cog/Frameworks/GME/gme/Sms_Apu.cpp

372 lines
8.7 KiB
C++

// Sms_Snd_Emu $vers. http://www.slack.net/~ant/
#include "Sms_Apu.h"
/* Copyright (C) 2003-2008 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"
int const noise_osc = 3;
void Sms_Apu::volume( double vol )
{
vol *= 0.85 / osc_count / 64;
norm_synth.volume( vol );
fast_synth.volume( vol );
}
void Sms_Apu::treble_eq( blip_eq_t const& eq )
{
norm_synth.treble_eq( eq );
fast_synth.treble_eq( eq );
}
inline int Sms_Apu::calc_output( int i ) const
{
int flags = ggstereo >> i;
return (flags >> 3 & 2) | (flags & 1);
}
void Sms_Apu::set_output( int i, Blip_Buffer* center, Blip_Buffer* left, Blip_Buffer* right )
{
// Must be silent (all NULL), mono (left and right NULL), or stereo (none NULL)
require( !center || (center && !left && !right) || (center && left && right) );
require( (unsigned) i < osc_count ); // fails if you pass invalid osc index
if ( center )
{
unsigned const divisor = 16384 * 16 * 2;
min_tone_period = ((unsigned) center->clock_rate() + divisor/2) / divisor;
}
if ( !center || !left || !right )
{
left = center;
right = center;
}
Osc& o = oscs [i];
o.outputs [0] = NULL;
o.outputs [1] = right;
o.outputs [2] = left;
o.outputs [3] = center;
o.output = o.outputs [calc_output( i )];
}
void Sms_Apu::set_output( Blip_Buffer* c, Blip_Buffer* l, Blip_Buffer* r )
{
for ( int i = osc_count; --i >= 0; )
set_output( i, c, l, r );
}
static inline unsigned fibonacci_to_galois_lfsr( unsigned fibonacci, int width )
{
unsigned galois = 0;
while ( --width >= 0 )
{
galois = (galois << 1) | (fibonacci & 1);
fibonacci >>= 1;
}
return galois;
}
void Sms_Apu::reset( unsigned feedback, int noise_width )
{
last_time = 0;
latch = 0;
ggstereo = 0;
// Calculate noise feedback values
if ( !feedback || !noise_width )
{
feedback = 0x0009;
noise_width = 16;
}
looped_feedback = 1 << (noise_width - 1);
noise_feedback = fibonacci_to_galois_lfsr( feedback, noise_width );
// Reset oscs
for ( int i = osc_count; --i >= 0; )
{
Osc& o = oscs [i];
o.output = NULL;
o.last_amp = 0;
o.delay = 0;
o.phase = 0;
o.period = 0;
o.volume = 15; // silent
}
oscs [noise_osc].phase = 0x8000;
write_ggstereo( 0, 0xFF );
}
Sms_Apu::Sms_Apu()
{
min_tone_period = 7;
// Clear outputs to NULL FIRST
ggstereo = 0;
set_output( NULL );
volume( 1.0 );
reset();
}
void Sms_Apu::run_until( blip_time_t end_time )
{
require( end_time >= last_time );
if ( end_time <= last_time )
return;
// Synthesize each oscillator
for ( int idx = osc_count; --idx >= 0; )
{
Osc& osc = oscs [idx];
int vol = 0;
int amp = 0;
// Determine what will be generated
Blip_Buffer* const out = osc.output;
if ( out )
{
// volumes [i] ~= 64 * pow( 1.26, 15 - i ) / pow( 1.26, 15 )
static unsigned char const volumes [16] = {
64, 50, 40, 32, 25, 20, 16, 13, 10, 8, 6, 5, 4, 3, 2, 0
};
vol = volumes [osc.volume];
amp = (osc.phase & 1) * vol;
// Square freq above 16 kHz yields constant amplitude at half volume
if ( idx != noise_osc && osc.period < min_tone_period )
{
amp = vol >> 1;
vol = 0;
}
// Update amplitude
int delta = amp - osc.last_amp;
if ( delta )
{
osc.last_amp = amp;
norm_synth.offset( last_time, delta, out );
out->set_modified();
}
}
// Generate wave
blip_time_t time = last_time + osc.delay;
if ( time < end_time )
{
// Calculate actual period
int period = osc.period;
if ( idx == noise_osc )
{
period = 0x20 << (period & 3);
if ( period == 0x100 )
period = oscs [2].period * 2;
}
period *= 0x10;
if ( !period )
period = 0x10;
// Maintain phase when silent
int phase = osc.phase;
if ( !vol )
{
int count = (end_time - time + period - 1) / period;
time += count * period;
if ( idx != noise_osc ) // TODO: maintain noise LFSR phase?
