int reg, int old_data, int data )
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{
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reg -= index * 5;
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switch ( index )
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{
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case 0: square1.write_register( frame_phase, reg, old_data, data ); break;
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case 1: square2.write_register( frame_phase, reg, old_data, data ); break;
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case 2: wave .write_register( frame_phase, reg, old_data, data ); break;
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case 3: noise .write_register( frame_phase, reg, old_data, data ); break;
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}
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}
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// Synthesis
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void Gb_Square::run( blip_time_t time, blip_time_t end_time )
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{
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// Calc duty and phase
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static byte const duty_offsets [4] = { 1, 1, 3, 7 };
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static byte const duties [4] = { 1, 2, 4, 6 };
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int const duty_code = regs [1] >> 6;
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int duty_offset = duty_offsets [duty_code];
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int duty = duties [duty_code];
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if ( mode == Gb_Apu::mode_agb )
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{
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// AGB uses inverted duty
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duty_offset -= duty;
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duty = 8 - duty;
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}
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int ph = (this->phase + duty_offset) & 7;
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// Determine what will be generated
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int vol = 0;
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Blip_Buffer* const out = this->output;
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if ( out )
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{
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int amp = dac_off_amp;
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if ( dac_enabled() )
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{
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if ( enabled )
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vol = this->volume;
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amp = -dac_bias;
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if ( mode == Gb_Apu::mode_agb )
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amp = -(vol >> 1);
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// Play inaudible frequencies as constant amplitude
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if ( frequency() >= 0x7FA && delay < 32 * clk_mul )
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{
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amp += (vol * duty) >> 3;
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vol = 0;
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}
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if ( ph < duty )
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{
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amp += vol;
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vol = -vol;
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}
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}
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update_amp( time, amp );
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}
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// Generate wave
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time += delay;
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if ( time < end_time )
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{
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int const per = this->period();
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if ( !vol )
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{
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// Maintain phase when not playing
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blip_long count = (end_time - time + per - 1) / per;
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ph += count; // will be masked below
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time += (blip_time_t) count * per;
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}
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else
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{
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// Output amplitude transitions
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int delta = vol;
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do
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{
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ph = (ph + 1) & 7;
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if ( ph == 0 || ph == duty )
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{
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good_synth->offset_inline( time, delta, out );
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delta = -delta;
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}
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time += per;
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}
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while ( time < end_time );
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if ( delta != vol )
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last_amp -= delta;
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}
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this->phase = (ph - duty_offset) & 7;
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}
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delay = time - end_time;
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}
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// Quickly runs LFSR for a large number of clocks. For use when noise is generating
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// no sound.
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static unsigned run_lfsr( unsigned s, unsigned mask, blip_long count )
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{
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bool const optimized = true; // set to false to use only unoptimized loop in middle
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// optimization used in several places:
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// ((s & (1 << b)) << n) ^ ((s & (1 << b)) << (n + 1)) = (s & (1 << b)) * (3 << n)
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if ( mask == 0x4000 && optimized )
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{
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if ( count >= 32767 )
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count %= 32767;
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// Convert from Fibonacci to Galois configuration,
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// shifted left 1 bit
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s ^= (s & 1) * 0x8000;
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// Each iteration is equivalent to clocking LFSR 255 times
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while ( (count -= 255) > 0 )
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s ^= ((s & 0xE) << 12) ^ ((s & 0xE) << 11) ^ (s >> 3);
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count += 255;
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// Each iteration is equivalent to clocking LFSR 15 times
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// (interesting similarity to single clocking below)
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while ( (count -= 15) > 0 )
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s ^= ((s & 2) * (3 << 13)) ^ (s >> 1);
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count += 15;
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// Remaining singles
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while ( --count >= 0 )
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s = ((s & 2) * (3 << 13)) ^ (s >> 1);
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// Convert back to Fibonacci configuration
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s &= 0x7FFF;
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}
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else if ( count < 8 || !optimized )
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{
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// won't fully replace upper 8 bits, so have to do the unoptimized way
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while ( --count >= 0 )
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s = (s >> 1 | mask) ^ (mask & -((s - 1) & 2));
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}
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else
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{
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if ( count > 127 )
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{
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count %= 127;
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if ( !count )
