Merge from raven-branch.

Subversion-branch: /branches/strife-branch
Subversion-revision: 2051

20 files changed, 4662 insertions, 0 deletions

diff --git a/opl/.gitignore b/opl/.gitignore
new file mode 100644
index 00000000..8aac4e77
--- /dev/null
+++ b/opl/.gitignore
@@ -0,0 +1,7 @@
+Makefile.in
+Makefile
+.deps
+libopl.a
+*.rc
+tags
+TAGS
diff --git a/opl/Makefile.am b/opl/Makefile.am
new file mode 100644
index 00000000..be1619d8
--- /dev/null
+++ b/opl/Makefile.am
@@ -0,0 +1,19 @@
+
+AM_CFLAGS=@SDLMIXER_CFLAGS@
+
+SUBDIRS = . examples
+
+noinst_LIBRARIES=libopl.a
+
+libopl_a_SOURCES =                                \
+                            opl_internal.h        \
+        opl.c               opl.h                 \
+        opl_linux.c                               \
+        opl_obsd.c                                \
+        opl_queue.c         opl_queue.h           \
+        opl_sdl.c                                 \
+        opl_timer.c         opl_timer.h           \
+        opl_win32.c                               \
+        ioperm_sys.c        ioperm_sys.h          \
+        dbopl.c             dbopl.h
+
diff --git a/opl/dbopl.c b/opl/dbopl.c
new file mode 100644
index 00000000..159cae45
--- /dev/null
+++ b/opl/dbopl.c
@@ -0,0 +1,1602 @@
+/*
+ *  Copyright (C) 2002-2010  The DOSBox Team
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program 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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+//
+// Chocolate Doom-related discussion:
+//
+// This is the DosBox OPL emulator code (src/hardware/dbopl.cpp) r3635,
+// converted to C.  The bulk of the work was done using the minus-minus
+// script in the Chocolate Doom SVN repository, then the result tweaked
+// by hand until working.
+//
+
+
+/*
+	DOSBox implementation of a combined Yamaha YMF262 and Yamaha YM3812 emulator.
+	Enabling the opl3 bit will switch the emulator to stereo opl3 output instead of regular mono opl2
+	Except for the table generation it's all integer math
+	Can choose different types of generators, using muls and bigger tables, try different ones for slower platforms
+	The generation was based on the MAME implementation but tried to have it use less memory and be faster in general
+	MAME uses much bigger envelope tables and this will be the biggest cause of it sounding different at times
+
+	//TODO Don't delay first operator 1 sample in opl3 mode
+	//TODO Maybe not use class method pointers but a regular function pointers with operator as first parameter
+	//TODO Fix panning for the Percussion channels, would any opl3 player use it and actually really change it though?
+	//TODO Check if having the same accuracy in all frequency multipliers sounds better or not
+
+	//DUNNO Keyon in 4op, switch to 2op without keyoff.
+*/
+
+/* $Id: dbopl.cpp,v 1.10 2009-06-10 19:54:51 harekiet Exp $ */
+
+
+#include <math.h>
+#include <stdlib.h>
+#include <string.h>
+//#include "dosbox.h"
+#include "dbopl.h"
+
+
+#define GCC_UNLIKELY(x) x
+
+#define TRUE 1
+#define FALSE 0
+
+#ifndef PI
+#define PI 3.14159265358979323846
+#endif
+
+#define OPLRATE		((double)(14318180.0 / 288.0))
+#define TREMOLO_TABLE 52
+
+//Try to use most precision for frequencies
+//Else try to keep different waves in synch
+//#define WAVE_PRECISION	1
+#ifndef WAVE_PRECISION
+//Wave bits available in the top of the 32bit range
+//Original adlib uses 10.10, we use 10.22
+#define WAVE_BITS	10
+#else
+//Need some extra bits at the top to have room for octaves and frequency multiplier
+//We support to 8 times lower rate
+//128 * 15 * 8 = 15350, 2^13.9, so need 14 bits
+#define WAVE_BITS	14
+#endif
+#define WAVE_SH		( 32 - WAVE_BITS )
+#define WAVE_MASK	( ( 1 << WAVE_SH ) - 1 )
+
+//Use the same accuracy as the waves
+#define LFO_SH ( WAVE_SH - 10 )
+//LFO is controlled by our tremolo 256 sample limit
+#define LFO_MAX ( 256 << ( LFO_SH ) )
+
+
+//Maximum amount of attenuation bits
+//Envelope goes to 511, 9 bits
+#if (DBOPL_WAVE == WAVE_TABLEMUL )
+//Uses the value directly
+#define ENV_BITS	( 9 )
+#else
+//Add 3 bits here for more accuracy and would have to be shifted up either way
+#define ENV_BITS	( 9 )
+#endif
+//Limits of the envelope with those bits and when the envelope goes silent
+#define ENV_MIN		0
+#define ENV_EXTRA	( ENV_BITS - 9 )
+#define ENV_MAX		( 511 << ENV_EXTRA )
+#define ENV_LIMIT	( ( 12 * 256) >> ( 3 - ENV_EXTRA ) )
+#define ENV_SILENT( _X_ ) ( (_X_) >= ENV_LIMIT )
+
+//Attack/decay/release rate counter shift
+#define RATE_SH		24
+#define RATE_MASK	( ( 1 << RATE_SH ) - 1 )
+//Has to fit within 16bit lookuptable
+#define MUL_SH		16
+
+//Check some ranges
+#if ENV_EXTRA > 3
+#error Too many envelope bits
+#endif
+
+static inline void Operator__SetState(Operator *self, Bit8u s );
+static inline Bit32u Chip__ForwardNoise(Chip *self);
+
+// C++'s template<> sure is useful sometimes.
+
+static Channel* Channel__BlockTemplate(Channel *self, Chip* chip,
+                                Bit32u samples, Bit32s* output,
+                                SynthMode mode );
+#define BLOCK_TEMPLATE(mode) \
+    static Channel* Channel__BlockTemplate_ ## mode(Channel *self, Chip* chip, \
+                                             Bit32u samples, Bit32s* output) \
+    { \
+       return Channel__BlockTemplate(self, chip, samples, output, mode); \
+    }
+
+BLOCK_TEMPLATE(sm2AM)
+BLOCK_TEMPLATE(sm2FM)
+BLOCK_TEMPLATE(sm3AM)
+BLOCK_TEMPLATE(sm3FM)
+BLOCK_TEMPLATE(sm3FMFM)
+BLOCK_TEMPLATE(sm3AMFM)
+BLOCK_TEMPLATE(sm3FMAM)
+BLOCK_TEMPLATE(sm3AMAM)
+BLOCK_TEMPLATE(sm2Percussion)
+BLOCK_TEMPLATE(sm3Percussion)
+
+//How much to substract from the base value for the final attenuation
+static const Bit8u KslCreateTable[16] = {
+	//0 will always be be lower than 7 * 8
+	64, 32, 24, 19, 
+	16, 12, 11, 10, 
+	 8,  6,  5,  4,
+	 3,  2,  1,  0,
+};
+
+#define M(_X_) ((Bit8u)( (_X_) * 2))
+static const Bit8u FreqCreateTable[16] = {
+	M(0.5), M(1 ), M(2 ), M(3 ), M(4 ), M(5 ), M(6 ), M(7 ),
+	M(8  ), M(9 ), M(10), M(10), M(12), M(12), M(15), M(15)
+};
+#undef M
+
+//We're not including the highest attack rate, that gets a special value
+static const Bit8u AttackSamplesTable[13] = {
+	69, 55, 46, 40,
+	35, 29, 23, 20,
+	19, 15, 11, 10,
+	9
+};
+//On a real opl these values take 8 samples to reach and are based upon larger tables
+static const Bit8u EnvelopeIncreaseTable[13] = {
+	4,  5,  6,  7,
+	8, 10, 12, 14,
+	16, 20, 24, 28,
+	32, 
+};
+
+#if ( DBOPL_WAVE == WAVE_HANDLER ) || ( DBOPL_WAVE == WAVE_TABLELOG )
+static Bit16u ExpTable[ 256 ];
+#endif
+
+#if ( DBOPL_WAVE == WAVE_HANDLER )
+//PI table used by WAVEHANDLER
+static Bit16u SinTable[ 512 ];
+#endif
+
+#if ( DBOPL_WAVE > WAVE_HANDLER )
+//Layout of the waveform table in 512 entry intervals
+//With overlapping waves we reduce the table to half it's size
+
+//	|    |//\\|____|WAV7|//__|/\  |____|/\/\|
+//	|\\//|    |    |WAV7|    |  \/|    |    |
+//	|06  |0126|17  |7   |3   |4   |4 5 |5   |
+
+//6 is just 0 shifted and masked
+
+static Bit16s WaveTable[ 8 * 512 ];
+//Distance into WaveTable the wave starts
+static const Bit16u WaveBaseTable[8] = {
+	0x000, 0x200, 0x200, 0x800,
+	0xa00, 0xc00, 0x100, 0x400,
+
+};
+//Mask the counter with this
+static const Bit16u WaveMaskTable[8] = {
+	1023, 1023, 511, 511,
+	1023, 1023, 512, 1023,
+};
+
+//Where to start the counter on at keyon
+static const Bit16u WaveStartTable[8] = {
+	512, 0, 0, 0,
+	0, 512, 512, 256,
+};
+#endif
+
+#if ( DBOPL_WAVE == WAVE_TABLEMUL )
+static Bit16u MulTable[ 384 ];
+#endif
+
+static Bit8u KslTable[ 8 * 16 ];
+static Bit8u TremoloTable[ TREMOLO_TABLE ];
+//Start of a channel behind the chip struct start
+static Bit16u ChanOffsetTable[32];
+//Start of an operator behind the chip struct start
+static Bit16u OpOffsetTable[64];
+
+//The lower bits are the shift of the operator vibrato value
+//The highest bit is right shifted to generate -1 or 0 for negation
+//So taking the highest input value of 7 this gives 3, 7, 3, 0, -3, -7, -3, 0
+static const Bit8s VibratoTable[ 8 ] = {	
+	1 - 0x00, 0 - 0x00, 1 - 0x00, 30 - 0x00, 
+	1 - 0x80, 0 - 0x80, 1 - 0x80, 30 - 0x80 
+};
+
+//Shift strength for the ksl value determined by ksl strength
+static const Bit8u KslShiftTable[4] = {
+	31,1,2,0
+};
+
+//Generate a table index and table shift value using input value from a selected rate
+static void EnvelopeSelect( Bit8u val, Bit8u *index, Bit8u *shift ) {
+	if ( val < 13 * 4 ) {				//Rate 0 - 12
+		*shift = 12 - ( val >> 2 );
+		*index = val & 3;
+	} else if ( val < 15 * 4 ) {		//rate 13 - 14
+		*shift = 0;
+		*index = val - 12 * 4;
+	} else {							//rate 15 and up
+		*shift = 0;
+		*index = 12;
+	}
+}
+
+#if ( DBOPL_WAVE == WAVE_HANDLER )
+/*
+	Generate the different waveforms out of the sine/exponetial table using handlers
+*/
+static inline Bits MakeVolume( Bitu wave, Bitu volume ) {
+	Bitu total = wave + volume;
+	Bitu index = total & 0xff;
+	Bitu sig = ExpTable[ index ];
+	Bitu exp = total >> 8;
+#if 0
+	//Check if we overflow the 31 shift limit
+	if ( exp >= 32 ) {
+		LOG_MSG( "WTF %d %d", total, exp );
+	}
+#endif
+	return (sig >> exp);
+};
+
+static Bits DB_FASTCALL WaveForm0( Bitu i, Bitu volume ) {
+	Bits neg = 0 - (( i >> 9) & 1);//Create ~0 or 0
+	Bitu wave = SinTable[i & 511];
+	return (MakeVolume( wave, volume ) ^ neg) - neg;
+}
+static Bits DB_FASTCALL WaveForm1( Bitu i, Bitu volume ) {
+	Bit32u wave = SinTable[i & 511];
+	wave |= ( ( (i ^ 512 ) & 512) - 1) >> ( 32 - 12 );
+	return MakeVolume( wave, volume );
+}
+static Bits DB_FASTCALL WaveForm2( Bitu i, Bitu volume ) {
+	Bitu wave = SinTable[i & 511];
+	return MakeVolume( wave, volume );
+}
+static Bits DB_FASTCALL WaveForm3( Bitu i, Bitu volume ) {
+	Bitu wave = SinTable[i & 255];
+	wave |= ( ( (i ^ 256 ) & 256) - 1) >> ( 32 - 12 );
+	return MakeVolume( wave, volume );
+}
+static Bits DB_FASTCALL WaveForm4( Bitu i, Bitu volume ) {
+	//Twice as fast
+	i <<= 1;
+	Bits neg = 0 - (( i >> 9) & 1);//Create ~0 or 0
+	Bitu wave = SinTable[i & 511];
+	wave |= ( ( (i ^ 512 ) & 512) - 1) >> ( 32 - 12 );
+	return (MakeVolume( wave, volume ) ^ neg) - neg;
+}
+static Bits DB_FASTCALL WaveForm5( Bitu i, Bitu volume ) {
+	//Twice as fast
+	i <<= 1;
+	Bitu wave = SinTable[i & 511];
+	wave |= ( ( (i ^ 512 ) & 512) - 1) >> ( 32 - 12 );
+	return MakeVolume( wave, volume );
+}
+static Bits DB_FASTCALL WaveForm6( Bitu i, Bitu volume ) {
+	Bits neg = 0 - (( i >> 9) & 1);//Create ~0 or 0
+	return (MakeVolume( 0, volume ) ^ neg) - neg;
+}
+static Bits DB_FASTCALL WaveForm7( Bitu i, Bitu volume ) {
+	//Negative is reversed here
+	Bits neg = (( i >> 9) & 1) - 1;
+	Bitu wave = (i << 3);
+	//When negative the volume also runs backwards
+	wave = ((wave ^ neg) - neg) & 4095;
+	return (MakeVolume( wave, volume ) ^ neg) - neg;
+}
+
+static const WaveHandler WaveHandlerTable[8] = {
+	WaveForm0, WaveForm1, WaveForm2, WaveForm3,
+	WaveForm4, WaveForm5, WaveForm6, WaveForm7
+};
+
+#endif
+
+/*
+	Operator
+*/
+
+//We zero out when rate == 0
+static inline void Operator__UpdateAttack(Operator *self, const Chip* chip ) {
+	Bit8u rate = self->reg60 >> 4;
+	if ( rate ) {
+		Bit8u val = (rate << 2) + self->ksr;
+		self->attackAdd = chip->attackRates[ val ];
+		self->rateZero &= ~(1 << ATTACK);
+	} else {
+		self->attackAdd = 0;
+		self->rateZero |= (1 << ATTACK);
+	}
+}
+static inline void Operator__UpdateDecay(Operator *self, const Chip* chip ) {
+	Bit8u rate = self->reg60 & 0xf;
+	if ( rate ) {
+		Bit8u val = (rate << 2) + self->ksr;
+		self->decayAdd = chip->linearRates[ val ];
+		self->rateZero &= ~(1 << DECAY);
+	} else {
+		self->decayAdd = 0;
+		self->rateZero |= (1 << DECAY);
+	}
+}
+static inline void Operator__UpdateRelease(Operator *self, const Chip* chip ) {
+	Bit8u rate = self->reg80 & 0xf;
+	if ( rate ) {
+		Bit8u val = (rate << 2) + self->ksr;
+		self->releaseAdd = chip->linearRates[ val ];
+		self->rateZero &= ~(1 << RELEASE);
+		if ( !(self->reg20 & MASK_SUSTAIN ) ) {
+			self->rateZero &= ~( 1 << SUSTAIN );
+		}	
+	} else {
+		self->rateZero |= (1 << RELEASE);
+		self->releaseAdd = 0;
+		if ( !(self->reg20 & MASK_SUSTAIN ) ) {
+			self->rateZero |= ( 1 << SUSTAIN );
+		}	
+	}
+}
+
+static inline void Operator__UpdateAttenuation(Operator *self) {
+	Bit8u kslBase = (Bit8u)((self->chanData >> SHIFT_KSLBASE) & 0xff);
+	Bit32u tl = self->reg40 & 0x3f;
+	Bit8u kslShift = KslShiftTable[ self->reg40 >> 6 ];
+	//Make sure the attenuation goes to the right bits
+	self->totalLevel = tl << ( ENV_BITS - 7 );	//Total level goes 2 bits below max
+	self->totalLevel += ( kslBase << ENV_EXTRA ) >> kslShift;
+}
+
+static void Operator__UpdateFrequency(Operator *self) {
+	Bit32u freq = self->chanData & (( 1 << 10 ) - 1);
+	Bit32u block = (self->chanData >> 10) & 0xff;
+#ifdef WAVE_PRECISION
+	block = 7 - block;
+	self->waveAdd = ( freq * self->freqMul ) >> block;
+#else
+	self->waveAdd = ( freq << block ) * self->freqMul;
+#endif
+	if ( self->reg20 & MASK_VIBRATO ) {
+		self->vibStrength = (Bit8u)(freq >> 7);
+
+#ifdef WAVE_PRECISION
+		self->vibrato = ( self->vibStrength * self->freqMul ) >> block;
+#else
+		self->vibrato = ( self->vibStrength << block ) * self->freqMul;
+#endif
+	} else {
+		self->vibStrength = 0;
+		self->vibrato = 0;
+	}
+}
+
+static void Operator__UpdateRates(Operator *self, const Chip* chip ) {
+	//Mame seems to reverse this where enabling ksr actually lowers
+	//the rate, but pdf manuals says otherwise?
