- Since our OPL chips are emulated, we can give them a feature that real OPL2 chips lacked:

Full stereo panning for the MIDI player. (The raw OPL players are unaffected.) To get the
  mono output back, you can set opl_stereo to false.
- Changed SoftSynthMIDIDevice::OpenStream() to allocate the same number of samples for stereo
  and mono streams.

SVN r3929 (trunk)

src/oplsynth/fmopl.cpp

@@ -115,6 +115,8 @@ Revision History:
 #define INLINE			__inline
 #endif
 
+#define CENTER_PANNING_POWER	0.70710678118	/* [RH] volume at center for EQP */
+#define HALF_PI					(PI/2)
 
 #define FREQ_SH			16  /* 16.16 fixed point (frequency calculations) */
 #define EG_SH			16  /* 16.16 fixed point (EG timing)              */
@@ -246,6 +248,8 @@ typedef struct{
 	UINT32  fc;			/* Freq. Increment base			*/
 	UINT32  ksl_base;	/* KeyScaleLevel Base step		*/
 	UINT8   kcode;		/* key code (for key scaling)	*/
+	float	LeftVol;	/* volumes for stereo panning	*/
+	float	RightVol;
 } OPL_CH;
 
 /* OPL state */
@@ -297,6 +301,7 @@ typedef struct fm_opl_f {
 	int rate;						/* sampling rate (Hz)			*/
 	double freqbase;				/* frequency base				*/
 	double TimerBase;				/* Timer base time (==sampling time)*/
+	bool IsStereo;					/* Write stereo output			*/
 } FM_OPL;
 
 
@@ -876,7 +881,7 @@ INLINE signed int op_calc1(UINT32 phase, unsigned int env, signed int pm, unsign
 #define volume_calc(OP) ((OP)->TLL + ((UINT32)(OP)->volume) + (LFO_AM & (OP)->AMmask))
 
 /* calculate output */
-INLINE void OPL_CALC_CH( OPL_CH *CH, float *buffer )
+INLINE float OPL_CALC_CH( OPL_CH *CH )
 {
 	OPL_SLOT *SLOT;
 	unsigned int env;
@@ -905,8 +910,9 @@ INLINE void OPL_CALC_CH( OPL_CH *CH, float *buffer )
 	{
 		output += op_calc(SLOT->Cnt, env, phase_modulation, SLOT->wavetable);
 		/* [RH] Convert to floating point. */
-		*buffer += float(output) / 10240;
+		return float(output) / 10240;
 	}
+	return 0;
 }
 
 /*
@@ -1282,6 +1288,13 @@ static void OPL_initalize(FM_OPL *OPL)
 	OPL->eg_timer_overflow = UINT32(( 1 ) * (1<<EG_SH));
 	/*logerror("OPLinit eg_timer_add=%8x eg_timer_overflow=%8x\n", OPL->eg_timer_add, OPL->eg_timer_overflow);*/
 
+	// [RH] Support full MIDI panning. (But default to mono and center panning.)
+	OPL->IsStereo = false;
+	for (int i = 0; i < 9; ++i)
+	{
+		OPL->P_CH[i].LeftVol = (float)CENTER_PANNING_POWER;
+		OPL->P_CH[i].RightVol = (float)CENTER_PANNING_POWER;
+	}
 }
 
 INLINE void FM_KEYON(OPL_SLOT *SLOT, UINT32 key_set)
@@ -1897,6 +1910,28 @@ void YM3812SetUpdateHandler(void *chip,OPL_UPDATEHANDLER UpdateHandler,int param
 	OPLSetUpdateHandler(YM3812, UpdateHandler, param);
 }
 
+/* [RH] Full support for MIDI panning */
+void YM3812SetStereo(void *chip, bool stereo)
+{
+	if (chip != NULL)
+	{
+		FM_OPL *YM3812 = (FM_OPL *)chip;
+		YM3812->IsStereo = stereo;
+	}
+}
+
+void YM3812SetPanning(void *chip, int c, int pan)
+{
+	if (chip != NULL)
+	{
+		FM_OPL *YM3812 = (FM_OPL *)chip;
+		// This is the MIDI-recommended pan formula. 0 and 1 are
+		// both hard left so that 64 can be perfectly center.
+		double level = (pan <= 1) ? 0 : (pan - 1) / 126.0;
+		YM3812->P_CH[c].LeftVol = (float)cos(HALF_PI * level);
+		YM3812->P_CH[c].RightVol = (float)sin(HALF_PI * level);
+	}
+}
 