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count = 127; // must run at least once
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}
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// Need to keep one extra bit of history
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s = s << 1 & 0xFF;
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// Convert from Fibonacci to Galois configuration,
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// shifted left 2 bits
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s ^= (s & 2) * 0x80;
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// Each iteration is equivalent to clocking LFSR 7 times
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// (interesting similarity to single clocking below)
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while ( (count -= 7) > 0 )
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s ^= ((s & 4) * (3 << 5)) ^ (s >> 1);
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count += 7;
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// Remaining singles
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while ( --count >= 0 )
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s = ((s & 4) * (3 << 5)) ^ (s >> 1);
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// Convert back to Fibonacci configuration and
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// repeat last 8 bits above significant 7
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s = (s << 7 & 0x7F80) | (s >> 1 & 0x7F);
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}
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return s;
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}
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void Gb_Noise::run( blip_time_t time, blip_time_t end_time )
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{
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// Determine what will be generated
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int vol = 0;
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Blip_Buffer* const out = this->output;
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if ( out )
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{
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int amp = dac_off_amp;
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if ( dac_enabled() )
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{
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if ( enabled )
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vol = this->volume;
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amp = -dac_bias;
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if ( mode == Gb_Apu::mode_agb )
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amp = -(vol >> 1);
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if ( !(phase & 1) )
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{
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amp += vol;
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vol = -vol;
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}
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}
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// AGB negates final output
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if ( mode == Gb_Apu::mode_agb )
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{
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vol = -vol;
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amp = -amp;
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}
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update_amp( time, amp );
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}
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// Run timer and calculate time of next LFSR clock
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static byte const period1s [8] = { 1, 2, 4, 6, 8, 10, 12, 14 };
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int const period1 = period1s [regs [3] & 7] * clk_mul;
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{
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blip_long extra = (end_time - time) - delay;
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int const per2 = this->period2();
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time += delay + ((divider ^ (per2 >> 1)) & (per2 - 1)) * period1;
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blip_long count = (extra < 0 ? 0 : (extra + period1 - 1) / period1);
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divider = (divider - count) & period2_mask;
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delay = count * period1 - extra;
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}
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// Generate wave
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if ( time < end_time )
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{
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unsigned const mask = this->lfsr_mask();
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unsigned bits = this->phase;
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int per = period2( period1 * 8 );
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if ( period2_index() >= 0xE )
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{
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time = end_time;
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}
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else if ( !vol )
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{
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// Maintain phase when not playing
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blip_long count = (end_time - time + per - 1) / per;
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time += (blip_time_t) count * per;
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bits = run_lfsr( bits, ~mask, count );
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}
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else
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{
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// Output amplitude transitions
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int delta = -vol;
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do
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{
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unsigned changed = bits + 1;
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bits = bits >> 1 & mask;
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if ( changed & 2 )
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{
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bits |= ~mask;
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delta = -delta;
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med_synth->offset_inline( time, delta, out );
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}
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time += per;
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}
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while ( time < end_time );
|
|
|
|
if ( delta == vol )
|
|
last_amp += delta;
|
|
}
|
|
this->phase = bits;
|
|
}
|
|
}
|
|
|
|
void Gb_Wave::run( blip_time_t time, blip_time_t end_time )
|
|
{
|
|
// Calc volume
|
|
static byte const volumes [8] = { 0, 4, 2, 1, 3, 3, 3, 3 };
|
|
int const volume_shift = 2;
|
|
int const volume_idx = regs [2] >> 5 & (agb_mask | 3); // 2 bits on DMG/CGB, 3 on AGB
|
|
int const volume_mul = volumes [volume_idx];
|
|
|
|
// Determine what will be generated
|
|
int playing = false;
|
|
Blip_Buffer* const out = this->output;
|
|
if ( out )
|
|
{
|
|
int amp = dac_off_amp;
|
|
if ( dac_enabled() )
|
|
{
|
|
// Play inaudible frequencies as constant amplitude
|
|
amp = 8 << 4; // really depends on average of all samples in wave
|
|
|
|
// if delay is larger, constant amplitude won't start yet
|
|
if ( frequency() <= 0x7FB || delay > 15 * clk_mul )
|
|
{
|
|
if ( volume_mul )
|
|
playing = (int) enabled;
|
|
|
|
amp = (sample_buf << (phase << 2 & 4) & 0xF0) * playing;
|
|
}
|
|
|
|
amp = ((amp * volume_mul) >> (volume_shift + 4)) - dac_bias;
|
|
}
|
|
update_amp( time, amp );
|
|
}
|
|
|
|
// Generate wave
|
|
time += delay;
|
|
if ( time < end_time )
|
|
{
|
|
byte const* wave = this->wave_ram;
|
|
|
|
// wave size and bank
|
|
int const size20_mask = 0x20;
|
|
int const flags = regs [0] & agb_mask;
|
|
int const wave_mask = (flags & size20_mask) | 0x1F;
|
|
int swap_banks = 0;
|
|
if ( flags & bank40_mask )
|
|
{
|
|
swap_banks = flags & size20_mask;
|
|
wave += bank_size/2 - (swap_banks >> 1);
|
|
}
|
|
|
|
int ph = this->phase ^ swap_banks;
|
|
ph = (ph + 1) & wave_mask; // pre-advance
|
|
|
|
int const per = this->period();
|
|
if ( !playing )
|
|
{
|
|
// Maintain phase when not playing
|
|
blip_long count = (end_time - time + per - 1) / per;
|
|
ph += count; // will be masked below
|
|
time += (blip_time_t) count * per;
|
|
}
|
|
else
|
|
{
|
|
// Output amplitude transitions
|
|
int lamp = this->last_amp + dac_bias;
|
|
do
|
|
{
|
|
// Extract nybble
|
|
int nybble = wave [ph >> 1] << (ph << 2 & 4) & 0xF0;
|
|
ph = (ph + 1) & wave_mask;
|
|
|
|
// Scale by volume
|
|
int amp = (nybble * volume_mul) >> (volume_shift + 4);
|
|
|
|
int delta = amp - lamp;
|
|
if ( delta )
|
|
{
|
|
lamp = amp;
|
|
med_synth->offset_inline( time, delta, out );
|
|
}
|
|
time += per;
|
|
}
|
|
while ( time < end_time );
|
|
this->last_amp = lamp - dac_bias;
|
|
}
|
|
ph = (ph - 1) & wave_mask; // undo pre-advance and mask position
|
|
|
|
// Keep track of last byte read
|
|
if ( enabled )
|
|
sample_buf = wave [ph >> 1];
|
|
|
|
this->phase = ph ^ swap_banks; // undo swapped banks
|
|
}
|
|
delay = time - end_time;
|
|
}
|
|
|
|
}
|