AUDIO: Add a class representing a real OPL

2 files changed, 101 insertions, 0 deletions

diff --git a/audio/fmopl.cpp b/audio/fmopl.cpp
index 4bc902eba0..b0b3273e82 100644
--- a/audio/fmopl.cpp
+++ b/audio/fmopl.cpp
@@ -29,6 +29,7 @@
 #include "common/config-manager.h"
 #include "common/system.h"
 #include "common/textconsole.h"
+#include "common/timer.h"
 #include "common/translation.h"
 
 namespace OPL {
@@ -185,6 +186,63 @@ void OPL::stop() {
 
 bool OPL::_hasInstance = false;
 
+RealOPL::RealOPL() : _baseFreq(0), _remainingTicks(0) {
+}
+
+RealOPL::~RealOPL() {
+	// Stop callbacks, just in case. If it's still playing at this
+	// point, there's probably a bigger issue, though. The subclass
+	// needs to call stop() or the pointer can still use be used in
+	// the mixer thread at the same time.
+	stop();
+}
+
+void RealOPL::setCallbackFrequency(int timerFrequency) {
+	stopCallbacks();
+	startCallbacks(timerFrequency);
+}
+
+void RealOPL::startCallbacks(int timerFrequency) {
+	_baseFreq = timerFrequency;
+	assert(_baseFreq > 0);
+
+	// We can't request more a timer faster than 100Hz. We'll handle this by calling
+	// the proc multiple times in onTimer() later on.
+	if (timerFrequency > kMaxFreq)
+		timerFrequency = kMaxFreq;
+
+	_remainingTicks = 0;
+	g_system->getTimerManager()->installTimerProc(timerProc, 1000000 / timerFrequency, this, "RealOPL");
+}
+
+void RealOPL::stopCallbacks() {
+	g_system->getTimerManager()->removeTimerProc(timerProc);
+	_baseFreq = 0;
+	_remainingTicks = 0;
+}
+
+void RealOPL::timerProc(void *refCon) {
+	static_cast<RealOPL *>(refCon)->onTimer();
+}
+
+void RealOPL::onTimer() {
+	uint callbacks = 1;
+
+	if (_baseFreq > kMaxFreq) {
+		// We run faster than our max, so run the callback multiple
+		// times to approximate the actual timer callback frequency.
+		uint totalTicks = _baseFreq + _remainingTicks;		
+		callbacks = totalTicks / kMaxFreq;
+		_remainingTicks = totalTicks % kMaxFreq;
+	}
+
+	// Call the callback multiple times. The if is on the inside of the
+	// loop in case the callback removes itself.
+	for (uint i = 0; i < callbacks; i++)
+		if (_callback && _callback->isValid())
+			(*_callback)();
+}
+
 EmulatedOPL::EmulatedOPL() :
 	_nextTick(0),
 	_samplesPerTick(0),
diff --git a/audio/fmopl.h b/audio/fmopl.h
index 091e0bd88d..ba0872d87b 100644
--- a/audio/fmopl.h
+++ b/audio/fmopl.h
@@ -106,8 +106,14 @@ private:
 	static const EmulatorDescription _drivers[];
 };
 
+/**
+ * The type of the OPL timer callback functor.
+ */
 typedef Common::Functor0<void> TimerCallback;
 
+/**
+ * A representation of a Yamaha OPL chip.
+ */
 class OPL {
 private:
 	static bool _hasInstance;
@@ -194,6 +200,43 @@ protected:
 	Common::ScopedPtr<TimerCallback> _callback;
 };
 
+/**
+ * An OPL that represents a real OPL, as opposed to an emulated one.
+ *
+ * This will use an actual timer instead of using one calculated from
+ * the number of samples in an AudioStream::readBuffer call.
+ */
+class RealOPL : public OPL {
+public:
+	RealOPL();
+	virtual ~RealOPL();
+
+	// OPL API
+	void setCallbackFrequency(int timerFrequency);
+
+protected:
+	// OPL API
+	void startCallbacks(int timerFrequency);
+	void stopCallbacks();
+
+private:
+	static void timerProc(void *refCon);
+	void onTimer();
+
+	uint _baseFreq;
+	uint _remainingTicks;
+
+	enum {
+		kMaxFreq = 100
+	};
+};
+
+/**
+ * An OPL that represents an emulated OPL.
+ *
+ * This will send callbacks based on the number of samples
+ * decoded in readBuffer().
+ */
 class EmulatedOPL : public OPL, protected Audio::AudioStream {
 public:
 	EmulatedOPL();