 /*
 ** Generate samples for one of the YM3812's
@@ -1969,7 +2004,16 @@ static bool CalcVoice (FM_OPL *OPL, int voice, float *buffer, int length)
 		advance_lfo(OPL);
 
 		output = 0;
-		OPL_CALC_CH(CH, buffer + i);
+		float sample = OPL_CALC_CH(CH);
+		if (!OPL->IsStereo)
+		{
+			buffer[i] += sample;
+		}
+		else
+		{
+			buffer[i*2] += sample * CH->LeftVol;
+			buffer[i*2+1] += sample * CH->RightVol;
+		}
 
 		advance(OPL, voice, voice);
 	}
@@ -1987,7 +2031,18 @@ static bool CalcRhythm (FM_OPL *OPL, float *buffer, int length)
 		output = 0;
 		OPL_CALC_RH(&OPL->P_CH[0], OPL->noise_rng & 1);
 		/* [RH] Convert to floating point. */
-		buffer[i] += float(output) / 10240;
+		float sample = float(output) / 10240;
+		if (!OPL->IsStereo)
+		{
+			buffer[i] += sample;
+		}
+		else
+		{
+			// [RH] Always use center panning for rhythm.
+			// The MIDI player doesn't use the rhythm section anyway.
+			buffer[i*2] += sample * CENTER_PANNING_POWER;
+			buffer[i*2+1] += sample * CENTER_PANNING_POWER;
+		}
 
 		advance(OPL, 6, 8);
 		advance_noise(OPL);

src/oplsynth/fmopl.h

@@ -32,6 +32,8 @@ int  YM3812Write(void *chip, int a, int v);
 unsigned char YM3812Read(void *chip, int a);
 int  YM3812TimerOver(void *chip, int c);
 void YM3812UpdateOne(void *chip, float *buffer, int length);
+void YM3812SetStereo(void *chip, bool stereo);
+void YM3812SetPanning(void *chip, int c, int pan);
 
 void YM3812SetTimerHandler(void *chip, OPL_TIMERHANDLER TimerHandler, int channelOffset);
 void YM3812SetIRQHandler(void *chip, OPL_IRQHANDLER IRQHandler, int param);

src/oplsynth/mlopl_io.cpp

@@ -252,6 +252,12 @@ void OPLio::OPLwritePan(uint channel, struct OPL2instrument *instr, int pan)
 		else bits = 0x30;			// both
 
 		OPLwriteValue(0xC0, channel, instr->feedback | bits);
+
+		// Set real panning if we're using emulated chips.
+		if (chips[0] != NULL)
+		{
+			YM3812SetPanning(chips[channel/9], channel%9, pan+64);
+		}
 	}
 }
 
@@ -298,13 +304,14 @@ void OPLio::OPLshutup(void)
 /*
 * Initialize hardware upon startup
 */
-int OPLio::OPLinit(uint numchips)
+int OPLio::OPLinit(uint numchips, bool stereo)
 {
 	assert(numchips >= 1 && numchips <= 2);
 	chips[0] = YM3812Init (3579545, int(OPL_SAMPLE_RATE));
 	chips[1] = NULL;
 	if (chips[0] != NULL)
 	{
+		YM3812SetStereo(chips[0], stereo);
 		if (numchips > 1)
 		{
 			chips[1] = YM3812Init (3579545, int(OPL_SAMPLE_RATE));
@@ -314,6 +321,10 @@ int OPLio::OPLinit(uint numchips)
 				chips[0] = NULL;
 				return -1;
 			}
+			else
+			{
+				YM3812SetStereo(chips[1], stereo);
+			}
 		}
 	}
 	else

src/oplsynth/music_opl_mididevice.cpp

@@ -64,6 +64,8 @@
 
 // PUBLIC DATA DEFINITIONS -------------------------------------------------
 
+CVAR(Bool, opl_stereo, true, CVAR_ARCHIVE);
+
 // CODE --------------------------------------------------------------------
 
 //==========================================================================
@@ -74,6 +76,7 @@
 
 OPLMIDIDevice::OPLMIDIDevice()
 {
+	IsStereo = opl_stereo;
 	FWadLump data = Wads.OpenLumpName("GENMIDI");
 	OPLloadBank(data);
 	SampleRate = (int)OPL_SAMPLE_RATE;
@@ -89,11 +92,11 @@ OPLMIDIDevice::OPLMIDIDevice()
 
 int OPLMIDIDevice::Open(void (*callback)(unsigned int, void *, DWORD, DWORD), void *userdata)
 {
-	if (io == NULL || io->OPLinit(TwoChips + 1))
+	if (io == NULL || io->OPLinit(TwoChips + 1, IsStereo))
 	{
 		return 1;
 	}
-	int ret = OpenStream(14, SoundStream::Mono, callback, userdata);
+	int ret = OpenStream(14, IsStereo ? 0 : SoundStream::Mono, callback, userdata);
 	if (ret == 0)
 	{
 		OPLstopMusic();

src/oplsynth/muslib.h

@@ -177,7 +177,7 @@ struct OPLio {
 	void	OPLshutup(void);
 	void	OPLwriteInitState();
 
