Added support class TimeComputer to compute smoother performance times.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34682 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/add-ons/media/media-add-ons/multi_audio/Jamfile

@@ -13,6 +13,7 @@ Addon hmulti_audio.media_addon :
 	MultiAudioDevice.cpp
 	MultiAudioNode.cpp
 	MultiAudioUtility.cpp
+	TimeComputer.cpp
 	: be media $(TARGET_LIBSUPC++)
 ;
 

src/add-ons/media/media-add-ons/multi_audio/TimeComputer.cpp

@@ -0,0 +1,94 @@
+/*
+ * Copyright 2009, Ingo Weinhold, ingo_weinhold@gmx.de.
+ * Distributed under the terms of the MIT License.
+ */
+
+
+#include "TimeComputer.h"
+
+
+TimeComputer::TimeComputer()
+	:
+	fRealTime(0),
+	fPerformanceTime(0),
+	fDrift(1),
+	fFrameRate(1000000),
+	fUsecsPerFrame(1),
+	fPerformanceTimeBase(0),
+	fFrameBase(0),
+	fResetTimeBase(true),
+	fFirstEntry(0),
+	fLastEntry(0)
+{
+}
+
+
+void
+TimeComputer::Init(float frameRate, bigtime_t realBaseTime)
+{
+	fRealTime = realBaseTime;
+	fPerformanceTime = 0;
+	fDrift = 1;
+	SetFrameRate(frameRate);
+}
+
+
+void
+TimeComputer::SetFrameRate(float frameRate)
+{
+	if (frameRate == fFrameRate)
+		return;
+
+	fFrameRate = frameRate;
+	fUsecsPerFrame = (double)1000000 / fFrameRate;
+	fResetTimeBase = true;
+	fFirstEntry = 0;
+	fLastEntry = 0;
+}
+
+
+void
+TimeComputer::AddTimeStamp(bigtime_t realTime, uint64 frames)
+{
+	bigtime_t estimatedPerformanceTime = fPerformanceTime
+		+ bigtime_t((realTime - fRealTime) * fDrift);
+
+	fRealTime = realTime;
+
+	if (fResetTimeBase) {
+		// use the extrapolated performance time at the given real time
+		fPerformanceTime = estimatedPerformanceTime;
+		fPerformanceTimeBase = estimatedPerformanceTime;
+		fFrameBase = frames;
+		fResetTimeBase = false;
+		_AddEntry(fRealTime, fPerformanceTime);
+		return;
+	}
+
+	// add entry
+	bigtime_t performanceTime = fPerformanceTimeBase
+		+ bigtime_t((frames - fFrameBase) * fUsecsPerFrame);
+	_AddEntry(realTime, performanceTime);
+
+	// Update performance time and drift. We don't use the given
+	// performance time directly, but average it with the estimated
+	// performance time.
+	fPerformanceTime = (performanceTime + estimatedPerformanceTime) / 2;
+
+	Entry& entry = fEntries[fFirstEntry];
+	fDrift = double(fPerformanceTime - entry.performanceTime)
+		/ double(fRealTime - entry.realTime);
+}
+
+
+void
+TimeComputer::_AddEntry(bigtime_t realTime, bigtime_t performanceTime)
+{
+	fLastEntry = (fLastEntry + 1) % kEntryCount;
+	Entry& entry = fEntries[fLastEntry];
+	entry.realTime = realTime;
+	entry.performanceTime = performanceTime;
+
+	if (fLastEntry == fFirstEntry)
+		fFirstEntry = (fFirstEntry + 1) % kEntryCount;
+}

src/add-ons/media/media-add-ons/multi_audio/TimeComputer.h

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2009, Ingo Weinhold, ingo_weinhold@gmx.de.
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef TIME_COMPUTER_H
+#define TIME_COMPUTER_H
+
+
+#include <SupportDefs.h>
+
+
+struct TimeComputer {
+								TimeComputer();
+
+			void				Init(float frameRate, bigtime_t realBaseTime);
+			void				SetFrameRate(float frameRate);
+
+			void				AddTimeStamp(bigtime_t realTime, uint64 frames);
+
+			bigtime_t			RealTime() const	{ return fRealTime; }
+			bigtime_t			PerformanceTime() const
+									{ return fPerformanceTime; }
+			double				Drift() const		{ return fDrift; }
+
+private:
+	static	const int32			kEntryCount = 32;
+
+			struct Entry {
+				bigtime_t	realTime;
+				bigtime_t	performanceTime;
+			};
+
+private:
+			void				_AddEntry(bigtime_t realTime,
+									bigtime_t performanceTime);
+
+private:
+			bigtime_t			fRealTime;
+			bigtime_t			fPerformanceTime;
+			double				fDrift;
+			float				fFrameRate;
+			double				fUsecsPerFrame;
+			bigtime_t			fPerformanceTimeBase;
+			uint64				fFrameBase;
+			bool				fResetTimeBase;
+			Entry				fEntries[kEntryCount];
+			int32				fFirstEntry;
+			int32				fLastEntry;
+};
+
+
+#endif	// TIME_COMPUTER_H