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audio/timestamp.cpp

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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * 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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "audio/timestamp.h"
+#include "common/algorithm.h"
+
+namespace Audio {
+
+Timestamp::Timestamp(uint ms, uint fr) {
+	assert(fr > 0);
+
+	_secs = ms / 1000;
+	_framerateFactor = 1000 / Common::gcd<uint>(1000, fr);
+	_framerate = fr * _framerateFactor;
+
+	// Note that _framerate is always divisible by 1000.
+	_numFrames = (ms % 1000) * (_framerate / 1000);
+}
+
+Timestamp::Timestamp(uint s, uint frames, uint fr) {
+	assert(fr > 0);
+
+	_secs = s + (frames / fr);
+	_framerateFactor = 1000 / Common::gcd<uint>(1000, fr);
+	_framerate = fr * _framerateFactor;
+	_numFrames = (frames % fr) * _framerateFactor;
+}
+
+Timestamp Timestamp::convertToFramerate(uint newFramerate) const {
+	Timestamp ts(*this);
+
+	if (ts.framerate() != newFramerate) {
+		ts._framerateFactor = 1000 / Common::gcd<uint>(1000, newFramerate);
+		ts._framerate = newFramerate * ts._framerateFactor;
+
+		const uint g = Common::gcd(_framerate, ts._framerate);
+		const uint p = _framerate / g;
+		const uint q = ts._framerate / g;
+
+		// Convert the frame offset to the new framerate.
+		// We round to the nearest (as opposed to always
+		// rounding down), to minimize rounding errors during
+		// round trip conversions.
+		ts._numFrames = (ts._numFrames * q + p/2) / p;
+
+		ts.normalize();
+	}
+
+	return ts;
+}
+
+void Timestamp::normalize() {
+	// Convert negative _numFrames values to positive ones by adjusting _secs
+	if (_numFrames < 0) {
+		int secsub = 1 + (-_numFrames / _framerate);
+
+		_numFrames += _framerate * secsub;
+		_secs -= secsub;
+	}
+
+	// Wrap around if necessary
+	_secs += (_numFrames / _framerate);
+	_numFrames %= _framerate;
+}
+
+bool Timestamp::operator==(const Timestamp &ts) const {
+	return cmp(ts) == 0;
+}
+
+bool Timestamp::operator!=(const Timestamp &ts) const {
+	return cmp(ts) != 0;
+}
+
+bool Timestamp::operator<(const Timestamp &ts) const {
+	return cmp(ts) < 0;
+}
+
+bool Timestamp::operator<=(const Timestamp &ts) const {
+	return cmp(ts) <= 0;
+}
+
+bool Timestamp::operator>(const Timestamp &ts) const {
+	return cmp(ts) > 0;
+}
+
+bool Timestamp::operator>=(const Timestamp &ts) const {
+	return cmp(ts) >= 0;
+}
+
+int Timestamp::cmp(const Timestamp &ts) const {
+	int delta = _secs - ts._secs;
+	if (!delta) {
+		const uint g = Common::gcd(_framerate, ts._framerate);
+		const uint p = _framerate / g;
+		const uint q = ts._framerate / g;
+
+		delta = (_numFrames * q - ts._numFrames * p);
+	}
+
+	return delta;
+}
+
+
+Timestamp Timestamp::addFrames(int frames) const {
+	Timestamp ts(*this);
+
+	// The frames are given in the original framerate, so we have to
+	// adjust by _framerateFactor accordingly.
+	ts._numFrames += frames * _framerateFactor;
+	ts.normalize();
+
+	return ts;
+}
+
+Timestamp Timestamp::addMsecs(int ms) const {
+	Timestamp ts(*this);
+	ts._secs += ms / 1000;
+	// Add the remaining frames. Note that _framerate is always divisible by 1000.
+	ts._numFrames += (ms % 1000) * (ts._framerate / 1000);
+
+	ts.normalize();
+
+	return ts;
+}
+
+void Timestamp::addIntern(const Timestamp &ts) {
+	assert(_framerate == ts._framerate);
+	_secs += ts._secs;
+	_numFrames += ts._numFrames;
+
+	normalize();
+}
+
+Timestamp Timestamp::operator-() const {
+	Timestamp result(*this);
+	result._secs = -_secs;
+	result._numFrames = -_numFrames;
+	result.normalize();
+	return result;
+}
+
+Timestamp Timestamp::operator+(const Timestamp &ts) const {
+	Timestamp result(*this);
+	result.addIntern(ts);
+	return result;
+}
+
+Timestamp Timestamp::operator-(const Timestamp &ts) const {
+	Timestamp result(*this);
+	result.addIntern(-ts);
+	return result;
+}
+
+int Timestamp::frameDiff(const Timestamp &ts) const {
+
+	int delta = 0;
+	if (_secs != ts._secs)
+		delta = (_secs - ts._secs) * _framerate;
+
+	delta += _numFrames;
+
+	if (_framerate == ts._framerate) {
+		delta -= ts._numFrames;
+	} else {
+		// We need to multiply by the quotient of the two framerates.
+		// We cancel the GCD in this fraction to reduce the risk of
+		// overflows.
+		const uint g = Common::gcd(_framerate, ts._framerate);
+		const uint p = _framerate / g;
+		const uint q = ts._framerate / g;
+
+		delta -= ((long)ts._numFrames * p + q/2) / (long)q;
+	}
+
+	return delta / (int)_framerateFactor;
+}
+
+int Timestamp::msecsDiff(const Timestamp &ts) const {
+	return msecs() - ts.msecs();
+}
+
+int Timestamp::msecs() const {
+	// Note that _framerate is always divisible by 1000.
+	return _secs * 1000 + _numFrames / (_framerate / 1000);
+}
+
+
+} // End of namespace Audio