+	Bit8u newKsr = (Bit8u)((self->chanData >> SHIFT_KEYCODE) & 0xff);
+	if ( !( self->reg20 & MASK_KSR ) ) {
+		newKsr >>= 2;
+	}
+	if ( self->ksr == newKsr )
+		return;
+	self->ksr = newKsr;
+	Operator__UpdateAttack( self, chip );
+	Operator__UpdateDecay( self, chip );
+	Operator__UpdateRelease( self, chip );
+}
+
+static inline Bit32s Operator__RateForward(Operator *self, Bit32u add ) {
+	self->rateIndex += add;
+	Bit32s ret = self->rateIndex >> RATE_SH;
+	self->rateIndex = self->rateIndex & RATE_MASK;
+	return ret;
+}
+
+static Bits Operator__TemplateVolume(Operator *self, OperatorState yes) {
+	Bit32s vol = self->volume;
+	Bit32s change;
+	switch ( yes ) {
+	case OFF:
+		return ENV_MAX;
+	case ATTACK:
+		change = Operator__RateForward( self, self->attackAdd );
+		if ( !change )
+			return vol;
+		vol += ( (~vol) * change ) >> 3;
+		if ( vol < ENV_MIN ) {
+			self->volume = ENV_MIN;
+			self->rateIndex = 0;
+			Operator__SetState( self, DECAY );
+			return ENV_MIN;
+		}
+		break;
+	case DECAY:
+		vol += Operator__RateForward( self, self->decayAdd );
+		if ( GCC_UNLIKELY(vol >= self->sustainLevel) ) {
+			//Check if we didn't overshoot max attenuation, then just go off
+			if ( GCC_UNLIKELY(vol >= ENV_MAX) ) {
+				self->volume = ENV_MAX;
+				Operator__SetState( self, OFF );
+				return ENV_MAX;
+			}
+			//Continue as sustain
+			self->rateIndex = 0;
+			Operator__SetState( self, SUSTAIN );
+		}
+		break;
+	case SUSTAIN:
+		if ( self->reg20 & MASK_SUSTAIN ) {
+			return vol;
+		}
+		//In sustain phase, but not sustaining, do regular release
+	case RELEASE: 
+		vol += Operator__RateForward( self, self->releaseAdd );;
+		if ( GCC_UNLIKELY(vol >= ENV_MAX) ) {
+			self->volume = ENV_MAX;
+			Operator__SetState( self, OFF );
+			return ENV_MAX;
+		}
+		break;
+	}
+	self->volume = vol;
+	return vol;
+}
+
+#define TEMPLATE_VOLUME(mode) \
+    static Bits Operator__TemplateVolume ## mode(Operator *self) \
+    { \
+        return Operator__TemplateVolume(self, mode); \
+    }
+
+TEMPLATE_VOLUME(OFF)
+TEMPLATE_VOLUME(RELEASE)
+TEMPLATE_VOLUME(SUSTAIN)
+TEMPLATE_VOLUME(ATTACK)
+TEMPLATE_VOLUME(DECAY)
+
+static const VolumeHandler VolumeHandlerTable[5] = {
+        &Operator__TemplateVolumeOFF,
+        &Operator__TemplateVolumeRELEASE,
+        &Operator__TemplateVolumeSUSTAIN,
+        &Operator__TemplateVolumeDECAY,
+        &Operator__TemplateVolumeATTACK,
+};
+
+static inline Bitu Operator__ForwardVolume(Operator *self) {
+	return self->currentLevel + (self->volHandler)(self);
+}
+
+
+static inline Bitu Operator__ForwardWave(Operator *self) {
+	self->waveIndex += self->waveCurrent;	
+	return self->waveIndex >> WAVE_SH;
+}
+
+static void Operator__Write20(Operator *self, const Chip* chip, Bit8u val ) {
+	Bit8u change = (self->reg20 ^ val );
+	if ( !change ) 
+		return;
+	self->reg20 = val;
+	//Shift the tremolo bit over the entire register, saved a branch, YES!
+	self->tremoloMask = (Bit8s)(val) >> 7;
+	self->tremoloMask &= ~(( 1 << ENV_EXTRA ) -1);
+	//Update specific features based on changes
+	if ( change & MASK_KSR ) {
+		Operator__UpdateRates( self, chip );
+	}
+	//With sustain enable the volume doesn't change
+	if ( self->reg20 & MASK_SUSTAIN || ( !self->releaseAdd ) ) {
+		self->rateZero |= ( 1 << SUSTAIN );
+	} else {
+		self->rateZero &= ~( 1 << SUSTAIN );
+	}
+	//Frequency multiplier or vibrato changed
+	if ( change & (0xf | MASK_VIBRATO) ) {
+		self->freqMul = chip->freqMul[ val & 0xf ];
+		Operator__UpdateFrequency(self);
+	}
+}
+
+static void Operator__Write40(Operator *self, const Chip *chip, Bit8u val ) {
+	if (!(self->reg40 ^ val )) 
+		return;
+	self->reg40 = val;
+	Operator__UpdateAttenuation( self );
+}
+
+static void Operator__Write60(Operator *self, const Chip* chip, Bit8u val ) {
+	Bit8u change = self->reg60 ^ val;
+	self->reg60 = val;
+	if ( change & 0x0f ) {
+		Operator__UpdateDecay( self, chip );
+	}
+	if ( change & 0xf0 ) {
+		Operator__UpdateAttack( self, chip );
+	}
+}
+
+static void Operator__Write80(Operator *self, const Chip* chip, Bit8u val ) {
+	Bit8u change = (self->reg80 ^ val );
+	if ( !change ) 
+		return;
+	self->reg80 = val;
+	Bit8u sustain = val >> 4;
+	//Turn 0xf into 0x1f
+	sustain |= ( sustain + 1) & 0x10;
+	self->sustainLevel = sustain << ( ENV_BITS - 5 );
+	if ( change & 0x0f ) {
+		Operator__UpdateRelease( self, chip );
+	}
+}
+
+static void Operator__WriteE0(Operator *self, const Chip* chip, Bit8u val ) {
+	if ( !(self->regE0 ^ val) ) 
+		return;
+	//in opl3 mode you can always selet 7 waveforms regardless of waveformselect
+	Bit8u waveForm = val & ( ( 0x3 & chip->waveFormMask ) | (0x7 & chip->opl3Active ) );
+	self->regE0 = val;
+#if( DBOPL_WAVE == WAVE_HANDLER )
+	self->waveHandler = WaveHandlerTable[ waveForm ];
+#else
+	self->waveBase = WaveTable + WaveBaseTable[ waveForm ];
+	self->waveStart = WaveStartTable[ waveForm ] << WAVE_SH;
+	self->waveMask = WaveMaskTable[ waveForm ];
+#endif
+}
+
+static inline void Operator__SetState(Operator *self, Bit8u s ) {
+	self->state = s;
+	self->volHandler = VolumeHandlerTable[ s ];
+}
+
+static inline int Operator__Silent(Operator *self) {
+	if ( !ENV_SILENT( self->totalLevel + self->volume ) )
+		return FALSE;
+	if ( !(self->rateZero & ( 1 << self->state ) ) )
+		return FALSE;
+	return TRUE;
+}
+
+static inline void Operator__Prepare(Operator *self, const Chip* chip )  {
+	self->currentLevel = self->totalLevel + (chip->tremoloValue & self->tremoloMask);
+	self->waveCurrent = self->waveAdd;
+	if ( self->vibStrength >> chip->vibratoShift ) {
+		Bit32s add = self->vibrato >> chip->vibratoShift;
+		//Sign extend over the shift value
+		Bit32s neg = chip->vibratoSign;
+		//Negate the add with -1 or 0
+		add = ( add ^ neg ) - neg; 
+		self->waveCurrent += add;
+	}
+}
+
+static void Operator__KeyOn(Operator *self, Bit8u mask ) {
+	if ( !self->keyOn ) {
+		//Restart the frequency generator
+#if( DBOPL_WAVE > WAVE_HANDLER )
+		self->waveIndex = self->waveStart;
+#else
+		self->waveIndex = 0;
+#endif
+		self->rateIndex = 0;
+		Operator__SetState( self, ATTACK );
+	}
+	self->keyOn |= mask;
+}
+
+static void Operator__KeyOff(Operator *self, Bit8u mask ) {
+	self->keyOn &= ~mask;
+	if ( !self->keyOn ) {
+		if ( self->state != OFF ) {
+			Operator__SetState( self, RELEASE );
+		}
+	}
+}
+
+static inline Bits Operator__GetWave(Operator *self, Bitu index, Bitu vol ) {
+#if( DBOPL_WAVE == WAVE_HANDLER )
+	return self->waveHandler( index, vol << ( 3 - ENV_EXTRA ) );
+#elif( DBOPL_WAVE == WAVE_TABLEMUL )
+	return(self->waveBase[ index & self->waveMask ] * MulTable[ vol >> ENV_EXTRA ]) >> MUL_SH;
+#elif( DBOPL_WAVE == WAVE_TABLELOG )
+	Bit32s wave = self->waveBase[ index & self->waveMask ];
+	Bit32u total = ( wave & 0x7fff ) + vol << ( 3 - ENV_EXTRA );
+	Bit32s sig = ExpTable[ total & 0xff ];
+	Bit32u exp = total >> 8;
+	Bit32s neg = wave >> 16;
+	return((sig ^ neg) - neg) >> exp;
+#else
+#error "No valid wave routine"
+#endif
+}
+
+static inline Bits Operator__GetSample(Operator *self, Bits modulation ) {
+	Bitu vol = Operator__ForwardVolume(self);
+	if ( ENV_SILENT( vol ) ) {
+		//Simply forward the wave
+		self->waveIndex += self->waveCurrent;
+		return 0;
+	} else {
+		Bitu index = Operator__ForwardWave(self);
+		index += modulation;
+		return Operator__GetWave( self, index, vol );
+	}
+}
+
+static void Operator__Operator(Operator *self) {
+	self->chanData = 0;
+	self->freqMul = 0;
+	self->waveIndex = 0;
+	self->waveAdd = 0;
+	self->waveCurrent = 0;
+	self->keyOn = 0;
+	self->ksr = 0;
+	self->reg20 = 0;
+	self->reg40 = 0;
+	self->reg60 = 0;
+	self->reg80 = 0;
+	self->regE0 = 0;
+	Operator__SetState( self, OFF );
+	self->rateZero = (1 << OFF);
+	self->sustainLevel = ENV_MAX;
+	self->currentLevel = ENV_MAX;
+	self->totalLevel = ENV_MAX;
+	self->volume = ENV_MAX;
+	self->releaseAdd = 0;
+}
+
+/*
+	Channel
+*/
+
+static void Channel__Channel(Channel *self) {
+        Operator__Operator(&self->op[0]);
+        Operator__Operator(&self->op[1]);
+	self->old[0] = self->old[1] = 0;
+	self->chanData = 0;
+	self->regB0 = 0;
+	self->regC0 = 0;
+	self->maskLeft = -1;
+	self->maskRight = -1;
+	self->feedback = 31;
+	self->fourMask = 0;
+	self->synthHandler = Channel__BlockTemplate_sm2FM;
+};
+
+static inline Operator* Channel__Op( Channel *self, Bitu index ) {
+        return &( ( self + (index >> 1) )->op[ index & 1 ]);
+}
+
+static void Channel__SetChanData(Channel *self, const Chip* chip, Bit32u data ) {
+	Bit32u change = self->chanData ^ data;
+	self->chanData = data;
+	Channel__Op( self, 0 )->chanData = data;
+	Channel__Op( self, 1 )->chanData = data;
+	//Since a frequency update triggered this, always update frequency
+        Operator__UpdateFrequency(Channel__Op( self, 0 ));
+        Operator__UpdateFrequency(Channel__Op( self, 1 ));
+	if ( change & ( 0xff << SHIFT_KSLBASE ) ) {
+                Operator__UpdateAttenuation(Channel__Op( self, 0 ));
+                Operator__UpdateAttenuation(Channel__Op( self, 1 ));
+	}
+	if ( change & ( 0xff << SHIFT_KEYCODE ) ) {
+                Operator__UpdateRates(Channel__Op( self, 0 ), chip);
+                Operator__UpdateRates(Channel__Op( self, 1 ), chip);
+	}
+}
+
+static void Channel__UpdateFrequency(Channel *self, const Chip* chip, Bit8u fourOp ) {
+	//Extrace the frequency bits
+	Bit32u data = self->chanData & 0xffff;
+	Bit32u kslBase = KslTable[ data >> 6 ];
+	Bit32u keyCode = ( data & 0x1c00) >> 9;
+	if ( chip->reg08 & 0x40 ) {
+		keyCode |= ( data & 0x100)>>8;	/* notesel == 1 */
+	} else {
+		keyCode |= ( data & 0x200)>>9;	/* notesel == 0 */
+	}
+	//Add the keycode and ksl into the highest bits of chanData
+	data |= (keyCode << SHIFT_KEYCODE) | ( kslBase << SHIFT_KSLBASE );
+        Channel__SetChanData( self + 0, chip, data );
+	if ( fourOp & 0x3f ) {
+                Channel__SetChanData( self + 1, chip, data );
+	}
+}
+
+static void Channel__WriteA0(Channel *self, const Chip* chip, Bit8u val ) {
+	Bit8u fourOp = chip->reg104 & chip->opl3Active & self->fourMask;
+	//Don't handle writes to silent fourop channels
+	if ( fourOp > 0x80 )
+		return;
+	Bit32u change = (self->chanData ^ val ) & 0xff;
+	if ( change ) {
+		self->chanData ^= change;
+		Channel__UpdateFrequency( self, chip, fourOp );
+	}
+}
+
+static void Channel__WriteB0(Channel *self, const Chip* chip, Bit8u val ) {
+	Bit8u fourOp = chip->reg104 & chip->opl3Active & self->fourMask;
+	//Don't handle writes to silent fourop channels
+	if ( fourOp > 0x80 )
+		return;
+	Bitu change = (self->chanData ^ ( val << 8 ) ) & 0x1f00;
+	if ( change ) {
+		self->chanData ^= change;
+		Channel__UpdateFrequency( self, chip, fourOp );
+	}
+	//Check for a change in the keyon/off state
+	if ( !(( val ^ self->regB0) & 0x20))
+		return;
+	self->regB0 = val;
+	if ( val & 0x20 ) {
+                Operator__KeyOn( Channel__Op(self, 0), 0x1 );
+                Operator__KeyOn( Channel__Op(self, 1), 0x1 );
+		if ( fourOp & 0x3f ) {
+                        Operator__KeyOn( Channel__Op(self + 1, 0), 1 );
+                        Operator__KeyOn( Channel__Op(self + 1, 1), 1 );
+		}
+	} else {
+                Operator__KeyOff( Channel__Op(self, 0), 0x1 );
+                Operator__KeyOff( Channel__Op(self, 1), 0x1 );
+		if ( fourOp & 0x3f ) {
+                        Operator__KeyOff( Channel__Op(self + 1, 0), 1 );
+                        Operator__KeyOff( Channel__Op(self + 1, 1), 1 );
+		}
+	}
+}
+
+static void Channel__WriteC0(Channel *self, const Chip* chip, Bit8u val ) {
+	Bit8u change = val ^ self->regC0;
+	if ( !change )
+		return;
+	self->regC0 = val;
+	self->feedback = ( val >> 1 ) & 7;
+	if ( self->feedback ) {
+		//We shift the input to the right 10 bit wave index value
+		self->feedback = 9 - self->feedback;
+	} else {
+		self->feedback = 31;
+	}
+	//Select the new synth mode
+	if ( chip->opl3Active ) {
+		//4-op mode enabled for this channel
+		if ( (chip->reg104 & self->fourMask) & 0x3f ) {
+			Channel* chan0, *chan1;
+			//Check if it's the 2nd channel in a 4-op
+			if ( !(self->fourMask & 0x80 ) ) {
+				chan0 = self;
+				chan1 = self + 1;
+			} else {
+				chan0 = self - 1;
+				chan1 = self;
+			}
+
+			Bit8u synth = ( (chan0->regC0 & 1) << 0 )| (( chan1->regC0 & 1) << 1 );
+			switch ( synth ) {
+			case 0:
+				chan0->synthHandler = Channel__BlockTemplate_sm3FMFM;
+				break;
+			case 1:
+				chan0->synthHandler = Channel__BlockTemplate_sm3AMFM;
+				break;
+			case 2:
+				chan0->synthHandler = Channel__BlockTemplate_sm3FMAM ;
+				break;
+			case 3:
+				chan0->synthHandler = Channel__BlockTemplate_sm3AMAM ;
+				break;
+			}
+		//Disable updating percussion channels
+		} else if ((self->fourMask & 0x40) && ( chip->regBD & 0x20) ) {
+
+		//Regular dual op, am or fm
+		} else if ( val & 1 ) {
+			self->synthHandler = Channel__BlockTemplate_sm3AM;
+		} else {
+			self->synthHandler = Channel__BlockTemplate_sm3FM;
+		}
+		self->maskLeft = ( val & 0x10 ) ? -1 : 0;
+		self->maskRight = ( val & 0x20 ) ? -1 : 0;
+	//opl2 active
+	} else { 
+		//Disable updating percussion channels
+		if ( (self->fourMask & 0x40) && ( chip->regBD & 0x20 ) ) {
+
+		//Regular dual op, am or fm
+		} else if ( val & 1 ) {
+			self->synthHandler = Channel__BlockTemplate_sm2AM;
+		} else {