-	virtual int		OPLinit(uint numchips);
+	virtual int		OPLinit(uint numchips, bool stereo=false);
 	virtual void	OPLdeinit(void);
 	virtual void	OPLwriteReg(int which, uint reg, uchar data);
 	virtual void	SetClockRate(double samples_per_tick);
@@ -192,7 +192,7 @@ struct DiskWriterIO : public OPLio
 	DiskWriterIO(const char *filename);
 	~DiskWriterIO();
 
-	int OPLinit(uint numchips);
+	int OPLinit(uint numchips, bool notused=false);
 	void OPLdeinit();
 	void OPLwriteReg(int which, uint reg, uchar data);
 	void SetClockRate(double samples_per_tick);

src/oplsynth/opl_mus_player.cpp

@@ -25,6 +25,7 @@ OPLmusicBlock::OPLmusicBlock()
 	LastOffset = 0;
 	TwoChips = !opl_onechip;
 	Looping = false;
+	IsStereo = false;
 	io = NULL;
 	io = new OPLio;
 }
@@ -39,7 +40,7 @@ void OPLmusicBlock::ResetChips ()
 	TwoChips = !opl_onechip;
 	ChipAccess.Enter();
 	io->OPLdeinit ();
-	io->OPLinit (TwoChips + 1);
+	io->OPLinit (TwoChips + 1, IsStereo);
 	ChipAccess.Leave();
 }
 
@@ -222,13 +223,11 @@ void OPLmusicFile::Restart ()
 
 bool OPLmusicBlock::ServiceStream (void *buff, int numbytes)
 {
-	float *samples = (float *)buff;
+	float *samples1 = (float *)buff;
-	float *samples1;
+	int numsamples = numbytes / (sizeof(float) << int(IsStereo));
-	int numsamples = numbytes / sizeof(float);
 	bool prevEnded = false;
 	bool res = true;
 
-	samples1 = samples;
 	memset(buff, 0, numbytes);
 
 	ChipAccess.Enter();
@@ -242,12 +241,12 @@ bool OPLmusicBlock::ServiceStream (void *buff, int numbytes)
 		{
 			YM3812UpdateOne (io->chips[0], samples1, samplesleft);
 			YM3812UpdateOne (io->chips[1], samples1, samplesleft);
-			OffsetSamples(samples1, samplesleft);
+			OffsetSamples(samples1, samplesleft << int(IsStereo));
 			assert(NextTickIn == ticky);
 			NextTickIn -= samplesleft;
 			assert (NextTickIn >= 0);
 			numsamples -= samplesleft;
-			samples1 += samplesleft;
+			samples1 += samplesleft << int(IsStereo);
 		}
 		
 		if (NextTickIn < 1)
@@ -262,7 +261,7 @@ bool OPLmusicBlock::ServiceStream (void *buff, int numbytes)
 					{
 						YM3812UpdateOne (io->chips[0], samples1, numsamples);
 						YM3812UpdateOne (io->chips[1], samples1, numsamples);
-						OffsetSamples(samples1, numsamples);
+						OffsetSamples(samples1, numsamples << int(IsStereo));
 					}
 					res = false;
 					break;

src/oplsynth/opl_mus_player.h

@@ -21,6 +21,7 @@ protected:
 	bool TwoChips;
 	bool Looping;
 	double LastOffset;
+	bool IsStereo;
 
 	FCriticalSection ChipAccess;
 };

src/sound/music_softsynth_mididevice.cpp

@@ -96,7 +96,12 @@ SoftSynthMIDIDevice::~SoftSynthMIDIDevice()
 
 int SoftSynthMIDIDevice::OpenStream(int chunks, int flags, void (*callback)(unsigned int, void *, DWORD, DWORD), void *userdata)
 {
-	Stream = GSnd->CreateStream(FillStream, (SampleRate / chunks) * 4, SoundStream::Float | flags, SampleRate, this);
+	int chunksize = (SampleRate / chunks) * 4;
+	if (!(flags & SoundStream::Mono))
+	{
+		chunksize *= 2;
+	}
+	Stream = GSnd->CreateStream(FillStream, chunksize, SoundStream::Float | flags, SampleRate, this);
 	if (Stream == NULL)
 	{
 		return 2;

wadsrc/static/menudef.txt

@@ -1409,6 +1409,7 @@ OptionMenu AdvSoundOptions
 	StaticText " "
 	StaticText "OPL Synthesis",	1
 	Option "Only emulate one OPL chip", "opl_onechip", "OnOff"
+	Option "Support MIDI stero panning", "opl_stereo", "OnOff"
 	StaticText " "
 	StaticText "GUS Emulation",	1
 	Slider "MIDI voices",	"midi_voices", 16, 256, 4, 0