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// Game_Music_Emu 0.5.5. http://www.slack.net/~ant/
#include "nes_fme7_apu.h"
#include <string.h>
/* Copyright (C) 2003-2006 Shay Green. This module is free software; you
can redistribute it and/or modify it under the terms of the GNU Lesser
General Public License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version. This
module is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
details. You should have received a copy of the GNU Lesser General Public
License along with this module; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */
#include "blargg_source.h"
void Fme7_init( struct Nes_Fme7_Apu* this )
{
Synth_init( &this->synth );
Fme7_output( this, NULL );
Fme7_volume( this, (int)FP_ONE_VOLUME );
Fme7_reset( this );
}
void Fme7_reset( struct Nes_Fme7_Apu* this )
{
this->last_time = 0;
int i;
for ( i = 0; i < fme7_osc_count; i++ )
this->oscs [i].last_amp = 0;
this->latch = 0;
memset( this->regs, 0, sizeof this->regs);
memset( this->phases, 0, sizeof this->phases );
memset( this->delays, 0, sizeof this->delays );
}
static unsigned char const amp_table [16] =
{
#define ENTRY( n ) (unsigned char) (n * amp_range + 0.5)
ENTRY(0.0000), ENTRY(0.0078), ENTRY(0.0110), ENTRY(0.0156),
ENTRY(0.0221), ENTRY(0.0312), ENTRY(0.0441), ENTRY(0.0624),
ENTRY(0.0883), ENTRY(0.1249), ENTRY(0.1766), ENTRY(0.2498),
ENTRY(0.3534), ENTRY(0.4998), ENTRY(0.7070), ENTRY(1.0000)
#undef ENTRY
};
void Fme7_run_until( struct Nes_Fme7_Apu* this, blip_time_t end_time )
{
require( end_time >= this->last_time );
int index;
for ( index = 0; index < fme7_osc_count; index++ )
{
int mode = this->regs [7] >> index;
int vol_mode = this->regs [010 + index];
int volume = amp_table [vol_mode & 0x0F];
struct Blip_Buffer* const osc_output = this->oscs [index].output;
if ( !osc_output )
continue;
// check for unsupported mode
#ifndef NDEBUG
if ( (mode & 011) <= 001 && vol_mode & 0x1F )
debug_printf( "FME7 used unimplemented sound mode: %02X, vol_mode: %02X\n",
mode, vol_mode & 0x1F );
#endif
if ( (mode & 001) | (vol_mode & 0x10) )
volume = 0; // noise and envelope aren't supported
// period
int const period_factor = 16;
unsigned period = (this->regs [index * 2 + 1] & 0x0F) * 0x100 * period_factor +
this->regs [index * 2] * period_factor;
if ( period < 50 ) // around 22 kHz
{
volume = 0;
if ( !period ) // on my AY-3-8910A, period doesn't have extra one added
period = period_factor;
}
// current amplitude
int amp = volume;
if ( !this->phases [index] )
amp = 0;
{
int delta = amp - this->oscs [index].last_amp;
if ( delta )
{
this->oscs [index].last_amp = amp;
Blip_set_modified( osc_output );
Synth_offset( &this->synth, this->last_time, delta, osc_output );
}
}
blip_time_t time = this->last_time + this->delays [index];
if ( time < end_time )
{
int delta = amp * 2 - volume;
Blip_set_modified( osc_output );
if ( volume )
{
do
{
delta = -delta;
Synth_offset_inline( &this->synth, time, delta, osc_output );
time += period;
}
while ( time < end_time );
this->oscs [index].last_amp = (delta + volume) >> 1;
this->phases [index] = (delta > 0);
}
else
{
// maintain phase when silent
int count = (end_time - time + period - 1) / period;
this->phases [index] ^= count & 1;
time += count * period;
}
}
this->delays [index] = time - end_time;
}
this->last_time = end_time;
}
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