+			self->synthHandler = Channel__BlockTemplate_sm2FM;
+		}
+	}
+}
+
+static void Channel__ResetC0(Channel *self, const Chip* chip ) {
+	Bit8u val = self->regC0;
+	self->regC0 ^= 0xff;
+	Channel__WriteC0( self, chip, val );
+};
+
+static inline void Channel__GeneratePercussion(Channel *self, Chip* chip,
+                                               Bit32s* output, int opl3Mode ) {
+	Channel* chan = self;
+
+	//BassDrum
+	Bit32s mod = (Bit32u)((self->old[0] + self->old[1])) >> self->feedback;
+	self->old[0] = self->old[1];
+	self->old[1] = Operator__GetSample( Channel__Op(self, 0), mod ); 
+
+	//When bassdrum is in AM mode first operator is ignoed
+	if ( chan->regC0 & 1 ) {
+		mod = 0;
+	} else {
+		mod = self->old[0];
+	}
+	Bit32s sample = Operator__GetSample( Channel__Op(self, 1), mod ); 
+
+	//Precalculate stuff used by other outputs
+	Bit32u noiseBit = Chip__ForwardNoise(chip) & 0x1;
+	Bit32u c2 = Operator__ForwardWave(Channel__Op(self, 2));
+	Bit32u c5 = Operator__ForwardWave(Channel__Op(self, 5));
+	Bit32u phaseBit = (((c2 & 0x88) ^ ((c2<<5) & 0x80)) | ((c5 ^ (c5<<2)) & 0x20)) ? 0x02 : 0x00;
+
+	//Hi-Hat
+	Bit32u hhVol = Operator__ForwardVolume(Channel__Op(self, 2));
+	if ( !ENV_SILENT( hhVol ) ) {
+		Bit32u hhIndex = (phaseBit<<8) | (0x34 << ( phaseBit ^ (noiseBit << 1 )));
+		sample += Operator__GetWave( Channel__Op(self, 2), hhIndex, hhVol );
+	}
+	//Snare Drum
+	Bit32u sdVol = Operator__ForwardVolume( Channel__Op(self, 3) );
+	if ( !ENV_SILENT( sdVol ) ) {
+		Bit32u sdIndex = ( 0x100 + (c2 & 0x100) ) ^ ( noiseBit << 8 );
+		sample += Operator__GetWave( Channel__Op(self, 3), sdIndex, sdVol );
+	}
+	//Tom-tom
+	sample += Operator__GetSample( Channel__Op(self, 4), 0 );
+
+	//Top-Cymbal
+	Bit32u tcVol = Operator__ForwardVolume(Channel__Op(self, 5));
+	if ( !ENV_SILENT( tcVol ) ) {
+		Bit32u tcIndex = (1 + phaseBit) << 8;
+		sample += Operator__GetWave( Channel__Op(self, 5), tcIndex, tcVol );
+	}
+	sample <<= 1;
+	if ( opl3Mode ) {
+		output[0] += sample;
+		output[1] += sample;
+	} else {
+		output[0] += sample;
+	}
+}
+
+Channel* Channel__BlockTemplate(Channel *self, Chip* chip,
+                                Bit32u samples, Bit32s* output,
+                                SynthMode mode ) {
+        Bitu i;
+
+	switch( mode ) {
+	case sm2AM:
+	case sm3AM:
+		if ( Operator__Silent(Channel__Op(self, 0))
+                 && Operator__Silent(Channel__Op(self, 1))) {
+			self->old[0] = self->old[1] = 0;
+			return(self + 1);
+		}
+		break;
+	case sm2FM:
+	case sm3FM:
+		if ( Operator__Silent(Channel__Op(self, 1))) {
+			self->old[0] = self->old[1] = 0;
+			return (self + 1);
+		}
+		break;
+	case sm3FMFM:
+		if ( Operator__Silent(Channel__Op(self, 3))) {
+			self->old[0] = self->old[1] = 0;
+			return (self + 2);
+		}
+		break;
+	case sm3AMFM:
+		if ( Operator__Silent( Channel__Op(self, 0) )
+                 && Operator__Silent( Channel__Op(self, 3) )) {
+			self->old[0] = self->old[1] = 0;
+			return (self + 2);
+		}
+		break;
+	case sm3FMAM:
+		if ( Operator__Silent( Channel__Op(self, 1))
+                 && Operator__Silent( Channel__Op(self, 3))) {
+			self->old[0] = self->old[1] = 0;
+			return (self + 2);
+		}
+		break;
+	case sm3AMAM:
+		if ( Operator__Silent( Channel__Op(self, 0) )
+                 && Operator__Silent( Channel__Op(self, 2) )
+                 && Operator__Silent( Channel__Op(self, 3) )) {
+			self->old[0] = self->old[1] = 0;
+			return (self + 2);
+		}
+		break;
+
+        default:
+                abort();
+	}
+	//Init the operators with the the current vibrato and tremolo values
+        Operator__Prepare( Channel__Op( self, 0 ), chip );
+        Operator__Prepare( Channel__Op( self, 1 ), chip );
+	if ( mode > sm4Start ) {
+                Operator__Prepare( Channel__Op( self, 2 ), chip );
+                Operator__Prepare( Channel__Op( self, 3 ), chip );
+	}
+	if ( mode > sm6Start ) {
+                Operator__Prepare( Channel__Op( self, 4 ), chip );
+                Operator__Prepare( Channel__Op( self, 5 ), chip );
+	}
+	for ( i = 0; i < samples; i++ ) {
+		//Early out for percussion handlers
+		if ( mode == sm2Percussion ) {
+			Channel__GeneratePercussion( self, chip, output + i, FALSE );
+			continue;	//Prevent some unitialized value bitching
+		} else if ( mode == sm3Percussion ) {
+			Channel__GeneratePercussion( self, chip, output + i * 2, TRUE );
+			continue;	//Prevent some unitialized value bitching
+		}
+
+		//Do unsigned shift so we can shift out all bits but still stay in 10 bit range otherwise
+		Bit32s mod = (Bit32u)((self->old[0] + self->old[1])) >> self->feedback;
+		self->old[0] = self->old[1];
+		self->old[1] = Operator__GetSample( Channel__Op(self, 0), mod );
+		Bit32s sample = 0;
+		Bit32s out0 = self->old[0];
+		if ( mode == sm2AM || mode == sm3AM ) {
+			sample = out0 + Operator__GetSample( Channel__Op(self, 1), 0 );
+		} else if ( mode == sm2FM || mode == sm3FM ) {
+			sample = Operator__GetSample( Channel__Op(self, 1), out0 );
+		} else if ( mode == sm3FMFM ) {
+			Bits next = Operator__GetSample( Channel__Op(self, 1), out0 );
+			next = Operator__GetSample( Channel__Op(self, 2), next );
+			sample = Operator__GetSample( Channel__Op(self, 3), next );
+		} else if ( mode == sm3AMFM ) {
+			sample = out0;
+			Bits next = Operator__GetSample( Channel__Op(self, 1), 0 );
+			next = Operator__GetSample( Channel__Op(self, 2), next );
+			sample += Operator__GetSample( Channel__Op(self, 3), next );
+		} else if ( mode == sm3FMAM ) {
+			sample = Operator__GetSample( Channel__Op(self, 1), out0 );
+			Bits next = Operator__GetSample( Channel__Op(self, 2), 0 );
+			sample += Operator__GetSample( Channel__Op(self, 3), next );
+		} else if ( mode == sm3AMAM ) {
+			sample = out0;
+			Bits next = Operator__GetSample( Channel__Op(self, 1), 0 );
+			sample += Operator__GetSample( Channel__Op(self, 2), next );
+			sample += Operator__GetSample( Channel__Op(self, 3), 0 );
+		}
+		switch( mode ) {
+		case sm2AM:
+		case sm2FM:
+			output[ i ] += sample;
+			break;
+		case sm3AM:
+		case sm3FM:
+		case sm3FMFM:
+		case sm3AMFM:
+		case sm3FMAM:
+		case sm3AMAM:
+			output[ i * 2 + 0 ] += sample & self->maskLeft;
+			output[ i * 2 + 1 ] += sample & self->maskRight;
+			break;
+                default:
+                        abort();
+		}
+	}
+	switch( mode ) {
+	case sm2AM:
+	case sm2FM:
+	case sm3AM:
+	case sm3FM:
+		return ( self + 1 );
+	case sm3FMFM:
+	case sm3AMFM:
+	case sm3FMAM:
+	case sm3AMAM:
+		return ( self + 2 );
+	case sm2Percussion:
+	case sm3Percussion:
+		return( self + 3 );
+        default:
+                abort();
+	}
+	return 0;
+}
+
+/*
+	Chip
+*/
+
+void Chip__Chip(Chip *self) {
+        int i;
+
+        for (i=0; i<18; ++i) {
+                Channel__Channel(&self->chan[i]);
+        }
+
+	self->reg08 = 0;
+	self->reg04 = 0;
+	self->regBD = 0;
+	self->reg104 = 0;
+	self->opl3Active = 0;
+}
+
+static inline Bit32u Chip__ForwardNoise(Chip *self) {
+	self->noiseCounter += self->noiseAdd;
+	Bitu count = self->noiseCounter >> LFO_SH;
+	self->noiseCounter &= WAVE_MASK;
+	for ( ; count > 0; --count ) {
+		//Noise calculation from mame
+		self->noiseValue ^= ( 0x800302 ) & ( 0 - (self->noiseValue & 1 ) );
+		self->noiseValue >>= 1;
+	}
+	return self->noiseValue;
+}
+
+static inline Bit32u Chip__ForwardLFO(Chip *self, Bit32u samples ) {
+	//Current vibrato value, runs 4x slower than tremolo
+	self->vibratoSign = ( VibratoTable[ self->vibratoIndex >> 2] ) >> 7;
+	self->vibratoShift = ( VibratoTable[ self->vibratoIndex >> 2] & 7) + self->vibratoStrength; 
+	self->tremoloValue = TremoloTable[ self->tremoloIndex ] >> self->tremoloStrength;
+
+	//Check hom many samples there can be done before the value changes
+	Bit32u todo = LFO_MAX - self->lfoCounter;
+	Bit32u count = (todo + self->lfoAdd - 1) / self->lfoAdd;
+	if ( count > samples ) {
+		count = samples;
+		self->lfoCounter += count * self->lfoAdd;
+	} else {
+		self->lfoCounter += count * self->lfoAdd;
+		self->lfoCounter &= (LFO_MAX - 1);
+		//Maximum of 7 vibrato value * 4
+		self->vibratoIndex = ( self->vibratoIndex + 1 ) & 31;
+		//Clip tremolo to the the table size
+		if ( self->tremoloIndex + 1 < TREMOLO_TABLE  )
+			++self->tremoloIndex;
+		else
+			self->tremoloIndex = 0;
+	}
+	return count;
+}
+
+
+static void Chip__WriteBD(Chip *self, Bit8u val ) {
+	Bit8u change = self->regBD ^ val;
+	if ( !change )
+		return;
+	self->regBD = val;
+	//TODO could do this with shift and xor?
+	self->vibratoStrength = (val & 0x40) ? 0x00 : 0x01;
+	self->tremoloStrength = (val & 0x80) ? 0x00 : 0x02;
+	if ( val & 0x20 ) {
+		//Drum was just enabled, make sure channel 6 has the right synth
+		if ( change & 0x20 ) {
+			if ( self->opl3Active ) {
+				self->chan[6].synthHandler
+                                    = Channel__BlockTemplate_sm3Percussion; 
+			} else {
+				self->chan[6].synthHandler
+                                    = Channel__BlockTemplate_sm2Percussion;
+			}
+		}
+		//Bass Drum
+		if ( val & 0x10 ) {
+                        Operator__KeyOn( &self->chan[6].op[0], 0x2 );
+                        Operator__KeyOn( &self->chan[6].op[1], 0x2 );
+		} else {
+                        Operator__KeyOff( &self->chan[6].op[0], 0x2 );
+                        Operator__KeyOff( &self->chan[6].op[1], 0x2 );
+		}
+		//Hi-Hat
+		if ( val & 0x1 ) {
+                        Operator__KeyOn( &self->chan[7].op[0], 0x2 );
+		} else {
+                        Operator__KeyOff( &self->chan[7].op[0], 0x2 );
+		}
+		//Snare
+		if ( val & 0x8 ) {
+                        Operator__KeyOn( &self->chan[7].op[1], 0x2 );
+		} else {
+                        Operator__KeyOff( &self->chan[7].op[1], 0x2 );
+		}
+		//Tom-Tom
+		if ( val & 0x4 ) {
+                        Operator__KeyOn( &self->chan[8].op[0], 0x2 );
+		} else {
+                        Operator__KeyOff( &self->chan[8].op[0], 0x2 );
+		}
+		//Top Cymbal
+		if ( val & 0x2 ) {
+                        Operator__KeyOn( &self->chan[8].op[1], 0x2 );
+		} else {
+                        Operator__KeyOff( &self->chan[8].op[1], 0x2 );
+		}
+	//Toggle keyoffs when we turn off the percussion
+	} else if ( change & 0x20 ) {
+		//Trigger a reset to setup the original synth handler
+                Channel__ResetC0( &self->chan[6], self );
+                Operator__KeyOff( &self->chan[6].op[0], 0x2 );
+                Operator__KeyOff( &self->chan[6].op[1], 0x2 );
+                Operator__KeyOff( &self->chan[7].op[0], 0x2 );
+                Operator__KeyOff( &self->chan[7].op[1], 0x2 );
+                Operator__KeyOff( &self->chan[8].op[0], 0x2 );
+                Operator__KeyOff( &self->chan[8].op[1], 0x2 );
+	}
+}
+
+
+#define REGOP( _FUNC_ )															\
+	index = ( ( reg >> 3) & 0x20 ) | ( reg & 0x1f );								\
+	if ( OpOffsetTable[ index ] ) {													\
+		Operator* regOp = (Operator*)( ((char *)self ) + OpOffsetTable[ index ] );	\
+                Operator__ ## _FUNC_ (regOp, self, val); \
+	}
+
+#define REGCHAN( _FUNC_ )																\
+	index = ( ( reg >> 4) & 0x10 ) | ( reg & 0xf );										\
+	if ( ChanOffsetTable[ index ] ) {													\
+		Channel* regChan = (Channel*)( ((char *)self ) + ChanOffsetTable[ index ] );	\
+                Channel__ ## _FUNC_ (regChan, self, val); \
+	}
+
+void Chip__WriteReg(Chip *self, Bit32u reg, Bit8u val ) {
+	Bitu index;
+	switch ( (reg & 0xf0) >> 4 ) {
+	case 0x00 >> 4:
+		if ( reg == 0x01 ) {
+			self->waveFormMask = ( val & 0x20 ) ? 0x7 : 0x0; 
+		} else if ( reg == 0x104 ) {
+			//Only detect changes in lowest 6 bits
+			if ( !((self->reg104 ^ val) & 0x3f) )
+				return;
+			//Always keep the highest bit enabled, for checking > 0x80
+			self->reg104 = 0x80 | ( val & 0x3f );
+		} else if ( reg == 0x105 ) {
+                        int i;
+
+			//MAME says the real opl3 doesn't reset anything on opl3 disable/enable till the next write in another register
+			if ( !((self->opl3Active ^ val) & 1 ) )
+				return;
+			self->opl3Active = ( val & 1 ) ? 0xff : 0;
+			//Update the 0xc0 register for all channels to signal the switch to mono/stereo handlers
+			for ( i = 0; i < 18;i++ ) {
+                                Channel__ResetC0( &self->chan[i], self );
+			}
+		} else if ( reg == 0x08 ) {
+			self->reg08 = val;
+		}
+	case 0x10 >> 4:
+		break;
+	case 0x20 >> 4:
+	case 0x30 >> 4:
+		REGOP( Write20 );
+		break;
+	case 0x40 >> 4:
+	case 0x50 >> 4:
+		REGOP( Write40 );
+		break;
+	case 0x60 >> 4:
+	case 0x70 >> 4:
+		REGOP( Write60 );
+		break;
+	case 0x80 >> 4:
+	case 0x90 >> 4:
+		REGOP( Write80 );
+		break;
+	case 0xa0 >> 4:
+		REGCHAN( WriteA0 );
+		break;
+	case 0xb0 >> 4:
+		if ( reg == 0xbd ) {
+			Chip__WriteBD( self, val );
+		} else {
+			REGCHAN( WriteB0 );
+		}
+		break;
+	case 0xc0 >> 4:
+		REGCHAN( WriteC0 );
+	case 0xd0 >> 4:
+		break;
+	case 0xe0 >> 4:
+	case 0xf0 >> 4:
+		REGOP( WriteE0 );
+		break;
+	}
+}
+
+Bit32u Chip__WriteAddr(Chip *self, Bit32u port, Bit8u val ) {
+	switch ( port & 3 ) {
+	case 0:
+		return val;
+	case 2:
+		if ( self->opl3Active || (val == 0x05) )
+			return 0x100 | val;
+		else
+			return val;
+	}
+	return 0;
+}
+
+void Chip__GenerateBlock2(Chip *self, Bitu total, Bit32s* output ) {