phase ^= count & 1;
}
else
{
int delta = amp * 2 - vol;
if ( idx != noise_osc )
{
// Square
do
{
delta = -delta;
norm_synth.offset( time, delta, out );
time += period;
}
while ( time < end_time );
phase = (delta >= 0);
}
else
{
// Noise
unsigned const feedback = (osc.period & 4 ? noise_feedback : looped_feedback);
do
{
unsigned changed = phase + 1;
phase = ((phase & 1) * feedback) ^ (phase >> 1);
if ( changed & 2 ) // true if bits 0 and 1 differ
{
delta = -delta;
fast_synth.offset_inline( time, delta, out );
}
time += period;
}
while ( time < end_time );
check( phase );
}
osc.last_amp = (phase & 1) * vol;
out->set_modified();
}
osc.phase = phase;
}
osc.delay = time - end_time;
}
last_time = end_time;
}
void Sms_Apu::write_ggstereo( blip_time_t time, int data )
{
require( (unsigned) data <= 0xFF );
run_until( time );
ggstereo = data;
for ( int i = osc_count; --i >= 0; )
{
Osc& osc = oscs [i];
Blip_Buffer* old = osc.output;
osc.output = osc.outputs [calc_output( i )];
if ( osc.output != old )
{
int delta = -osc.last_amp;
if ( delta )
{
osc.last_amp = 0;
if ( old )
{
old->set_modified();
fast_synth.offset( last_time, delta, old );
}
}
}
}
}
void Sms_Apu::write_data( blip_time_t time, int data )
{
require( (unsigned) data <= 0xFF );
run_until( time );
if ( data & 0x80 )
latch = data;
// We want the raw values written so our save state format can be
// as close to hardware as possible and unspecific to any emulator.
int idx = latch >> 5 & 3;
Osc& osc = oscs [idx];
if ( latch & 0x10 )
{
osc.volume = data & 0x0F;
}
else
{
if ( idx == noise_osc )
osc.phase = 0x8000; // reset noise LFSR
// Replace high 6 bits/low 4 bits of register with data
int lo = osc.period;
int hi = data << 4;
if ( idx == noise_osc || (data & 0x80) )
{
hi = lo;
lo = data;
}
osc.period = (hi & 0x3F0) | (lo & 0x00F);
}
}
void Sms_Apu::end_frame( blip_time_t end_time )
{
if ( end_time > last_time )
run_until( end_time );
last_time -= end_time;
assert( last_time >= 0 );
}
#if SMS_APU_CUSTOM_STATE
#define REFLECT( x, y ) (save ? (io->y) = (x) : (x) = (io->y) )
#else
#define REFLECT( x, y ) (save ? set_val( io->y, x ) : (void) ((x) = get_val( io->y )))
static unsigned get_val( byte const p [] )
{
return p [3] * 0x1000000 + p [2] * 0x10000 + p [1] * 0x100 + p [0];
}
static void set_val( byte p [], unsigned n )
{
p [0] = (byte) (n );
p [1] = (byte) (n >> 8);
p [2] = (byte) (n >> 16);
p [3] = (byte) (n >> 24);
}
#endif
inline const char* Sms_Apu::save_load( sms_apu_state_t* io, bool save )
{
#if !SMS_APU_CUSTOM_STATE
assert( sizeof (sms_apu_state_t) == 128 );
#endif
// Format of data, where later format is incompatible with earlier
int format = io->format0;
REFLECT( format, format );
if ( format != io->format0 )
return "Unsupported sound save state format";
// Version of data, where later versions just add fields to the end
int version = 0;
REFLECT( version, version );
REFLECT( latch, latch );
REFLECT( ggstereo, ggstereo );
for ( int i = osc_count; --i >= 0; )
{
Osc& osc = oscs [i];
REFLECT( osc.period, periods [i] );
REFLECT( osc.volume, volumes [i] );
REFLECT( osc.delay, delays [i] );
REFLECT( osc.phase, phases [i] );
}
return 0;
}
void Sms_Apu::save_state( sms_apu_state_t* out )
{
save_load( out, true );
#if !SMS_APU_CUSTOM_STATE
memset( out->unused, 0, sizeof out->unused );
#endif
}
blargg_err_t Sms_Apu::load_state( sms_apu_state_t const& in )
{
RETURN_ERR( save_load( CONST_CAST(sms_apu_state_t*,&in), false ) );
write_ggstereo( 0, ggstereo );
return blargg_ok;
}