+	while ( total > 0 ) {
+                Channel *ch;
+		int count;
+
+		Bit32u samples = Chip__ForwardLFO( self, total );
+		memset(output, 0, sizeof(Bit32s) * samples);
+		count = 0;
+		for ( ch = self->chan; ch < self->chan + 9; ) {
+			count++;
+			ch = (ch->synthHandler)( ch, self, samples, output );
+		}
+		total -= samples;
+		output += samples;
+	}
+}
+
+void Chip__GenerateBlock3(Chip *self, Bitu total, Bit32s* output  ) {
+	while ( total > 0 ) {
+                int count;
+                Channel *ch;
+
+		Bit32u samples = Chip__ForwardLFO( self, total );
+		memset(output, 0, sizeof(Bit32s) * samples *2);
+		count = 0;
+		for ( ch = self->chan; ch < self->chan + 18; ) {
+			count++;
+			ch = (ch->synthHandler)( ch, self, samples, output );
+		}
+		total -= samples;
+		output += samples * 2;
+	}
+}
+
+void Chip__Setup(Chip *self, Bit32u rate ) {
+	double original = OPLRATE;
+        Bit32u i;
+//	double original = rate;
+	double scale = original / (double)rate;
+
+	//Noise counter is run at the same precision as general waves
+	self->noiseAdd = (Bit32u)( 0.5 + scale * ( 1 << LFO_SH ) );
+	self->noiseCounter = 0;
+	self->noiseValue = 1;	//Make sure it triggers the noise xor the first time
+	//The low frequency oscillation counter
+	//Every time his overflows vibrato and tremoloindex are increased
+	self->lfoAdd = (Bit32u)( 0.5 + scale * ( 1 << LFO_SH ) );
+	self->lfoCounter = 0;
+	self->vibratoIndex = 0;
+	self->tremoloIndex = 0;
+
+	//With higher octave this gets shifted up
+	//-1 since the freqCreateTable = *2
+#ifdef WAVE_PRECISION
+	double freqScale = ( 1 << 7 ) * scale * ( 1 << ( WAVE_SH - 1 - 10));
+	for ( i = 0; i < 16; i++ ) {
+		self->freqMul[i] = (Bit32u)( 0.5 + freqScale * FreqCreateTable[ i ] );
+	}
+#else
+	Bit32u freqScale = (Bit32u)( 0.5 + scale * ( 1 << ( WAVE_SH - 1 - 10)));
+	for ( i = 0; i < 16; i++ ) {
+		self->freqMul[i] = freqScale * FreqCreateTable[ i ];
+	}
+#endif
+
+	//-3 since the real envelope takes 8 steps to reach the single value we supply
+	for ( i = 0; i < 76; i++ ) {
+		Bit8u index, shift;
+		EnvelopeSelect( i, &index, &shift );
+		self->linearRates[i] = (Bit32u)( scale * (EnvelopeIncreaseTable[ index ] << ( RATE_SH + ENV_EXTRA - shift - 3 )));
+	}
+	//Generate the best matching attack rate
+	for ( i = 0; i < 62; i++ ) {
+		Bit8u index, shift;
+		EnvelopeSelect( i, &index, &shift );
+		//Original amount of samples the attack would take
+		Bit32s original = (Bit32u)( (AttackSamplesTable[ index ] << shift) / scale);
+		 
+		Bit32s guessAdd = (Bit32u)( scale * (EnvelopeIncreaseTable[ index ] << ( RATE_SH - shift - 3 )));
+		Bit32s bestAdd = guessAdd;
+		Bit32u bestDiff = 1 << 30;
+                Bit32u passes;
+
+		for ( passes = 0; passes < 16; passes ++ ) {
+			Bit32s volume = ENV_MAX;
+			Bit32s samples = 0;
+			Bit32u count = 0;
+			while ( volume > 0 && samples < original * 2 ) {
+				count += guessAdd;
+				Bit32s change = count >> RATE_SH;
+				count &= RATE_MASK;
+				if ( GCC_UNLIKELY(change) ) { // less than 1 % 
+					volume += ( ~volume * change ) >> 3;
+				}
+				samples++;
+
+			}
+			Bit32s diff = original - samples;
+			Bit32u lDiff = labs( diff );
+			//Init last on first pass
+			if ( lDiff < bestDiff ) {
+				bestDiff = lDiff;
+				bestAdd = guessAdd;
+				if ( !bestDiff )
+					break;
+			}
+			//Below our target
+			if ( diff < 0 ) {
+				//Better than the last time
+				Bit32s mul = ((original - diff) << 12) / original;
+				guessAdd = ((guessAdd * mul) >> 12);
+				guessAdd++;
+			} else if ( diff > 0 ) {
+				Bit32s mul = ((original - diff) << 12) / original;
+				guessAdd = (guessAdd * mul) >> 12;
+				guessAdd--;
+			}
+		}
+		self->attackRates[i] = bestAdd;
+	}
+	for ( i = 62; i < 76; i++ ) {
+		//This should provide instant volume maximizing
+		self->attackRates[i] = 8 << RATE_SH;
+	}
+	//Setup the channels with the correct four op flags
+	//Channels are accessed through a table so they appear linear here
+	self->chan[ 0].fourMask = 0x00 | ( 1 << 0 );
+	self->chan[ 1].fourMask = 0x80 | ( 1 << 0 );
+	self->chan[ 2].fourMask = 0x00 | ( 1 << 1 );
+	self->chan[ 3].fourMask = 0x80 | ( 1 << 1 );
+	self->chan[ 4].fourMask = 0x00 | ( 1 << 2 );
+	self->chan[ 5].fourMask = 0x80 | ( 1 << 2 );
+
+	self->chan[ 9].fourMask = 0x00 | ( 1 << 3 );
+	self->chan[10].fourMask = 0x80 | ( 1 << 3 );
+	self->chan[11].fourMask = 0x00 | ( 1 << 4 );
+	self->chan[12].fourMask = 0x80 | ( 1 << 4 );
+	self->chan[13].fourMask = 0x00 | ( 1 << 5 );
+	self->chan[14].fourMask = 0x80 | ( 1 << 5 );
+
+	//mark the percussion channels
+	self->chan[ 6].fourMask = 0x40;
+	self->chan[ 7].fourMask = 0x40;
+	self->chan[ 8].fourMask = 0x40;
+
+	//Clear Everything in opl3 mode
+	Chip__WriteReg( self, 0x105, 0x1 );
+	for ( i = 0; i < 512; i++ ) {
+		if ( i == 0x105 )
+			continue;
+		Chip__WriteReg( self, i, 0xff );
+		Chip__WriteReg( self, i, 0x0 );
+	}
+	Chip__WriteReg( self, 0x105, 0x0 );
+	//Clear everything in opl2 mode
+	for ( i = 0; i < 255; i++ ) {
+		Chip__WriteReg( self, i, 0xff );
+		Chip__WriteReg( self, i, 0x0 );
+	}
+}
+
+static int doneTables = FALSE;
+void DBOPL_InitTables( void ) {
+        int i, oct;
+
+	if ( doneTables )
+		return;
+	doneTables = TRUE;
+#if ( DBOPL_WAVE == WAVE_HANDLER ) || ( DBOPL_WAVE == WAVE_TABLELOG )
+	//Exponential volume table, same as the real adlib
+	for ( i = 0; i < 256; i++ ) {
+		//Save them in reverse
+		ExpTable[i] = (int)( 0.5 + ( pow(2.0, ( 255 - i) * ( 1.0 /256 ) )-1) * 1024 );
+		ExpTable[i] += 1024; //or remove the -1 oh well :)
+		//Preshift to the left once so the final volume can shift to the right
+		ExpTable[i] *= 2;
+	}
+#endif
+#if ( DBOPL_WAVE == WAVE_HANDLER )
+	//Add 0.5 for the trunc rounding of the integer cast
+	//Do a PI sinetable instead of the original 0.5 PI
+	for ( i = 0; i < 512; i++ ) {
+		SinTable[i] = (Bit16s)( 0.5 - log10( sin( (i + 0.5) * (PI / 512.0) ) ) / log10(2.0)*256 );
+	}
+#endif
+#if ( DBOPL_WAVE == WAVE_TABLEMUL )
+	//Multiplication based tables
+	for ( i = 0; i < 384; i++ ) {
+		int s = i * 8;
+		//TODO maybe keep some of the precision errors of the original table?
+		double val = ( 0.5 + ( pow(2.0, -1.0 + ( 255 - s) * ( 1.0 /256 ) )) * ( 1 << MUL_SH ));
+		MulTable[i] = (Bit16u)(val);
+	}
+
+	//Sine Wave Base
+	for ( i = 0; i < 512; i++ ) {
+		WaveTable[ 0x0200 + i ] = (Bit16s)(sin( (i + 0.5) * (PI / 512.0) ) * 4084);
+		WaveTable[ 0x0000 + i ] = -WaveTable[ 0x200 + i ];
+	}
+	//Exponential wave
+	for ( i = 0; i < 256; i++ ) {
+		WaveTable[ 0x700 + i ] = (Bit16s)( 0.5 + ( pow(2.0, -1.0 + ( 255 - i * 8) * ( 1.0 /256 ) ) ) * 4085 );
+		WaveTable[ 0x6ff - i ] = -WaveTable[ 0x700 + i ];
+	}
+#endif
+#if ( DBOPL_WAVE == WAVE_TABLELOG )
+	//Sine Wave Base
+	for ( i = 0; i < 512; i++ ) {
+		WaveTable[ 0x0200 + i ] = (Bit16s)( 0.5 - log10( sin( (i + 0.5) * (PI / 512.0) ) ) / log10(2.0)*256 );
+		WaveTable[ 0x0000 + i ] = ((Bit16s)0x8000) | WaveTable[ 0x200 + i];
+	}
+	//Exponential wave
+	for ( i = 0; i < 256; i++ ) {
+		WaveTable[ 0x700 + i ] = i * 8;
+		WaveTable[ 0x6ff - i ] = ((Bit16s)0x8000) | i * 8;
+	} 
+#endif
+
+	//	|    |//\\|____|WAV7|//__|/\  |____|/\/\|
+	//	|\\//|    |    |WAV7|    |  \/|    |    |
+	//	|06  |0126|27  |7   |3   |4   |4 5 |5   |
+
+#if (( DBOPL_WAVE == WAVE_TABLELOG ) || ( DBOPL_WAVE == WAVE_TABLEMUL ))
+	for ( i = 0; i < 256; i++ ) {
+		//Fill silence gaps
+		WaveTable[ 0x400 + i ] = WaveTable[0];
+		WaveTable[ 0x500 + i ] = WaveTable[0];
+		WaveTable[ 0x900 + i ] = WaveTable[0];
+		WaveTable[ 0xc00 + i ] = WaveTable[0];
+		WaveTable[ 0xd00 + i ] = WaveTable[0];
+		//Replicate sines in other pieces
+		WaveTable[ 0x800 + i ] = WaveTable[ 0x200 + i ];
+		//double speed sines
+		WaveTable[ 0xa00 + i ] = WaveTable[ 0x200 + i * 2 ];
+		WaveTable[ 0xb00 + i ] = WaveTable[ 0x000 + i * 2 ];
+		WaveTable[ 0xe00 + i ] = WaveTable[ 0x200 + i * 2 ];
+		WaveTable[ 0xf00 + i ] = WaveTable[ 0x200 + i * 2 ];
+	} 
+#endif
+
+	//Create the ksl table
+	for ( oct = 0; oct < 8; oct++ ) {
+		int base = oct * 8;
+		for ( i = 0; i < 16; i++ ) {
+			int val = base - KslCreateTable[i];
+			if ( val < 0 )
+				val = 0;
+			//*4 for the final range to match attenuation range
+			KslTable[ oct * 16 + i ] = val * 4;
+		}
+	}
+	//Create the Tremolo table, just increase and decrease a triangle wave
+	for ( i = 0; i < TREMOLO_TABLE / 2; i++ ) {
+		Bit8u val = i << ENV_EXTRA;
+		TremoloTable[i] = val;
+		TremoloTable[TREMOLO_TABLE - 1 - i] = val;
+	}
+	//Create a table with offsets of the channels from the start of the chip
+        Chip *chip = NULL;
+	for ( i = 0; i < 32; i++ ) {
+		Bitu index = i & 0xf;
+		if ( index >= 9 ) {
+			ChanOffsetTable[i] = 0;
+			continue;
+		}
+		//Make sure the four op channels follow eachother
+		if ( index < 6 ) {
+			index = (index % 3) * 2 + ( index / 3 );
+		}
+		//Add back the bits for highest ones
+		if ( i >= 16 )
+			index += 9;
+		Bitu blah = (Bitu) ( &(chip->chan[ index ]) );
+		ChanOffsetTable[i] = blah;
+	}
+	//Same for operators
+	for ( i = 0; i < 64; i++ ) {
+		if ( i % 8 >= 6 || ( (i / 8) % 4 == 3 ) ) {
+			OpOffsetTable[i] = 0;
+			continue;
+		}
+		Bitu chNum = (i / 8) * 3 + (i % 8) % 3;
+		//Make sure we use 16 and up for the 2nd range to match the chanoffset gap
+		if ( chNum >= 12 )
+			chNum += 16 - 12;
+		Bitu opNum = ( i % 8 ) / 3;
+		Channel* chan = NULL;
+		Bitu blah = (Bitu) ( &(chan->op[opNum]) );
+		OpOffsetTable[i] = ChanOffsetTable[ chNum ] + blah;
+	}
+#if 0
+	//Stupid checks if table's are correct
+	for ( Bitu i = 0; i < 18; i++ ) {
+		Bit32u find = (Bit16u)( &(chip->chan[ i ]) );
+		for ( Bitu c = 0; c < 32; c++ ) {
+			if ( ChanOffsetTable[c] == find ) {
+				find = 0;
+				break;
+			}
+		}
+		if ( find ) {
+			find = find;
+		}
+	}
+	for ( Bitu i = 0; i < 36; i++ ) {
+		Bit32u find = (Bit16u)( &(chip->chan[ i / 2 ].op[i % 2]) );
+		for ( Bitu c = 0; c < 64; c++ ) {
+			if ( OpOffsetTable[c] == find ) {
+				find = 0;
+				break;
+			}
+		}
+		if ( find ) {
+			find = find;
+		}
+	}
+#endif
+}
+
+/*
+
+Bit32u Handler::WriteAddr( Bit32u port, Bit8u val ) {
+	return chip.WriteAddr( port, val );
+
+}
+void Handler::WriteReg( Bit32u addr, Bit8u val ) {
+	chip.WriteReg( addr, val );
+}
+
+void Handler::Generate( MixerChannel* chan, Bitu samples ) {
+	Bit32s buffer[ 512 * 2 ];
+	if ( GCC_UNLIKELY(samples > 512) )
+		samples = 512;
+	if ( !chip.opl3Active ) {
+		chip.GenerateBlock2( samples, buffer );
+		chan->AddSamples_m32( samples, buffer );
+	} else {
+		chip.GenerateBlock3( samples, buffer );
+		chan->AddSamples_s32( samples, buffer );
+	}
+}
+
+void Handler::Init( Bitu rate ) {
+	InitTables();
+	chip.Setup( rate );
+}
+*/
+
diff --git a/opl/dbopl.h b/opl/dbopl.h
new file mode 100644
index 00000000..a5c10bfd
--- /dev/null
+++ b/opl/dbopl.h
@@ -0,0 +1,203 @@
+/*
+ *  Copyright (C) 2002-2010  The DOSBox Team
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program 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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#include <inttypes.h>
+
+//Use 8 handlers based on a small logatirmic wavetabe and an exponential table for volume
+#define WAVE_HANDLER	10
+//Use a logarithmic wavetable with an exponential table for volume
+#define WAVE_TABLELOG	11
+//Use a linear wavetable with a multiply table for volume
+#define WAVE_TABLEMUL	12
+
+//Select the type of wave generator routine
+#define DBOPL_WAVE WAVE_TABLEMUL
+
+typedef struct _Chip Chip;
+typedef struct _Operator Operator;
+typedef struct _Channel Channel;
+
+typedef uintptr_t       Bitu;
+typedef intptr_t        Bits;
+typedef uint32_t        Bit32u;
+typedef int32_t         Bit32s;
+typedef uint16_t        Bit16u;
+typedef int16_t         Bit16s;
+typedef uint8_t         Bit8u;
+typedef int8_t          Bit8s;
+
+#if (DBOPL_WAVE == WAVE_HANDLER)
+typedef Bits ( DB_FASTCALL *WaveHandler) ( Bitu i, Bitu volume );
+#endif
+
+#define DB_FASTCALL
+
+typedef Bits (*VolumeHandler)(Operator *self);
+typedef Channel* (*SynthHandler)(Channel *self, Chip* chip, Bit32u samples, Bit32s* output );
+
+//Different synth modes that can generate blocks of data
+typedef enum {
+	sm2AM,
+	sm2FM,
+	sm3AM,
+	sm3FM,
+	sm4Start,
+	sm3FMFM,
+	sm3AMFM,
+	sm3FMAM,
+	sm3AMAM,
+	sm6Start,
+	sm2Percussion,
+	sm3Percussion,
+} SynthMode;
+
+//Shifts for the values contained in chandata variable
+enum {
+	SHIFT_KSLBASE = 16,
+	SHIFT_KEYCODE = 24,
+};
+
+//Masks for operator 20 values
+enum {
+        MASK_KSR = 0x10,
+        MASK_SUSTAIN = 0x20,
+        MASK_VIBRATO = 0x40,
+        MASK_TREMOLO = 0x80,
+};
+
+typedef enum {
+        OFF,
+        RELEASE,
+        SUSTAIN,
+        DECAY,
+        ATTACK,
+} OperatorState;
+
+struct _Operator {
+	VolumeHandler volHandler;
+
+#if (DBOPL_WAVE == WAVE_HANDLER)
+	WaveHandler waveHandler;	//Routine that generate a wave 
+#else
+	Bit16s* waveBase;
+	Bit32u waveMask;
+	Bit32u waveStart;
+#endif
+	Bit32u waveIndex;			//WAVE_BITS shifted counter of the frequency index
+	Bit32u waveAdd;				//The base frequency without vibrato
+	Bit32u waveCurrent;			//waveAdd + vibratao
+
+	Bit32u chanData;			//Frequency/octave and derived data coming from whatever channel controls this
+	Bit32u freqMul;				//Scale channel frequency with this, TODO maybe remove?
+	Bit32u vibrato;				//Scaled up vibrato strength
+	Bit32s sustainLevel;		//When stopping at sustain level stop here
+	Bit32s totalLevel;			//totalLevel is added to every generated volume
+	Bit32u currentLevel;		//totalLevel + tremolo
+	Bit32s volume;				//The currently active volume
+	
+	Bit32u attackAdd;			//Timers for the different states of the envelope
+	Bit32u decayAdd;
+	Bit32u releaseAdd;
+	Bit32u rateIndex;			//Current position of the evenlope
+
+	Bit8u rateZero;				//Bits for the different states of the envelope having no changes
+	Bit8u keyOn;				//Bitmask of different values that can generate keyon
+	//Registers, also used to check for changes
+	Bit8u reg20, reg40, reg60, reg80, regE0;
+	//Active part of the envelope we're in
+	Bit8u state;
+	//0xff when tremolo is enabled
+	Bit8u tremoloMask;
+	//Strength of the vibrato
+	Bit8u vibStrength;
+	//Keep track of the calculated KSR so we can check for changes
+	Bit8u ksr;
+};
+
+struct _Channel {
+	Operator op[2];
+	SynthHandler synthHandler;
+	Bit32u chanData;		//Frequency/octave and derived values
+	Bit32s old[2];			//Old data for feedback
+
+	Bit8u feedback;			//Feedback shift
+	Bit8u regB0;			//Register values to check for changes
+	Bit8u regC0;
+	//This should correspond with reg104, bit 6 indicates a Percussion channel, bit 7 indicates a silent channel
+	Bit8u fourMask;
+	Bit8s maskLeft;		//Sign extended values for both channel's panning
+	Bit8s maskRight;
+
+};
+
+struct _Chip {
+	//This is used as the base counter for vibrato and tremolo
+	Bit32u lfoCounter;
+	Bit32u lfoAdd;
+	
+
+	Bit32u noiseCounter;
+	Bit32u noiseAdd;
+	Bit32u noiseValue;
+
+	//Frequency scales for the different multiplications
+	Bit32u freqMul[16];
+	//Rates for decay and release for rate of this chip
+	Bit32u linearRates[76];
+	//Best match attack rates for the rate of this chip
+	Bit32u attackRates[76];
+
+	//18 channels with 2 operators each
+	Channel chan[18];
+
+	Bit8u reg104;
+	Bit8u reg08;
+	Bit8u reg04;
+	Bit8u regBD;
+	Bit8u vibratoIndex;
+	Bit8u tremoloIndex;
+	Bit8s vibratoSign;
+	Bit8u vibratoShift;
+	Bit8u tremoloValue;
+	Bit8u vibratoStrength;
+	Bit8u tremoloStrength;
+	//Mask for allowed wave forms
+	Bit8u waveFormMask;
+	//0 or -1 when enabled
+	Bit8s opl3Active;
+
+};
+
+/*
+struct Handler : public Adlib::Handler {
+	DBOPL::Chip chip;
+	virtual Bit32u WriteAddr( Bit32u port, Bit8u val );
+	virtual void WriteReg( Bit32u addr, Bit8u val );
+	virtual void Generate( MixerChannel* chan, Bitu samples );
+	virtual void Init( Bitu rate );
+};
+*/
+
+
+void Chip__Setup(Chip *self, Bit32u rate );
+void DBOPL_InitTables( void );
+void Chip__Chip(Chip *self);
+void Chip__WriteReg(Chip *self, Bit32u reg, Bit8u val );
+void Chip__GenerateBlock2(Chip *self, Bitu total, Bit32s* output );
+
+
diff --git a/opl/examples/.gitignore b/opl/examples/.gitignore
new file mode 100644
index 00000000..4d589c73
--- /dev/null
+++ b/opl/examples/.gitignore
@@ -0,0 +1,7 @@
+Makefile.in
+Makefile
+.deps
+droplay
+*.exe
+tags
+TAGS
diff --git a/opl/examples/Makefile.am b/opl/examples/Makefile.am
new file mode 100644
index 00000000..7c2c7c8a
--- /dev/null
+++ b/opl/examples/Makefile.am
@@ -0,0 +1,8 @@
+
+AM_CFLAGS = -I..
+
+noinst_PROGRAMS=droplay
+
+droplay_LDADD = ../libopl.a @LDFLAGS@ @SDL_LIBS@ @SDLMIXER_LIBS@
+droplay_SOURCES = droplay.c
+
diff --git a/opl/examples/droplay.c b/opl/examples/droplay.c
new file mode 100644
index 00000000..36f5c3c0
--- /dev/null
+++ b/opl/examples/droplay.c
@@ -0,0 +1,217 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     Demonstration program for OPL library to play back DRO
+//     format files.
+//
+//-----------------------------------------------------------------------------
+
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "SDL.h"
+
+#include "opl.h"
+
+#define HEADER_STRING "DBRAWOPL"
+#define ADLIB_PORT 0x388
+
+void WriteReg(unsigned int reg, unsigned int val)
+{
+    int i;
+
+    // This was recorded from an OPL2, but we are probably playing
+    // back on an OPL3, so we need to enable the original OPL2
+    // channels.  Doom does this already, but other games don't.
+
+    if ((reg & 0xf0) == OPL_REGS_FEEDBACK)
+    {
+        val |= 0x30;
+    }
+
+    OPL_WritePort(OPL_REGISTER_PORT, reg);
+
+    for (i=0; i<6; ++i)
+    {
+        OPL_ReadPort(OPL_REGISTER_PORT);
+    }
+
+    OPL_WritePort(OPL_DATA_PORT, val);
+
+    for (i=0; i<35; ++i)
+    {
+        OPL_ReadPort(OPL_REGISTER_PORT);
+    }
+}
+
+void ClearAllRegs(void)
+{
+    int i;
+
+    for (i=0; i<=0xff; ++i)
+    {
+	WriteReg(i, 0x00);
+    }
+}
+
+void Init(void)
+{
+    if (SDL_Init(SDL_INIT_TIMER) < 0)
+    {
+        fprintf(stderr, "Unable to initialise SDL timer\n");
+        exit(-1);
+    }
+
+    if (!OPL_Init(ADLIB_PORT))
+    {
+        fprintf(stderr, "Unable to initialise OPL layer\n");
+        exit(-1);
+    }
+}
+
+void Shutdown(void)
+{
+    OPL_Shutdown();
+}
+
+struct timer_data
+{
+    int running;
+    FILE *fstream;
+};
+
+void TimerCallback(void *data)
+{
+    struct timer_data *timer_data = data;
+    int delay;
+
+    if (!timer_data->running)
+    {
+        return;
+    }
+
+    // Read data until we must make a delay.
+
+    for (;;)
+    {
+        int reg, val;
+
+        // End of file?
+
+        if (feof(timer_data->fstream))
+        {
+            timer_data->running = 0;
+            return;
+        }
+
+        reg = fgetc(timer_data->fstream);
+        val = fgetc(timer_data->fstream);
+
+        // Register value of 0 or 1 indicates a delay.
+
+        if (reg == 0x00)
+        {
+            delay = val;
+            break;
+        }
+        else if (reg == 0x01)
+        {
+            val |= (fgetc(timer_data->fstream) << 8);
+            delay = val;
+            break;
+        }
+        else
+        {
+            WriteReg(reg, val);
+        }
+    }
+
+    // Schedule the next timer callback.
+
+    OPL_SetCallback(delay, TimerCallback, timer_data);
+}
+
+void PlayFile(char *filename)
+{
+    struct timer_data timer_data;
+    int running;
+    char buf[8];
+
+    timer_data.fstream = fopen(filename, "rb");
+
+    if (timer_data.fstream == NULL)
+    {
+        fprintf(stderr, "Failed to open %s\n", filename);
+        exit(-1);
+    }
+
+    if (fread(buf, 1, 8, timer_data.fstream) < 8)
+    {
+        fprintf(stderr, "failed to read raw OPL header\n");
+        exit(-1);
+    }
+
+    if (strncmp(buf, HEADER_STRING, 8) != 0)
+    {
+        fprintf(stderr, "Raw OPL header not found\n");
+        exit(-1);
+    }
+
+    fseek(timer_data.fstream, 28, SEEK_SET);
+    timer_data.running = 1;
+
+    // Start callback loop sequence.
+
+    OPL_SetCallback(0, TimerCallback, &timer_data);
+
+    // Sleep until the playback finishes.
+
+    do
+    {
+        OPL_Lock();
+        running = timer_data.running;
+        OPL_Unlock();
+
+        SDL_Delay(100);
+    } while (running);
+
+    fclose(timer_data.fstream);
+}
+
+int main(int argc, char *argv[])
+{
+    if (argc < 2)
+    {
+        printf("Usage: %s <filename>\n", argv[0]);
+        exit(-1);
+    }
+
+    Init();
+
+    PlayFile(argv[1]);
+
+    ClearAllRegs();
+    Shutdown();
+
+    return 0;
+}
+
diff --git a/opl/ioperm_sys.c b/opl/ioperm_sys.c
new file mode 100644
index 00000000..8f50bcd3
--- /dev/null
+++ b/opl/ioperm_sys.c
@@ -0,0 +1,361 @@
+// Emacs style mode select   -*- C++ -*-
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2002, 2003 Marcel Telka
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     Interface to the ioperm.sys driver, based on code from the
+//     Cygwin ioperm library.
+//
+//-----------------------------------------------------------------------------
+
+#ifdef _WIN32
+
+#include <stdio.h>
+
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#include <winioctl.h>
+
+#include <errno.h>
+
+#include "ioperm_sys.h"
+
+#define IOPERM_FILE L"\\\\.\\ioperm"
+
+#define IOCTL_IOPERM               \
+    CTL_CODE(FILE_DEVICE_UNKNOWN, 0xA00, METHOD_BUFFERED, FILE_ANY_ACCESS)
+
+struct ioperm_data
+{
+    unsigned long from;
+    unsigned long num;
+    int turn_on;
+};
+
+// Function pointers for advapi32.dll.  This DLL does not exist on
+// Windows 9x, so they are dynamically loaded from the DLL at runtime.
+
+static SC_HANDLE WINAPI (*MyOpenSCManagerW)(wchar_t *lpMachineName,
+                                            wchar_t *lpDatabaseName,
+                                            DWORD dwDesiredAccess) = NULL;
+static SC_HANDLE WINAPI (*MyCreateServiceW)(SC_HANDLE hSCManager,
+                                            wchar_t *lpServiceName,
+                                            wchar_t *lpDisplayName,
+                                            DWORD dwDesiredAccess,
+                                            DWORD dwServiceType,
+                                            DWORD dwStartType,
+                                            DWORD dwErrorControl,
+                                            wchar_t *lpBinaryPathName,
+                                            wchar_t *lpLoadOrderGroup,
+                                            LPDWORD lpdwTagId,
+                                            wchar_t *lpDependencies,
+                                            wchar_t *lpServiceStartName,
+                                            wchar_t *lpPassword);
+static SC_HANDLE WINAPI (*MyOpenServiceW)(SC_HANDLE hSCManager,
+                                          wchar_t *lpServiceName,
+                                          DWORD dwDesiredAccess);
+static BOOL WINAPI (*MyStartServiceW)(SC_HANDLE hService,
+                                      DWORD dwNumServiceArgs,
+                                      wchar_t **lpServiceArgVectors);
+static BOOL WINAPI (*MyControlService)(SC_HANDLE hService,
+                                       DWORD dwControl,
+                                       LPSERVICE_STATUS lpServiceStatus);
+static BOOL WINAPI (*MyCloseServiceHandle)(SC_HANDLE hSCObject);
+static BOOL WINAPI (*MyDeleteService)(SC_HANDLE hService);
+
+static struct
+{
+    char *name;
+    void **fn;
+} dll_functions[] = {
+    { "OpenSCManagerW",     (void **) &MyOpenSCManagerW },
+    { "CreateServiceW",     (void **) &MyCreateServiceW },
+    { "OpenServiceW",       (void **) &MyOpenServiceW },
+    { "StartServiceW",      (void **) &MyStartServiceW },
+    { "ControlService",     (void **) &MyControlService },
+    { "CloseServiceHandle", (void **) &MyCloseServiceHandle },
+    { "DeleteService",      (void **) &MyDeleteService },
+};
+
+// Globals
+
+static SC_HANDLE scm = NULL;
+static SC_HANDLE svc = NULL;
+static int service_was_created = 0;
+static int service_was_started = 0;
+
+static int LoadLibraryPointers(void)
+{
+    HMODULE dll;
+    int i;
+
+    // Already loaded?
+
+    if (MyOpenSCManagerW != NULL)
+    {
+        return 1;
+    }
+
+    dll = LoadLibraryW(L"advapi32.dll");
+
+    if (dll == NULL)
+    {
+        fprintf(stderr, "LoadLibraryPointers: Failed to open advapi32.dll\n");
+        return 0;
+    }
+
+    for (i = 0; i < sizeof(dll_functions) / sizeof(*dll_functions); ++i)
+    {
+        *dll_functions[i].fn = GetProcAddress(dll, dll_functions[i].name);
+
+        if (*dll_functions[i].fn == NULL)
+        {
+            fprintf(stderr, "LoadLibraryPointers: Failed to get address "
+                            "for '%s'\n", dll_functions[i].name);
+            return 0;
+        }
+    }
+
+    return 1;
+}
+
+int IOperm_EnablePortRange(unsigned int from, unsigned int num, int turn_on)
+{
+    HANDLE h;
+    struct ioperm_data ioperm_data;
+    DWORD BytesReturned;
+    BOOL r;
+
+    h = CreateFileW(IOPERM_FILE, GENERIC_READ, 0, NULL,
+                    OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
+
+    if (h == INVALID_HANDLE_VALUE)
+    {
+        errno = ENODEV;
+        return -1;
+    }
+
+    ioperm_data.from = from;
+    ioperm_data.num = num;
+    ioperm_data.turn_on = turn_on;
+
+    r = DeviceIoControl(h, IOCTL_IOPERM,
+                        &ioperm_data, sizeof ioperm_data,
+                        NULL, 0,
+                        &BytesReturned, NULL);
+
+    if (!r)
+    {
+        errno = EPERM;
+    }
+
+    CloseHandle(h);
+
+    return r != 0;
+}
+
+// Load ioperm.sys driver.
+// Returns 1 for success, 0 for failure.
+// Remember to call IOperm_UninstallDriver to uninstall the driver later.
+
+int IOperm_InstallDriver(void)
+{
+    wchar_t driver_path[MAX_PATH];
+    int error;
+    int result = 1;
+
+    if (!LoadLibraryPointers())
+    {
+        return 0;
+    }
+
+    scm = MyOpenSCManagerW(NULL, NULL, SC_MANAGER_ALL_ACCESS);
+
+    if (scm == NULL)
+    {
+        error = GetLastError();
+        fprintf(stderr, "IOperm_InstallDriver: OpenSCManager failed (%i).\n",
+                        error);
+        return 0;
+    }
+
+    // Get the full path to the driver file.
+
+    GetFullPathNameW(L"ioperm.sys", MAX_PATH, driver_path, NULL);
+
+    // Create the service.
+
+    svc = MyCreateServiceW(scm,
+                           L"ioperm",
+                           L"ioperm support for Cygwin driver",
+                           SERVICE_ALL_ACCESS,
+                           SERVICE_KERNEL_DRIVER,
+                           SERVICE_AUTO_START,
+                           SERVICE_ERROR_NORMAL,
+                           driver_path,
+                           NULL,
+                           NULL,
+                           NULL,
+                           NULL,
+                           NULL);
+
+    if (svc == NULL)
+    {
+        error = GetLastError();
+
+        if (error != ERROR_SERVICE_EXISTS)
+        {
+            fprintf(stderr,
+                    "IOperm_InstallDriver: Failed to create service (%i).\n",
+                    error);
+        }
+        else
+        {
+            svc = MyOpenServiceW(scm, L"ioperm", SERVICE_ALL_ACCESS);
+
+            if (svc == NULL)
+            {
+                error = GetLastError();
+
+                fprintf(stderr,
+                        "IOperm_InstallDriver: Failed to open service (%i).\n",
+                        error);
+            }
+        }
+
+        if (svc == NULL)
+        {
+            MyCloseServiceHandle(scm);
+            return 0;
+        }
+    }
+    else
+    {
+        service_was_created = 1;
+    }
+
+    // Start the service.  If the service already existed, it might have
+    // already been running as well.
+
+    if (!MyStartServiceW(svc, 0, NULL))
+    {
+        error = GetLastError();
+
+        if (error != ERROR_SERVICE_ALREADY_RUNNING)
+        {
+            fprintf(stderr, "IOperm_InstallDriver: Failed to start service (%i).\n",
+                            error);
+
+            result = 0;
+        }
+        else
+        {
+            printf("IOperm_InstallDriver: ioperm driver already running.\n");
+        }
+    }
+    else
+    {
+        printf("IOperm_InstallDriver: ioperm driver installed.\n");
+        service_was_started = 1;
+    }
+
+    // If we failed to start the driver running, we need to clean up
+    // before finishing.
+
+    if (result == 0)
+    {
+        IOperm_UninstallDriver();
+    }
+
+    return result;
+}
+
+int IOperm_UninstallDriver(void)
+{
+    SERVICE_STATUS stat;
+    int result = 1;
+    int error;
+
+    // If we started the service, stop it.
+
+    if (service_was_started)
+    {
+        if (!MyControlService(svc, SERVICE_CONTROL_STOP, &stat))
+        {
+            error = GetLastError();
+
+            if (error == ERROR_SERVICE_NOT_ACTIVE)
+            {
+                fprintf(stderr,
+                        "IOperm_UninstallDriver: Service not active? (%i)\n",
+                        error);
+            }
+            else
+            {
+                fprintf(stderr,
+                        "IOperm_UninstallDriver: Failed to stop service (%i).\n",
+                        error);
+                result = 0;
+            }
+        }
+    }
+
+    // If we created the service, delete it.
+
+    if (service_was_created)
+    {
+        if (!MyDeleteService(svc))
+        {
+            error = GetLastError();
+
+            fprintf(stderr,
+                    "IOperm_UninstallDriver: DeleteService failed (%i).\n",
+                    error);
+
+            result = 0;
+        }
+        else if (service_was_started)
+        {
+            printf("IOperm_UnInstallDriver: ioperm driver uninstalled.\n");
+        }
+    }
+
+    // Close handles.
+
+    if (svc != NULL)
+    {
+        MyCloseServiceHandle(svc);
+        svc = NULL;
+    }
+
+    if (scm != NULL)
+    {
+        MyCloseServiceHandle(scm);
+        scm = NULL;
+    }
+
+    service_was_created = 0;
+    service_was_started = 0;
+
+    return result;
+}
+
+#endif /* #ifndef _WIN32 */
+
diff --git a/opl/ioperm_sys.h b/opl/ioperm_sys.h
new file mode 100644
index 00000000..faf17bf3
--- /dev/null
+++ b/opl/ioperm_sys.h
@@ -0,0 +1,36 @@
+// Emacs style mode select   -*- C++ -*-
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2002, 2003 Marcel Telka
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     Interface to the ioperm.sys driver, based on code from the
+//     Cygwin ioperm library.
+//
+//-----------------------------------------------------------------------------
+
+#ifndef IOPERM_SYS_H
+#define IOPERM_SYS_H
+
+int IOperm_EnablePortRange(unsigned int from, unsigned int num, int turn_on);
+int IOperm_InstallDriver(void);
+int IOperm_UninstallDriver(void);
+
+#endif /* #ifndef IOPERM_SYS_H */
+
diff --git a/opl/opl.c b/opl/opl.c
new file mode 100644
index 00000000..6d0e16db
--- /dev/null
+++ b/opl/opl.c
@@ -0,0 +1,466 @@
+// Emacs style mode select   -*- C++ -*-
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL interface.
+//
+//-----------------------------------------------------------------------------
+
+#include "config.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#ifdef _WIN32_WCE
+#include "libc_wince.h"
+#endif
+
+#include "SDL.h"
+
+#include "opl.h"
+#include "opl_internal.h"
+
+//#define OPL_DEBUG_TRACE
+
+#ifdef HAVE_IOPERM
+extern opl_driver_t opl_linux_driver;
+#endif
+#if defined(HAVE_LIBI386) || defined(HAVE_LIBAMD64)
+extern opl_driver_t opl_openbsd_driver;
+#endif
+#ifdef _WIN32
+extern opl_driver_t opl_win32_driver;
+#endif
+extern opl_driver_t opl_sdl_driver;
+
+static opl_driver_t *drivers[] =
+{
+#ifdef HAVE_IOPERM
+    &opl_linux_driver,
+#endif
+#if defined(HAVE_LIBI386) || defined(HAVE_LIBAMD64)
+    &opl_openbsd_driver,
+#endif
+#ifdef _WIN32
+    &opl_win32_driver,
+#endif
+    &opl_sdl_driver,
+    NULL
+};
+
+static opl_driver_t *driver = NULL;
+static int init_stage_reg_writes = 1;
+
+unsigned int opl_sample_rate = 22050;
+
+//
+// Init/shutdown code.
+//
+
+// Initialize the specified driver and detect an OPL chip.  Returns
+// true if an OPL is detected.
+
+static int InitDriver(opl_driver_t *_driver, unsigned int port_base)
+{
+    // Initialize the driver.
+
+    if (!_driver->init_func(port_base))
+    {
+        return 0;
+    }
+
+    // The driver was initialized okay, so we now have somewhere
+    // to write to.  It doesn't mean there's an OPL chip there,
+    // though.  Perform the detection sequence to make sure.
+    // (it's done twice, like how Doom does it).
+
+    driver = _driver;
+    init_stage_reg_writes = 1;
+
+    if (!OPL_Detect() || !OPL_Detect())
+    {
+        printf("OPL_Init: No OPL detected using '%s' driver.\n", _driver->name);
+        _driver->shutdown_func();
+        driver = NULL;
+        return 0;
+    }
+
+    // Initialize all registers.
+
+    OPL_InitRegisters();
+
+    init_stage_reg_writes = 0;
+
+    printf("OPL_Init: Using driver '%s'.\n", driver->name);
+
+    return 1;
+}
+
+// Find a driver automatically by trying each in the list.
+
+static int AutoSelectDriver(unsigned int port_base)
+{
+    int i;
+
+    for (i=0; drivers[i] != NULL; ++i)
+    {
+        if (InitDriver(drivers[i], port_base))
+        {
+            return 1;
+        }
+    }
+
+    printf("OPL_Init: Failed to find a working driver.\n");
+
+    return 0;
+}
+
+// Initialize the OPL library.  Returns true if initialized
+// successfully.
+
+int OPL_Init(unsigned int port_base)
+{
+    char *driver_name;
+    int i;
+
+    driver_name = getenv("OPL_DRIVER");
+
+    if (driver_name != NULL)
+    {
+        // Search the list until we find the driver with this name.
+
+        for (i=0; drivers[i] != NULL; ++i)
+        {
+            if (!strcmp(driver_name, drivers[i]->name))
+            {
+                if (InitDriver(drivers[i], port_base))
+                {
+                    return 1;
+                }
+                else
+                {
+                    printf("OPL_Init: Failed to initialize "
+                           "driver: '%s'.\n", driver_name);
+                    return 0;
+                }
+            }
+        }
+
+        printf("OPL_Init: unknown driver: '%s'.\n", driver_name);
+
+        return 0;
+    }
+    else
+    {
+        return AutoSelectDriver(port_base);
+    }
+}
+
+// Shut down the OPL library.
+
+void OPL_Shutdown(void)
+{
+    if (driver != NULL)
+    {
+        driver->shutdown_func();
+        driver = NULL;
+    }
+}
+
+// Set the sample rate used for software OPL emulation.
+
+void OPL_SetSampleRate(unsigned int rate)
+{
+    opl_sample_rate = rate;
+}
+
+void OPL_WritePort(opl_port_t port, unsigned int value)
+{
+    if (driver != NULL)
+    {
+#ifdef OPL_DEBUG_TRACE
+        printf("OPL_write: %i, %x\n", port, value);
+        fflush(stdout);
+#endif
+        driver->write_port_func(port, value);
+    }
+}
+
+unsigned int OPL_ReadPort(opl_port_t port)
+{
+    if (driver != NULL)
+    {
+        unsigned int result;
+
+#ifdef OPL_DEBUG_TRACE
+        printf("OPL_read: %i...\n", port);
+        fflush(stdout);
+#endif
+
+        result = driver->read_port_func(port);
+
+#ifdef OPL_DEBUG_TRACE
+        printf("OPL_read: %i -> %x\n", port, result);
+        fflush(stdout);
+#endif
+
+        return result;
+    }
+    else
+    {
+        return 0;
+    }
+}
+
+//
+// Higher-level functions, based on the lower-level functions above
+// (register write, etc).
+//
+
+unsigned int OPL_ReadStatus(void)
+{
+    return OPL_ReadPort(OPL_REGISTER_PORT);
+}
+
+// Write an OPL register value
+
+void OPL_WriteRegister(int reg, int value)
+{
+    int i;
+
+    OPL_WritePort(OPL_REGISTER_PORT, reg);
+
+    // For timing, read the register port six times after writing the
+    // register number to cause the appropriate delay
+
+    for (i=0; i<6; ++i)
+    {
+        // An oddity of the Doom OPL code: at startup initialization,
+        // the spacing here is performed by reading from the register
+        // port; after initialization, the data port is read, instead.
+
+        if (init_stage_reg_writes)
+        {
+            OPL_ReadPort(OPL_REGISTER_PORT);
+        }
+        else
+        {
+            OPL_ReadPort(OPL_DATA_PORT);
+        }
+    }
+
+    OPL_WritePort(OPL_DATA_PORT, value);
+
+    // Read the register port 24 times after writing the value to
+    // cause the appropriate delay
+
+    for (i=0; i<24; ++i)
+    {
+        OPL_ReadStatus();
+    }
+}
+
+// Detect the presence of an OPL chip
+
+int OPL_Detect(void)
+{
+    int result1, result2;
+    int i;
+
+    // Reset both timers:
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL, 0x60);
+
+    // Enable interrupts:
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL, 0x80);
+
+    // Read status
+    result1 = OPL_ReadStatus();
+
+    // Set timer:
+    OPL_WriteRegister(OPL_REG_TIMER1, 0xff);
+
+    // Start timer 1:
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL, 0x21);
+
+    // Wait for 80 microseconds
+    // This is how Doom does it:
+
+    for (i=0; i<200; ++i)
+    {
+        OPL_ReadStatus();
+    }
+
+    OPL_Delay(1);
+
+    // Read status
+    result2 = OPL_ReadStatus();
+
+    // Reset both timers:
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL, 0x60);
+
+    // Enable interrupts:
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL, 0x80);
+
+    return (result1 & 0xe0) == 0x00
+        && (result2 & 0xe0) == 0xc0;
+}
+
+// Initialize registers on startup
+
+void OPL_InitRegisters(void)
+{
+    int r;
+
+    // Initialize level registers
+
+    for (r=OPL_REGS_LEVEL; r <= OPL_REGS_LEVEL + OPL_NUM_OPERATORS; ++r)
+    {
+        OPL_WriteRegister(r, 0x3f);
+    }
+
+    // Initialize other registers
+    // These two loops write to registers that actually don't exist,
+    // but this is what Doom does ...
+    // Similarly, the <= is also intenational.
+
+    for (r=OPL_REGS_ATTACK; r <= OPL_REGS_WAVEFORM + OPL_NUM_OPERATORS; ++r)
+    {
+        OPL_WriteRegister(r, 0x00);
+    }
+
+    // More registers ...
+
+    for (r=1; r < OPL_REGS_LEVEL; ++r)
+    {
+        OPL_WriteRegister(r, 0x00);
+    }
+
+    // Re-initialize the low registers:
+
+    // Reset both timers and enable interrupts:
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL,      0x60);
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL,      0x80);
+
+    // "Allow FM chips to control the waveform of each operator":
+    OPL_WriteRegister(OPL_REG_WAVEFORM_ENABLE, 0x20);
+
+    // Keyboard split point on (?)
+    OPL_WriteRegister(OPL_REG_FM_MODE,         0x40);
+}
+
+//
+// Timer functions.
+//
+
+void OPL_SetCallback(unsigned int ms, opl_callback_t callback, void *data)
+{
+    if (driver != NULL)
+    {
+        driver->set_callback_func(ms, callback, data);
+    }
+}
+
+void OPL_ClearCallbacks(void)
+{
+    if (driver != NULL)
+    {
+        driver->clear_callbacks_func();
+    }
+}
+
+void OPL_Lock(void)
+{
+    if (driver != NULL)
+    {
+        driver->lock_func();
+    }
+}
+
+void OPL_Unlock(void)
+{
+    if (driver != NULL)
+    {
+        driver->unlock_func();
+    }
+}
+
+typedef struct
+{
+    int finished;
+
+    SDL_mutex *mutex;
+    SDL_cond *cond;
+} delay_data_t;
+
+static void DelayCallback(void *_delay_data)
+{
+    delay_data_t *delay_data = _delay_data;
+
+    SDL_LockMutex(delay_data->mutex);
+    delay_data->finished = 1;
+
+    SDL_CondSignal(delay_data->cond);
+
+    SDL_UnlockMutex(delay_data->mutex);
+}
+
+void OPL_Delay(unsigned int ms)
+{
+    delay_data_t delay_data;
+
+    if (driver == NULL)
+    {
+        return;
+    }
+
+    // Create a callback that will signal this thread after the
+    // specified time.
+
+    delay_data.finished = 0;
+    delay_data.mutex = SDL_CreateMutex();
+    delay_data.cond = SDL_CreateCond();
+
+    OPL_SetCallback(ms, DelayCallback, &delay_data);
+
+    // Wait until the callback is invoked.
+
+    SDL_LockMutex(delay_data.mutex);
+
+    while (!delay_data.finished)
+    {
+        SDL_CondWait(delay_data.cond, delay_data.mutex);
+    }
+
+    SDL_UnlockMutex(delay_data.mutex);
+
+    // Clean up.
+
+    SDL_DestroyMutex(delay_data.mutex);
+    SDL_DestroyCond(delay_data.cond);
+}
+
+void OPL_SetPaused(int paused)
+{
+    if (driver != NULL)
+    {
+        driver->set_paused_func(paused);
+    }
+}
+
diff --git a/opl/opl.h b/opl/opl.h
new file mode 100644
index 00000000..04d3cf27
--- /dev/null
+++ b/opl/opl.h
@@ -0,0 +1,137 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL interface.
+//
+//-----------------------------------------------------------------------------
+
+
+#ifndef OPL_OPL_H
+#define OPL_OPL_H
+
+typedef void (*opl_callback_t)(void *data);
+
+typedef enum
+{
+    OPL_REGISTER_PORT = 0,
+    OPL_DATA_PORT = 1
+} opl_port_t;
+
+#define OPL_NUM_OPERATORS   21
+#define OPL_NUM_VOICES      9
+
+#define OPL_REG_WAVEFORM_ENABLE   0x01
+#define OPL_REG_TIMER1            0x02
+#define OPL_REG_TIMER2            0x03
+#define OPL_REG_TIMER_CTRL        0x04
+#define OPL_REG_FM_MODE           0x08
+
+// Operator registers (21 of each):
+
+#define OPL_REGS_TREMOLO          0x20
+#define OPL_REGS_LEVEL            0x40
+#define OPL_REGS_ATTACK           0x60
+#define OPL_REGS_SUSTAIN          0x80
+#define OPL_REGS_WAVEFORM         0xE0
+
+// Voice registers (9 of each):
+
+#define OPL_REGS_FREQ_1           0xA0
+#define OPL_REGS_FREQ_2           0xB0
+#define OPL_REGS_FEEDBACK         0xC0
+
+//
+// Low-level functions.
+//
+
+// Initialize the OPL subsystem.
+
+int OPL_Init(unsigned int port_base);
+
+// Shut down the OPL subsystem.
+
+void OPL_Shutdown(void);
+
+// Set the sample rate used for software emulation.
+
+void OPL_SetSampleRate(unsigned int rate);
+
+// Write to one of the OPL I/O ports:
+
+void OPL_WritePort(opl_port_t port, unsigned int value);
+
+// Read from one of the OPL I/O ports:
+
+unsigned int OPL_ReadPort(opl_port_t port);
+
+//
+// Higher-level functions.
+//
+
+// Read the cuurrent status byte of the OPL chip.
+
+unsigned int OPL_ReadStatus(void);
+
+// Write to an OPL register.
+
+void OPL_WriteRegister(int reg, int value);
+
+// Perform a detection sequence to determine that an
+// OPL chip is present.
+
+int OPL_Detect(void);
+
+// Initialize all registers, performed on startup.
+
+void OPL_InitRegisters(void);
+
+//
+// Timer callback functions.
+//
+
+// Set a timer callback.  After the specified number of milliseconds
+// have elapsed, the callback will be invoked.
+
+void OPL_SetCallback(unsigned int ms, opl_callback_t callback, void *data);
+
+// Clear all OPL callbacks that have been set.
+
+void OPL_ClearCallbacks(void);
+
+// Begin critical section, during which, OPL callbacks will not be
+// invoked.
+
+void OPL_Lock(void);
+
+// End critical section.
+
+void OPL_Unlock(void);
+
+// Block until the specified number of milliseconds have elapsed.
+
+void OPL_Delay(unsigned int ms);
+
+// Pause the OPL callbacks.
+
+void OPL_SetPaused(int paused);
+
+#endif
+
diff --git a/opl/opl_internal.h b/opl/opl_internal.h
new file mode 100644
index 00000000..4a46b060
--- /dev/null
+++ b/opl/opl_internal.h
@@ -0,0 +1,64 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL internal interface.
+//
+//-----------------------------------------------------------------------------
+
+
+#ifndef OPL_INTERNAL_H
+#define OPL_INTERNAL_H
+
+#include "opl.h"
+
+typedef int (*opl_init_func)(unsigned int port_base);
+typedef void (*opl_shutdown_func)(void);
+typedef unsigned int (*opl_read_port_func)(opl_port_t port);
+typedef void (*opl_write_port_func)(opl_port_t port, unsigned int value);
+typedef void (*opl_set_callback_func)(unsigned int ms,
+                                      opl_callback_t callback,
+                                      void *data);
+typedef void (*opl_clear_callbacks_func)(void);
+typedef void (*opl_lock_func)(void);
+typedef void (*opl_unlock_func)(void);
+typedef void (*opl_set_paused_func)(int paused);
+
+typedef struct
+{
+    char *name;
+
+    opl_init_func init_func;
+    opl_shutdown_func shutdown_func;
+    opl_read_port_func read_port_func;
+    opl_write_port_func write_port_func;
+    opl_set_callback_func set_callback_func;
+    opl_clear_callbacks_func clear_callbacks_func;
+    opl_lock_func lock_func;
+    opl_unlock_func unlock_func;
+    opl_set_paused_func set_paused_func;
+} opl_driver_t;
+
+// Sample rate to use when doing software emulation.
+
+extern unsigned int opl_sample_rate;
+
+#endif /* #ifndef OPL_INTERNAL_H */
+
diff --git a/opl/opl_linux.c b/opl/opl_linux.c
new file mode 100644
index 00000000..319686b8
--- /dev/null
+++ b/opl/opl_linux.c
@@ -0,0 +1,110 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL Linux interface.
+//
+//-----------------------------------------------------------------------------
+
+#include "config.h"
+
+#ifdef HAVE_IOPERM
+
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/io.h>
+
+#include "opl.h"
+#include "opl_internal.h"
+#include "opl_timer.h"
+
+static unsigned int opl_port_base;
+
+static int OPL_Linux_Init(unsigned int port_base)
+{
+    // Try to get permissions:
+
+    if (ioperm(port_base, 2, 1) < 0)
+    {
+        fprintf(stderr, "Failed to get I/O port permissions for 0x%x: %s\n",
+                        port_base, strerror(errno));
+
+        if (errno == EPERM)
+        {
+            fprintf(stderr,
+                    "\tYou may need to run the program as root in order\n"
+                    "\tto acquire I/O port permissions for OPL MIDI playback.\n");
+        }
+
+        return 0;
+    }
+
+    opl_port_base = port_base;
+
+    // Start callback thread
+
+    if (!OPL_Timer_StartThread())
+    {
+        ioperm(port_base, 2, 0);
+        return 0;
+    }
+
+    return 1;
+}
+
+static void OPL_Linux_Shutdown(void)
+{
+    // Stop callback thread
+
+    OPL_Timer_StopThread();
+
+    // Release permissions
+
+    ioperm(opl_port_base, 2, 0);
+}
+
+static unsigned int OPL_Linux_PortRead(opl_port_t port)
+{
+    return inb(opl_port_base + port);
+}
+
+static void OPL_Linux_PortWrite(opl_port_t port, unsigned int value)
+{
+    outb(value, opl_port_base + port);
+}
+
+opl_driver_t opl_linux_driver =
+{
+    "Linux",
+    OPL_Linux_Init,
+    OPL_Linux_Shutdown,
+    OPL_Linux_PortRead,
+    OPL_Linux_PortWrite,
+    OPL_Timer_SetCallback,
+    OPL_Timer_ClearCallbacks,
+    OPL_Timer_Lock,
+    OPL_Timer_Unlock,
+    OPL_Timer_SetPaused
+};
+
+#endif /* #ifdef HAVE_IOPERM */
+
diff --git a/opl/opl_obsd.c b/opl/opl_obsd.c
new file mode 100644
index 00000000..b07a0421
--- /dev/null
+++ b/opl/opl_obsd.c
@@ -0,0 +1,125 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL OpenBSD interface (also NetBSD)
+//
+//-----------------------------------------------------------------------------
+
+#include "config.h"
+
+// OpenBSD has a i386_iopl on i386 and amd64_iopl on x86_64,
+// even though they do the same thing.  Take care of this
+// here, and map set_iopl to point to the appropriate name.
+
+#if defined(HAVE_LIBI386)
+
+#include <sys/types.h>
+#include <machine/sysarch.h>
+#include <i386/pio.h>
+#define set_iopl i386_iopl
+
+#elif defined(HAVE_LIBAMD64)
+
+#include <sys/types.h>
+#include <machine/sysarch.h>
+#include <amd64/pio.h>
+#define set_iopl amd64_iopl
+
+#else
+#define NO_OBSD_DRIVER
+#endif
+
+// If the above succeeded, proceed with the rest.
+
+#ifndef NO_OBSD_DRIVER
+
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+
+#include "opl.h"
+#include "opl_internal.h"
+#include "opl_timer.h"
+
+static unsigned int opl_port_base;
+
+static int OPL_OpenBSD_Init(unsigned int port_base)
+{
+    // Try to get permissions:
+
+    if (set_iopl(3) < 0)
+    {
+        fprintf(stderr, "Failed to get raise I/O privilege level: "
+                        "check that you are running as root.\n");
+        return 0;
+    }
+
+    opl_port_base = port_base;
+
+    // Start callback thread
+
+    if (!OPL_Timer_StartThread())
+    {
+        set_iopl(0);
+        return 0;
+    }
+
+    return 1;
+}
+
+static void OPL_OpenBSD_Shutdown(void)
+{
+    // Stop callback thread
+
+    OPL_Timer_StopThread();
+
+    // Release I/O port permissions:
+
+    set_iopl(0);
+}
+
+static unsigned int OPL_OpenBSD_PortRead(opl_port_t port)
+{
+    return inb(opl_port_base + port);
+}
+
+static void OPL_OpenBSD_PortWrite(opl_port_t port, unsigned int value)
+{
+    outb(opl_port_base + port, value);
+}
+
+opl_driver_t opl_openbsd_driver =
+{
+    "OpenBSD",
+    OPL_OpenBSD_Init,
+    OPL_OpenBSD_Shutdown,
+    OPL_OpenBSD_PortRead,
+    OPL_OpenBSD_PortWrite,
+    OPL_Timer_SetCallback,
+    OPL_Timer_ClearCallbacks,
+    OPL_Timer_Lock,
+    OPL_Timer_Unlock,
+    OPL_Timer_SetPaused
+};
+
+#endif /* #ifndef NO_OBSD_DRIVER */
+
diff --git a/opl/opl_queue.c b/opl/opl_queue.c
new file mode 100644
index 00000000..f9d4c377
--- /dev/null
+++ b/opl/opl_queue.c
@@ -0,0 +1,280 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     Queue of waiting callbacks, stored in a binary min heap, so that we
+//     can always get the first callback.
+//
+//-----------------------------------------------------------------------------
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "opl_queue.h"
+
+#define MAX_OPL_QUEUE 64
+
+typedef struct
+{
+    opl_callback_t callback;
+    void *data;
+    unsigned int time;
+} opl_queue_entry_t;
+
+struct opl_callback_queue_s
+{
+    opl_queue_entry_t entries[MAX_OPL_QUEUE];
+    unsigned int num_entries;
+};
+
+opl_callback_queue_t *OPL_Queue_Create(void)
+{
+    opl_callback_queue_t *queue;
+
+    queue = malloc(sizeof(opl_callback_queue_t));
+    queue->num_entries = 0;
+
+    return queue;
+}
+
+void OPL_Queue_Destroy(opl_callback_queue_t *queue)
+{
+    free(queue);
+}
+
+int OPL_Queue_IsEmpty(opl_callback_queue_t *queue)
+{
+    return queue->num_entries == 0;
+}
+
+void OPL_Queue_Clear(opl_callback_queue_t *queue)
+{
+    queue->num_entries = 0;
+}
+
+void OPL_Queue_Push(opl_callback_queue_t *queue,
+                    opl_callback_t callback, void *data,
+                    unsigned int time)
+{
+    int entry_id;
+    int parent_id;
+
+    if (queue->num_entries >= MAX_OPL_QUEUE)
+    {
+        fprintf(stderr, "OPL_Queue_Push: Exceeded maximum callbacks\n");
+        return;
+    }
+
+    // Add to last queue entry.
+
+    entry_id = queue->num_entries;
+    ++queue->num_entries;
+
+    // Shift existing entries down in the heap.
+
+    while (entry_id > 0)
+    {
+        parent_id = (entry_id - 1) / 2;
+
+        // Is the heap condition satisfied?
+
+        if (time >= queue->entries[parent_id].time)
+        {
+            break;
+        }
+
+        // Move the existing entry down in the heap.
+
+        memcpy(&queue->entries[entry_id],
+               &queue->entries[parent_id],
+               sizeof(opl_queue_entry_t));
+
+        // Advance to the parent.
+
+        entry_id = parent_id;
+    }
+
+    // Insert new callback data.
+
+    queue->entries[entry_id].callback = callback;
+    queue->entries[entry_id].data = data;
+    queue->entries[entry_id].time = time;
+}
+
+int OPL_Queue_Pop(opl_callback_queue_t *queue,
+                  opl_callback_t *callback, void **data)
+{
+    opl_queue_entry_t *entry;
+    int child1, child2;
+    int i, next_i;
+
+    // Empty?
+
+    if (queue->num_entries <= 0)
+    {
+        return 0;
+    }
+
+    // Store the result:
+
+    *callback = queue->entries[0].callback;
+    *data = queue->entries[0].data;
+
+    // Decrease the heap size, and keep pointer to the last entry in
+    // the heap, which must now be percolated down from the top.
+
+    --queue->num_entries;
+    entry = &queue->entries[queue->num_entries];
+
+    // Percolate down.
+
+    i = 0;
+
+    for (;;)
+    {
+        child1 = i * 2 + 1;
+        child2 = i * 2 + 2;
+
+        if (child1 < queue->num_entries
+         && queue->entries[child1].time < entry->time)
+        {
+            // Left child is less than entry.
+            // Use the minimum of left and right children.
+
+            if (child2 < queue->num_entries
+             && queue->entries[child2].time < queue->entries[child1].time)
+            {
+                next_i = child2;
+            }
+            else
+            {
+                next_i = child1;
+            }
+        }
+        else if (child2 < queue->num_entries
+              && queue->entries[child2].time < entry->time)
+        {
+            // Right child is less than entry.  Go down the right side.
+
+            next_i = child2;
+        }
+        else
+        {
+            // Finished percolating.
+            break;
+        }
+
+        // Percolate the next value up and advance.
+
+        memcpy(&queue->entries[i],
+               &queue->entries[next_i],
+               sizeof(opl_queue_entry_t));
+        i = next_i;
+    }
+
+    // Store the old last-entry at its new position.
+
+    memcpy(&queue->entries[i], entry, sizeof(opl_queue_entry_t));
+
+    return 1;
+}
+
+unsigned int OPL_Queue_Peek(opl_callback_queue_t *queue)
+{
+    if (queue->num_entries > 0)
+    {
+        return queue->entries[0].time;
+    }
+    else
+    {
+        return 0;
+    }
+}
+
+#ifdef TEST
+
+#include <assert.h>
+
+static void PrintQueueNode(opl_callback_queue_t *queue, int node, int depth)
+{
+    int i;
+
+    if (node >= queue->num_entries)
+    {
+        return;
+    }
+
+    for (i=0; i<depth * 3; ++i)
+    {
+        printf(" ");
+    }
+
+    printf("%i\n", queue->entries[node].time);
+
+    PrintQueueNode(queue, node * 2 + 1, depth + 1);
+    PrintQueueNode(queue, node * 2 + 2, depth + 1);
+}
+
+static void PrintQueue(opl_callback_queue_t *queue)
+{
+    PrintQueueNode(queue, 0, 0);
+}
+
+int main()
+{
+    opl_callback_queue_t *queue;
+    int iteration;
+
+    queue = OPL_Queue_Create();
+
+    for (iteration=0; iteration<5000; ++iteration)
+    {
+        opl_callback_t callback;
+        void *data;
+        unsigned int time;
+        unsigned int newtime;
+        int i;
+
+        for (i=0; i<MAX_OPL_QUEUE; ++i)
+        {
+            time = rand() % 0x10000;
+            OPL_Queue_Push(queue, NULL, NULL, time);
+        }
+
+        time = 0;
+
+        for (i=0; i<MAX_OPL_QUEUE; ++i)
+        {
+            assert(!OPL_Queue_IsEmpty(queue));
+            newtime = OPL_Queue_Peek(queue);
+            assert(OPL_Queue_Pop(queue, &callback, &data));
+
+            assert(newtime >= time);
+            time = newtime;
+        }
+
+        assert(OPL_Queue_IsEmpty(queue));
+        assert(!OPL_Queue_Pop(queue, &callback, &data));
+    }
+}
+
+#endif
+
diff --git a/opl/opl_queue.h b/opl/opl_queue.h
new file mode 100644
index 00000000..2447702b
--- /dev/null
+++ b/opl/opl_queue.h
@@ -0,0 +1,45 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL callback queue.
+//
+//-----------------------------------------------------------------------------
+
+#ifndef OPL_QUEUE_H
+#define OPL_QUEUE_H
+
+#include "opl.h"
+
+typedef struct opl_callback_queue_s opl_callback_queue_t;
+
+opl_callback_queue_t *OPL_Queue_Create(void);
+int OPL_Queue_IsEmpty(opl_callback_queue_t *queue);
+void OPL_Queue_Clear(opl_callback_queue_t *queue);
+void OPL_Queue_Destroy(opl_callback_queue_t *queue);
+void OPL_Queue_Push(opl_callback_queue_t *queue,
+                    opl_callback_t callback, void *data,
+                    unsigned int time);
+int OPL_Queue_Pop(opl_callback_queue_t *queue,
+                  opl_callback_t *callback, void **data);
+unsigned int OPL_Queue_Peek(opl_callback_queue_t *queue);
+
+#endif /* #ifndef OPL_QUEUE_H */
+
diff --git a/opl/opl_sdl.c b/opl/opl_sdl.c
new file mode 100644
index 00000000..f6a3b229
--- /dev/null
+++ b/opl/opl_sdl.c
@@ -0,0 +1,510 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL SDL interface.
+//
+//-----------------------------------------------------------------------------
+
+#include "config.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <assert.h>
+
+#include "SDL.h"
+#include "SDL_mixer.h"
+
+#include "dbopl.h"
+
+#include "opl.h"
+#include "opl_internal.h"
+
+#include "opl_queue.h"
+
+#define MAX_SOUND_SLICE_TIME 100 /* ms */
+
+typedef struct
+{
+    unsigned int rate;        // Number of times the timer is advanced per sec.
+    unsigned int enabled;     // Non-zero if timer is enabled.
+    unsigned int value;       // Last value that was set.
+    unsigned int expire_time; // Calculated time that timer will expire.
+} opl_timer_t;
+
+// When the callback mutex is locked using OPL_Lock, callback functions
+// are not invoked.
+
+static SDL_mutex *callback_mutex = NULL;
+
+// Queue of callbacks waiting to be invoked.
+
+static opl_callback_queue_t *callback_queue;
+
+// Mutex used to control access to the callback queue.
+
+static SDL_mutex *callback_queue_mutex = NULL;
+
+// Current time, in number of samples since startup:
+
+static int current_time;
+
+// If non-zero, playback is currently paused.
+
+static int opl_sdl_paused;
+
+// Time offset (in samples) due to the fact that callbacks
+// were previously paused.
+
+static unsigned int pause_offset;
+
+// OPL software emulator structure.
+
+static Chip opl_chip;
+
+// Temporary mixing buffer used by the mixing callback.
+
+static int32_t *mix_buffer = NULL;
+
+// Register number that was written.
+
+static int register_num = 0;
+
+// Timers; DBOPL does not do timer stuff itself.
+
+static opl_timer_t timer1 = { 12500, 0, 0, 0 };
+static opl_timer_t timer2 = { 3125, 0, 0, 0 };
+
+// SDL parameters.
+
+static int sdl_was_initialized = 0;
+static int mixing_freq, mixing_channels;
+static Uint16 mixing_format;
+
+static int SDLIsInitialized(void)
+{
+    int freq, channels;
+    Uint16 format;
+
+    return Mix_QuerySpec(&freq, &format, &channels);
+}
+
+// Advance time by the specified number of samples, invoking any
+// callback functions as appropriate.
+
+static void AdvanceTime(unsigned int nsamples)
+{
+    opl_callback_t callback;
+    void *callback_data;
+
+    SDL_LockMutex(callback_queue_mutex);
+
+    // Advance time.
+
+    current_time += nsamples;
+
+    if (opl_sdl_paused)
+    {
+        pause_offset += nsamples;
+    }
+
+    // Are there callbacks to invoke now?  Keep invoking them
+    // until there are none more left.
+
+    while (!OPL_Queue_IsEmpty(callback_queue)
+        && current_time >= OPL_Queue_Peek(callback_queue) + pause_offset)
+    {
+        // Pop the callback from the queue to invoke it.
+
+        if (!OPL_Queue_Pop(callback_queue, &callback, &callback_data))
+        {
+            break;
+        }
+
+        // The mutex stuff here is a bit complicated.  We must
+        // hold callback_mutex when we invoke the callback (so that
+        // the control thread can use OPL_Lock() to prevent callbacks
+        // from being invoked), but we must not be holding
+        // callback_queue_mutex, as the callback must be able to
+        // call OPL_SetCallback to schedule new callbacks.
+
+        SDL_UnlockMutex(callback_queue_mutex);
+
+        SDL_LockMutex(callback_mutex);
+        callback(callback_data);
+        SDL_UnlockMutex(callback_mutex);
+
+        SDL_LockMutex(callback_queue_mutex);
+    }
+
+    SDL_UnlockMutex(callback_queue_mutex);
+}
+
+// Call the OPL emulator code to fill the specified buffer.
+
+static void FillBuffer(int16_t *buffer, unsigned int nsamples)
+{
+    unsigned int i;
+
+    // This seems like a reasonable assumption.  mix_buffer is
+    // 1 second long, which should always be much longer than the
+    // SDL mix buffer.
+
+    assert(nsamples < mixing_freq);
+
+    Chip__GenerateBlock2(&opl_chip, nsamples, mix_buffer);
+
+    // Mix into the destination buffer, doubling up into stereo.
+
+    for (i=0; i<nsamples; ++i)
+    {
+        buffer[i * 2] = (int16_t) (mix_buffer[i] * 2);
+        buffer[i * 2 + 1] = (int16_t) (mix_buffer[i] * 2);
+    }
+}
+
+// Callback function to fill a new sound buffer:
+
+static void OPL_Mix_Callback(void *udata,
+                             Uint8 *byte_buffer,
+                             int buffer_bytes)
+{
+    int16_t *buffer;
+    unsigned int buffer_len;
+    unsigned int filled = 0;
+
+    // Buffer length in samples (quadrupled, because of 16-bit and stereo)
+
+    buffer = (int16_t *) byte_buffer;
+    buffer_len = buffer_bytes / 4;
+
+    // Repeatedly call the OPL emulator update function until the buffer is
+    // full.
+
+    while (filled < buffer_len)
+    {
+        unsigned int next_callback_time;
+        unsigned int nsamples;
+
+        SDL_LockMutex(callback_queue_mutex);
+
+        // Work out the time until the next callback waiting in
+        // the callback queue must be invoked.  We can then fill the
+        // buffer with this many samples.
+
+        if (opl_sdl_paused || OPL_Queue_IsEmpty(callback_queue))
+        {
+            nsamples = buffer_len - filled;
+        }
+        else
+        {
+            next_callback_time = OPL_Queue_Peek(callback_queue) + pause_offset;
+
+            nsamples = next_callback_time - current_time;
+
+            if (nsamples > buffer_len - filled)
+            {
+                nsamples = buffer_len - filled;
+            }
+        }
+
+        SDL_UnlockMutex(callback_queue_mutex);
+
+        // Add emulator output to buffer.
+
+        FillBuffer(buffer + filled * 2, nsamples);
+        filled += nsamples;
+
+        // Invoke callbacks for this point in time.
+
+        AdvanceTime(nsamples);
+    }
+}
+
+static void OPL_SDL_Shutdown(void)
+{
+    Mix_HookMusic(NULL, NULL);
+
+    if (sdl_was_initialized)
+    {
+        Mix_CloseAudio();
+        SDL_QuitSubSystem(SDL_INIT_AUDIO);
+        OPL_Queue_Destroy(callback_queue);
+        free(mix_buffer);
+        sdl_was_initialized = 0;
+    }
+
+/*
+    if (opl_chip != NULL)
+    {
+        OPLDestroy(opl_chip);
+        opl_chip = NULL;
+    }
+    */
+
+    if (callback_mutex != NULL)
+    {
+        SDL_DestroyMutex(callback_mutex);
+        callback_mutex = NULL;
+    }
+
+    if (callback_queue_mutex != NULL)
+    {
+        SDL_DestroyMutex(callback_queue_mutex);
+        callback_queue_mutex = NULL;
+    }
+}
+
+static unsigned int GetSliceSize(void)
+{
+    int limit;
+    int n;
+
+    limit = (opl_sample_rate * MAX_SOUND_SLICE_TIME) / 1000;
+
+    // Try all powers of two, not exceeding the limit.
+
+    for (n=0;; ++n)
+    {
+        // 2^n <= limit < 2^n+1 ?
+
+        if ((1 << (n + 1)) > limit)
+        {
+            return (1 << n);
+        }
+    }
+
+    // Should never happen?
+
+    return 1024;
+}
+
+static int OPL_SDL_Init(unsigned int port_base)
+{
+    // Check if SDL_mixer has been opened already
+    // If not, we must initialize it now
+
+    if (!SDLIsInitialized())
+    {
+        if (SDL_Init(SDL_INIT_AUDIO) < 0)
+        {
+            fprintf(stderr, "Unable to set up sound.\n");
+            return 0;
+        }
+
+        if (Mix_OpenAudio(opl_sample_rate, AUDIO_S16SYS, 2, GetSliceSize()) < 0)
+        {
+            fprintf(stderr, "Error initialising SDL_mixer: %s\n", Mix_GetError());
+
+            SDL_QuitSubSystem(SDL_INIT_AUDIO);
+            return 0;
+        }
+
+        SDL_PauseAudio(0);
+
+        // When this module shuts down, it has the responsibility to 
+        // shut down SDL.
+
+        sdl_was_initialized = 1;
+    }
+    else
+    {
+        sdl_was_initialized = 0;
+    }
+
+    opl_sdl_paused = 0;
+    pause_offset = 0;
+
+    // Queue structure of callbacks to invoke.
+
+    callback_queue = OPL_Queue_Create();
+    current_time = 0;
+
+    // Get the mixer frequency, format and number of channels.
+
+    Mix_QuerySpec(&mixing_freq, &mixing_format, &mixing_channels);
+
+    // Only supports AUDIO_S16SYS
+
+    if (mixing_format != AUDIO_S16SYS || mixing_channels != 2)
+    {
+        fprintf(stderr, 
+                "OPL_SDL only supports native signed 16-bit LSB, "
+                "stereo format!\n");
+
+        OPL_SDL_Shutdown();
+        return 0;
+    }
+
+    // Mix buffer:
+
+    mix_buffer = malloc(mixing_freq * sizeof(uint32_t));
+
+    // Create the emulator structure:
+
+    DBOPL_InitTables();
+    Chip__Chip(&opl_chip);
+    Chip__Setup(&opl_chip, mixing_freq);
+
+    callback_mutex = SDL_CreateMutex();
+    callback_queue_mutex = SDL_CreateMutex();
+
+    // TODO: This should be music callback? or-?
+    Mix_HookMusic(OPL_Mix_Callback, NULL);
+
+    return 1;
+}
+
+static unsigned int OPL_SDL_PortRead(opl_port_t port)
+{
+    unsigned int result = 0;
+
+    if (timer1.enabled && current_time > timer1.expire_time)
+    {
+        result |= 0x80;   // Either have expired
+        result |= 0x40;   // Timer 1 has expired
+    }
+
+    if (timer2.enabled && current_time > timer2.expire_time)
+    {
+        result |= 0x80;   // Either have expired
+        result |= 0x20;   // Timer 2 has expired
+    }
+
+    return result;
+}
+
+static void OPLTimer_CalculateEndTime(opl_timer_t *timer)
+{
+    int tics;
+
+    // If the timer is enabled, calculate the time when the timer
+    // will expire.
+
+    if (timer->enabled)
+    {
+        tics = 0x100 - timer->value;
+        timer->expire_time = current_time
+                           + (tics * opl_sample_rate) / timer->rate;
+    }
+}
+
+static void WriteRegister(unsigned int reg_num, unsigned int value)
+{
+    switch (reg_num)
+    {
+        case OPL_REG_TIMER1:
+            timer1.value = value;
+            OPLTimer_CalculateEndTime(&timer1);
+            break;
+
+        case OPL_REG_TIMER2:
+            timer2.value = value;
+            OPLTimer_CalculateEndTime(&timer2);
+            break;
+
+        case OPL_REG_TIMER_CTRL:
+            if (value & 0x80)
+            {
+                timer1.enabled = 0;
+                timer2.enabled = 0;
+            }
+            else
+            {
+                if ((value & 0x40) == 0)
+                {
+                    timer1.enabled = (value & 0x01) != 0;
+                    OPLTimer_CalculateEndTime(&timer1);
+                }
+
+                if ((value & 0x20) == 0)
+                {
+                    timer1.enabled = (value & 0x02) != 0;
+                    OPLTimer_CalculateEndTime(&timer2);
+                }
+            }
+
+            break;
+
+        default:
+            Chip__WriteReg(&opl_chip, reg_num, value);
+            break;
+    }
+}
+
+static void OPL_SDL_PortWrite(opl_port_t port, unsigned int value)
+{
+    if (port == OPL_REGISTER_PORT)
+    {
+        register_num = value;
+    }
+    else if (port == OPL_DATA_PORT)
+    {
+        WriteRegister(register_num, value);
+    }
+}
+
+static void OPL_SDL_SetCallback(unsigned int ms,
+                                opl_callback_t callback,
+                                void *data)
+{
+    SDL_LockMutex(callback_queue_mutex);
+    OPL_Queue_Push(callback_queue, callback, data,
+                   current_time - pause_offset + (ms * mixing_freq) / 1000);
+    SDL_UnlockMutex(callback_queue_mutex);
+}
+
+static void OPL_SDL_ClearCallbacks(void)
+{
+    SDL_LockMutex(callback_queue_mutex);
+    OPL_Queue_Clear(callback_queue);
+    SDL_UnlockMutex(callback_queue_mutex);
+}
+
+static void OPL_SDL_Lock(void)
+{
+    SDL_LockMutex(callback_mutex);
+}
+
+static void OPL_SDL_Unlock(void)
+{
+    SDL_UnlockMutex(callback_mutex);
+}
+
+static void OPL_SDL_SetPaused(int paused)
+{
+    opl_sdl_paused = paused;
+}
+
+opl_driver_t opl_sdl_driver =
+{
+    "SDL",
+    OPL_SDL_Init,
+    OPL_SDL_Shutdown,
+    OPL_SDL_PortRead,
+    OPL_SDL_PortWrite,
+    OPL_SDL_SetCallback,
+    OPL_SDL_ClearCallbacks,
+    OPL_SDL_Lock,
+    OPL_SDL_Unlock,
+    OPL_SDL_SetPaused
+};
+
diff --git a/opl/opl_timer.c b/opl/opl_timer.c
new file mode 100644
index 00000000..35b2092f
--- /dev/null
+++ b/opl/opl_timer.c
@@ -0,0 +1,251 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL timer thread.
+//     Once started using OPL_Timer_StartThread, the thread sleeps,
+//     waking up to invoke callbacks set using OPL_Timer_SetCallback.
+//
+//-----------------------------------------------------------------------------
+
+#include "SDL.h"
+
+#include "opl_timer.h"
+#include "opl_queue.h"
+
+typedef enum
+{
+    THREAD_STATE_STOPPED,
+    THREAD_STATE_RUNNING,
+    THREAD_STATE_STOPPING,
+} thread_state_t;
+
+static SDL_Thread *timer_thread = NULL;
+static thread_state_t timer_thread_state;
+static int current_time;
+
+// If non-zero, callbacks are currently paused.
+
+static int opl_timer_paused;
+
+// Offset in milliseconds to adjust time due to the fact that playback
+// was paused.
+
+static unsigned int pause_offset = 0;
+
+// Queue of callbacks waiting to be invoked.
+// The callback queue mutex is held while the callback queue structure
+// or current_time is being accessed.
+
+static opl_callback_queue_t *callback_queue;
+static SDL_mutex *callback_queue_mutex;
+
+// The timer mutex is held while timer callback functions are being
+// invoked, so that the calling code can prevent clashes.
+
+static SDL_mutex *timer_mutex;
+
+// Returns true if there is a callback at the head of the queue ready
+// to be invoked.  Otherwise, next_time is set to the time when the
+// timer thread must wake up again to check.
+
+static int CallbackWaiting(unsigned int *next_time)
+{
+    // If paused, just wait in 50ms increments until unpaused.
+    // Update pause_offset so after we unpause, the callback 
+    // times will be right.
+
+    if (opl_timer_paused)
+    {
+        *next_time = current_time + 50;
+        pause_offset += 50;
+        return 0;
+    }
+
+    // If there are no queued callbacks, sleep for 50ms at a time
+    // until a callback is added.
+
+    if (OPL_Queue_IsEmpty(callback_queue))
+    {
+        *next_time = current_time + 50;
+        return 0;
+    }
+
+    // Read the time of the first callback in the queue.
+    // If the time for the callback has not yet arrived,
+    // we must sleep until the callback time.
+
+    *next_time = OPL_Queue_Peek(callback_queue) + pause_offset;
+
+    return *next_time <= current_time;
+}
+
+static unsigned int GetNextTime(void)
+{
+    opl_callback_t callback;
+    void *callback_data;
+    unsigned int next_time;
+    int have_callback;
+
+    // Keep running through callbacks until there are none ready to
+    // run. When we run out of callbacks, next_time will be set.
+
+    do
+    {
+        SDL_LockMutex(callback_queue_mutex);
+
+        // Check if the callback at the head of the list is ready to
+        // be invoked.  If so, pop from the head of the queue.
+
+        have_callback = CallbackWaiting(&next_time);
+
+        if (have_callback)
+        {
+            OPL_Queue_Pop(callback_queue, &callback, &callback_data);
+        }
+
+        SDL_UnlockMutex(callback_queue_mutex);
+
+        // Now invoke the callback, if we have one.
+        // The timer mutex is held while the callback is invoked.
+
+        if (have_callback)
+        {
+            SDL_LockMutex(timer_mutex);
+            callback(callback_data);
+            SDL_UnlockMutex(timer_mutex);
+        }
+    } while (have_callback);
+
+    return next_time;
+}
+
+static int ThreadFunction(void *unused)
+{
+    unsigned int next_time;
+    unsigned int now;
+
+    // Keep running until OPL_Timer_StopThread is called.
+
+    while (timer_thread_state == THREAD_STATE_RUNNING)
+    {
+        // Get the next time that we must sleep until, and
+        // wait until that time.
+
+        next_time = GetNextTime();
+        now = SDL_GetTicks();
+
+        if (next_time > now)
+        {
+            SDL_Delay(next_time - now);
+        }
+
+        // Update the current time.
+
+        SDL_LockMutex(callback_queue_mutex);
+        current_time = next_time;
+        SDL_UnlockMutex(callback_queue_mutex);
+    }
+
+    timer_thread_state = THREAD_STATE_STOPPED;
+
+    return 0;
+}
+
+static void InitResources(void)
+{
+    callback_queue = OPL_Queue_Create();
+    timer_mutex = SDL_CreateMutex();
+    callback_queue_mutex = SDL_CreateMutex();
+}
+
+static void FreeResources(void)
+{
+    OPL_Queue_Destroy(callback_queue);
+    SDL_DestroyMutex(callback_queue_mutex);
+    SDL_DestroyMutex(timer_mutex);
+}
+
+int OPL_Timer_StartThread(void)
+{
+    InitResources();
+
+    timer_thread_state = THREAD_STATE_RUNNING;
+    current_time = SDL_GetTicks();
+    opl_timer_paused = 0;
+    pause_offset = 0;
+
+    timer_thread = SDL_CreateThread(ThreadFunction, NULL);
+
+    if (timer_thread == NULL)
+    {
+        timer_thread_state = THREAD_STATE_STOPPED;
+        FreeResources();
+
+        return 0;
+    }
+
+    return 1;
+}
+
+void OPL_Timer_StopThread(void)
+{
+    timer_thread_state = THREAD_STATE_STOPPING;
+
+    while (timer_thread_state != THREAD_STATE_STOPPED)
+    {
+        SDL_Delay(1);
+    }
+
+    FreeResources();
+}
+
+void OPL_Timer_SetCallback(unsigned int ms, opl_callback_t callback, void *data)
+{
+    SDL_LockMutex(callback_queue_mutex);
+    OPL_Queue_Push(callback_queue, callback, data,
+                   current_time + ms - pause_offset);
+    SDL_UnlockMutex(callback_queue_mutex);
+}
+
+void OPL_Timer_ClearCallbacks(void)
+{
+    SDL_LockMutex(callback_queue_mutex);
+    OPL_Queue_Clear(callback_queue);
+    SDL_UnlockMutex(callback_queue_mutex);
+}
+
+void OPL_Timer_Lock(void)
+{
+    SDL_LockMutex(timer_mutex);
+}
+
+void OPL_Timer_Unlock(void)
+{
+    SDL_UnlockMutex(timer_mutex);
+}
+
+void OPL_Timer_SetPaused(int paused)
+{
+    SDL_LockMutex(callback_queue_mutex);
+    opl_timer_paused = paused;
+    SDL_UnlockMutex(callback_queue_mutex);
+}
+
diff --git a/opl/opl_timer.h b/opl/opl_timer.h
new file mode 100644
index 00000000..f03fc499
--- /dev/null
+++ b/opl/opl_timer.h
@@ -0,0 +1,42 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL timer thread.
+//
+//-----------------------------------------------------------------------------
+
+#ifndef OPL_TIMER_H
+#define OPL_TIMER_H
+
+#include "opl.h"
+
+int OPL_Timer_StartThread(void);
+void OPL_Timer_StopThread(void);
+void OPL_Timer_SetCallback(unsigned int ms,
+                           opl_callback_t callback,
+                           void *data);
+void OPL_Timer_ClearCallbacks(void);
+void OPL_Timer_Lock(void);
+void OPL_Timer_Unlock(void);
+void OPL_Timer_SetPaused(int paused);
+
+#endif /* #ifndef OPL_TIMER_H */
+
diff --git a/opl/opl_win32.c b/opl/opl_win32.c
new file mode 100644
index 00000000..29df3643
--- /dev/null
+++ b/opl/opl_win32.c
@@ -0,0 +1,172 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL Win32 native interface.
+//
+//-----------------------------------------------------------------------------
+
+#include "config.h"
+
+#ifdef _WIN32
+
+#include <stdio.h>
+
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+#include "opl.h"
+#include "opl_internal.h"
+#include "opl_timer.h"
+
+#include "ioperm_sys.h"
+
+static unsigned int opl_port_base;
+
+// MingW?
+
+#if defined(__GNUC__) && defined(__i386__)
+
+static unsigned int OPL_Win32_PortRead(opl_port_t port)
+{
+    unsigned char result;
+
+    __asm__ volatile (
+       "movl %1, %%edx\n"
+       "inb  %%dx, %%al\n"
+       "movb %%al, %0"
+       :   "=m" (result)
+       :   "r" (opl_port_base + port)
+       :   "edx", "al", "memory"
+    );
+
+    return result;
+}
+
+static void OPL_Win32_PortWrite(opl_port_t port, unsigned int value)
+{
+    __asm__ volatile (
+       "movl %0, %%edx\n"
+       "movb %1, %%al\n"
+       "outb %%al, %%dx"
+       :
+       :   "r" (opl_port_base + port), "r" ((unsigned char) value)
+       :   "edx", "al"
+    );
+}
+
+// TODO: MSVC version
+// #elif defined(_MSC_VER) && defined(_M_IX6) ...
+
+#else
+
+// Not x86, or don't know how to do port R/W on this compiler.
+
+#define NO_PORT_RW
+
+static unsigned int OPL_Win32_PortRead(opl_port_t port)
+{
+    return 0;
+}
+
+static void OPL_Win32_PortWrite(opl_port_t port, unsigned int value)
+{
+}
+
+#endif
+
+static int OPL_Win32_Init(unsigned int port_base)
+{
+#ifndef NO_PORT_RW
+
+    OSVERSIONINFO version_info;
+
+    opl_port_base = port_base;
+
+    // Check the OS version.
+
+    memset(&version_info, 0, sizeof(version_info));
+    version_info.dwOSVersionInfoSize = sizeof(version_info);
+
+    GetVersionEx(&version_info);
+
+    // On NT-based systems, we must acquire I/O port permissions
+    // using the ioperm.sys driver.
+
+    if (version_info.dwPlatformId == VER_PLATFORM_WIN32_NT)
+    {
+        // Install driver.
+
+        if (!IOperm_InstallDriver())
+        {
+            return 0;
+        }
+
+        // Open port range.
+
+        if (!IOperm_EnablePortRange(opl_port_base, 2, 1))
+        {
+            IOperm_UninstallDriver();
+            return 0;
+        }
+    }
+
+    // Start callback thread
+
+    if (!OPL_Timer_StartThread())
+    {
+        IOperm_UninstallDriver();
+        return 0;
+    }
+
+    return 1;
+
+#endif
+
+    return 0;
+}
+
+static void OPL_Win32_Shutdown(void)
+{
+    // Stop callback thread
+
+    OPL_Timer_StopThread();
+
+    // Unload IOperm library.
+
+    IOperm_UninstallDriver();
+}
+
+opl_driver_t opl_win32_driver =
+{
+    "Win32",
+    OPL_Win32_Init,
+    OPL_Win32_Shutdown,
+    OPL_Win32_PortRead,
+    OPL_Win32_PortWrite,
+    OPL_Timer_SetCallback,
+    OPL_Timer_ClearCallbacks,
+    OPL_Timer_Lock,
+    OPL_Timer_Unlock,
+    OPL_Timer_SetPaused
+};
+
+#endif /* #ifdef _WIN32 */
+